llvfs.cpp

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#include "linden_common.h"

#include <sys/stat.h>
#include <set>
#include <map>
#if LL_WINDOWS
#include <share.h>
#elif LL_SOLARIS
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#else
#include <sys/file.h>
#endif
    
#include "llvfs.h"
#include "llstl.h"
    
const S32 FILE_BLOCK_MASK = 0x000003FF;  // 1024-byte blocks
const S32 VFS_CLEANUP_SIZE = 5242880;  // how much space we free up in a single stroke
const S32 BLOCK_LENGTH_INVALID = -1;    // mLength for invalid LLVFSFileBlocks

LLVFS *gVFS = NULL;

// internal class definitions
class LLVFSBlock
{
public:
        LLVFSBlock() 
        {
                mLocation = 0;
                mLength = 0;
        }
    
        LLVFSBlock(U32 loc, S32 size)
        {
                mLocation = loc;
                mLength = size;
        }
    
        static bool locationSortPredicate(
                const LLVFSBlock* lhs,
                const LLVFSBlock* rhs)
        {
                return lhs->mLocation < rhs->mLocation;
        }

public:
        U32 mLocation;
        S32     mLength;                // allocated block size
};
    
LLVFSFileSpecifier::LLVFSFileSpecifier()
:       mFileID(),
        mFileType( LLAssetType::AT_NONE )
{
}
    
LLVFSFileSpecifier::LLVFSFileSpecifier(const LLUUID &file_id, const LLAssetType::EType file_type)
{
        mFileID = file_id;
        mFileType = file_type;
}
    
bool LLVFSFileSpecifier::operator<(const LLVFSFileSpecifier &rhs) const
{
        return (mFileID == rhs.mFileID)
                ? mFileType < rhs.mFileType
                : mFileID < rhs.mFileID;
}
    
bool LLVFSFileSpecifier::operator==(const LLVFSFileSpecifier &rhs) const
{
        return (mFileID == rhs.mFileID && 
                        mFileType == rhs.mFileType);
}
    
    
class LLVFSFileBlock : public LLVFSBlock, public LLVFSFileSpecifier
{
public:
        LLVFSFileBlock() : LLVFSBlock(), LLVFSFileSpecifier()
        {
                init();
        }
    
        LLVFSFileBlock(const LLUUID &file_id, LLAssetType::EType file_type, U32 loc = 0, S32 size = 0)
                : LLVFSBlock(loc, size), LLVFSFileSpecifier( file_id, file_type )
        {
                init();
        }

        void init()
        {
                mSize = 0;
                mIndexLocation = -1;
                mAccessTime = (U32)time(NULL);

                for (S32 i = 0; i < (S32)VFSLOCK_COUNT; i++)
                {
                        mLocks[(EVFSLock)i] = 0;
                }
        }

        #ifdef LL_LITTLE_ENDIAN
        inline void swizzleCopy(void *dst, void *src, int size) { memcpy(dst, src, size); /* Flawfinder: ignore */}

        #else
        
        inline U32 swizzle32(U32 x)
        {
                return(((x >> 24) & 0x000000FF) | ((x >> 8)  & 0x0000FF00) | ((x << 8)  & 0x00FF0000) |((x << 24) & 0xFF000000));
        }
        
        inline U16 swizzle16(U16 x)
        {
                return( ((x >> 8)  & 0x000000FF) | ((x << 8)  & 0x0000FF00) );
        }
        
        inline void swizzleCopy(void *dst, void *src, int size) 
        {
                if(size == 4)
                {
                        ((U32*)dst)[0] = swizzle32(((U32*)src)[0]); 
                }
                else if(size == 2)
                {
                        ((U16*)dst)[0] = swizzle16(((U16*)src)[0]); 
                }
                else
                {
                        // Perhaps this should assert...
                        memcpy(dst, src, size); /* Flawfinder: ignore */
                }
        }
        
        #endif

        void serialize(U8 *buffer)
        {
                swizzleCopy(buffer, &mLocation, 4);
                buffer += 4;
                swizzleCopy(buffer, &mLength, 4);
                buffer +=4;
                swizzleCopy(buffer, &mAccessTime, 4);
                buffer +=4;
                memcpy(buffer, &mFileID.mData, 16); /* Flawfinder: ignore */    
                buffer += 16;
                S16 temp_type = mFileType;
                swizzleCopy(buffer, &temp_type, 2);
                buffer += 2;
                swizzleCopy(buffer, &mSize, 4);
        }
    
        void deserialize(U8 *buffer, const S32 index_loc)
        {
                mIndexLocation = index_loc;
    
                swizzleCopy(&mLocation, buffer, 4);
                buffer += 4;
                swizzleCopy(&mLength, buffer, 4);
                buffer += 4;
                swizzleCopy(&mAccessTime, buffer, 4);
                buffer += 4;
                memcpy(&mFileID.mData, buffer, 16);
                buffer += 16;
                S16 temp_type;
                swizzleCopy(&temp_type, buffer, 2);
                mFileType = (LLAssetType::EType)temp_type;
                buffer += 2;
                swizzleCopy(&mSize, buffer, 4);
        }
    
        static BOOL insertLRU(LLVFSFileBlock* const& first,
                                                  LLVFSFileBlock* const& second)
        {
                return (first->mAccessTime == second->mAccessTime)
                        ? *first < *second
                        : first->mAccessTime < second->mAccessTime;
        }
    
public:
        S32  mSize;
        S32  mIndexLocation; // location of index entry
        U32  mAccessTime;
        BOOL mLocks[VFSLOCK_COUNT]; // number of outstanding locks of each type
    
        static const S32 SERIAL_SIZE;
};

// Helper structure for doing lru w/ stl... is there a simpler way?
struct LLVFSFileBlock_less
{
        bool operator()(LLVFSFileBlock* const& lhs, LLVFSFileBlock* const& rhs) const
        {
                return (LLVFSFileBlock::insertLRU(lhs, rhs)) ? true : false;
        }
};


const S32 LLVFSFileBlock::SERIAL_SIZE = 34;
     
    
LLVFS::LLVFS(const char *index_filename, const char *data_filename, const BOOL read_only, const U32 presize, const BOOL remove_after_crash)
:       mRemoveAfterCrash(remove_after_crash)
{
        mDataMutex = new LLMutex(0);

        S32 i;
        for (i = 0; i < VFSLOCK_COUNT; i++)
        {
                mLockCounts[i] = 0;
        }
        mValid = VFSVALID_OK;
        mReadOnly = read_only;
        mIndexFilename = new char[strlen(index_filename) + 1];  /* Flawfinder: ignore */
        mDataFilename = new char[strlen(data_filename) + 1];    /* Flawfinder: ignore */
        if (mIndexFilename == NULL || mDataFilename  == NULL)
        {
                llerrs << "Memory Allocation Failure" << llendl;
                return;
        }
        strcpy(mIndexFilename, index_filename); /* Flawfinder: ignore */
        strcpy(mDataFilename, data_filename);   /* Flawfinder: ignore */
    
        const char *file_mode = mReadOnly ? "rb" : "r+b";
    
        if (! (mDataFP = openAndLock(mDataFilename, file_mode, mReadOnly)))
        {
        
                if (mReadOnly)
                {
                        llwarns << "Can't find " << mDataFilename << " to open read-only VFS" << llendl;
                        mValid = VFSVALID_BAD_CANNOT_OPEN_READONLY;
                        return;
                }
    
                if((mDataFP = openAndLock(mDataFilename, "w+b", FALSE)))
                {
                        // Since we're creating this data file, assume any index file is bogus
                        // remove the index, since this vfs is now blank
                        LLFile::remove(mIndexFilename);
                }
                else
                {
                        llwarns << "Can't open VFS data file " << mDataFilename << " attempting to use alternate" << llendl;
    
                        char *temp_index = new char[strlen(mIndexFilename) + 10];       /* Flawfinder: ignore */
                        if (!temp_index)
                        {
                                llerrs << "Out of the memory in LLVFS::LLVFS(const char *index_filename, const char *data_filename, const BOOL read_only, const U32 presize, const BOOL remove_after_crash)" << llendl;
                                return;
                        }
                        char *temp_data = new char[strlen(mDataFilename) + 10]; /* Flawfinder: ignore */
                        if (!temp_data)
                        {
                                llerrs << "Out of the memory in LLVFS::LLVFS(const char *index_filename, const char *data_filename, const BOOL read_only, const U32 presize, const BOOL remove_after_crash)" << llendl;
                                return;
                        }

