feat(compress): move ordinary block emission into Rust

Move the post-sequence-store body of ZSTD_compressBlock_internal behind a
small C/Rust state projection. C continues to build the sequence store and
handle the no-compress and sequence-producer error paths, while Rust now owns
sequence collection, entropy emission, the legacy non-first-frame RLE gate,
compressed-block confirmation, and offcode repeat cleanup. Remove the C
wrappers that became dead after those leaves moved behind the Rust body.

The first integration run exposed that leaving the old C finalization label in
place confirmed compressed block state twice, undoing Rust's pointer swap and
breaking a later sparse-file checksum. The C wrapper now returns directly for
the Rust-owned path and retains only its C-owned no-compress cleanup.

Test Plan:
- cargo test --manifest-path rust/Cargo.toml --lib -- --test-threads=1
- cargo check --manifest-path rust/Cargo.toml --lib
- cargo clippy --manifest-path rust/Cargo.toml --lib -- -D warnings
- cargo clippy --manifest-path rust/Cargo.toml -- -D warnings
- cargo +nightly fmt --manifest-path rust/Cargo.toml -- --check
- make -B -C lib -j2 lib
- make -B -C tests -j2 test-zstd
- make -B -C tests -j2 test-cli-tests
- ZSTREAM_TESTTIME=-T2s make -B -C tests -j2 test-zstream
- FUZZERTEST=-T5s make -B -C tests -j2 test-fuzzer
- make -B -C tests/fuzz -j2 all
- make -B -C tests/fuzz -j2 sequence_compression_api
- cargo clippy --manifest-path rust/Cargo.toml --tests -- -D warnings (pre-existing manual_repeat_n failure)
- cargo clippy --manifest-path rust/Cargo.toml --benches -- -D warnings (pre-existing manual_repeat_n failure)

