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Don't write files into the save file when the content fully matches t…
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…he underlying file system
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@schellingb
schellingb committed Oct 18, 2024
1 parent db5ae57 commit 1b2e004
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Showing 3 changed files with 75 additions and 64 deletions.
1 change: 0 additions & 1 deletion src/dos/drive_patch.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -850,7 +850,6 @@ bool patchDrive::ApplyVariant(std::string& yml, int enable_variant_number)
{
DOS_File *df;
if (!drv->FileOpen(&df, (char*)path, OPEN_READ)) return;
df->AddRef();
if (yml.length()) yml += '\n';
ReadAndClose(df, yml);
}
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137 changes: 74 additions & 63 deletions src/dos/drive_union.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -311,84 +311,89 @@ struct unionDriveImpl
struct Saver
{
FILE* f;
DOS_Drive* drv;
DOS_Drive *over, *under;
Bit32u local_file_offset, save_size;
Bit16u file_count;
bool failed;
bool failed, write_mods;
std::vector<Bit8u> central_dir;
std::string mods;
std::string buf;

static void WriteFiles(const char* path, bool is_dir, Bit32u size, Bit16u date, Bit16u time, Bit8u attr, Bitu data)
{
Saver& s = *(Saver*)data;
Bit8u buf[4096];
Bit16u pathLen = (Bit16u)(strlen(path) + (is_dir ? 1 : 0));
Bit32u crc32 = 0, extAttr = (is_dir ? 0x10 : 0);

if (!is_dir && size)
// Read file data in both over and under drive to compare
bool under_match_size = false;
Bit32u under_crc32 = 0;
if (!is_dir && !s.write_mods)
{
fseek_wrap(s.f, 30 + pathLen, SEEK_CUR);
if (s.mods.size())
{
crc32 = DriveCalculateCRC32((Bit8u*)&s.mods[0], size, crc32);
s.failed |= !fwrite(&s.mods[0], size, 1, s.f);
}
else
DOS_File* df;
if (s.under->FileOpen(&df, (char*)path, 0))
{
// Write file and calculate CRC32 along the way
DOS_File* df = nullptr;
bool opened = s.drv->FileOpen(&df, (char*)path, 0);
DBP_ASSERT(opened);
Bit32u under_size = 0;
df->AddRef();
Bit32u remain = size;
for (Bit16u read; remain && df->Read(buf, &(read = sizeof(buf))) && read; remain -= read)
{
crc32 = DriveCalculateCRC32(buf, read, crc32);
s.failed |= !fwrite(buf, read, 1, s.f);
}
DBP_ASSERT(remain == 0);
df->Close();
delete df;
s.save_size += size;
df->Seek(&under_size, DOS_SEEK_END);
under_match_size = (under_size == size);
s.buf.clear();
ReadAndClose(df, s.buf, (under_match_size ? 0xFFFFFFFF : 0));
if (under_match_size && size) under_crc32 = DriveCalculateCRC32((Bit8u*)&s.buf[0], size);
}
fseek_wrap(s.f, s.local_file_offset, SEEK_SET);

bool opened = s.over->FileOpen(&df, (char*)path, 0);
DBP_ASSERT(opened);
s.buf.clear();
ReadAndClose(df, s.buf, 0xFFFFFFFF);
}

ZIP_WRITE_LE32(buf+ 0, 0x04034b50); // Local file header signature
ZIP_WRITE_LE16(buf+ 4, 0); // Version needed to extract (minimum)
ZIP_WRITE_LE16(buf+ 6, 0); // General purpose bit flag
ZIP_WRITE_LE16(buf+ 8, 0); // Compression method
ZIP_WRITE_LE16(buf+10, time); // File last modification time
ZIP_WRITE_LE16(buf+12, date); // File last modification date
ZIP_WRITE_LE32(buf+14, crc32); // CRC-32 of uncompressed data
ZIP_WRITE_LE32(buf+18, size); // Compressed size
ZIP_WRITE_LE32(buf+22, size); // Uncompressed size
ZIP_WRITE_LE16(buf+26, pathLen); // File name length
ZIP_WRITE_LE16(buf+28, 0); // Extra field length

//File name (with \ changed to /)
for (char* pIn = (char*)path, *pOut = (char*)(buf+30); *pIn; pIn++, pOut++)
// If content matches, don't store in save file
Bit32u crc32 = (size ? DriveCalculateCRC32((Bit8u*)&s.buf[0], size) : 0);
if (under_match_size && under_crc32 == crc32) return;

// Don't write 0 sized files with .SWP ending (temporary swap files)
Bit16u pathLen = (Bit16u)(strlen(path) + (is_dir ? 1 : 0));
if (!size && !is_dir && pathLen > 4 && !memcmp(path + pathLen - 4, ".SWP", 4)) return;