                        for (U32 count = 0; count < 256; count++)
                        {
                                sprintf(temp_index, "%s.%u", mIndexFilename, count);    /* Flawfinder: ignore */
                                sprintf(temp_data, "%s.%u", mDataFilename, count);      /* Flawfinder: ignore */
    
                                // try just opening, then creating, each alternate
                                if ((mDataFP = openAndLock(temp_data, "r+b", FALSE)))
                                {
                                        break;
                                }

                                if ((mDataFP = openAndLock(temp_data, "w+b", FALSE)))
                                {
                                        // we're creating the datafile, so nuke the indexfile
                                        LLFile::remove(temp_index);
                                        break;
                                }
                        }
    
                        if (! mDataFP)
                        {
                                llwarns << "Couldn't open vfs data file after trying many alternates" << llendl;
                                mValid = VFSVALID_BAD_CANNOT_CREATE;
                                delete[] temp_index;
                                delete[] temp_data;
                                return;
                        }

                        delete[] mIndexFilename;
                        delete[] mDataFilename;
    
                        mIndexFilename = temp_index;
                        mDataFilename = temp_data;
                }
    
                if (presize)
                {
                        presizeDataFile(presize);
                }
        }

        // Did we leave this file open for writing last time?
        // If so, close it and start over.
        if (!mReadOnly && mRemoveAfterCrash)
        {
                llstat marker_info;
                char* marker = new char[strlen(mDataFilename) + strlen(".open") + 1];   /* Flawfinder: ignore */
                if (!marker )
                {
                        llerrs << "Out of memory in LLVFS::LLVFS(const char *index_filename, const char *data_filename, const BOOL read_only, const U32 presize, const BOOL remove_after_crash)" << llendl;
                        return;
                }
                sprintf(marker, "%s.open", mDataFilename);      /* Flawfinder: ignore */
                if (!LLFile::stat(marker, &marker_info))
                {
                        // marker exists, kill the lock and the VFS files
                        unlockAndClose(mDataFP);
                        mDataFP = NULL;

                        llwarns << "VFS: File left open on last run, removing old VFS file " << mDataFilename << llendl;
                        LLFile::remove(mIndexFilename);
                        LLFile::remove(mDataFilename);
                        LLFile::remove(marker);

                        mDataFP = openAndLock(mDataFilename, "w+b", FALSE);
                        if (!mDataFP)
                        {
                                llwarns << "Can't open VFS data file in crash recovery" << llendl;
                                mValid = VFSVALID_BAD_CANNOT_CREATE;
                                return;
                        }

                        if (presize)
                        {
                                presizeDataFile(presize);
                        }
                }
                delete [] marker;
                marker = NULL;
        }

        // determine the real file size
        fseek(mDataFP, 0, SEEK_END);
        U32 data_size = ftell(mDataFP);

        // read the index file
        // make sure there's at least one file in it too
        // if not, we'll treat this as a new vfs
        llstat fbuf;
        if (! LLFile::stat(mIndexFilename, &fbuf) &&
                fbuf.st_size >= LLVFSFileBlock::SERIAL_SIZE &&
                (mIndexFP = openAndLock(mIndexFilename, file_mode, mReadOnly))
                )
        {       
                U8 *buffer = new U8[fbuf.st_size];
                size_t nread = fread(buffer, 1, fbuf.st_size, mIndexFP);
    
                U8 *tmp_ptr = buffer;
    
                std::vector<LLVFSFileBlock*> files_by_loc;
                
                while (tmp_ptr < buffer + nread)
                {
                        LLVFSFileBlock *block = new LLVFSFileBlock();
    
                        block->deserialize(tmp_ptr, (S32)(tmp_ptr - buffer));
    
                        // Do sanity check on this block.
                        // Note that this skips zero size blocks, which helps VFS
                        // to heal after some errors. JC
                        if (block->mLength > 0 &&
                                (U32)block->mLength <= data_size &&
                                block->mLocation < data_size &&
                                block->mSize > 0 &&
                                block->mSize <= block->mLength &&
                                block->mFileType >= LLAssetType::AT_NONE &&
                                block->mFileType < LLAssetType::AT_COUNT)
                        {
                                mFileBlocks.insert(fileblock_map::value_type(*block, block));
                                files_by_loc.push_back(block);
                        }
                        else
                        if (block->mLength && block->mSize > 0)
                        {
                                // this is corrupt, not empty
                                llwarns << "VFS corruption: " << block->mFileID << " (" << block->mFileType << ") at index " << block->mIndexLocation << " DS: " << data_size << llendl;
                                llwarns << "Length: " << block->mLength << "\tLocation: " << block->mLocation << "\tSize: " << block->mSize << llendl;
                                llwarns << "File has bad data - VFS removed" << llendl;

                                delete[] buffer;
                                delete block;

                                unlockAndClose( mIndexFP );
                                mIndexFP = NULL;
                                LLFile::remove( mIndexFilename );

                                unlockAndClose( mDataFP );
                                mDataFP = NULL;
                                LLFile::remove( mDataFilename );

                                mValid = VFSVALID_BAD_CORRUPT;
                                return;
                        }
                        else
                        {
                                // this is a null or bad entry, skip it
                                S32 index_loc = (S32)(tmp_ptr - buffer);
                                mIndexHoles.push_back(index_loc);
    
                                delete block;
                        }
    
                        tmp_ptr += LLVFSFileBlock::SERIAL_SIZE;
                }
                delete[] buffer;

                std::sort(
                        files_by_loc.begin(),
                        files_by_loc.end(),
                        LLVFSFileBlock::locationSortPredicate);

                // There are 3 cases that have to be considered.
                // 1. No blocks
                // 2. One block.
                // 3. Two or more blocks.
                if (!files_by_loc.empty())
                {
                        // cur walks through the list.
                        std::vector<LLVFSFileBlock*>::iterator cur = files_by_loc.begin();
                        std::vector<LLVFSFileBlock*>::iterator end = files_by_loc.end();
                        LLVFSFileBlock* last_file_block = *cur;
                        
                        // Check to see if there is an empty space before the first file.
                        if (last_file_block->mLocation > 0)
                        {
                                // If so, create a free block.
                                addFreeBlock(new LLVFSBlock(0, last_file_block->mLocation));
                        }

                        // Walk through the 2nd+ block.  If there is a free space
                        // between cur_file_block and last_file_block, add it to
                        // the free space collection.  This block will not need to
                        // run in the case there is only one entry in the VFS.
                        ++cur;
                        while( cur != end )
                        {
                                LLVFSFileBlock* cur_file_block = *cur;

                                // Dupe check on the block
                                if (cur_file_block->mLocation == last_file_block->mLocation
                                        && cur_file_block->mLength == last_file_block->mLength)
                                {
                                        llwarns << "VFS: removing duplicate entry"
                                                << " at " << cur_file_block->mLocation 
                                                << " length " << cur_file_block->mLength 
                                                << " size " << cur_file_block->mSize
                                                << " ID " << cur_file_block->mFileID 
                                                << " type " << cur_file_block->mFileType 
                                                << llendl;

                                        // Duplicate entries.  Nuke them both for safety.
                                        mFileBlocks.erase(*cur_file_block);     // remove ID/type entry
                                        if (cur_file_block->mLength > 0)
                                        {
                                                // convert to hole
                                                addFreeBlock(
                                                        new LLVFSBlock(
                                                                cur_file_block->mLocation,
                                                                cur_file_block->mLength));
                                        }
                                        lockData();                                             // needed for sync()
                                        sync(cur_file_block, TRUE);             // remove first on disk
                                        sync(last_file_block, TRUE);    // remove last on disk
                                        unlockData();                                   // needed for sync()
                                        last_file_block = cur_file_block;
                                        ++cur;
                                        continue;
                                }

                                // Figure out where the last block ended.
                                S32 loc = last_file_block->mLocation+last_file_block->mLength;

                                // Figure out how much space there is between where
                                // the last block ended and this block begins.
                                S32 length = cur_file_block->mLocation - loc;
    
                                // Check for more errors...  Seeing if the current
                                // entry and the last entry make sense together.
                                if (length < 0 || loc < 0 || (U32)loc > data_size)
                                {
                                        // Invalid VFS
                                        unlockAndClose( mIndexFP );
                                        mIndexFP = NULL;
                                        LLFile::remove( mIndexFilename );

                                        unlockAndClose( mDataFP );
                                        mDataFP = NULL;
                                        LLFile::remove( mDataFilename );

                                        llwarns << "VFS: overlapping entries"
                                                << " at " << cur_file_block->mLocation 
                                                << " length " << cur_file_block->mLength 
                                                << " ID " << cur_file_block->mFileID 
                                                << " type " << cur_file_block->mFileType 
                                                << llendl;
                                        mValid = VFSVALID_BAD_CORRUPT;
                                        return;
                                }

