Rename "External Matchfinder" to "Block-Level Sequence Producer" (#3484)

* change "external matchfinder" to "external sequence producer" * migrate contrib/ to new naming convention * fix contrib build * fix error message * update debug strings * fix def of invalid sequences in zstd.h * nit * update CHANGELOG * fix .gitignore
2025-10-31 08:37:43 +02:00 · 2023-02-09 17:01:17 -05:00
parent 4aa3bc49da
commit ff42ed1582
20 changed files with 231 additions and 220 deletions
--- a/2
+++ b/2
@@ -29,7 +29,7 @@ cli: Fix empty string as argument for `--output-dir-*` (#3220, @embg)
 cli: Fix decompression memory usage reported by `-vv --long` (#3042, @u1f35c, and #3232, @zengyijing)
 cli: Fix infinite loop when empty input is passed to trainer (#3081, @terrelln)
 cli: Fix `--adapt` doesn't work when `--no-progress` is also set (#3354, @terrelln)
-api: Support for External matchfinder (#3333, @embg)
+api: Support for Block-Level Sequence Producer (#3333, @embg)
 api: Support for in-place decompression (#3432, @terrelln)
 api: New  `ZSTD_CCtx_setCParams()`  function, set all parameters defined in a  `ZSTD_compressionParameters`  structure (#3403, @Cyan4973)
 api: Streaming decompression detects incorrect header ID sooner (#3175, @Cyan4973)
--- a/4
+++ b/4
@@ -123,7 +123,7 @@ contrib: lib
 	$(MAKE) -C contrib/seekable_format/examples all
 	$(MAKE) -C contrib/seekable_format/tests test
 	$(MAKE) -C contrib/largeNbDicts all
-	$(MAKE) -C contrib/externalMatchfinder all
+	$(MAKE) -C contrib/externalSequenceProducer all
 	cd build/single_file_libs/ ; ./build_decoder_test.sh
 	cd build/single_file_libs/ ; ./build_library_test.sh

@@ -143,7 +143,7 @@ clean:
 	$(Q)$(MAKE) -C contrib/seekable_format/examples $@ > $(VOID)
 	$(Q)$(MAKE) -C contrib/seekable_format/tests $@ > $(VOID)
 	$(Q)$(MAKE) -C contrib/largeNbDicts $@ > $(VOID)
-	$(Q)$(MAKE) -C contrib/externalMatchfinder $@ > $(VOID)
+	$(Q)$(MAKE) -C contrib/externalSequenceProducer $@ > $(VOID)
 	$(Q)$(RM) zstd$(EXT) zstdmt$(EXT) tmp*
 	$(Q)$(RM) -r lz4
 	@echo Cleaning completed
--- a/contrib/externalMatchfinder/.gitignore
+++ b/contrib/externalMatchfinder/.gitignore
@@ -1,2 +0,0 @@
-# build artifacts
-externalMatchfinder
--- a/contrib/externalMatchfinder/README.md
+++ b/contrib/externalMatchfinder/README.md
@@ -1,14 +0,0 @@
-externalMatchfinder
-=====================
-
-`externalMatchfinder` is a test tool for the external matchfinder API.
-It demonstrates how to use the API to perform a simple round-trip test.
-
-A sample matchfinder is provided in matchfinder.c, but the user can swap
-this out with a different one if desired. The sample matchfinder implements
-LZ compression with a 1KB hashtable. Dictionary compression is not currently supported.
-
-Command line :
-```
-externalMatchfinder filename
-```
--- a/contrib/externalSequenceProducer/.gitignore
+++ b/contrib/externalSequenceProducer/.gitignore
@@ -0,0 +1,2 @@
+# build artifacts
+externalSequenceProducer
--- a/contrib/externalSequenceProducer/Makefile
+++ b/contrib/externalSequenceProducer/Makefile
@@ -23,11 +23,11 @@ DEBUGFLAGS= -Wall -Wextra -Wcast-qual -Wcast-align -Wshadow \
            -Wredundant-decls
 CFLAGS  += $(DEBUGFLAGS) $(MOREFLAGS)

-default: externalMatchfinder
+default: externalSequenceProducer

-all: externalMatchfinder
+all: externalSequenceProducer

-externalMatchfinder: matchfinder.c main.c $(LIBZSTD)
+externalSequenceProducer: sequence_producer.c main.c $(LIBZSTD)
 	$(CC) $(CPPFLAGS) $(CFLAGS) $^ $(LDFLAGS) -o $@