lib/compress/zstd_compress.c

@@ -83,7 +83,7 @@ int ZSTD_rust_dictTooBig(size_t loadedDictSize);
  * Matchfinder/window state, sequence-store construction, and outer repeat-mode
  * cleanup remain in C. */
 typedef struct {
-    SeqStore_t* seqStore;
+    const SeqStore_t* seqStore;
     ZSTD_compressedBlockState_t** prevCBlock;
     ZSTD_compressedBlockState_t** nextCBlock;
     void* tmpWorkspace;
@@ -165,6 +165,42 @@ typedef char ZSTD_rust_split_block_state_layout[
          && sizeof(ZSTD_rust_splitBlockState)
                 == 10 * sizeof(void*) + 4 * sizeof(int))
         ? 1 : -1];
+/* The ordinary sequence-block body only needs this projection of ZSTD_CCtx.
+ * Sequence-store construction and the no-compress fallback remain in C. */
+typedef struct {
+    const SeqStore_t* seqStore;
+    ZSTD_compressedBlockState_t** prevCBlock;
+    ZSTD_compressedBlockState_t** nextCBlock;
+    void* tmpWorkspace;
+    size_t tmpWkspSize;
+    SeqCollector* seqCollector;
+    int strategy;
+    int disableLiteralCompression;
+    int bmi2;
+    int isFirstBlock;
+} ZSTD_rust_blockInternalState;
+size_t ZSTD_rust_compressBlockInternal(
+        const ZSTD_rust_blockInternalState* state,
+        void* dst, size_t dstCapacity,
+        const void* src, size_t srcSize,
+        U32 frame);
+typedef char ZSTD_rust_block_internal_state_layout[
+        (offsetof(ZSTD_rust_blockInternalState, seqStore) == 0
+         && offsetof(ZSTD_rust_blockInternalState, prevCBlock) == sizeof(void*)
+         && offsetof(ZSTD_rust_blockInternalState, nextCBlock) == 2 * sizeof(void*)
+         && offsetof(ZSTD_rust_blockInternalState, tmpWorkspace) == 3 * sizeof(void*)
+         && offsetof(ZSTD_rust_blockInternalState, tmpWkspSize) == 4 * sizeof(void*)
+         && offsetof(ZSTD_rust_blockInternalState, seqCollector) == 5 * sizeof(void*)
+         && offsetof(ZSTD_rust_blockInternalState, strategy) == 6 * sizeof(void*)
+         && offsetof(ZSTD_rust_blockInternalState, disableLiteralCompression)
+                == 6 * sizeof(void*) + sizeof(int)
+         && offsetof(ZSTD_rust_blockInternalState, bmi2)
+                == 6 * sizeof(void*) + 2 * sizeof(int)
+         && offsetof(ZSTD_rust_blockInternalState, isFirstBlock)
+                == 6 * sizeof(void*) + 3 * sizeof(int)
+         && sizeof(ZSTD_rust_blockInternalState)
+                == 6 * sizeof(void*) + 4 * sizeof(int))
+        ? 1 : -1];
 size_t ZSTD_rust_nextInputSizeHint(int inBufferMode,
                                    size_t blockSizeMax,
                                    size_t stableInNotConsumed,
@@ -405,15 +441,6 @@ size_t ZSTD_rust_entropyCompressSeqStore_internal(
         int strategy, int disableLiteralCompression,
         void* entropyWorkspace, size_t entropyWkspSize,
         int bmi2);
-size_t ZSTD_rust_entropyCompressSeqStore(
-        const SeqStore_t* seqStorePtr,
-        const ZSTD_entropyCTables_t* prevEntropy,
-        ZSTD_entropyCTables_t* nextEntropy,
-        int strategy, int disableLiteralCompression,
-        void* dst, size_t dstCapacity,
-        size_t srcSize,
-        void* entropyWorkspace, size_t entropyWkspSize,
-        int bmi2);
 size_t ZSTD_rust_buildBlockEntropyStats(
         const SeqStore_t* seqStorePtr,
         const ZSTD_entropyCTables_t* prevEntropy,
@@ -421,9 +448,6 @@ size_t ZSTD_rust_buildBlockEntropyStats(
         int strategy, int disableLiteralCompression,
         ZSTD_entropyCTablesMetadata_t* entropyMetadata,
         void* workspace, size_t wkspSize);
-size_t ZSTD_rust_copyBlockSequences(
-        SeqCollector* seqCollector, const SeqStore_t* seqStore,
-        const U32 prevRepcodes[ZSTD_REP_NUM]);
 void ZSTD_rust_resetCompressedBlockState(ZSTD_compressedBlockState_t* bs);
 void ZSTD_rust_invalidateRepCodes(U32 rep[ZSTD_REP_NUM]);
 typedef char ZSTD_rust_invalidate_rep_count[(ZSTD_REP_NUM == 3) ? 1 : -1];
@@ -440,7 +464,6 @@ size_t ZSTD_rust_convertSequencesNoRepcodes(
         SeqDef* dstSeqs, const ZSTD_Sequence* inSeqs, size_t nbSequences);
 BlockSummary ZSTD_rust_get1BlockSummary(const ZSTD_Sequence* seqs,
                                         size_t nbSeqs);
-int ZSTD_rust_isRLE(const BYTE* src, size_t length);
 size_t ZSTD_rust_postProcessSequenceProducerResult(
         ZSTD_Sequence* outSeqs, size_t nbExternalSeqs,
         size_t outSeqsCapacity, size_t srcSize);
@@ -2309,27 +2332,6 @@ ZSTD_entropyCompressSeqStore_internal(
                 entropyWorkspace, entropyWkspSize, bmi2);
 }
 