                                // we don't want to add empty blocks to the list...
                                if (length > 0)
                                {
                                        addFreeBlock(new LLVFSBlock(loc, length));
                                }
                                last_file_block = cur_file_block;
                                ++cur;
                        }
    
                        // also note any empty space at the end
                        U32 loc = last_file_block->mLocation + last_file_block->mLength;
                        if (loc < data_size)
                        {
                                addFreeBlock(new LLVFSBlock(loc, data_size - loc));
                        }
                }
                else // There where no blocks in the file.
                {
                        addFreeBlock(new LLVFSBlock(0, data_size));
                }
        }
        else
        {
                if (mReadOnly)
                {
                        llwarns << "Can't find " << mIndexFilename << " to open read-only VFS" << llendl;
                        mValid = VFSVALID_BAD_CANNOT_OPEN_READONLY;
                        return;
                }
    
        
                mIndexFP = openAndLock(mIndexFilename, "w+b", FALSE);
                if (!mIndexFP)
                {
                        llwarns << "Couldn't open an index file for the VFS, probably a sharing violation!" << llendl;

                        unlockAndClose( mDataFP );
                        mDataFP = NULL;
                        LLFile::remove( mDataFilename );
                        
                        mValid = VFSVALID_BAD_CANNOT_CREATE;
                        return;
                }
        
                // no index file, start from scratch w/ 1GB allocation
                LLVFSBlock *first_block = new LLVFSBlock(0, data_size ? data_size : 0x40000000);
                addFreeBlock(first_block);
        }

        // Open marker file to look for bad shutdowns
        if (!mReadOnly && mRemoveAfterCrash)
        {
                char* marker = new char[strlen(mDataFilename) + strlen(".open") + 1];
                if (!marker)
                {
                        llerrs << "Out of memory in LLVFS::LLVFS(const char *index_filename, const char *data_filename, const BOOL read_only, const U32 presize, const BOOL remove_after_crash)" << llendl;
                        return;
                }
                sprintf(marker, "%s.open", mDataFilename);      /* Flawfinder: ignore */
                FILE* marker_fp = LLFile::fopen(marker, "w");   /* Flawfinder: ignore */
                if (marker_fp)
                {
                        fclose(marker_fp);
                        marker_fp = NULL;
                }
                delete [] marker;
                marker = NULL;
        }

        llinfos << "VFS: Using index file " << mIndexFilename << " and data file " << mDataFilename << llendl;

        mValid = VFSVALID_OK;
}
    
LLVFS::~LLVFS()
{
        if (mDataMutex->isLocked())
        {
                llerrs << "LLVFS destroyed with mutex locked" << llendl;
        }
        
        unlockAndClose(mIndexFP);
        mIndexFP = NULL;

        fileblock_map::const_iterator it;
        for (it = mFileBlocks.begin(); it != mFileBlocks.end(); ++it)
        {
                delete (*it).second;
        }
        mFileBlocks.clear();
        
        mFreeBlocksByLength.clear();

        for_each(mFreeBlocksByLocation.begin(), mFreeBlocksByLocation.end(), DeletePairedPointer());
    
        unlockAndClose(mDataFP);
        mDataFP = NULL;
    
        // Remove marker file
        if (!mReadOnly && mRemoveAfterCrash)
        {
                char* marker_file = new char[strlen(mDataFilename) + strlen(".open") + 1];
                if (marker_file == NULL)
                {
                        llerrs << "Memory Allocation Failure" << llendl;
                        return;
                }
                sprintf(marker_file, "%s.open", mDataFilename); /* Flawfinder: ignore */
                LLFile::remove(marker_file);
                delete [] marker_file;
                marker_file = NULL;
        }

        delete[] mIndexFilename;
        mIndexFilename = NULL;
        delete[] mDataFilename;
        mDataFilename = NULL;

        delete mDataMutex;
}

void LLVFS::presizeDataFile(const U32 size)
{
        if (!mDataFP)
        {
                llerrs << "LLVFS::presizeDataFile() with no data file open" << llendl;
                return;
        }

        // we're creating this file for the first time, size it
        fseek(mDataFP, size-1, SEEK_SET);
        S32 tmp = 0;
        tmp = (S32)fwrite(&tmp, 1, 1, mDataFP);
        // fflush(mDataFP);

        // also remove any index, since this vfs is now blank
        LLFile::remove(mIndexFilename);

        if (tmp)
        {
                llinfos << "Pre-sized VFS data file to " << ftell(mDataFP) << " bytes" << llendl;
        }
        else
        {
                llwarns << "Failed to pre-size VFS data file" << llendl;
        }
}

BOOL LLVFS::getExists(const LLUUID &file_id, const LLAssetType::EType file_type)
{
        LLVFSFileBlock *block = NULL;
                
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;
        }

        lockData();
        
        LLVFSFileSpecifier spec(file_id, file_type);
        fileblock_map::iterator it = mFileBlocks.find(spec);
        if (it != mFileBlocks.end())
        {
                block = (*it).second;
                block->mAccessTime = (U32)time(NULL);
        }

        BOOL res = (block && block->mLength > 0) ? TRUE : FALSE;
        
        unlockData();
        
        return res;
}
    
S32      LLVFS::getSize(const LLUUID &file_id, const LLAssetType::EType file_type)
{
        S32 size = 0;
        
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;

        }

        lockData();
        
        LLVFSFileSpecifier spec(file_id, file_type);
        fileblock_map::iterator it = mFileBlocks.find(spec);
        if (it != mFileBlocks.end())
        {
                LLVFSFileBlock *block = (*it).second;

                block->mAccessTime = (U32)time(NULL);
                size = block->mSize;
        }

        unlockData();
        
        return size;
}
    
S32  LLVFS::getMaxSize(const LLUUID &file_id, const LLAssetType::EType file_type)
{
        S32 size = 0;
        
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;
        }

        lockData();
        
        LLVFSFileSpecifier spec(file_id, file_type);
        fileblock_map::iterator it = mFileBlocks.find(spec);
        if (it != mFileBlocks.end())
        {
                LLVFSFileBlock *block = (*it).second;

                block->mAccessTime = (U32)time(NULL);
                size = block->mLength;
        }

        unlockData();

        return size;
}

BOOL LLVFS::checkAvailable(S32 max_size)
{
        blocks_length_map_t::iterator iter = mFreeBlocksByLength.lower_bound(max_size); // first entry >= size
        return (iter == mFreeBlocksByLength.end()) ? FALSE : TRUE;
}

BOOL LLVFS::setMaxSize(const LLUUID &file_id, const LLAssetType::EType file_type, S32 max_size)
{
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;
        }
        if (mReadOnly)
        {
                llerrs << "Attempt to write to read-only VFS" << llendl;
        }
        if (max_size <= 0)
        {
                llwarns << "VFS: Attempt to assign size " << max_size << " to vfile " << file_id << llendl;
                return FALSE;
        }

        lockData();
        
        LLVFSFileSpecifier spec(file_id, file_type);
        LLVFSFileBlock *block = NULL;
        fileblock_map::iterator it = mFileBlocks.find(spec);
        if (it != mFileBlocks.end())
        {
                block = (*it).second;
        }
    
        // round all sizes upward to KB increments
        // SJB: Need to not round for the new texture-pipeline code so we know the correct
        //      max file size. Need to investigate the potential problems with this...
        if (file_type != LLAssetType::AT_TEXTURE)
        {
                if (max_size & FILE_BLOCK_MASK)
                {
                        max_size += FILE_BLOCK_MASK;
                        max_size &= ~FILE_BLOCK_MASK;
                }
    }
        
        if (block && block->mLength > 0)
        {    
                block->mAccessTime = (U32)time(NULL);
    
                if (max_size == block->mLength)
                {
                        unlockData();
                        return TRUE;
                }
                else if (max_size < block->mLength)
                {
                        // this file is shrinking
                        LLVFSBlock *free_block = new LLVFSBlock(block->mLocation + max_size, block->mLength - max_size);

                        addFreeBlock(free_block);
    
                        block->mLength = max_size;
    
                        if (block->mLength < block->mSize)
                        {
                                // JC: Was a warning, but Ian says it's bad.
                                llerrs << "Truncating virtual file " << file_id << " to " << block->mLength << " bytes" << llendl;
                                block->mSize = block->mLength;
                        }
    
                        sync(block);
                        //mergeFreeBlocks();

                        unlockData();
                        return TRUE;
                }
                else if (max_size > block->mLength)
                {
                        // this file is growing
                        // first check for an adjacent free block to grow into
                        S32 size_increase = max_size - block->mLength;