 .PHONY: $(LIBZSTD)
@@ -37,4 +37,4 @@ $(LIBZSTD):
 clean:
 	$(RM) *.o
 	$(MAKE) -C $(LIBDIR) clean > /dev/null
-	$(RM) externalMatchfinder
+	$(RM) externalSequenceProducer
--- a/contrib/externalSequenceProducer/README.md
+++ b/contrib/externalSequenceProducer/README.md
@@ -0,0 +1,14 @@
+externalSequenceProducer
+=====================
+
+`externalSequenceProducer` is a test tool for the Block-Level Sequence Producer API.
+It demonstrates how to use the API to perform a simple round-trip test.
+
+A sample sequence producer is provided in sequence_producer.c, but the user can swap
+this out with a different one if desired. The sample sequence producer implements
+LZ parsing with a 1KB hashtable. Dictionary-based parsing is not currently supported.
+
+Command line :
+```
+externalSequenceProducer filename
+```
--- a/contrib/externalSequenceProducer/main.c
+++ b/contrib/externalSequenceProducer/main.c
@@ -16,7 +16,7 @@
 #define ZSTD_STATIC_LINKING_ONLY
 #include "zstd.h"
 #include "zstd_errors.h"
-#include "matchfinder.h" // simpleExternalMatchFinder
+#include "sequence_producer.h" // simpleSequenceProducer

 #define CHECK(res)                                      \
 do {                                                    \
@@ -28,23 +28,23 @@ do {                                                    \

 int main(int argc, char *argv[]) {
    if (argc != 2) {
-        printf("Usage: exampleMatchfinder <file>\n");
+        printf("Usage: externalSequenceProducer <file>\n");
        return 1;
    }

    ZSTD_CCtx* const zc = ZSTD_createCCtx();

-    int simpleExternalMatchState = 0xdeadbeef;
+    int simpleSequenceProducerState = 0xdeadbeef;

    // Here is the crucial bit of code!
-    ZSTD_registerExternalMatchFinder(
+    ZSTD_registerSequenceProducer(
        zc,
-        &simpleExternalMatchState,
-        simpleExternalMatchFinder
+        &simpleSequenceProducerState,
+        simpleSequenceProducer
    );

    {
-        size_t const res = ZSTD_CCtx_setParameter(zc, ZSTD_c_enableMatchFinderFallback, 1);
+        size_t const res = ZSTD_CCtx_setParameter(zc, ZSTD_c_enableSeqProducerFallback, 1);
        CHECK(res);
    }

--- a/contrib/externalSequenceProducer/sequence_producer.c
+++ b/contrib/externalSequenceProducer/sequence_producer.c
@@ -9,15 +9,15 @@
 */

 #include "zstd_compress_internal.h"
-#include "matchfinder.h"
+#include "sequence_producer.h"

 #define HSIZE 1024
 static U32 const HLOG = 10;
 static U32 const MLS = 4;
 static U32 const BADIDX = 0xffffffff;

-size_t simpleExternalMatchFinder(
-  void* externalMatchState,
+size_t simpleSequenceProducer(
+  void* sequenceProducerState,
  ZSTD_Sequence* outSeqs, size_t outSeqsCapacity,
  const void* src, size_t srcSize,
  const void* dict, size_t dictSize,
@@ -31,7 +31,7 @@ size_t simpleExternalMatchFinder(
    size_t seqCount = 0;
    U32 hashTable[HSIZE];

-    (void)externalMatchState;
+    (void)sequenceProducerState;
    (void)dict;
    (void)dictSize;
    (void)outSeqsCapacity;
--- a/contrib/externalSequenceProducer/sequence_producer.h
+++ b/contrib/externalSequenceProducer/sequence_producer.h
@@ -14,8 +14,8 @@
 #define ZSTD_STATIC_LINKING_ONLY
 #include "zstd.h"

-size_t simpleExternalMatchFinder(
-  void* externalMatchState,
+size_t simpleSequenceProducer(
+  void* sequenceProducerState,
  ZSTD_Sequence* outSeqs, size_t outSeqsCapacity,
  const void* src, size_t srcSize,
  const void* dict, size_t dictSize,
--- a/lib/common/error_private.c
+++ b/lib/common/error_private.c
@@ -54,7 +54,7 @@ const char* ERR_getErrorString(ERR_enum code)
    case PREFIX(seekableIO): return "An I/O error occurred when reading/seeking";
    case PREFIX(dstBuffer_wrong): return "Destination buffer is wrong";
    case PREFIX(srcBuffer_wrong): return "Source buffer is wrong";
-    case PREFIX(externalMatchFinder_failed): return "External matchfinder returned an error code";
+    case PREFIX(sequenceProducer_failed): return "Block-level external sequence producer returned an error code";
    case PREFIX(externalSequences_invalid): return "External sequences are not valid";
    case PREFIX(maxCode):
    default: return notErrorCode;
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -615,7 +615,7 @@ ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter param)
        bounds.upperBound = (int)ZSTD_ps_disable;
        return bounds;