-static size_t
-ZSTD_entropyCompressSeqStore(
-                    const SeqStore_t* seqStorePtr,
-                    const ZSTD_entropyCTables_t* prevEntropy,
-                          ZSTD_entropyCTables_t* nextEntropy,
-                    const ZSTD_CCtx_params* cctxParams,
-                          void* dst, size_t dstCapacity,
-                          size_t srcSize,
-                          void* entropyWorkspace, size_t entropyWkspSize,
-                          int bmi2)
-{
-    return ZSTD_rust_entropyCompressSeqStore(
-                seqStorePtr, prevEntropy, nextEntropy,
-                (int)cctxParams->cParams.strategy,
-                ZSTD_literalsCompressionIsDisabled(cctxParams),
-                dst, dstCapacity,
-                srcSize,
-                entropyWorkspace, entropyWkspSize,
-                bmi2);
-}
-
 /* ZSTD_selectBlockCompressor() :
  * Not static, but internal use only (used by long distance matcher)
  * assumption : strat is a valid strategy */
@@ -2642,12 +2644,6 @@ static size_t ZSTD_buildSeqStore(ZSTD_CCtx* zc, const void* src, size_t srcSize)
     return ZSTDbss_compress;
 }
 
-static size_t ZSTD_copyBlockSequences(SeqCollector* seqCollector, const SeqStore_t* seqStore, const U32 prevRepcodes[ZSTD_REP_NUM])
-{
-    /* The implementation lives in rust/src/zstd_compress_stats.rs. */
-    return ZSTD_rust_copyBlockSequences(seqCollector, seqStore, prevRepcodes);
-}
-
 /* ZSTD_sequenceBound() lives in rust/src/zstd_compress_api.rs. */
 
 size_t ZSTD_generateSequences(ZSTD_CCtx* zc, ZSTD_Sequence* outSeqs,
@@ -2687,11 +2683,6 @@ size_t ZSTD_generateSequences(ZSTD_CCtx* zc, ZSTD_Sequence* outSeqs,
 
 /* ZSTD_mergeBlockDelimiters() lives in rust/src/zstd_compress_api.rs. */
 
-/* Unrolled loop to read four size_ts of input at a time. Returns 1 if is RLE, 0 if not. */
-static int ZSTD_isRLE(const BYTE* src, size_t length) {
-    return ZSTD_rust_isRLE(src, length);
-}
-
 static void
 ZSTD_blockState_confirmRepcodesAndEntropyTables(ZSTD_blockState_t* const bs)
 {
@@ -2816,14 +2807,7 @@ ZSTD_compressBlock_internal(ZSTD_CCtx* zc,
                             void* dst, size_t dstCapacity,
                             const void* src, size_t srcSize, U32 frame)
 {
-    /* This is an estimated upper bound for the length of an rle block.
-     * This isn't the actual upper bound.
-     * Finding the real threshold needs further investigation.
-     */
-    const U32 rleMaxLength = 25;
-    size_t cSize;
-    const BYTE* ip = (const BYTE*)src;
-    BYTE* op = (BYTE*)dst;
+    ZSTD_rust_blockInternalState state;
     DEBUGLOG(5, "ZSTD_compressBlock_internal (dstCapacity=%u, dictLimit=%u, nextToUpdate=%u)",
                 (unsigned)dstCapacity, (unsigned)zc->blockState.matchState.window.dictLimit,
                 (unsigned)zc->blockState.matchState.nextToUpdate);
@@ -2832,51 +2816,24 @@ ZSTD_compressBlock_internal(ZSTD_CCtx* zc,
         FORWARD_IF_ERROR(bss, "ZSTD_buildSeqStore failed");
         if (bss == ZSTDbss_noCompress) {
             RETURN_ERROR_IF(zc->seqCollector.collectSequences, sequenceProducer_failed, "Uncompressible block");
-            cSize = 0;
-            goto out;
+            if (zc->blockState.prevCBlock->entropy.fse.offcode_repeatMode == FSE_repeat_valid)
+                zc->blockState.prevCBlock->entropy.fse.offcode_repeatMode = FSE_repeat_check;
+            return 0;
         }
     }
 