                        // Find the first free block with and addres > block->mLocation
                        LLVFSBlock *free_block;
                        blocks_location_map_t::iterator iter = mFreeBlocksByLocation.upper_bound(block->mLocation);
                        if (iter != mFreeBlocksByLocation.end())
                        {
                                free_block = iter->second;
                        
                                if (free_block->mLocation == block->mLocation + block->mLength &&
                                        free_block->mLength >= size_increase)
                                {
                                        // this free block is at the end of the file and is large enough

                                        // Must call useFreeSpace before sync(), as sync()
                                        // unlocks data structures.
                                        useFreeSpace(free_block, size_increase);
                                        block->mLength += size_increase;
                                        sync(block);

                                        unlockData();
                                        return TRUE;
                                }
                        }
                        
                        // no adjecent free block, find one in the list
                        free_block = findFreeBlock(max_size, block);
    
                        if (free_block)
                        {
                                if (block->mLength > 0)
                                {
                                        // create a new free block where this file used to be
                                        LLVFSBlock *new_free_block = new LLVFSBlock(block->mLocation, block->mLength);

                                        addFreeBlock(new_free_block);
    
                                        if (block->mSize > 0)
                                        {
                                                // move the file into the new block
                                                U8 *buffer = new U8[block->mSize];
                                                fseek(mDataFP, block->mLocation, SEEK_SET);
                                                if (fread(buffer, block->mSize, 1, mDataFP) == 1)
                                                {
                                                        fseek(mDataFP, free_block->mLocation, SEEK_SET);
                                                        if (fwrite(buffer, block->mSize, 1, mDataFP) != 1)
                                                        {
                                                                llwarns << "Short write" << llendl;
                                                        }
                                                } else {
                                                        llwarns << "Short read" << llendl;
                                                }
    
                                                delete[] buffer;
                                        }
                                }
    
                                block->mLocation = free_block->mLocation;
    
                                block->mLength = max_size;

                                // Must call useFreeSpace before sync(), as sync()
                                // unlocks data structures.
                                useFreeSpace(free_block, max_size);

                                sync(block);

                                unlockData();
                                return TRUE;
                        }
                        else
                        {
                                llwarns << "VFS: No space (" << max_size << ") to resize existing vfile " << file_id << llendl;
                                //dumpMap();
                                unlockData();
                                dumpStatistics();
                                return FALSE;
                        }
                }
        }
        else
        {
                // find a free block in the list
                LLVFSBlock *free_block = findFreeBlock(max_size);
    
                if (free_block)
                {        
                        if (block)
                        {
                                block->mLocation = free_block->mLocation;
                                block->mLength = max_size;
                        }
                        else
                        {
                                // this file doesn't exist, create it
                                block = new LLVFSFileBlock(file_id, file_type, free_block->mLocation, max_size);
                                mFileBlocks.insert(fileblock_map::value_type(spec, block));
                        }

                        // Must call useFreeSpace before sync(), as sync()
                        // unlocks data structures.
                        useFreeSpace(free_block, max_size);
                        block->mAccessTime = (U32)time(NULL);

                        sync(block);
                }
                else
                {
                        llwarns << "VFS: No space (" << max_size << ") for new virtual file " << file_id << llendl;
                        //dumpMap();
                        unlockData();
                        dumpStatistics();
                        return FALSE;
                }
        }
        unlockData();
        return TRUE;
}


// WARNING: HERE BE DRAGONS!
// rename is the weirdest VFS op, because the file moves but the locks don't!
void LLVFS::renameFile(const LLUUID &file_id, const LLAssetType::EType file_type,
                                           const LLUUID &new_id, const LLAssetType::EType &new_type)
{
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;
        }
        if (mReadOnly)
        {
                llerrs << "Attempt to write to read-only VFS" << llendl;
        }

        lockData();
        
        LLVFSFileSpecifier new_spec(new_id, new_type);
        LLVFSFileSpecifier old_spec(file_id, file_type);
        
        fileblock_map::iterator it = mFileBlocks.find(old_spec);
        if (it != mFileBlocks.end())
        {
                LLVFSFileBlock *src_block = (*it).second;

                // this will purge the data but leave the file block in place, w/ locks, if any
                // WAS: removeFile(new_id, new_type); NOW uses removeFileBlock() to avoid mutex lock recursion
                fileblock_map::iterator new_it = mFileBlocks.find(new_spec);
                if (new_it != mFileBlocks.end())
                {
                        LLVFSFileBlock *new_block = (*new_it).second;
                        removeFileBlock(new_block);
                }
                
                // if there's something in the target location, remove it but inherit its locks
                it = mFileBlocks.find(new_spec);
                if (it != mFileBlocks.end())
                {
                        LLVFSFileBlock *dest_block = (*it).second;

                        for (S32 i = 0; i < (S32)VFSLOCK_COUNT; i++)
                        {
                                if(dest_block->mLocks[i])
                                {
                                        llerrs << "Renaming VFS block to a locked file." << llendl;
                                }
                                dest_block->mLocks[i] = src_block->mLocks[i];
                        }
                        
                        mFileBlocks.erase(new_spec);
                        delete dest_block;
                }

                src_block->mFileID = new_id;
                src_block->mFileType = new_type;
                src_block->mAccessTime = (U32)time(NULL);
   
                mFileBlocks.erase(old_spec);
                mFileBlocks.insert(fileblock_map::value_type(new_spec, src_block));

                sync(src_block);
        }
        else
        {
                llwarns << "VFS: Attempt to rename nonexistent vfile " << file_id << ":" << file_type << llendl;
        }
        unlockData();
}

// mDataMutex must be LOCKED before calling this
void LLVFS::removeFileBlock(LLVFSFileBlock *fileblock)
{
        // convert this into an unsaved, dummy fileblock to preserve locks
        // a more rubust solution would store the locks in a seperate data structure
        sync(fileblock, TRUE);
        
        if (fileblock->mLength > 0)
        {
                // turn this file into an empty block
                LLVFSBlock *free_block = new LLVFSBlock(fileblock->mLocation, fileblock->mLength);
                
                addFreeBlock(free_block);
        }
        
        fileblock->mLocation = 0;
        fileblock->mSize = 0;
        fileblock->mLength = BLOCK_LENGTH_INVALID;
        fileblock->mIndexLocation = -1;

        //mergeFreeBlocks();
}

void LLVFS::removeFile(const LLUUID &file_id, const LLAssetType::EType file_type)
{
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;
        }
        if (mReadOnly)
        {
                llerrs << "Attempt to write to read-only VFS" << llendl;
        }

    lockData();
        
        LLVFSFileSpecifier spec(file_id, file_type);
        fileblock_map::iterator it = mFileBlocks.find(spec);
        if (it != mFileBlocks.end())
        {
                LLVFSFileBlock *block = (*it).second;
                removeFileBlock(block);
        }
        else
        {
                llwarns << "VFS: attempting to remove nonexistent file " << file_id << " type " << file_type << llendl;
        }

        unlockData();
}
    
    
S32 LLVFS::getData(const LLUUID &file_id, const LLAssetType::EType file_type, U8 *buffer, S32 location, S32 length)
{
        S32 bytesread = 0;
        
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;
        }
        llassert(location >= 0);
        llassert(length >= 0);

        BOOL do_read = FALSE;
        
    lockData();
        
        LLVFSFileSpecifier spec(file_id, file_type);
        fileblock_map::iterator it = mFileBlocks.find(spec);
        if (it != mFileBlocks.end())
        {
                LLVFSFileBlock *block = (*it).second;

                block->mAccessTime = (U32)time(NULL);
    
                if (location > block->mSize)
                {
                        llwarns << "VFS: Attempt to read location " << location << " in file " << file_id << " of length " << block->mSize << llendl;
                }
                else
                {
                        if (length > block->mSize - location)
                        {
                                length = block->mSize - location;
                        }
                        location += block->mLocation;
                        do_read = TRUE;
                }
        }

        unlockData();

        if (do_read)
        {
                fseek(mDataFP, location, SEEK_SET);
                bytesread = (S32)fread(buffer, 1, length, mDataFP);
        }
        
        return bytesread;
}
    
S32 LLVFS::storeData(const LLUUID &file_id, const LLAssetType::EType file_type, const U8 *buffer, S32 location, S32 length)
{
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;
        }
        if (mReadOnly)
        {
                llerrs << "Attempt to write to read-only VFS" << llendl;
        }
    
        llassert(length > 0);

    lockData();
    
