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build: support decoding legacy zstd formats v0.4-v0.7 #73

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Merged
dfa1 merged 1 commit into from
Jul 17, 2026
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build: support decoding legacy zstd formats v0.4-v0.7 #73

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17 changes: 14 additions & 3 deletions scripts/build-zstd.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -59,7 +59,10 @@ CROSS=""
echo "[build-zstd] Building zstd $CLASSIFIER$CROSS with zig cc (jobs=$JOBS)..."

# Library sources: core (common/compress/decompress) plus the dictionary
# builder (ZDICT_* API). legacy/ and deprecated/ are intentionally excluded.
# builder (ZDICT_* API), plus the legacy decoders for format versions 0.4-0.7
# (matching ZSTD_LEGACY_SUPPORT=4 below — see the CFLAGS comment).
# deprecated/ (the old ZBUFF_* streaming wrapper, superseded by ZSTD_CCtx
# streaming) stays excluded — unrelated to legacy *decoding*.
# huf_decompress_amd64.S is hand-written BMI2 Huffman-decode asm; its body is
# entirely wrapped in `#if ZSTD_ENABLE_ASM_X86_64_BMI2` (gated on __x86_64__),
# so it compiles to a no-op object on every non-x86_64 target and only kicks
Expand All @@ -68,7 +71,11 @@ echo "[build-zstd] Building zstd $CLASSIFIER$CROSS with zig cc (jobs=$JOBS)..."
SRCS=$(find "$ZSTD_LIB/common" "$ZSTD_LIB/compress" "$ZSTD_LIB/decompress" \
"$ZSTD_LIB/dictBuilder" -name '*.c' | sort)
SRCS="$SRCS
$ZSTD_LIB/decompress/huf_decompress_amd64.S"
$ZSTD_LIB/decompress/huf_decompress_amd64.S
$ZSTD_LIB/legacy/zstd_v04.c
$ZSTD_LIB/legacy/zstd_v05.c
$ZSTD_LIB/legacy/zstd_v06.c
$ZSTD_LIB/legacy/zstd_v07.c"

WORK="$(mktemp -d)"
trap 'rm -rf "$WORK"' EXIT
Expand Down Expand Up @@ -103,7 +110,11 @@ case "$CLASSIFIER" in
*-aarch64) ARCH_FLAG="-mcpu=generic+crc" ;;
esac

CFLAGS="-O3 $ARCH_FLAG -DNDEBUG -DXXH_NAMESPACE=ZSTD_ $VIS_FLAG \
# Decode (not encode) formats back to zstd v0.4, matching what zstd-jni
# ships by default. v0.1-v0.3 stay off (ZSTD_LEGACY_SUPPORT>=4 skips their
# zstd_v0{1,2,3}.c decoders per legacy/zstd_legacy.h) — those predate zstd's
# 1.0 stabilization and are vanishingly unlikely to show up in the wild.
CFLAGS="-O3 $ARCH_FLAG -DNDEBUG -DZSTD_LEGACY_SUPPORT=4 -DXXH_NAMESPACE=ZSTD_ $VIS_FLAG \
-I$ZSTD_LIB -I$ZSTD_LIB/common -fPIC"

i=0
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