-    if (zc->seqCollector.collectSequences) {
-        FORWARD_IF_ERROR(ZSTD_copyBlockSequences(&zc->seqCollector, ZSTD_getSeqStore(zc), zc->blockState.prevCBlock->rep), "copyBlockSequences failed");
-        ZSTD_blockState_confirmRepcodesAndEntropyTables(&zc->blockState);
-        return 0;
-    }
-
-    /* encode sequences and literals */
-    cSize = ZSTD_entropyCompressSeqStore(&zc->seqStore,
-            &zc->blockState.prevCBlock->entropy, &zc->blockState.nextCBlock->entropy,
-            &zc->appliedParams,
-            dst, dstCapacity,
-            srcSize,
-            zc->tmpWorkspace, zc->tmpWkspSize /* statically allocated in resetCCtx */,
-            zc->bmi2);
-
-    if (frame &&
-        /* We don't want to emit our first block as a RLE even if it qualifies because
-         * doing so will cause the decoder (cli only) to throw a "should consume all input error."
-         * This is only an issue for zstd <= v1.4.3
-         */
-        !zc->isFirstBlock &&
-        cSize < rleMaxLength &&
-        ZSTD_isRLE(ip, srcSize))
-    {
-        cSize = 1;
-        op[0] = ip[0];
-    }
-
-out:
-    if (!ZSTD_isError(cSize) && cSize > 1) {
-        ZSTD_blockState_confirmRepcodesAndEntropyTables(&zc->blockState);
-    }
-    /* We check that dictionaries have offset codes available for the first
-     * block. After the first block, the offcode table might not have large
-     * enough codes to represent the offsets in the data.
-     */
-    if (zc->blockState.prevCBlock->entropy.fse.offcode_repeatMode == FSE_repeat_valid)
-        zc->blockState.prevCBlock->entropy.fse.offcode_repeatMode = FSE_repeat_check;
-
-    return cSize;
+    state.seqStore = &zc->seqStore;
+    state.prevCBlock = &zc->blockState.prevCBlock;
+    state.nextCBlock = &zc->blockState.nextCBlock;
+    state.tmpWorkspace = zc->tmpWorkspace;
+    state.tmpWkspSize = zc->tmpWkspSize;
+    state.seqCollector = &zc->seqCollector;
+    state.strategy = (int)zc->appliedParams.cParams.strategy;
+    state.disableLiteralCompression = ZSTD_literalsCompressionIsDisabled(&zc->appliedParams);
+    state.bmi2 = zc->bmi2;
+    state.isFirstBlock = zc->isFirstBlock;
+    return ZSTD_rust_compressBlockInternal(
+            &state, dst, dstCapacity, src, srcSize, frame);
 }
 
 static size_t ZSTD_compressBlock_targetCBlockSize(ZSTD_CCtx* zc,

rust/README.md

@@ -41,7 +41,10 @@ zstd ABI:
   - `zstd_compress_block_split` searches for profitable sequence-store
     partitions, while `zstd_compress` emits those partitions through the
     Rust single-block serializer. C retains split discovery's context setup
-    and the outer block-dispatch decision.
+    and the outer block-dispatch decision. `zstd_compress` also owns ordinary
+    sequence-block entropy emission, sequence collection, and the legacy RLE
+    compatibility gate after C builds the sequence store; C retains the
+    sequence-store builder and no-compress fallback.
   - `zstd_compress_frame` serializes frame headers, skippable frames, and the
     last empty block; it takes scalar frame parameters so the C-owned
     `ZSTD_CCtx_params` layout never crosses the language boundary.

rust/src/zstd_compress.rs

@@ -275,6 +275,52 @@ const _: () = {
     );
 };
 
