ddidderr/zstd-rs
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

feat(decompress): move platform BMI2 init to Rust

Browse Source 
The decoder context remains allocated and laid out by C because optional members
change with the active build configuration. Previously, the C adapter also
owned the platform leaf: its DYNAMIC_BMI2 branch queried CPU features and
assigned the private bmi2 member directly. That kept the policy in C and made
the Rust boundary depend on the context layout.

Move the leaf to Rust and give it an opaque scalar address plus the active
configuration value. The C adapter now only extracts the optional address when
that member exists and forwards it, while DYNAMIC_BMI2=0 passes NULL. Rust
performs the dynamic decision, queries CPU support, and writes the scalar. The
existing 68-word DCtx view is unchanged. Focused unit coverage verifies that
disabled dynamic dispatch leaves the scalar untouched and enabled dispatch
publishes the CPU feature result.

Test Plan:
- `cc -fsyntax-only -Werror -DDYNAMIC_BMI2=0 -Ilib -Ilib/common -Ilib/compress -Ilib/decompress -Ilib/dict -Ilib/legacy lib/decompress/zstd_decompress.c` -- passed
- `cc -fsyntax-only -Werror -DDYNAMIC_BMI2=1 -Ilib -Ilib/common -Ilib/compress -Ilib/decompress -Ilib/dict -Ilib/legacy lib/decompress/zstd_decompress.c` -- passed
- `rustfmt --edition 2021 --check rust/src/zstd_decompress.rs` -- passed
- `git diff --check -- lib/decompress/zstd_decompress.c rust/src/zstd_decompress.rs` -- passed
This commit is contained in:
ddidderr
2026-07-20 14:59:22 +02:00
parent 40137b28bf
commit c2bed1242c
2 changed files with 38 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/decompress/zstd_decompress.c
+5 -3
View File
@@ -133,7 +133,8 @@ void ZSTD_rust_dctx_view(ZSTD_DCtx* dctx, ZSTD_rustDctxView* out);
void ZSTD_rust_dctx_trace_view(ZSTD_DCtx* dctx,
ZSTD_rustDctxTraceView* out);
size_t ZSTD_rust_dctx_sizeof(void);
void ZSTD_rust_dctx_init_platform(ZSTD_DCtx* dctx);
void ZSTD_dctx_init_platform(ZSTD_DCtx* dctx);
void ZSTD_rust_dctx_init_platform(void* bmi2, int dynamic_bmi2);
size_t ZSTD_rust_dctx_default_max_window_size(void);
int ZSTD_rust_no_forward_progress_max(void);
int ZSTD_rust_heapmode(void);
@@ -245,12 +246,13 @@ size_t ZSTD_rust_dctx_sizeof(void)
return sizeof(ZSTD_DCtx);
}
void ZSTD_rust_dctx_init_platform(ZSTD_DCtx* dctx)
void ZSTD_dctx_init_platform(ZSTD_DCtx* dctx)
{
#if DYNAMIC_BMI2
dctx->bmi2 = ZSTD_cpuSupportsBmi2();
ZSTD_rust_dctx_init_platform(&dctx->bmi2, DYNAMIC_BMI2);
#else
(void)dctx;
ZSTD_rust_dctx_init_platform(NULL, DYNAMIC_BMI2);
#endif
}