-    case ZSTD_c_enableMatchFinderFallback:
+    case ZSTD_c_enableSeqProducerFallback:
        bounds.lowerBound = 0;
        bounds.upperBound = 1;
        return bounds;
@@ -695,7 +695,7 @@ static int ZSTD_isUpdateAuthorized(ZSTD_cParameter param)
    case ZSTD_c_useRowMatchFinder:
    case ZSTD_c_deterministicRefPrefix:
    case ZSTD_c_prefetchCDictTables:
-    case ZSTD_c_enableMatchFinderFallback:
+    case ZSTD_c_enableSeqProducerFallback:
    case ZSTD_c_maxBlockSize:
    case ZSTD_c_searchForExternalRepcodes:
    default:
@@ -754,7 +754,7 @@ size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value)
    case ZSTD_c_useRowMatchFinder:
    case ZSTD_c_deterministicRefPrefix:
    case ZSTD_c_prefetchCDictTables:
-    case ZSTD_c_enableMatchFinderFallback:
+    case ZSTD_c_enableSeqProducerFallback:
    case ZSTD_c_maxBlockSize:
    case ZSTD_c_searchForExternalRepcodes:
        break;
@@ -989,8 +989,8 @@ size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* CCtxParams,
        CCtxParams->prefetchCDictTables = (ZSTD_paramSwitch_e)value;
        return CCtxParams->prefetchCDictTables;

-    case ZSTD_c_enableMatchFinderFallback:
-        BOUNDCHECK(ZSTD_c_enableMatchFinderFallback, value);
+    case ZSTD_c_enableSeqProducerFallback:
+        BOUNDCHECK(ZSTD_c_enableSeqProducerFallback, value);
        CCtxParams->enableMatchFinderFallback = value;
        return CCtxParams->enableMatchFinderFallback;

@@ -1140,7 +1140,7 @@ size_t ZSTD_CCtxParams_getParameter(
    case ZSTD_c_prefetchCDictTables:
        *value = (int)CCtxParams->prefetchCDictTables;
        break;
-    case ZSTD_c_enableMatchFinderFallback:
+    case ZSTD_c_enableSeqProducerFallback:
        *value = CCtxParams->enableMatchFinderFallback;
        break;
    case ZSTD_c_maxBlockSize:
@@ -1610,8 +1610,8 @@ ZSTD_sizeof_matchState(const ZSTD_compressionParameters* const cParams,

 /* Helper function for calculating memory requirements.
 * Gives a tighter bound than ZSTD_sequenceBound() by taking minMatch into account. */
-static size_t ZSTD_maxNbSeq(size_t blockSize, unsigned minMatch, int useExternalMatchFinder) {
-    U32 const divider = (minMatch==3 || useExternalMatchFinder) ? 3 : 4;
+static size_t ZSTD_maxNbSeq(size_t blockSize, unsigned minMatch, int useSequenceProducer) {
+    U32 const divider = (minMatch==3 || useSequenceProducer) ? 3 : 4;
    return blockSize / divider;
 }

@@ -1623,12 +1623,12 @@ static size_t ZSTD_estimateCCtxSize_usingCCtxParams_internal(
        const size_t buffInSize,
        const size_t buffOutSize,
        const U64 pledgedSrcSize,
-        int useExternalMatchFinder,
+        int useSequenceProducer,
        size_t maxBlockSize)
 {
    size_t const windowSize = (size_t) BOUNDED(1ULL, 1ULL << cParams->windowLog, pledgedSrcSize);
    size_t const blockSize = MIN(ZSTD_resolveMaxBlockSize(maxBlockSize), windowSize);
-    size_t const maxNbSeq = ZSTD_maxNbSeq(blockSize, cParams->minMatch, useExternalMatchFinder);
+    size_t const maxNbSeq = ZSTD_maxNbSeq(blockSize, cParams->minMatch, useSequenceProducer);
    size_t const tokenSpace = ZSTD_cwksp_alloc_size(WILDCOPY_OVERLENGTH + blockSize)
                            + ZSTD_cwksp_aligned_alloc_size(maxNbSeq * sizeof(seqDef))
                            + 3 * ZSTD_cwksp_alloc_size(maxNbSeq * sizeof(BYTE));
@@ -1648,7 +1648,7 @@ static size_t ZSTD_estimateCCtxSize_usingCCtxParams_internal(
    size_t const cctxSpace = isStatic ? ZSTD_cwksp_alloc_size(sizeof(ZSTD_CCtx)) : 0;

    size_t const maxNbExternalSeq = ZSTD_sequenceBound(blockSize);
-    size_t const externalSeqSpace = useExternalMatchFinder
+    size_t const externalSeqSpace = useSequenceProducer
        ? ZSTD_cwksp_aligned_alloc_size(maxNbExternalSeq * sizeof(ZSTD_Sequence))
        : 0;

