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Work around ProDOS sparse block issue

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It appears that some programs, notably Copy ][+ and the GS/OS FST,
expect that the first block of a sparse file will always be
allocated, even if it's just 512 zeroes.  I've only seen this fail
in cases where the first entry in the master index block of a "tree"
file is zero, because the first 128KB are sparse, but rumor has it
that the issue can affect "sapling" files as well.

This changes CiderPress to work the way ProDOS does: always allocate
a block to hold the first 512 bytes of the file.  The only exception
to this is a file that is nothing but zeroes (perhaps populated by
creating a file and setting its EOF to something large), which can
be stored as a seedling.

(for issues #15 and #49)
This commit is contained in:
Andy McFadden 2021-07-23 18:52:23 -07:00
parent e098069b10
commit d39c61255c
1 changed files with 74 additions and 23 deletions
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97
diskimg/ProDOS.cpp
View File

@ -1133,8 +1133,9 @@ DIError DiskFSProDOS::ScanFileUsage(void)
&sparseCount);
pFile->fSparseDataEof =
(di_off_t) pFile->fExtData.eof - sparseCount * kBlkSize;
//LOGI(" SparseCount %d dataEof %d '%s'",
// sparseCount, pFile->fSparseDataEof, pFile->fDirEntry.fileName);
//LOGI(" SparseCount %ld dataEof %ld -> %lld '%s'",
// sparseCount, pFile->fExtData.eof, pFile->fSparseDataEof,
// pFile->fDirEntry.fileName);
delete[] blockList;
blockList = NULL;
delete[] indexList;
@ -1168,9 +1169,9 @@ DIError DiskFSProDOS::ScanFileUsage(void)
&sparseCount);
pFile->fSparseDataEof =
(di_off_t) pFile->fDirEntry.eof - sparseCount * kBlkSize;
//LOGI(" +++ sparseCount=%ld blockCount=%ld sparseDataEof=%ld '%s'",
// sparseCount, blockCount, (long) pFile->fSparseDataEof,
// pFile->fDirEntry.fileName);
//LOGI(" +++ sparseCount=%ld blockCount=%ld sparseDataEof=%lld '%s'",
// sparseCount, blockCount, pFile->fSparseDataEof,
// pFile->fDirEntry.fileName);
delete[] blockList;
blockList = NULL;
@ -4572,13 +4573,34 @@ DIError A2FDProDOS::Write(const void* buf, size_t len, size_t* pActual)
keyBlock = pFile->fExtData.keyBlock;
}
/*
* See if the file is completely empty. This lets us do an optimization
* where we store it as a seedling. (GS/OS seems to do this, ProDOS 8
* v2.0.3 tends to allocate the first block.)
*/
bool allZero = true;
const uint8_t* scanPtr = (const uint8_t*)buf;
for (unsigned int i = 0; i < len; ++i, ++scanPtr) {
if (*scanPtr != 0x00) {
allZero = false;
break;
}
}
if (allZero) {
LOGI("+++ found file filled with %zd zeroes", len);
}
/*
* Special-case seedling files. Just write the data into the key block
* and we're done.
*/
if (len <= (size_t)kBlkSize) {
if (allZero || len <= (size_t)kBlkSize) {
memset(blkBuf, 0, sizeof(blkBuf));
memcpy(blkBuf, buf, len);
if (!allZero) {
memcpy(blkBuf, buf, len);
} else {
LOGI("+++ ProDOS storing large but empty file as seedling");
}
dierr = pDiskFS->GetDiskImg()->WriteBlock(keyBlock, blkBuf);
if (dierr != kDIErrNone)
goto bail;
@ -4613,11 +4635,9 @@ DIError A2FDProDOS::Write(const void* buf, size_t len, size_t* pActual)
*/
const uint8_t* blkPtr;
long blockIdx;
bool allZero;
long progressCounter;
progressCounter = 0;
allZero = true;
blkPtr = (const uint8_t*) buf;
for (blockIdx = 0; blockIdx < fBlockCount; blockIdx++) {
long newBlock;
@ -4631,12 +4651,24 @@ DIError A2FDProDOS::Write(const void* buf, size_t len, size_t* pActual)