// Generate local file header
Bit8u lfh[30 + DOS_PATHLENGTH + 8];
ZIP_WRITE_LE32(lfh+ 0, 0x04034b50); // Local file header signature
ZIP_WRITE_LE16(lfh+ 4, 0); // Version needed to extract (minimum)
ZIP_WRITE_LE16(lfh+ 6, 0); // General purpose bit flag
ZIP_WRITE_LE16(lfh+ 8, 0); // Compression method
ZIP_WRITE_LE16(lfh+10, time); // File last modification time
ZIP_WRITE_LE16(lfh+12, date); // File last modification date
ZIP_WRITE_LE32(lfh+14, crc32); // CRC-32 of uncompressed data
ZIP_WRITE_LE32(lfh+18, size); // Compressed size
ZIP_WRITE_LE32(lfh+22, size); // Uncompressed size
ZIP_WRITE_LE16(lfh+26, pathLen); // File name length
ZIP_WRITE_LE16(lfh+28, 0); // Extra field length

// File name (with \ changed to /)
for (char* pIn = (char*)path, *pOut = (char*)(lfh+30); *pIn; pIn++, pOut++)
*pOut = (*pIn == '\\' ? '/' : *pIn);
if (is_dir)
buf[30 + pathLen - 1] = '/';
lfh[30 + pathLen - 1] = '/';

s.failed |= !fwrite(buf, 30 + pathLen, 1, s.f);
if (size) { fseek_wrap(s.f, size, SEEK_CUR); }
// Write local file header followed by file data
s.failed |= !fwrite(lfh, 30 + pathLen, 1, s.f);
if (size)
{
s.failed |= !fwrite(&s.buf[0], size, 1, s.f);
s.save_size += size;
}

// Generate central directory file header
size_t centralDirPos = s.central_dir.size();
s.central_dir.resize(centralDirPos + 46 + pathLen);
Bit8u* cd = &s.central_dir[0] + centralDirPos;

ZIP_WRITE_LE32(cd+0, 0x02014b50); // Central directory file header signature
ZIP_WRITE_LE16(cd+4, 0); // Version made by (0 = DOS)
memcpy(cd+6, buf+4, 26); // copy middle section shared with local file header
ZIP_WRITE_LE16(cd+32, 0); // File comment length
ZIP_WRITE_LE16(cd+34, 0); // Disk number where file starts
ZIP_WRITE_LE16(cd+36, 0); // Internal file attributes
ZIP_WRITE_LE32(cd+38, extAttr); // External file attributes
ZIP_WRITE_LE32(cd+0, 0x02014b50); // Central directory file header signature
ZIP_WRITE_LE16(cd+4, 0); // Version made by (0 = DOS)
memcpy(cd+6, lfh+4, 26); // Copy middle section shared with local file header
ZIP_WRITE_LE16(cd+32, 0); // File comment length
ZIP_WRITE_LE16(cd+34, 0); // Disk number where file starts
ZIP_WRITE_LE16(cd+36, 0); // Internal file attributes
ZIP_WRITE_LE32(cd+38, (is_dir ? 0x10 : 0)); // External file attributes
ZIP_WRITE_LE32(cd+42, s.local_file_offset); // Relative offset of local file header
memcpy(cd + 46, buf + 30, pathLen); // File name

memcpy(cd + 46, lfh + 30, pathLen); // File name
s.local_file_offset += 30 + pathLen + size;
s.file_count++;
}
Expand All @@ -404,16 +409,22 @@ struct unionDriveImpl
impl->ScheduleSave(5000.f);
return;
}
s.drv = impl->over;
s.over = impl->over;
s.under = impl->under;
s.local_file_offset = s.save_size = 0;
s.file_count = 0;
s.failed = false;
DriveFileIterator(s.drv, Saver::WriteFiles, (Bitu)&s);
s.failed = s.write_mods = false;
DriveFileIterator(s.over, Saver::WriteFiles, (Bitu)&s);

for (Union_Modification* m : impl->modifications)
m->Serialize(s.mods);
if (s.mods.size())
Saver::WriteFiles("FILEMODS.DBP", false, (Bit32u)s.mods.size(), 0, 0, 0, (Bitu)&s);
if (impl->modifications.Len())
{
s.write_mods = true;
s.buf.clear();
for (Union_Modification* m : impl->modifications)
m->Serialize(s.buf);
if (s.buf.size())
Saver::WriteFiles("FILEMODS.DBP", false, (Bit32u)s.buf.size(), 0, 0, 0, (Bitu)&s);
}

if (s.file_count)
s.failed |= !fwrite(&s.central_dir[0], s.central_dir.size(), 1, s.f);
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1 change: 1 addition & 0 deletions src/dos/drives.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -547,6 +547,7 @@ DOS_File *FindAndOpenDosFile(char const* filename, Bit32u *bsize, bool* writable
bool ReadAndClose(DOS_File *df, std::string& out, Bit32u maxsize)
{
if (!df) return false;
if (!df->refCtr) df->AddRef();
Bit32u curlen = (Bit32u)out.size(), filesize = 0, seekzero = 0;
df->Seek(&filesize, DOS_SEEK_END);
df->Seek(&seekzero, DOS_SEEK_SET);
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