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feat(checksum): --checksum-choice/--cc and --checksum-seed for whole-file digest

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Adds real algorithm selection (xxh64 default, plus md5 via OpenSSL EVP) and a
64-bit seed for the per-file whole-file digest used by the --incremental/
--checksum handshake and basis-dir content verification. The seed also feeds
the delta path's per-block xxHash32 strong checksum (low 32 bits) so an
explicit seed deterministically changes those digests too. Sender and receiver
hash identically: the algorithm id and seed cross the config wire frame and the
STATUS_CHECK handshake now carries a length-prefixed, bounded digest instead of
a fixed 64-bit value. Unsupported algorithm names are rejected at parse time
(never a silent no-op). PROTOCOL_VERSION bumped 2.9.0 -> 2.10.0; defaults
(xxh64, seed 0) preserve prior byte-for-byte behavior.
This commit is contained in:
TapTap
2026-09-07 17:42:47 +02:00
parent 6701c103cb
commit 0afda6b094
12 changed files with 316 additions and 43 deletions
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src/client/usage.c
+6 -2
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@@ -91,8 +91,12 @@ void print_usage(void) {
printf(" into the destination instead of transferring its data\n");
printf(" --link-dest <dir> Like --copy-dest, but hard-links the unchanged file from DIR\n");
printf(" into the destination (repeatable; earlier DIRs win)\n");
printf(" --checksum-choice, --cc <alg> Checksum algorithm (not supported yet; xxHash64 is "
"used)\n");
printf(" --checksum-choice, --cc <alg> Whole-file checksum algorithm for --incremental/\n");
printf(" --checksum compares (xxh64/xxhash or md5; default xxh64 with\n");
printf(" seed 0). The seed comes from --checksum-seed\n");
printf(" --checksum-seed <num> Seed for the whole-file xxHash64 digest (and the delta\n");
printf(" block strong hash, low 32 bits); md5 ignores the seed. The\n");
printf(" digest algorithm and seed must match on sender and receiver\n");
printf(" --delta Delta transfer for changed files (requires --incremental)\n");
printf(" -W, --whole-file Transfer changed files without delta processing\n");
printf(" -y, --fuzzy Use a similar-named file already in the destination\n");