@@ -1679,7 +1679,7 @@ size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params)
     * be needed. However, we still allocate two 0-sized buffers, which can
     * take space under ASAN. */
    return ZSTD_estimateCCtxSize_usingCCtxParams_internal(
-        &cParams, &params->ldmParams, 1, useRowMatchFinder, 0, 0, ZSTD_CONTENTSIZE_UNKNOWN, params->useExternalMatchFinder, params->maxBlockSize);
+        &cParams, &params->ldmParams, 1, useRowMatchFinder, 0, 0, ZSTD_CONTENTSIZE_UNKNOWN, params->useSequenceProducer, params->maxBlockSize);
 }

 size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams)
@@ -1740,7 +1740,7 @@ size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params)

        return ZSTD_estimateCCtxSize_usingCCtxParams_internal(
            &cParams, &params->ldmParams, 1, useRowMatchFinder, inBuffSize, outBuffSize,
-            ZSTD_CONTENTSIZE_UNKNOWN, params->useExternalMatchFinder, params->maxBlockSize);
+            ZSTD_CONTENTSIZE_UNKNOWN, params->useSequenceProducer, params->maxBlockSize);
    }
 }

@@ -2024,7 +2024,7 @@ static size_t ZSTD_resetCCtx_internal(ZSTD_CCtx* zc,

    {   size_t const windowSize = MAX(1, (size_t)MIN(((U64)1 << params->cParams.windowLog), pledgedSrcSize));
        size_t const blockSize = MIN(params->maxBlockSize, windowSize);
-        size_t const maxNbSeq = ZSTD_maxNbSeq(blockSize, params->cParams.minMatch, params->useExternalMatchFinder);
+        size_t const maxNbSeq = ZSTD_maxNbSeq(blockSize, params->cParams.minMatch, params->useSequenceProducer);
        size_t const buffOutSize = (zbuff == ZSTDb_buffered && params->outBufferMode == ZSTD_bm_buffered)
                ? ZSTD_compressBound(blockSize) + 1
                : 0;
@@ -2041,7 +2041,7 @@ static size_t ZSTD_resetCCtx_internal(ZSTD_CCtx* zc,
        size_t const neededSpace =
            ZSTD_estimateCCtxSize_usingCCtxParams_internal(
                &params->cParams, &params->ldmParams, zc->staticSize != 0, params->useRowMatchFinder,
-                buffInSize, buffOutSize, pledgedSrcSize, params->useExternalMatchFinder, params->maxBlockSize);
+                buffInSize, buffOutSize, pledgedSrcSize, params->useSequenceProducer, params->maxBlockSize);
        int resizeWorkspace;

        FORWARD_IF_ERROR(neededSpace, "cctx size estimate failed!");
@@ -2155,7 +2155,7 @@ static size_t ZSTD_resetCCtx_internal(ZSTD_CCtx* zc,
        }

        /* reserve space for block-level external sequences */
-        if (params->useExternalMatchFinder) {
+        if (params->useSequenceProducer) {
            size_t const maxNbExternalSeq = ZSTD_sequenceBound(blockSize);
            zc->externalMatchCtx.seqBufferCapacity = maxNbExternalSeq;
            zc->externalMatchCtx.seqBuffer =
@@ -3022,26 +3022,26 @@ void ZSTD_resetSeqStore(seqStore_t* ssPtr)
    ssPtr->longLengthType = ZSTD_llt_none;
 }

-/* ZSTD_postProcessExternalMatchFinderResult() :
+/* ZSTD_postProcessSequenceProducerResult() :
 * Validates and post-processes sequences obtained through the external matchfinder API:
 *   - Checks whether nbExternalSeqs represents an error condition.
 *   - Appends a block delimiter to outSeqs if one is not already present.
 *     See zstd.h for context regarding block delimiters.
 * Returns the number of sequences after post-processing, or an error code. */
-static size_t ZSTD_postProcessExternalMatchFinderResult(
+static size_t ZSTD_postProcessSequenceProducerResult(
    ZSTD_Sequence* outSeqs, size_t nbExternalSeqs, size_t outSeqsCapacity, size_t srcSize
 ) {
    RETURN_ERROR_IF(
        nbExternalSeqs > outSeqsCapacity,
-        externalMatchFinder_failed,
-        "External matchfinder returned error code %lu",
+        sequenceProducer_failed,
+        "External sequence producer returned error code %lu",
        (unsigned long)nbExternalSeqs
    );

    RETURN_ERROR_IF(
        nbExternalSeqs == 0 && srcSize > 0,
-        externalMatchFinder_failed,
-        "External matchfinder produced zero sequences for a non-empty src buffer!"
+        sequenceProducer_failed,
+        "Got zero sequences from external sequence producer for a non-empty src buffer!"
    );

    if (srcSize == 0) {
@@ -3061,7 +3061,7 @@ static size_t ZSTD_postProcessExternalMatchFinderResult(
         * produced an invalid parse, by definition of ZSTD_sequenceBound(). */
        RETURN_ERROR_IF(
            nbExternalSeqs == outSeqsCapacity,
-            externalMatchFinder_failed,
+            sequenceProducer_failed,
            "nbExternalSeqs == outSeqsCapacity but lastSeq is not a block delimiter!"
        );