+/// Explicit projection of the state used by `ZSTD_compressBlock_internal`.
+///
+/// Sequence-store construction and the no-compress fallback remain in C.
+/// Rust owns sequence collection, entropy emission, the legacy first-block
+/// RLE gate, and the compressed-block state transitions after the store is
+/// ready.
+#[repr(C)]
+pub struct ZSTD_rust_blockInternalState {
+    seq_store: *const SeqStore_t,
+    prev_c_block: *mut *mut ZSTD_compressedBlockState_t,
+    next_c_block: *mut *mut ZSTD_compressedBlockState_t,
+    tmp_workspace: *mut c_void,
+    tmp_wksp_size: usize,
+    seq_collector: *mut SeqCollector,
+    strategy: c_int,
+    disable_literal_compression: c_int,
+    bmi2: c_int,
+    is_first_block: c_int,
+}
+
+const _: () = {
+    assert!(offset_of!(ZSTD_rust_blockInternalState, seq_store) == 0);
+    assert!(offset_of!(ZSTD_rust_blockInternalState, prev_c_block) == size_of::<usize>());
+    assert!(offset_of!(ZSTD_rust_blockInternalState, next_c_block) == 2 * size_of::<usize>());
+    assert!(offset_of!(ZSTD_rust_blockInternalState, tmp_workspace) == 3 * size_of::<usize>());
+    assert!(offset_of!(ZSTD_rust_blockInternalState, tmp_wksp_size) == 4 * size_of::<usize>());
+    assert!(offset_of!(ZSTD_rust_blockInternalState, seq_collector) == 5 * size_of::<usize>());
+    assert!(offset_of!(ZSTD_rust_blockInternalState, strategy) == 6 * size_of::<usize>());
+    assert!(
+        offset_of!(ZSTD_rust_blockInternalState, disable_literal_compression)
+            == 6 * size_of::<usize>() + size_of::<c_int>()
+    );
+    assert!(
+        offset_of!(ZSTD_rust_blockInternalState, bmi2)
+            == 6 * size_of::<usize>() + 2 * size_of::<c_int>()
+    );
+    assert!(
+        offset_of!(ZSTD_rust_blockInternalState, is_first_block)
+            == 6 * size_of::<usize>() + 3 * size_of::<c_int>()
+    );
+    assert!(
+        size_of::<ZSTD_rust_blockInternalState>()
+            == 6 * size_of::<usize>() + 4 * size_of::<c_int>()
+    );
+};
+
 /// Explicit projection of the state used by the target-sized block body.
 ///
 /// Sequence-store construction and the matchfinder remain in C.  This state
@@ -398,6 +444,120 @@ impl SingleBlockSeams {
     }
 }
 
+/// Rust implementation of `ZSTD_compressBlock_internal` after the C caller
+/// has built the sequence store.
+#[allow(clippy::too_many_arguments)]
+unsafe fn compress_block_internal_body_with(
+    state: &ZSTD_rust_blockInternalState,
+    dst: *mut c_void,
+    dst_capacity: usize,
+    src: *const c_void,
+    src_size: usize,
+    frame: c_uint,
+    seams: SingleBlockSeams,
+) -> usize {
+    const RLE_MAX_LENGTH: usize = 25;
+    const FSE_REPEAT_CHECK: c_int = 1;
+    const FSE_REPEAT_VALID: c_int = 2;
+
+    if state.seq_store.is_null()
+        || state.prev_c_block.is_null()
+        || state.next_c_block.is_null()