        LLVFSFileSpecifier spec(file_id, file_type);
        fileblock_map::iterator it = mFileBlocks.find(spec);
        if (it != mFileBlocks.end())
        {
                LLVFSFileBlock *block = (*it).second;

                S32 in_loc = location;
                if (location == -1)
                {
                        location = block->mSize;
                }
                llassert(location >= 0);
                
                block->mAccessTime = (U32)time(NULL);
    
                if (block->mLength == BLOCK_LENGTH_INVALID)
                {
                        // Block was removed, ignore write
                        llwarns << "VFS: Attempt to write to invalid block"
                                        << " in file " << file_id 
                                        << " location: " << in_loc
                                        << " bytes: " << length
                                        << llendl;
                        unlockData();
                        return length;
                }
                else if (location > block->mLength)
                {
                        llwarns << "VFS: Attempt to write to location " << location 
                                        << " in file " << file_id 
                                        << " type " << S32(file_type)
                                        << " of size " << block->mSize
                                        << " block length " << block->mLength
                                        << llendl;
                        unlockData();
                        return length;
                }
                else
                {
                        if (length > block->mLength - location )
                        {
                                llwarns << "VFS: Truncating write to virtual file " << file_id << " type " << S32(file_type) << llendl;
                                length = block->mLength - location;
                        }
                        U32 file_location = location + block->mLocation;
                        
                        unlockData();
                        
                        fseek(mDataFP, file_location, SEEK_SET);
                        S32 write_len = (S32)fwrite(buffer, 1, length, mDataFP);
                        if (write_len != length)
                        {
                                llwarns << llformat("VFS Write Error: %d != %d",write_len,length) << llendl;
                        }
                        // fflush(mDataFP);
                        
                        lockData();
                        if (location + length > block->mSize)
                        {
                                block->mSize = location + write_len;
                                sync(block);
                        }
                        unlockData();
                        
                        return write_len;
                }
        }
        else
        {
                unlockData();
                return 0;
        }
}
 
void LLVFS::incLock(const LLUUID &file_id, const LLAssetType::EType file_type, EVFSLock lock)
{
        lockData();

        LLVFSFileSpecifier spec(file_id, file_type);
        LLVFSFileBlock *block;
        
        fileblock_map::iterator it = mFileBlocks.find(spec);
        if (it != mFileBlocks.end())
        {
                block = (*it).second;
        }
        else
        {
                // Create a dummy block which isn't saved
                block = new LLVFSFileBlock(file_id, file_type, 0, BLOCK_LENGTH_INVALID);
        block->mAccessTime = (U32)time(NULL);
                mFileBlocks.insert(fileblock_map::value_type(spec, block));
        }

        block->mLocks[lock]++;
        mLockCounts[lock]++;
        
        unlockData();
}

void LLVFS::decLock(const LLUUID &file_id, const LLAssetType::EType file_type, EVFSLock lock)
{
        lockData();

        LLVFSFileSpecifier spec(file_id, file_type);
        fileblock_map::iterator it = mFileBlocks.find(spec);
        if (it != mFileBlocks.end())
        {
                LLVFSFileBlock *block = (*it).second;

                if (block->mLocks[lock] > 0)
                {
                        block->mLocks[lock]--;
                }
                else
                {
                        llwarns << "VFS: Decrementing zero-value lock " << lock << llendl;
                }
                mLockCounts[lock]--;
        }

        unlockData();
}

BOOL LLVFS::isLocked(const LLUUID &file_id, const LLAssetType::EType file_type, EVFSLock lock)
{
        lockData();
        
        BOOL res = FALSE;
        
        LLVFSFileSpecifier spec(file_id, file_type);
        fileblock_map::iterator it = mFileBlocks.find(spec);
        if (it != mFileBlocks.end())
        {
                LLVFSFileBlock *block = (*it).second;
                res = (block->mLocks[lock] > 0);
        }

        unlockData();

        return res;
}

//============================================================================
// protected
//============================================================================

void LLVFS::eraseBlockLength(LLVFSBlock *block)
{
        // find the corresponding map entry in the length map and erase it
        S32 length = block->mLength;
        blocks_length_map_t::iterator iter = mFreeBlocksByLength.lower_bound(length);
        blocks_length_map_t::iterator end = mFreeBlocksByLength.end();
        bool found_block = false;
        while(iter != end)
        {
                LLVFSBlock *tblock = iter->second;
                llassert(tblock->mLength == length); // there had -better- be an entry with our length!
                if (tblock == block)
                {
                        mFreeBlocksByLength.erase(iter);
                        found_block = true;
                        break;
                }
                ++iter;
        }
        if(!found_block)
        {
                llwarns << "eraseBlock could not find block" << llendl;
        }
}


// Remove block from both free lists (by location and by length).
void LLVFS::eraseBlock(LLVFSBlock *block)
{
        eraseBlockLength(block);
        // find the corresponding map entry in the location map and erase it    
        U32 location = block->mLocation;
        llverify(mFreeBlocksByLocation.erase(location) == 1); // we should only have one entry per location.
}


// Add the region specified by block location and length to the free lists.
// Also incrementally defragment by merging with previous and next free blocks.
void LLVFS::addFreeBlock(LLVFSBlock *block)
{
#if LL_DEBUG
        size_t dbgcount = mFreeBlocksByLocation.count(block->mLocation);
        if(dbgcount > 0)
        {
                llerrs << "addFreeBlock called with block already in list" << llendl;
        }
#endif

        // Get a pointer to the next free block (by location).
        blocks_location_map_t::iterator next_free_it = mFreeBlocksByLocation.lower_bound(block->mLocation);

        // We can merge with previous if it ends at our requested location.
        LLVFSBlock* prev_block = NULL;
        bool merge_prev = false;
        if (next_free_it != mFreeBlocksByLocation.begin())
        {
                blocks_location_map_t::iterator prev_free_it = next_free_it;
                --prev_free_it;
                prev_block = prev_free_it->second;
                merge_prev = (prev_block->mLocation + prev_block->mLength == block->mLocation);
        }

        // We can merge with next if our block ends at the next block's location.
        LLVFSBlock* next_block = NULL;
        bool merge_next = false;
        if (next_free_it != mFreeBlocksByLocation.end())
        {
                next_block = next_free_it->second;
                merge_next = (block->mLocation + block->mLength == next_block->mLocation);
        }

        if (merge_prev && merge_next)
        {
                // llinfos << "VFS merge BOTH" << llendl;
                // Previous block is changing length (a lot), so only need to update length map.
                // Next block is going away completely. JC
                eraseBlockLength(prev_block);
                eraseBlock(next_block);
                prev_block->mLength += block->mLength + next_block->mLength;
                mFreeBlocksByLength.insert(blocks_length_map_t::value_type(prev_block->mLength, prev_block));
                delete block;
                block = NULL;
                delete next_block;
                next_block = NULL;
        }
        else if (merge_prev)
        {
                // llinfos << "VFS merge previous" << llendl;
                // Previous block is maintaining location, only changing length,
                // therefore only need to update the length map. JC
                eraseBlockLength(prev_block);
                prev_block->mLength += block->mLength;
                mFreeBlocksByLength.insert(blocks_length_map_t::value_type(prev_block->mLength, prev_block)); // multimap insert
                delete block;
                block = NULL;
        }
        else if (merge_next)
        {
                // llinfos << "VFS merge next" << llendl;
                // Next block is changing both location and length,
                // so both free lists must update. JC
                eraseBlock(next_block);
                next_block->mLocation = block->mLocation;
                next_block->mLength += block->mLength;
                // Don't hint here, next_free_it iterator may be invalid.
                mFreeBlocksByLocation.insert(blocks_location_map_t::value_type(next_block->mLocation, next_block)); // multimap insert
                mFreeBlocksByLength.insert(blocks_length_map_t::value_type(next_block->mLength, next_block)); // multimap insert                        
                delete block;
                block = NULL;
        }
        else
        {
                // Can't merge with other free blocks.
                // Hint that insert should go near next_free_it.
                mFreeBlocksByLocation.insert(next_free_it, blocks_location_map_t::value_type(block->mLocation, block)); // multimap insert
                mFreeBlocksByLength.insert(blocks_length_map_t::value_type(block->mLength, block)); // multimap insert
        }
}

