refactor(compress): expose stream size and level leaves from Rust

Move the public stream-size and predefined compression-level leaves to their
caller-facing Rust symbols, removing the remaining C-only forwarding bodies.
Keep crate-local aliases where Rust implementation modules still use the old
internal names, while the public C ABI now lands directly in Rust.

Test Plan: Nightly Rust formatting and staged diff checks passed; capped native and upstream gates pending.

rust/src/zstd_compress_api.rs

@@ -45,13 +45,13 @@ pub extern "C" fn ZSTD_compressBound(src_size: usize) -> usize {
 
 /// Returns the recommended input buffer size for the public streaming API.
 #[no_mangle]
-pub extern "C" fn ZSTD_rust_CStreamInSize() -> usize {
+pub extern "C" fn ZSTD_CStreamInSize() -> usize {
     ZSTD_BLOCKSIZE_MAX
 }
 
 /// Returns the recommended output buffer size for the public streaming API.
 #[no_mangle]
-pub extern "C" fn ZSTD_rust_CStreamOutSize() -> usize {
+pub extern "C" fn ZSTD_CStreamOutSize() -> usize {
     ZSTD_compressBound(ZSTD_BLOCKSIZE_MAX) + ZSTD_BLOCK_HEADER_SIZE + 4
 }
 
@@ -105,12 +105,12 @@ mod tests {
 
     #[test]
     fn cstream_sizes_match_the_public_formulas() {
-        assert_eq!(ZSTD_rust_CStreamInSize(), 128 * 1024);
+        assert_eq!(ZSTD_CStreamInSize(), 128 * 1024);
         assert_eq!(
-            ZSTD_rust_CStreamOutSize(),
+            ZSTD_CStreamOutSize(),
             ZSTD_compressBound(ZSTD_BLOCKSIZE_MAX) + ZSTD_BLOCK_HEADER_SIZE + 4
         );
-        assert_eq!(ZSTD_rust_CStreamOutSize(), 131_591);
+        assert_eq!(ZSTD_CStreamOutSize(), 131_591);
     }
 
     #[test]

rust/src/zstd_compress_params.rs

@@ -344,7 +344,7 @@ fn cparams_from_row(row: [u32; 7]) -> ZSTD_compressionParameters {
 #[inline]
 fn bounds(param: c_int) -> ZSTD_bounds {
     let (lowerBound, upperBound) = match param {
-        ZSTD_C_COMPRESSION_LEVEL => (ZSTD_rust_params_minCLevel(), ZSTD_rust_params_maxCLevel()),
+        ZSTD_C_COMPRESSION_LEVEL => (ZSTD_minCLevel(), ZSTD_maxCLevel()),
         ZSTD_C_WINDOW_LOG => (ZSTD_WINDOWLOG_MIN, ZSTD_WINDOWLOG_MAX),
         ZSTD_C_HASH_LOG => (ZSTD_HASHLOG_MIN, ZSTD_HASHLOG_MAX),
         ZSTD_C_CHAIN_LOG => (ZSTD_CHAINLOG_MIN, ZSTD_CHAINLOG_MAX),
@@ -937,7 +937,7 @@ fn select_cparams(
 
     let mut cparams = cparams_from_row(DEFAULT_CPARAMS[table_id][row]);
     if compression_level < 0 {
-        let clamped = compression_level.max(ZSTD_rust_params_minCLevel());
+        let clamped = compression_level.max(ZSTD_minCLevel());
         cparams.targetLength = (-clamped) as u32;
     }
     cparams
@@ -1119,22 +1119,26 @@ fn assert_equal_cparams(
 
 /// Returns the highest table-backed compression level (`ZSTD_MAX_CLEVEL`).
 #[no_mangle]
-pub extern "C" fn ZSTD_rust_params_maxCLevel() -> c_int {
+pub extern "C" fn ZSTD_maxCLevel() -> c_int {
     ZSTD_MAX_CLEVEL
 }
 
 /// Returns the lowest public fast level (`-ZSTD_TARGETLENGTH_MAX`).
 #[no_mangle]
-pub extern "C" fn ZSTD_rust_params_minCLevel() -> c_int {
+pub extern "C" fn ZSTD_minCLevel() -> c_int {
     -ZSTD_TARGETLENGTH_MAX
 }
 
 /// Returns the default compression level from `zstd.h`.
 #[no_mangle]
-pub extern "C" fn ZSTD_rust_params_defaultCLevel() -> c_int {
+pub extern "C" fn ZSTD_defaultCLevel() -> c_int {
     ZSTD_CLEVEL_DEFAULT
 }
 
+/* Keep existing Rust parameter-module callers source-compatible while the
+ * public C symbols are owned directly by these Rust leaves. */
+pub(crate) use ZSTD_defaultCLevel as ZSTD_rust_params_defaultCLevel;
+
 /// Returns bounds for the seven core compression parameters and compression
 /// level.  Other `ZSTD_cParameter` cases remain C-owned.
 #[no_mangle]