+        || state.seq_collector.is_null()
+    {
+        return ERROR(ZstdErrorCode::Generic);
+    }
+
+    let prev_c_block = unsafe { *state.prev_c_block };
+    let next_c_block = unsafe { *state.next_c_block };
+    if prev_c_block.is_null() || next_c_block.is_null() {
+        return ERROR(ZstdErrorCode::Generic);
+    }
+
+    if unsafe { (*state.seq_collector).collectSequences } != 0 {
+        let result = unsafe {
+            (seams.copy_sequences)(
+                state.seq_collector,
+                state.seq_store,
+                (*prev_c_block).rep.as_ptr(),
+            )
+        };
+        if ERR_isError(result) {
+            return result;
+        }
+        unsafe { (seams.confirm)(state.prev_c_block, state.next_c_block) };
+        return 0;
+    }
+
+    let mut c_size = unsafe {
+        (seams.entropy_compress)(
+            state.seq_store,
+            ptr::addr_of!((*prev_c_block).entropy),
+            ptr::addr_of_mut!((*next_c_block).entropy),
+            state.strategy,
+            state.disable_literal_compression,
+            dst,
+            dst_capacity,
+            src_size,
+            state.tmp_workspace,
+            state.tmp_wksp_size,
+            state.bmi2,
+        )
+    };
+
+    if frame != 0
+        && state.is_first_block == 0
+        && c_size < RLE_MAX_LENGTH
+        && unsafe { (seams.is_rle)(src.cast(), src_size) } != 0
+    {
+        /* Preserve the legacy decoder compatibility rule for the first frame
+         * block: later repeated blocks may use the one-byte RLE form. */
+        c_size = 1;
+        unsafe {
+            *dst.cast::<u8>() = *src.cast::<u8>();
+        }
+    }
+
+    if !ERR_isError(c_size) && c_size > 1 {
+        unsafe { (seams.confirm)(state.prev_c_block, state.next_c_block) };
+    }
+
+    let prev_c_block = unsafe { *state.prev_c_block };
+    if prev_c_block.is_null() {
+        return ERROR(ZstdErrorCode::Generic);
+    }
+    if unsafe { (*prev_c_block).entropy.fse.offcode_repeatMode } == FSE_REPEAT_VALID {
+        unsafe { (*prev_c_block).entropy.fse.offcode_repeatMode = FSE_REPEAT_CHECK };
+    }
+
+    c_size
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn ZSTD_rust_compressBlockInternal(
+    state: *const ZSTD_rust_blockInternalState,
+    dst: *mut c_void,
+    dst_capacity: usize,
+    src: *const c_void,
+    src_size: usize,
+    frame: c_uint,
+) -> usize {
+    if state.is_null() {
+        return ERROR(ZstdErrorCode::Generic);
+    }
+    unsafe {
+        compress_block_internal_body_with(
+            &*state,
+            dst,
+            dst_capacity,
+            src,
+            src_size,
+            frame,
+            SingleBlockSeams::production(),
+        )
+    }
+}
+
 #[inline]
 fn sequence_block_action(
     is_first_block: c_int,
@@ -3657,6 +3817,32 @@ mod tests {
         }
     }
 