// Superceeded by new addFreeBlock which does incremental free space merging.
// Incremental is faster overall.
//void LLVFS::mergeFreeBlocks()
//{
//      if (!isValid())
//      {
//              llerrs << "Attempting to use invalid VFS!" << llendl;
//      }
//      // TODO: could we optimize this with hints from the calling code?
//      blocks_location_map_t::iterator iter = mFreeBlocksByLocation.begin();   
//      blocks_location_map_t::iterator end = mFreeBlocksByLocation.end();      
//      LLVFSBlock *first_block = iter->second;
//      while(iter != end)
//      {
//              blocks_location_map_t::iterator first_iter = iter; // save for if we do a merge
//              if (++iter == end)
//                      break;
//              LLVFSBlock *second_block = iter->second;
//              if (first_block->mLocation + first_block->mLength == second_block->mLocation)
//              {
//                      // remove the first block from the length map
//                      eraseBlockLength(first_block);
//                      // merge first_block with second_block, since they're adjacent
//                      first_block->mLength += second_block->mLength;
//                      // add the first block to the length map (with the new size)
//                      mFreeBlocksByLength.insert(blocks_length_map_t::value_type(first_block->mLength, first_block)); // multimap insert
//
//                      // erase and delete the second block
//                      eraseBlock(second_block);
//                      delete second_block;
//
//                      // reset iterator
//                      iter = first_iter; // haven't changed first_block, so corresponding iterator is still valid
//                      end = mFreeBlocksByLocation.end();
//              }
//              first_block = second_block;
//      }
//}
        

void LLVFS::useFreeSpace(LLVFSBlock *free_block, S32 length)
{
        if (free_block->mLength == length)
        {
                eraseBlock(free_block);
                delete free_block;
        }
        else
        {
                eraseBlock(free_block);
                
                free_block->mLocation += length;
                free_block->mLength -= length;

                addFreeBlock(free_block);
        }
}

// NOTE! mDataMutex must be LOCKED before calling this
// sync this index entry out to the index file
// we need to do this constantly to avoid corruption on viewer crash
void LLVFS::sync(LLVFSFileBlock *block, BOOL remove)
{
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;
        }
        if (mReadOnly)
        {
                llwarns << "Attempt to sync read-only VFS" << llendl;
                return;
        }
        if (block->mLength == BLOCK_LENGTH_INVALID)
        {
                // This is a dummy file, don't save
                return;
        }
        if (block->mLength == 0)
        {
                llerrs << "VFS syncing zero-length block" << llendl;
        }

    BOOL set_index_to_end = FALSE;
        long seek_pos = block->mIndexLocation;
                
        if (-1 == seek_pos)
        {
                if (!mIndexHoles.empty())
                {
                        seek_pos = mIndexHoles.front();
                        mIndexHoles.pop_front();
                }
                else
                {
                        set_index_to_end = TRUE;
                }
        }

    if (set_index_to_end)
        {
                // Need fseek/ftell to update the seek_pos and hence data
                // structures, so can't unlockData() before this.
                fseek(mIndexFP, 0, SEEK_END);
                seek_pos = ftell(mIndexFP);
        }
            
        block->mIndexLocation = seek_pos;
        if (remove)
        {
                mIndexHoles.push_back(seek_pos);
        }

        U8 buffer[LLVFSFileBlock::SERIAL_SIZE];
        if (remove)
        {
                memset(buffer, 0, LLVFSFileBlock::SERIAL_SIZE);
        }
        else
        {
                block->serialize(buffer);
        }

        unlockData();

        // If set_index_to_end, file pointer is already at seek_pos
        // and we don't need to do anything.  Only seek if not at end.
        if (!set_index_to_end)
        {
                fseek(mIndexFP, seek_pos, SEEK_SET);
        }

        if (fwrite(buffer, LLVFSFileBlock::SERIAL_SIZE, 1, mIndexFP) != 1)
        {
                llwarns << "Short write" << llendl;
        }
        
        // fflush(mIndexFP);
        
        lockData();
        
        return;
}

// mDataMutex must be LOCKED before calling this
// Can initiate LRU-based file removal to make space.
// The immune file block will not be removed.
LLVFSBlock *LLVFS::findFreeBlock(S32 size, LLVFSFileBlock *immune)
{
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;
        }

        LLVFSBlock *block = NULL;
        BOOL have_lru_list = FALSE;
        
        typedef std::set<LLVFSFileBlock*, LLVFSFileBlock_less> lru_set;
        lru_set lru_list;
    
        LLTimer timer;

        while (! block)
        {
                // look for a suitable free block
                blocks_length_map_t::iterator iter = mFreeBlocksByLength.lower_bound(size); // first entry >= size
                if (iter != mFreeBlocksByLength.end())
                        block = iter->second;
        
                // no large enough free blocks, time to clean out some junk
                if (! block)
                {
                        // create a list of files sorted by usage time
                        // this is far faster than sorting a linked list
                        if (! have_lru_list)
                        {
                                for (fileblock_map::iterator it = mFileBlocks.begin(); it != mFileBlocks.end(); ++it)
                                {
                                        LLVFSFileBlock *tmp = (*it).second;

                                        if (tmp != immune &&
                                                tmp->mLength > 0 &&
                                                ! tmp->mLocks[VFSLOCK_READ] &&
                                                ! tmp->mLocks[VFSLOCK_APPEND] &&
                                                ! tmp->mLocks[VFSLOCK_OPEN])
                                        {
                                                lru_list.insert(tmp);
                                        }
                                }
                                
                                have_lru_list = TRUE;
                        }

                        if (lru_list.size() == 0)
                        {
                                // No more files to delete, and still not enough room!
                                llwarns << "VFS: Can't make " << size << " bytes of free space in VFS, giving up" << llendl;
                                break;
                        }

                        // is the oldest file big enough?  (Should be about half the time)
                        lru_set::iterator it = lru_list.begin();
                        LLVFSFileBlock *file_block = *it;
                        if (file_block->mLength >= size && file_block != immune)
                        {
                                // ditch this file and look again for a free block - should find it
                                // TODO: it'll be faster just to assign the free block and break
                                llinfos << "LRU: Removing " << file_block->mFileID << ":" << file_block->mFileType << llendl;
                                lru_list.erase(it);
                                removeFileBlock(file_block);
                                file_block = NULL;
                                continue;
                        }

                        
                        llinfos << "VFS: LRU: Aggressive: " << (S32)lru_list.size() << " files remain" << llendl;
                        dumpLockCounts();
                        
                        // Now it's time to aggressively make more space
                        // Delete the oldest 5MB of the vfs or enough to hold the file, which ever is larger
                        // This may yield too much free space, but we'll use it up soon enough
                        U32 cleanup_target = (size > VFS_CLEANUP_SIZE) ? size : VFS_CLEANUP_SIZE;
                        U32 cleaned_up = 0;
                        for (it = lru_list.begin();
                                 it != lru_list.end() && cleaned_up < cleanup_target;
                                 )
                        {
                                file_block = *it;
                                
                                // TODO: it would be great to be able to batch all these sync() calls
                                // llinfos << "LRU2: Removing " << file_block->mFileID << ":" << file_block->mFileType << " last accessed" << file_block->mAccessTime << llendl;

                                cleaned_up += file_block->mLength;
                                lru_list.erase(it++);
                                removeFileBlock(file_block);
                                file_block = NULL;
                        }
                        //mergeFreeBlocks();
                }
        }
    
        F32 time = timer.getElapsedTimeF32();
        if (time > 0.5f)
        {
                llwarns << "VFS: Spent " << time << " seconds in findFreeBlock!" << llendl;
        }

        return block;
}

//============================================================================
// public
//============================================================================

void LLVFS::pokeFiles()
{
        if (!isValid())
        {
                llerrs << "Attempting to use invalid VFS!" << llendl;
        }
        U32 word;
        
        // only write data if we actually read 4 bytes
        // otherwise we're writing garbage and screwing up the file
        fseek(mDataFP, 0, SEEK_SET);
        if (fread(&word, sizeof(word), 1, mDataFP) == 1)
        {
                fseek(mDataFP, 0, SEEK_SET);
                if (fwrite(&word, sizeof(word), 1, mDataFP) != 1)
                {
                        llwarns << "Could not write to data file" << llendl;
                }
                fflush(mDataFP);
        }

        fseek(mIndexFP, 0, SEEK_SET);
        if (fread(&word, sizeof(word), 1, mIndexFP) == 1)
        {
                fseek(mIndexFP, 0, SEEK_SET);
                if (fwrite(&word, sizeof(word), 1, mIndexFP) != 1)
                {
                        llwarns << "Could not write to index file" << llendl;
                }
                fflush(mIndexFP);
        }
}

    
void LLVFS::dumpMap()
{
        llinfos << "Files:" << llendl;
        for (fileblock_map::iterator it = mFileBlocks.begin(); it != mFileBlocks.end(); ++it)
        {
                LLVFSFileBlock *file_block = (*it).second;
                llinfos << "Location: " << file_block->mLocation << "\tLength: " << file_block->mLength << "\t" << file_block->mFileID << "\t" << file_block->mFileType << llendl;
        }
    
        llinfos << "Free Blocks:" << llendl;
        for (blocks_location_map_t::iterator iter = mFreeBlocksByLocation.begin(),
                         end = mFreeBlocksByLocation.end();
                 iter != end; iter++)
        {
                LLVFSBlock *free_block = iter->second;
                llinfos << "Location: " << free_block->mLocation << "\tLength: " << free_block->mLength << llendl;
        }
}
    