@@ -3139,9 +3139,9 @@ static size_t ZSTD_buildSeqStore(ZSTD_CCtx* zc, const void* src, size_t srcSize)
            /* External matchfinder + LDM is technically possible, just not implemented yet.
             * We need to revisit soon and implement it. */
            RETURN_ERROR_IF(
-                zc->appliedParams.useExternalMatchFinder,
+                zc->appliedParams.useSequenceProducer,
                parameter_combination_unsupported,
-                "Long-distance matching with external matchfinder enabled is not currently supported."
+                "Long-distance matching with external sequence producer enabled is not currently supported."
            );

            /* Updates ldmSeqStore.pos */
@@ -3158,9 +3158,9 @@ static size_t ZSTD_buildSeqStore(ZSTD_CCtx* zc, const void* src, size_t srcSize)
            /* External matchfinder + LDM is technically possible, just not implemented yet.
             * We need to revisit soon and implement it. */
            RETURN_ERROR_IF(
-                zc->appliedParams.useExternalMatchFinder,
+                zc->appliedParams.useSequenceProducer,
                parameter_combination_unsupported,
-                "Long-distance matching with external matchfinder enabled is not currently supported."
+                "Long-distance matching with external sequence producer enabled is not currently supported."
            );

            ldmSeqStore.seq = zc->ldmSequences;
@@ -3177,7 +3177,7 @@ static size_t ZSTD_buildSeqStore(ZSTD_CCtx* zc, const void* src, size_t srcSize)
                                       zc->appliedParams.useRowMatchFinder,
                                       src, srcSize);
            assert(ldmSeqStore.pos == ldmSeqStore.size);
-        } else if (zc->appliedParams.useExternalMatchFinder) {
+        } else if (zc->appliedParams.useSequenceProducer) {
            assert(
                zc->externalMatchCtx.seqBufferCapacity >= ZSTD_sequenceBound(srcSize)
            );
@@ -3195,7 +3195,7 @@ static size_t ZSTD_buildSeqStore(ZSTD_CCtx* zc, const void* src, size_t srcSize)
                    windowSize
                );

-                size_t const nbPostProcessedSeqs = ZSTD_postProcessExternalMatchFinderResult(
+                size_t const nbPostProcessedSeqs = ZSTD_postProcessSequenceProducerResult(
                    zc->externalMatchCtx.seqBuffer,
                    nbExternalSeqs,
                    zc->externalMatchCtx.seqBufferCapacity,
@@ -3217,7 +3217,7 @@ static size_t ZSTD_buildSeqStore(ZSTD_CCtx* zc, const void* src, size_t srcSize)
                        "Failed to copy external sequences to seqStore!"
                    );
                    ms->ldmSeqStore = NULL;
-                    DEBUGLOG(5, "Copied %lu sequences from external matchfinder to internal seqStore.", (unsigned long)nbExternalSeqs);
+                    DEBUGLOG(5, "Copied %lu sequences from external sequence producer to internal seqStore.", (unsigned long)nbExternalSeqs);
                    return ZSTDbss_compress;
                }

@@ -3233,7 +3233,7 @@ static size_t ZSTD_buildSeqStore(ZSTD_CCtx* zc, const void* src, size_t srcSize)
                    ms->ldmSeqStore = NULL;
                    DEBUGLOG(
                        5,
-                        "External matchfinder returned error code %lu. Falling back to internal matchfinder.",
+                        "External sequence producer returned error code %lu. Falling back to internal parser.",
                        (unsigned long)nbExternalSeqs
                    );
                    lastLLSize = blockCompressor(ms, &zc->seqStore, zc->blockState.nextCBlock->rep, src, srcSize);
@@ -6033,9 +6033,9 @@ static size_t ZSTD_CCtx_init_compressStream2(ZSTD_CCtx* cctx,
 #ifdef ZSTD_MULTITHREAD
    /* If external matchfinder is enabled, make sure to fail before checking job size (for consistency) */
    RETURN_ERROR_IF(
-        params.useExternalMatchFinder == 1 && params.nbWorkers >= 1,
+        params.useSequenceProducer == 1 && params.nbWorkers >= 1,
        parameter_combination_unsupported,
-        "External matchfinder isn't supported with nbWorkers >= 1"
+        "External sequence producer isn't supported with nbWorkers >= 1"
    );

