Add an accumulating SHA256 API (SHA256State, UpdateSHA256, UpdateSHA256File) - #6509
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fingolfin wants to merge 2 commits into
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Add an accumulating SHA256 API (SHA256State, UpdateSHA256, UpdateSHA256File)#6509fingolfin wants to merge 2 commits into
SHA256State, UpdateSHA256, UpdateSHA256File)#6509fingolfin wants to merge 2 commits into
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GAP can hash a string, a stream, or a file, but not a concatenation of those without building it in memory first. Git object hashes are exactly that shape -- a header followed by a file's contents -- and packages computing them have to fall back on the IO package, on piping through sha256sum, or on reading the whole file into a string. s := SHA256State(); UpdateSHA256( s, "blob 15\000" ); UpdateSHA256File( s, name, false ); HexSHA256( s ); The kernel already had the accumulator; it was undocumented, could not consume a file, and its FINAL pads the state in place, so reading a digest twice silently gave a wrong answer. GAP_SHA256_DIGEST finalizes a copy instead, which makes reading a digest an ordinary operation rather than one the caller must know is destructive. HexSHA256 gains a state as its third case; HexSHA256File is unchanged. Also: - give the state a category and a print method, so it can be tested for and does not display as <object>; - fix the state bag being allocated 4 bytes short of what it addresses, masked until now by GASMAN rounding bag sizes up; - take the state by value when building the result list, since allocating it may move bags. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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SHA256State, UpdateSHA256, UpdateSHA256File)
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## master #6509 +/- ##
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- Coverage 78.87% 78.66% -0.21%
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Files 685 685
Lines 294150 294164 +14
Branches 8646 8669 +23
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- Misses 60348 60941 +593
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fingolfin
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Aug 14, 2026
fingolfin
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Aug 14, 2026
fingolfin
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Aug 14, 2026
fingolfin
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Aug 14, 2026
Addresses review: the kernel one-shot GAP_SHA256_FILE is gone, and HexSHA256File is three lines of GAP over SHA256State, UpdateSHA256File and HexSHA256. Its argument checking goes too, since UpdateSHA256File already raises the same errors. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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GAP can hash a string, a stream, or a file, but not a concatenation of those without building it in memory first. Git object hashes are exactly that shape:
"blob <size>\0"followed by a file's contentsThis PR adds functionality to allow handling that within GAP:
Two drive-by fixes:
sizeof(UInt4) + sizeof(sha256_state_t)but addressed fromADDR_OBJ(result)[1], i.e. 4 bytes short. Masked by GASMAN rounding bag sizes up to whole words.UInt4is always an immediate integer, which is why this has never bitten.Written with Claude Opus 5 via Claude Code; reviewed by me. The commit lists
the tool as co-author.