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Cyan4973
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Apr 30, 2021
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| while (startOffset < endOffset) { | ||
| size_t const result = ZSTD_seekable_decompress(seekable, buffOut, MIN(endOffset - startOffset, buffOutSize), startOffset); | ||
| if (!result) { |
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Nice optimization.
Is there more to it ? (does it dodge an error case ?)
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Is there more to it ?
Added the same for seekable_decompression_mem.c
(does it dodge an error case ?)
In theory before fixing frame overrun and not using checksums it is possible to go to endless loop
Cyan4973
reviewed
Apr 30, 2021
It tries to check the buffer boundary, but there is no buffer for from-file reading.
This will allow to read the whole file w/o gotting corruption error if
the offset is more then the data left in file, i.e.:
$ ./seekable_compression seekable_compression.c 8192 | head
$ zstd -cdq seekable_compression.c.zst | wc -c
4737
Before this patch:
$ ./seekable_decompression seekable_compression.c.zst 0 10000000 | wc -c
ZSTD_seekable_decompress() error : Corrupted block detected
0
After:
$ ./seekable_decompression seekable_compression.c.zst 0 10000000 | wc -c
4737
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Changelog:
seekable_format: cap the offset+len up to the last dOffset
This will allow to read the whole file w/o gotting corruption error if
the offset is more then the data left in file, i.e.:
Before this patch:
After:
seekable_decompression: break when ZSTD_seekable_decompress() returns zero
seekable_decompression_mem: break when ZSTD_seekable_decompress() returns zero
seekable_format: fix from-file reading (not in-memory)