    if ((cctx->pledgedSrcSizePlusOne-1) <= ZSTDMT_JOBSIZE_MIN) {
@@ -6251,7 +6251,7 @@ size_t ZSTD_compress2(ZSTD_CCtx* cctx,
 */
 static size_t
 ZSTD_validateSequence(U32 offCode, U32 matchLength, U32 minMatch,
-                      size_t posInSrc, U32 windowLog, size_t dictSize, int useExternalMatchFinder)
+                      size_t posInSrc, U32 windowLog, size_t dictSize, int useSequenceProducer)
 {
    U32 const windowSize = 1u << windowLog;
    /* posInSrc represents the amount of data the decoder would decode up to this point.
@@ -6260,7 +6260,7 @@ ZSTD_validateSequence(U32 offCode, U32 matchLength, U32 minMatch,
     * window size. After output surpasses windowSize, we're limited to windowSize offsets again.
     */
    size_t const offsetBound = posInSrc > windowSize ? (size_t)windowSize : posInSrc + (size_t)dictSize;
-    size_t const matchLenLowerBound = (minMatch == 3 || useExternalMatchFinder) ? 3 : 4;
+    size_t const matchLenLowerBound = (minMatch == 3 || useSequenceProducer) ? 3 : 4;
    RETURN_ERROR_IF(offCode > OFFSET_TO_OFFBASE(offsetBound), externalSequences_invalid, "Offset too large!");
    /* Validate maxNbSeq is large enough for the given matchLength and minMatch */
    RETURN_ERROR_IF(matchLength < matchLenLowerBound, externalSequences_invalid, "Matchlength too small for the minMatch");
@@ -6325,7 +6325,7 @@ ZSTD_copySequencesToSeqStoreExplicitBlockDelim(ZSTD_CCtx* cctx,
        if (cctx->appliedParams.validateSequences) {
            seqPos->posInSrc += litLength + matchLength;
            FORWARD_IF_ERROR(ZSTD_validateSequence(offBase, matchLength, cctx->appliedParams.cParams.minMatch, seqPos->posInSrc,
-                                                cctx->appliedParams.cParams.windowLog, dictSize, cctx->appliedParams.useExternalMatchFinder),
+                                                cctx->appliedParams.cParams.windowLog, dictSize, cctx->appliedParams.useSequenceProducer),
                                                "Sequence validation failed");
        }
        RETURN_ERROR_IF(idx - seqPos->idx >= cctx->seqStore.maxNbSeq, externalSequences_invalid,
@@ -6463,7 +6463,7 @@ ZSTD_copySequencesToSeqStoreNoBlockDelim(ZSTD_CCtx* cctx, ZSTD_sequencePosition*
        if (cctx->appliedParams.validateSequences) {
            seqPos->posInSrc += litLength + matchLength;
            FORWARD_IF_ERROR(ZSTD_validateSequence(offBase, matchLength, cctx->appliedParams.cParams.minMatch, seqPos->posInSrc,
-                                                   cctx->appliedParams.cParams.windowLog, dictSize, cctx->appliedParams.useExternalMatchFinder),
+                                                   cctx->appliedParams.cParams.windowLog, dictSize, cctx->appliedParams.useSequenceProducer),
                                                   "Sequence validation failed");
        }
        DEBUGLOG(6, "Storing sequence: (of: %u, ml: %u, ll: %u)", offBase, matchLength, litLength);
@@ -6908,9 +6908,9 @@ ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long srcSizeH
    return ZSTD_getParams_internal(compressionLevel, srcSizeHint, dictSize, ZSTD_cpm_unknown);
 }

-void ZSTD_registerExternalMatchFinder(
+void ZSTD_registerSequenceProducer(
    ZSTD_CCtx* zc, void* mState,
-    ZSTD_externalMatchFinder_F* mFinder
+    ZSTD_sequenceProducer_F* mFinder
 ) {
    if (mFinder != NULL) {
        ZSTD_externalMatchCtx emctx;
@@ -6919,9 +6919,9 @@ void ZSTD_registerExternalMatchFinder(
        emctx.seqBuffer = NULL;
        emctx.seqBufferCapacity = 0;
        zc->externalMatchCtx = emctx;
-        zc->requestedParams.useExternalMatchFinder = 1;
+        zc->requestedParams.useSequenceProducer = 1;
    } else {
        ZSTD_memset(&zc->externalMatchCtx, 0, sizeof(zc->externalMatchCtx));
-        zc->requestedParams.useExternalMatchFinder = 0;
+        zc->requestedParams.useSequenceProducer = 0;
    }
 }
--- a/lib/compress/zstd_compress_internal.h
+++ b/lib/compress/zstd_compress_internal.h
@@ -353,8 +353,8 @@ struct ZSTD_CCtx_params_s {

    /* Indicates whether an external matchfinder has been referenced.
     * Users can't set this externally.
-     * It is set internally in ZSTD_registerExternalMatchFinder(). */
-    int useExternalMatchFinder;
+     * It is set internally in ZSTD_registerSequenceProducer(). */
+    int useSequenceProducer;