blkPtr = blkBuf;
}
if (allocSparse && IsEmptyBlock(blkPtr))
newBlock = 0;
else {
if (allocSparse && IsEmptyBlock(blkPtr)) {
if (blockIdx == 0) {
// Fix for issues #18 and #49. GS/OS appears to get confused
// if the first entry in the master index block for a "tree"
// file is zero. We can avoid the problem by always allocating
// the first data block, which causes allocation of the first
// index block. (The "all zeroes" case was handled earlier,
// so if we got here we know this won't be an empty seedling.)
LOGI("+++ allocating storage for empty first block");
newBlock = pDiskFS->AllocBlock();
fOpenBlocksUsed++;
} else {
// Sparse.
newBlock = 0;
}
} else {
newBlock = pDiskFS->AllocBlock();
fOpenBlocksUsed++;
allZero = false;
}
if (newBlock < 0) {
@ -4692,7 +4724,9 @@ DIError A2FDProDOS::Write(const void* buf, size_t len, size_t* pActual)
/*
* Now we have a full block map. Allocate any needed index blocks and
* write them.
*
*/
#if 0 // now done earlier
/*
* If our block map is empty, i.e. the entire file is sparse, then
* there's no need to create a sapling. We just leave the file in
* seedling form. This can only happen for a completely empty file.
@ -4706,7 +4740,9 @@ DIError A2FDProDOS::Write(const void* buf, size_t len, size_t* pActual)
goto bail;
fOpenStorageType = A2FileProDOS::kStorageSeedling;
fBlockList[0] = keyBlock;
} else if (fBlockCount <= 256) {
} else
#endif
if (fBlockCount <= 256) {
/* sapling file, write an index block into the key block */
//bool allzero = true; <-- should this be getting used?
assert(fBlockCount > 1);
@ -5013,12 +5049,27 @@ DIError A2FDProDOS::Close(void)
}
/*
* Find the #of sparse blocks.
* Find the #of sparse blocks. We do this to update the "sparse EOF",
* which determines the "compressed" size shown in the file list. We
* have two cases: normal file with sparse contents, and seedling file
* that is entirely sparse except for the first block.
*
* In the normal case, we walk through the list of data blocks,
* looking for gaps. In the seedling case, we just use the EOF.
*
* This is just for display. The value seen after adding a file should
* not change if you reload the disk image.
*/
int sparseCount = 0;
for (int i = 0; i < fBlockCount; i++) {
if (fBlockList[i] == 0)
sparseCount++;
int sparseBlocks = 0;
if (fBlockCount == 1 && fOpenEOF > kBlkSize) {
// 1023/1024 = 2 blocks = 1 sparse
// 1025 = 3 blocks = 2 sparse
sparseBlocks = (int)((fOpenEOF-1) / kBlkSize);
} else {
for (int i = 0; i < fBlockCount; i++) {
if (fBlockList[i] == 0)
sparseBlocks++;
}
}
/*
@ -5036,19 +5087,19 @@ DIError A2FDProDOS::Close(void)
pFile->fExtData.storageType = fOpenStorageType;
pFile->fExtData.blocksUsed = newBlocksUsed;
pFile->fExtData.eof = newEOF;
pFile->fSparseDataEof = (di_off_t) newEOF - (sparseCount * kBlkSize);
pFile->fSparseDataEof = (di_off_t) newEOF - (sparseBlocks * kBlkSize);
if (pFile->fSparseDataEof < 0)
pFile->fSparseDataEof = 0;
} else {
pFile->fExtRsrc.storageType = fOpenStorageType;
pFile->fExtRsrc.blocksUsed = newBlocksUsed;
pFile->fExtRsrc.eof = newEOF;
pFile->fSparseRsrcEof = (di_off_t) newEOF - (sparseCount * kBlkSize);
pFile->fSparseRsrcEof = (di_off_t) newEOF - (sparseBlocks * kBlkSize);
if (pFile->fSparseRsrcEof < 0)
pFile->fSparseRsrcEof = 0;
}
} else {
pFile->fSparseDataEof = (di_off_t) newEOF - (sparseCount * kBlkSize);
pFile->fSparseDataEof = (di_off_t) newEOF - (sparseBlocks * kBlkSize);
if (pFile->fSparseDataEof < 0)
pFile->fSparseDataEof = 0;
}