// verify that the index file contents match the in-memory file structure
// Very slow, do not call routinely. JC
void LLVFS::audit()
{
        // Lock the mutex through this whole function.
        LLMutexLock lock_data(mDataMutex);
        
        fflush(mIndexFP);

        fseek(mIndexFP, 0, SEEK_END);
        long index_size = ftell(mIndexFP);
        fseek(mIndexFP, 0, SEEK_SET);
    
        BOOL vfs_corrupt = FALSE;
        
        U8 *buffer = new U8[index_size];

        if (fread(buffer, 1, index_size, mIndexFP) != index_size)
        {
                llwarns << "Index truncated" << llendl;
                vfs_corrupt = TRUE;
        }
    
        U8 *tmp_ptr = buffer;
    
        std::map<LLVFSFileSpecifier, LLVFSFileBlock*>   found_files;
        U32 cur_time = (U32)time(NULL);

        std::vector<LLVFSFileBlock*> audit_blocks;
        while (!vfs_corrupt && tmp_ptr < buffer + index_size)
        {
                LLVFSFileBlock *block = new LLVFSFileBlock();
                audit_blocks.push_back(block);
                
                block->deserialize(tmp_ptr, (S32)(tmp_ptr - buffer));
                tmp_ptr += block->SERIAL_SIZE;
    
                // do sanity check on this block
                if (block->mLength >= 0 &&
                        block->mSize >= 0 &&
                        block->mSize <= block->mLength &&
                        block->mFileType >= LLAssetType::AT_NONE &&
                        block->mFileType < LLAssetType::AT_COUNT &&
                        block->mAccessTime <= cur_time &&
                        block->mFileID != LLUUID::null)
                {
                        if (mFileBlocks.find(*block) == mFileBlocks.end())
                        {
                                llwarns << "VFile " << block->mFileID << ":" << block->mFileType << " on disk, not in memory, loc " << block->mIndexLocation << llendl;
                        }
                        else if (found_files.find(*block) != found_files.end())
                        {
                                std::map<LLVFSFileSpecifier, LLVFSFileBlock*>::iterator it;
                                it = found_files.find(*block);
                                LLVFSFileBlock* dupe = it->second;
                                // try to keep data from being lost
                                unlockAndClose(mIndexFP);
                                mIndexFP = NULL;
                                unlockAndClose(mDataFP);
                                mDataFP = NULL;
                                llwarns << "VFS: Original block index " << block->mIndexLocation
                                        << " location " << block->mLocation 
                                        << " length " << block->mLength 
                                        << " size " << block->mSize 
                                        << " id " << block->mFileID
                                        << " type " << block->mFileType
                                        << llendl;
                                llwarns << "VFS: Duplicate block index " << dupe->mIndexLocation
                                        << " location " << dupe->mLocation 
                                        << " length " << dupe->mLength 
                                        << " size " << dupe->mSize 
                                        << " id " << dupe->mFileID
                                        << " type " << dupe->mFileType
                                        << llendl;
                                llwarns << "VFS: Index size " << index_size << llendl;
                                llwarns << "VFS: INDEX CORRUPT" << llendl;
                                vfs_corrupt = TRUE;
                                break;
                        }
                        else
                        {
                                found_files[*block] = block;
                        }
                }
                else
                {
                        if (block->mLength)
                        {
                                llwarns << "VFile " << block->mFileID << ":" << block->mFileType << " corrupt on disk" << llendl;
                        }
                        // else this is just a hole
                }
        }
    
        delete[] buffer;

        if (!vfs_corrupt)
        {
                for (fileblock_map::iterator it = mFileBlocks.begin(); it != mFileBlocks.end(); ++it)
                {
                        LLVFSFileBlock* block = (*it).second;

                        if (block->mSize > 0)
                        {
                                if (! found_files.count(*block))
                                {
                                        llwarns << "VFile " << block->mFileID << ":" << block->mFileType << " in memory, not on disk, loc " << block->mIndexLocation<< llendl;
                                        fseek(mIndexFP, block->mIndexLocation, SEEK_SET);
                                        U8 buf[LLVFSFileBlock::SERIAL_SIZE];
                                        if (fread(buf, LLVFSFileBlock::SERIAL_SIZE, 1, mIndexFP) != 1)
                                        {
                                                llwarns << "VFile " << block->mFileID
                                                                << " gave short read" << llendl;
                                        }
                        
                                        LLVFSFileBlock disk_block;
                                        disk_block.deserialize(buf, block->mIndexLocation);
                                
                                        llwarns << "Instead found " << disk_block.mFileID << ":" << block->mFileType << llendl;
                                }
                                else
                                {
                                        block = found_files.find(*block)->second;
                                        found_files.erase(*block);
                                }
                        }
                }
    
                for (std::map<LLVFSFileSpecifier, LLVFSFileBlock*>::iterator iter = found_files.begin();
                         iter != found_files.end(); iter++)
                {
                        LLVFSFileBlock* block = iter->second;
                        llwarns << "VFile " << block->mFileID << ":" << block->mFileType << " szie:" << block->mSize << " leftover" << llendl;
                }
    
                llinfos << "VFS: audit OK" << llendl;
                // mutex released by LLMutexLock() destructor.
        }

        for_each(audit_blocks.begin(), audit_blocks.end(), DeletePointer());
}
    
    
// quick check for uninitialized blocks
// Slow, do not call in release.
void LLVFS::checkMem()
{
        lockData();
        
        for (fileblock_map::iterator it = mFileBlocks.begin(); it != mFileBlocks.end(); ++it)
        {
                LLVFSFileBlock *block = (*it).second;
                llassert(block->mFileType >= LLAssetType::AT_NONE &&
                                 block->mFileType < LLAssetType::AT_COUNT &&
                                 block->mFileID != LLUUID::null);
    
                for (std::deque<S32>::iterator iter = mIndexHoles.begin();
                         iter != mIndexHoles.end(); ++iter)
                {
                        S32 index_loc = *iter;
                        if (index_loc == block->mIndexLocation)
                        {
                                llwarns << "VFile block " << block->mFileID << ":" << block->mFileType << " is marked as a hole" << llendl;
                        }
                }
        }
    
        llinfos << "VFS: mem check OK" << llendl;

        unlockData();
}

void LLVFS::dumpLockCounts()
{
        S32 i;
        for (i = 0; i < VFSLOCK_COUNT; i++)
        {
                llinfos << "LockType: " << i << ": " << mLockCounts[i] << llendl;
        }
}

void LLVFS::dumpStatistics()
{
        lockData();
        
        // Investigate file blocks.
        std::map<S32, S32> size_counts;
        std::map<U32, S32> location_counts;
        std::map<LLAssetType::EType, std::pair<S32,S32> > filetype_counts;

        S32 max_file_size = 0;
        S32 total_file_size = 0;
        S32 invalid_file_count = 0;
        for (fileblock_map::iterator it = mFileBlocks.begin(); it != mFileBlocks.end(); ++it)
        {
                LLVFSFileBlock *file_block = (*it).second;
                if (file_block->mLength == BLOCK_LENGTH_INVALID)
                {
                        invalid_file_count++;
                }
                else if (file_block->mLength <= 0)
                {
                        llinfos << "Bad file block at: " << file_block->mLocation << "\tLength: " << file_block->mLength << "\t" << file_block->mFileID << "\t" << file_block->mFileType << llendl;
                        size_counts[file_block->mLength]++;
                        location_counts[file_block->mLocation]++;
                }
                else
                {
                        total_file_size += file_block->mLength;
                }

                if (file_block->mLength > max_file_size)
                {
                        max_file_size = file_block->mLength;
                }

                filetype_counts[file_block->mFileType].first++;
                filetype_counts[file_block->mFileType].second += file_block->mLength;
        }
    
        for (std::map<S32,S32>::iterator it = size_counts.begin(); it != size_counts.end(); ++it)
        {
                S32 size = it->first;
                S32 size_count = it->second;
                llinfos << "Bad files size " << size << " count " << size_count << llendl;
        }
        for (std::map<U32,S32>::iterator it = location_counts.begin(); it != location_counts.end(); ++it)
        {
                U32 location = it->first;
                S32 location_count = it->second;
                llinfos << "Bad files location " << location << " count " << location_count << llendl;
        }