+    fn block_internal_test_state(
+        seq_store: &mut SeqStore_t,
+        prev_block: &mut ZSTD_compressedBlockState_t,
+        next_block: &mut ZSTD_compressedBlockState_t,
+        prev_c_block: &mut *mut ZSTD_compressedBlockState_t,
+        next_c_block: &mut *mut ZSTD_compressedBlockState_t,
+        seq_collector: &mut SeqCollector,
+        strategy: c_int,
+        is_first_block: c_int,
+    ) -> ZSTD_rust_blockInternalState {
+        *prev_c_block = prev_block;
+        *next_c_block = next_block;
+        ZSTD_rust_blockInternalState {
+            seq_store,
+            prev_c_block,
+            next_c_block,
+            tmp_workspace: ptr::null_mut(),
+            tmp_wksp_size: 0,
+            seq_collector,
+            strategy,
+            disable_literal_compression: 0,
+            bmi2: 0,
+            is_first_block,
+        }
+    }
+
     struct SplitBlockTestStore {
         seq_store: SeqStore_t,
         _sequences: Box<[SeqDef; 2]>,
@@ -3789,6 +3975,147 @@ mod tests {
         assert!(std::ptr::eq(prev_c_block, &prev_block));
     }
 
+    #[test]
+    fn block_internal_body_collects_sequences_before_entropy_emission() {
+        let (mut seq_store, _sequences, _literals) = target_block_test_seq_store();
+        let mut prev_block = zeroed_state();
+        prev_block.entropy.fse.offcode_repeatMode = 2;
+        let mut next_block = zeroed_state();
+        let mut prev_c_block = ptr::null_mut();
+        let mut next_c_block = ptr::null_mut();
+        let mut output_sequences = [ZSTD_Sequence {
+            offset: 0xa5,
+            litLength: 0xa5,
+            matchLength: 0xa5,
+            rep: 0xa5,
+        }];
+        let mut seq_collector = SeqCollector {
+            collectSequences: 1,
+            seqStart: output_sequences.as_mut_ptr(),
+            seqIndex: 0,
+            maxSequences: output_sequences.len(),
+        };
+        let state = block_internal_test_state(
+            &mut seq_store,
+            &mut prev_block,
+            &mut next_block,
+            &mut prev_c_block,
+            &mut next_c_block,
+            &mut seq_collector,
+            1,
+            0,
+        );
+        let source = [0x5au8; 16];
+        let mut output = [0xa5u8; 16];
+
+        let result = unsafe {
+            compress_block_internal_body_with(
+                &state,
+                output.as_mut_ptr().cast(),
+                output.len(),
+                source.as_ptr().cast(),
+                source.len(),
+                1,
+                single_block_test_seams(),
+            )
+        };
+
+        assert_eq!(result, 0);
+        assert_eq!(seq_collector.seqIndex, 1);
+        assert_eq!(output_sequences[0].litLength, 0);
+        assert!(std::ptr::eq(prev_c_block, &next_block));
+        assert!(std::ptr::eq(next_c_block, &prev_block));
+        assert_eq!(prev_block.entropy.fse.offcode_repeatMode, 2);
+    }
+
+    #[test]
+    fn block_internal_body_gates_rle_and_cleans_repeat_mode() {
+        let (mut seq_store, _sequences, _literals) = target_block_test_seq_store();
+        let mut prev_block = zeroed_state();
+        prev_block.entropy.fse.offcode_repeatMode = 2;
+        let mut next_block = zeroed_state();
+        let mut prev_c_block = ptr::null_mut();
+        let mut next_c_block = ptr::null_mut();
+        let mut seq_collector = SeqCollector {
+            collectSequences: 0,
+            seqStart: ptr::null_mut(),
+            seqIndex: 0,
+            maxSequences: 0,
+        };
+        let state = block_internal_test_state(
+            &mut seq_store,
+            &mut prev_block,
+            &mut next_block,
+            &mut prev_c_block,
+            &mut next_c_block,
+            &mut seq_collector,
+            1,
+            0,
+        );
+        let source = [0x5au8; 16];
+        let mut output = [0xa5u8; 32];
+
+        let result = unsafe {
+            compress_block_internal_body_with(
+                &state,
+                output.as_mut_ptr().cast(),
+                output.len(),
+                source.as_ptr().cast(),
+                source.len(),
+                1,
+                single_block_test_seams(),
+            )
+        };
+
+        assert_eq!(result, 1);
+        assert_eq!(output[0], source[0]);
+        assert_eq!(prev_block.entropy.fse.offcode_repeatMode, 1);
+    }
+
+    #[test]
+    fn block_internal_body_propagates_entropy_error_through_repeat_cleanup() {
+        let (mut seq_store, _sequences, _literals) = target_block_test_seq_store();
+        let mut prev_block = zeroed_state();
+        prev_block.entropy.fse.offcode_repeatMode = 2;
+        let mut next_block = zeroed_state();
+        let mut prev_c_block = ptr::null_mut();
+        let mut next_c_block = ptr::null_mut();
+        let mut seq_collector = SeqCollector {
+            collectSequences: 0,
+            seqStart: ptr::null_mut(),
+            seqIndex: 0,
+            maxSequences: 0,
+        };
+        let state = block_internal_test_state(
+            &mut seq_store,
+            &mut prev_block,
+            &mut next_block,
+            &mut prev_c_block,
+            &mut next_c_block,
+            &mut seq_collector,
+            -1,
+            0,
+        );
+        let source = [0x5au8; 16];
+        let mut output = [0xa5u8; 32];
+
+        let result = unsafe {
+            compress_block_internal_body_with(
+                &state,
+                output.as_mut_ptr().cast(),
+                output.len(),
+                source.as_ptr().cast(),
+                source.len(),
+                1,
+                single_block_test_seams(),
+            )
+        };
+
+        assert_eq!(result, ERROR(ZstdErrorCode::Generic));
+        assert_eq!(output, [0xa5u8; 32]);
+        assert_eq!(prev_block.entropy.fse.offcode_repeatMode, 1);
+    }
+
     #[test]
     fn single_block_body_propagates_entropy_errors_without_serializing() {
         let (seq_store, _sequences, _literals) = target_block_test_seq_store();