feat(compress): move parameter update policy to Rust

Move ZSTD_isUpdateAuthorized behind the existing Rust parameter API while retaining the C context-stage checks, diagnostics, and mutation flow.

Test Plan:

- cargo test --manifest-path rust/Cargo.toml --no-default-features --features compression (187 tests)

- cargo clippy for library, benches, and tests

- make -B -C lib -j2 lib

lib/compress/zstd_compress.c

@@ -106,6 +106,7 @@ int ZSTD_rust_cctx_params_is_multithreaded(void);
 int ZSTD_rust_cctx_params_nb_workers_max(void);
 int ZSTD_rust_cctx_params_job_size_min(void);
 int ZSTD_rust_cctx_params_job_size_max(void);
+int ZSTD_rust_isUpdateAuthorized(int param);
 ZSTD_CCtx_params* ZSTD_rust_createCCtxParams(ZSTD_customMem customMem);
 size_t ZSTD_rust_freeCCtxParams(ZSTD_CCtx_params* params);
 size_t ZSTD_rust_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams,
@@ -684,52 +685,7 @@ int ZSTD_rust_cctx_params_job_size_max(void)
 
 static int ZSTD_isUpdateAuthorized(ZSTD_cParameter param)
 {
-    switch(param)
-    {
-    case ZSTD_c_compressionLevel:
-    case ZSTD_c_hashLog:
-    case ZSTD_c_chainLog:
-    case ZSTD_c_searchLog:
-    case ZSTD_c_minMatch:
-    case ZSTD_c_targetLength:
-    case ZSTD_c_strategy:
-    case ZSTD_c_blockSplitterLevel:
-        return 1;
-
-    case ZSTD_c_format:
-    case ZSTD_c_windowLog:
-    case ZSTD_c_contentSizeFlag:
-    case ZSTD_c_checksumFlag:
-    case ZSTD_c_dictIDFlag:
-    case ZSTD_c_forceMaxWindow :
-    case ZSTD_c_nbWorkers:
-    case ZSTD_c_jobSize:
-    case ZSTD_c_overlapLog:
-    case ZSTD_c_rsyncable:
-    case ZSTD_c_enableDedicatedDictSearch:
-    case ZSTD_c_enableLongDistanceMatching:
-    case ZSTD_c_ldmHashLog:
-    case ZSTD_c_ldmMinMatch:
-    case ZSTD_c_ldmBucketSizeLog:
-    case ZSTD_c_ldmHashRateLog:
-    case ZSTD_c_forceAttachDict:
-    case ZSTD_c_literalCompressionMode:
-    case ZSTD_c_targetCBlockSize:
-    case ZSTD_c_srcSizeHint:
-    case ZSTD_c_stableInBuffer:
-    case ZSTD_c_stableOutBuffer:
-    case ZSTD_c_blockDelimiters:
-    case ZSTD_c_validateSequences:
-    case ZSTD_c_splitAfterSequences:
-    case ZSTD_c_useRowMatchFinder:
-    case ZSTD_c_deterministicRefPrefix:
-    case ZSTD_c_prefetchCDictTables:
-    case ZSTD_c_enableSeqProducerFallback:
-    case ZSTD_c_maxBlockSize:
-    case ZSTD_c_repcodeResolution:
-    default:
-        return 0;
-    }
+    return ZSTD_rust_isUpdateAuthorized((int)param);
 }
 
 size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value)

rust/src/zstd_compress_params_api.rs

@@ -176,6 +176,26 @@ const C_MAX_BLOCK_SIZE: c_int = 1015;
 const C_REPCODE_RESOLUTION: c_int = 1016;
 const C_BLOCK_SPLITTER_LEVEL: c_int = 1017;
 
+#[inline]
+fn is_update_authorized(param: c_int) -> bool {
+    matches!(
+        param,
+        C_COMPRESSION_LEVEL
+            | C_HASH_LOG
+            | C_CHAIN_LOG
+            | C_SEARCH_LOG
+            | C_MIN_MATCH
+            | C_TARGET_LENGTH
+            | C_STRATEGY
+            | C_BLOCK_SPLITTER_LEVEL
+    )
+}
+
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_isUpdateAuthorized(param: c_int) -> c_int {
+    is_update_authorized(param) as c_int
+}
+
 #[cfg(not(test))]
 unsafe extern "C" {
     fn ZSTD_rust_cctx_params_is_multithreaded() -> c_int;
@@ -974,6 +994,64 @@ mod tests {
     use std::mem::{align_of, offset_of, size_of, MaybeUninit};
     use std::sync::atomic::{AtomicUsize, Ordering};
 
+    #[test]
+    fn update_authorization_matches_the_c_parameter_policy() {
+        let authorized = [
+            C_COMPRESSION_LEVEL,
+            C_HASH_LOG,
+            C_CHAIN_LOG,
+            C_SEARCH_LOG,
+            C_MIN_MATCH,
+            C_TARGET_LENGTH,
+            C_STRATEGY,
+            C_BLOCK_SPLITTER_LEVEL,
+        ];
+        let unauthorized = [
+            C_FORMAT,
+            C_WINDOW_LOG,
+            C_CONTENT_SIZE_FLAG,
+            C_CHECKSUM_FLAG,
+            C_DICT_ID_FLAG,
+            C_FORCE_MAX_WINDOW,
+            C_NB_WORKERS,
+            C_JOB_SIZE,
+            C_OVERLAP_LOG,
+            C_RSYNCABLE,
+            C_ENABLE_DEDICATED_DICT_SEARCH,
+            C_ENABLE_LDM,
+            C_LDM_HASH_LOG,
+            C_LDM_MIN_MATCH,
+            C_LDM_BUCKET_SIZE_LOG,
+            C_LDM_HASH_RATE_LOG,
+            C_FORCE_ATTACH_DICT,
+            C_LITERAL_COMPRESSION_MODE,
+            C_TARGET_C_BLOCK_SIZE,
+            C_SRC_SIZE_HINT,
+            C_STABLE_IN_BUFFER,
+            C_STABLE_OUT_BUFFER,
+            C_BLOCK_DELIMITERS,
+            C_VALIDATE_SEQUENCES,
+            C_SPLIT_AFTER_SEQUENCES,
+            C_USE_ROW_MATCH_FINDER,
+            C_DETERMINISTIC_REF_PREFIX,
+            C_PREFETCH_CDICT_TABLES,
+            C_ENABLE_SEQ_PRODUCER_FALLBACK,
+            C_MAX_BLOCK_SIZE,
+            C_REPCODE_RESOLUTION,
+            -1,
+            1018,
+        ];
+
+        for param in authorized {
+            assert!(is_update_authorized(param));
+            assert_eq!(ZSTD_rust_isUpdateAuthorized(param), 1);
+        }
+        for param in unauthorized {
+            assert!(!is_update_authorized(param));
+            assert_eq!(ZSTD_rust_isUpdateAuthorized(param), 0);
+        }
+    }
+
     #[test]
     fn private_parameter_mirror_matches_the_c_layout() {
         let pointer_size = size_of::<usize>();