        // Investigate free list.
        S32 max_free_size = 0;
        S32 total_free_size = 0;
        std::map<S32, S32> free_length_counts;
        for (blocks_location_map_t::iterator iter = mFreeBlocksByLocation.begin(),
                         end = mFreeBlocksByLocation.end();
                 iter != end; iter++)
        {
                LLVFSBlock *free_block = iter->second;
                if (free_block->mLength <= 0)
                {
                        llinfos << "Bad free block at: " << free_block->mLocation << "\tLength: " << free_block->mLength << llendl;
                }
                else
                {
                        llinfos << "Block: " << free_block->mLocation
                                        << "\tLength: " << free_block->mLength
                                        << "\tEnd: " << free_block->mLocation + free_block->mLength
                                        << llendl;
                        total_free_size += free_block->mLength;
                }

                if (free_block->mLength > max_free_size)
                {
                        max_free_size = free_block->mLength;
                }

                free_length_counts[free_block->mLength]++;
        }

        // Dump histogram of free block sizes
        for (std::map<S32,S32>::iterator it = free_length_counts.begin(); it != free_length_counts.end(); ++it)
        {
                llinfos << "Free length " << it->first << " count " << it->second << llendl;
        }

        llinfos << "Invalid blocks: " << invalid_file_count << llendl;
        llinfos << "File blocks:    " << mFileBlocks.size() << llendl;

        S32 length_list_count = (S32)mFreeBlocksByLength.size();
        S32 location_list_count = (S32)mFreeBlocksByLocation.size();
        if (length_list_count == location_list_count)
        {
                llinfos << "Free list lengths match, free blocks: " << location_list_count << llendl;
        }
        else
        {
                llwarns << "Free list lengths do not match!" << llendl;
                llwarns << "By length: " << length_list_count << llendl;
                llwarns << "By location: " << location_list_count << llendl;
        }
        llinfos << "Max file: " << max_file_size/1024 << "K" << llendl;
        llinfos << "Max free: " << max_free_size/1024 << "K" << llendl;
        llinfos << "Total file size: " << total_file_size/1024 << "K" << llendl;
        llinfos << "Total free size: " << total_free_size/1024 << "K" << llendl;
        llinfos << "Sum: " << (total_file_size + total_free_size) << " bytes" << llendl;
        llinfos << llformat("%.0f%% full",((F32)(total_file_size)/(F32)(total_file_size+total_free_size))*100.f) << llendl;

        llinfos << " " << llendl;
        for (std::map<LLAssetType::EType, std::pair<S32,S32> >::iterator iter = filetype_counts.begin();
                 iter != filetype_counts.end(); ++iter)
        {
                llinfos << "Type: " << LLAssetType::getDesc(iter->first)
                                << " Count: " << iter->second.first
                                << " Bytes: " << (iter->second.second>>20) << " MB" << llendl;
        }
        
        // Look for potential merges 
        {
                blocks_location_map_t::iterator iter = mFreeBlocksByLocation.begin();   
                blocks_location_map_t::iterator end = mFreeBlocksByLocation.end();      
                LLVFSBlock *first_block = iter->second;
                while(iter != end)
                {
                        if (++iter == end)
                                break;
                        LLVFSBlock *second_block = iter->second;
                        if (first_block->mLocation + first_block->mLength == second_block->mLocation)
                        {
                                llinfos << "Potential merge at " << first_block->mLocation << llendl;
                        }
                        first_block = second_block;
                }
        }
        unlockData();
}

// Debug Only!
LLString get_extension(LLAssetType::EType type)
{
        LLString extension;
        switch(type)
        {
          case LLAssetType::AT_TEXTURE:
                extension = ".j2c";
                break;
          case LLAssetType::AT_SOUND:
                extension = ".ogg";
                break;
          case LLAssetType::AT_SOUND_WAV:
                extension = ".wav";
                break;
          case LLAssetType::AT_TEXTURE_TGA:
                extension = ".tga";
                break;
          case LLAssetType::AT_IMAGE_JPEG:
                extension = ".jpeg";
                break;
          case LLAssetType::AT_ANIMATION:
                extension = ".lla";
                break;
          default:
                extension = ".data";
                break;
        }
        return extension;
}

void LLVFS::listFiles()
{
        lockData();
        
        for (fileblock_map::iterator it = mFileBlocks.begin(); it != mFileBlocks.end(); ++it)
        {
                LLVFSFileSpecifier file_spec = it->first;
                LLVFSFileBlock *file_block = it->second;
                S32 length = file_block->mLength;
                S32 size = file_block->mSize;
                if (length != BLOCK_LENGTH_INVALID && size > 0)
                {
                        LLUUID id = file_spec.mFileID;
                        LLString extension = get_extension(file_spec.mFileType);
                        llinfos << " File: " << id
                                        << " Type: " << LLAssetType::getDesc(file_spec.mFileType)
                                        << " Size: " << size
                                        << llendl;
                }
        }
        
        unlockData();
}

#include "llapr.h"
void LLVFS::dumpFiles()
{
        lockData();
        
        for (fileblock_map::iterator it = mFileBlocks.begin(); it != mFileBlocks.end(); ++it)
        {
                LLVFSFileSpecifier file_spec = it->first;
                LLVFSFileBlock *file_block = it->second;
                S32 length = file_block->mLength;
                S32 size = file_block->mSize;
                if (length != BLOCK_LENGTH_INVALID && size > 0)
                {
                        LLUUID id = file_spec.mFileID;
                        LLAssetType::EType type = file_spec.mFileType;
                        U8* buffer = new U8[size];

                        unlockData();
                        getData(id, type, buffer, 0, size);
                        lockData();
                        
                        LLString extension = get_extension(type);
                        LLString filename = id.asString() + extension;
                        llinfos << " Writing " << filename << llendl;
                        apr_file_t* file = ll_apr_file_open(filename, LL_APR_WB);
                        ll_apr_file_write(file, buffer, size);
                        apr_file_close(file);
                        delete[] buffer;
                }
        }
        
        unlockData();
}

//============================================================================
// protected
//============================================================================

// static
FILE *LLVFS::openAndLock(const char *filename, const char *mode, BOOL read_lock)
{
#if LL_WINDOWS
        
        return LLFile::_fsopen(filename, mode, (read_lock ? _SH_DENYWR : _SH_DENYRW));
        
#else

        FILE *fp;
        int fd;
        
        // first test the lock in a non-destructive way
#if LL_SOLARIS
        struct flock fl;
        fl.l_whence = SEEK_SET;
        fl.l_start = 0;
        fl.l_len = 1;
#else // !LL_SOLARIS
        if (strstr(mode, "w"))
        {
                fp = LLFile::fopen(filename, "rb");     /* Flawfinder: ignore */
                if (fp)
                {
                        fd = fileno(fp);
                        if (flock(fd, (read_lock ? LOCK_SH : LOCK_EX) | LOCK_NB) == -1)
                        {
                                fclose(fp);
                                return NULL;
                        }
                  
                        fclose(fp);
                }
        }
#endif // !LL_SOLARIS

        // now actually open the file for use
        fp = LLFile::fopen(filename, mode);     /* Flawfinder: ignore */
        if (fp)
        {
                fd = fileno(fp);
#if LL_SOLARIS
                fl.l_type = read_lock ? F_RDLCK : F_WRLCK;
                if (fcntl(fd, F_SETLK, &fl) == -1)
#else
                if (flock(fd, (read_lock ? LOCK_SH : LOCK_EX) | LOCK_NB) == -1)
#endif
                {
                        fclose(fp);
                        fp = NULL;
                }
        }

        return fp;
        
#endif
}
    
// static
void LLVFS::unlockAndClose(FILE *fp)
{
        if (fp)
        {
        // IW: we don't actually want to unlock on linux
        // this is because a forked process can kill the parent's lock
        // with an explicit unlock
        // however, fclose() will implicitly remove the lock
        // but only once both parent and child have closed the file
    /*  
          #if !LL_WINDOWS
          int fd = fileno(fp);
          flock(fd, LOCK_UN);
          #endif
    */
#if LL_SOLARIS
                struct flock fl;
                fl.l_whence = SEEK_SET;
                fl.l_start = 0;
                fl.l_len = 1;
                fl.l_type = F_UNLCK;
                fcntl(fileno(fp), F_SETLK, &fl);
#endif
                fclose(fp);
        }
}

---