    /* Adjust the max block size*/
    size_t maxBlockSize;
@@ -395,7 +395,7 @@ typedef struct {
 /* Context for block-level external matchfinder API */
 typedef struct {
  void* mState;
-  ZSTD_externalMatchFinder_F* mFinder;
+  ZSTD_sequenceProducer_F* mFinder;
  ZSTD_Sequence* seqBuffer;
  size_t seqBufferCapacity;
 } ZSTD_externalMatchCtx;
--- a/lib/zstd.h
+++ b/lib/zstd.h
@@ -478,7 +478,7 @@ typedef enum {
     * ZSTD_c_useBlockSplitter
     * ZSTD_c_useRowMatchFinder
     * ZSTD_c_prefetchCDictTables
-     * ZSTD_c_enableMatchFinderFallback
+     * ZSTD_c_enableSeqProducerFallback
     * ZSTD_c_maxBlockSize
     * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
     * note : never ever use experimentalParam? names directly;
@@ -565,7 +565,7 @@ typedef enum {
 *                  They will be used to compress next frame.
 *                  Resetting session never fails.
 *  - The parameters : changes all parameters back to "default".
- *                  This also removes any reference to any dictionary or external matchfinder.
+ *                  This also removes any reference to any dictionary or external sequence producer.
 *                  Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
 *                  otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
 *  - Both : similar to resetting the session, followed by resetting parameters.
@@ -1627,8 +1627,8 @@ ZSTDLIB_API unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size);
 *  Note : only single-threaded compression is supported.
 *  ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
 *
- *  Note 2 : ZSTD_estimateCCtxSize* functions are not compatible with the external matchfinder API at this time.
- *  Size estimates assume that no external matchfinder is registered.
+ *  Note 2 : ZSTD_estimateCCtxSize* functions are not compatible with the Block-Level Sequence Producer API at this time.
+ *  Size estimates assume that no external sequence producer is registered.
 */
 ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize(int compressionLevel);
 ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
@@ -1650,8 +1650,8 @@ ZSTDLIB_STATIC_API size_t ZSTD_estimateDCtxSize(void);
 *         In this case, get total size by adding ZSTD_estimate?DictSize
 *  Note 2 : only single-threaded compression is supported.
 *  ZSTD_estimateCStreamSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
- *  Note 3 : ZSTD_estimateCStreamSize* functions are not compatible with the external matchfinder API at this time.
- *  Size estimates assume that no external matchfinder is registered.
+ *  Note 3 : ZSTD_estimateCStreamSize* functions are not compatible with the Block-Level Sequence Producer API at this time.
+ *  Size estimates assume that no external sequence producer is registered.
 */
 ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize(int compressionLevel);
 ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
@@ -2113,19 +2113,19 @@ ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const vo
 */
 #define ZSTD_c_prefetchCDictTables ZSTD_c_experimentalParam16

-/* ZSTD_c_enableMatchFinderFallback
+/* ZSTD_c_enableSeqProducerFallback
 * Allowed values are 0 (disable) and 1 (enable). The default setting is 0.
 *
- * Controls whether zstd will fall back to an internal matchfinder if an
- * external matchfinder is registered and returns an error code. This fallback is
- * block-by-block: the internal matchfinder will only be called for blocks where
- * the external matchfinder returns an error code. Fallback compression will
+ * Controls whether zstd will fall back to an internal sequence producer if an
+ * external sequence producer is registered and returns an error code. This fallback
+ * is block-by-block: the internal sequence producer will only be called for blocks
+ * where the external sequence producer returns an error code. Fallback parsing will
 * follow any other cParam settings, such as compression level, the same as in a
 * normal (fully-internal) compression operation.
 *
- * The user is strongly encouraged to read the full external matchfinder API
+ * The user is strongly encouraged to read the full Block-Level Sequence Producer API
 * documentation (below) before setting this parameter. */
-#define ZSTD_c_enableMatchFinderFallback ZSTD_c_experimentalParam17
+#define ZSTD_c_enableSeqProducerFallback ZSTD_c_experimentalParam17

 /* ZSTD_c_maxBlockSize
 * Allowed values are between 1KB and ZSTD_BLOCKSIZE_MAX (128KB).
@@ -2141,12 +2141,13 @@ ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const vo

 /* ZSTD_c_searchForExternalRepcodes
 * This parameter affects how zstd parses external sequences, such as sequences
- * provided through the compressSequences() API or from an external matchfinder.
+ * provided through the compressSequences() API or from an external block-level
+ * sequence producer.
 *
 * If set to ZSTD_ps_enable, the library will check for repeated offsets in
 * external sequences, even if those repcodes are not explicitly indicated in
 * the "rep" field. Note that this is the only way to exploit repcode matches
- * while using compressSequences() or an external matchfinder, since zstd
+ * while using compressSequences() or an external sequence producer, since zstd
 * currently ignores the "rep" field of external sequences.
 *
 * If set to ZSTD_ps_disable, the library will not exploit repeated offsets in
@@ -2805,43 +2806,52 @@ ZSTDLIB_STATIC_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_
 ZSTDLIB_STATIC_API size_t ZSTD_insertBlock    (ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize);  /**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */


-/* ********************** EXTERNAL MATCHFINDER API **********************
+/* ********************* BLOCK-LEVEL SEQUENCE PRODUCER API *********************
 *
 * *** OVERVIEW ***
- * This API allows users to replace the zstd internal block-level matchfinder
- * with an external matchfinder function. Potential applications of the API
- * include hardware-accelerated matchfinders and matchfinders specialized to
- * particular types of data.
+ * The Block-Level Sequence Producer API allows users to provide their own custom
+ * sequence producer which libzstd invokes to process each block. The produced list
+ * of sequences (literals and matches) is then post-processed by libzstd to produce
+ * valid compressed blocks.
 *
- * See contrib/externalMatchfinder for an example program employing the
- * external matchfinder API.
+ * This block-level offload API is a more granular complement of the existing
+ * frame-level offload API compressSequences() (introduced in v1.5.1). It offers
+ * an easier migration story for applications already integrated with libzstd: the
+ * user application continues to invoke the same compression functions
+ * ZSTD_compress2() or ZSTD_compressStream2() as usual, and transparently benefits
+ * from the specific advantages of the external sequence producer. For example,
+ * the sequence producer could be tuned to take advantage of known characteristics
+ * of the input, to offer better speed / ratio, or could leverage hardware
+ * acceleration not available within libzstd itself.
+ *
+ * See contrib/externalSequenceProducer for an example program employing the
+ * Block-Level Sequence Producer API.
 *
 * *** USAGE ***
 * The user is responsible for implementing a function of type
- * ZSTD_externalMatchFinder_F. For each block, zstd will pass the following
+ * ZSTD_sequenceProducer_F. For each block, zstd will pass the following
 * arguments to the user-provided function:
 *
- *   - externalMatchState: a pointer to a user-managed state for the external
- *     matchfinder.
+ *   - sequenceProducerState: a pointer to a user-managed state for the sequence
+ *     producer.
 *
- *   - outSeqs, outSeqsCapacity: an output buffer for sequences produced by the
- *     external matchfinder. outSeqsCapacity is guaranteed >=
- *     ZSTD_sequenceBound(srcSize). The memory backing outSeqs is managed by
- *     the CCtx.
+ *   - outSeqs, outSeqsCapacity: an output buffer for the sequence producer.
+ *     outSeqsCapacity is guaranteed >= ZSTD_sequenceBound(srcSize). The memory
+ *     backing outSeqs is managed by the CCtx.
 *
- *   - src, srcSize: an input buffer which the external matchfinder must parse
- *     into sequences. srcSize is guaranteed to be <= ZSTD_BLOCKSIZE_MAX.
+ *   - src, srcSize: an input buffer for the sequence producer to parse.
+ *     srcSize is guaranteed to be <= ZSTD_BLOCKSIZE_MAX.
 *
- *   - dict, dictSize: a history buffer, which may be empty, which the external
- *     matchfinder may reference as it produces sequences for the src buffer.
- *     Currently, zstd will always pass dictSize == 0 into external matchfinders,
- *     but this will change in the future.
+ *   - dict, dictSize: a history buffer, which may be empty, which the sequence
+ *     producer may reference as it parses the src buffer. Currently, zstd will
+ *     always pass dictSize == 0 into external sequence producers, but this will
+ *     change in the future.
 *
 *   - compressionLevel: a signed integer representing the zstd compression level
- *     set by the user for the current operation. The external matchfinder may
- *     choose to use this information to change its compression strategy and
- *     speed/ratio tradeoff. Note: The compression level does not reflect zstd
- *     parameters set through the advanced API.
+ *     set by the user for the current operation. The sequence producer may choose
+ *     to use this information to change its compression strategy and speed/ratio
+ *     tradeoff. Note: the compression level does not reflect zstd parameters set
+ *     through the advanced API.
 *
 *   - windowSize: a size_t representing the maximum allowed offset for external
 *     sequences. Note that sequence offsets are sometimes allowed to exceed the
@@ -2851,7 +2861,7 @@ ZSTDLIB_STATIC_API size_t ZSTD_insertBlock    (ZSTD_DCtx* dctx, const void* bloc
 * The user-provided function shall return a size_t representing the number of
 * sequences written to outSeqs. This return value will be treated as an error
 * code if it is greater than outSeqsCapacity. The return value must be non-zero
- * if srcSize is non-zero. The ZSTD_EXTERNAL_MATCHFINDER_ERROR macro is provided
+ * if srcSize is non-zero. The ZSTD_SEQUENCE_PRODUCER_ERROR macro is provided
 * for convenience, but any value greater than outSeqsCapacity will be treated as
 * an error code.
 *
@@ -2859,68 +2869,71 @@ ZSTDLIB_STATIC_API size_t ZSTD_insertBlock    (ZSTD_DCtx* dctx, const void* bloc
 * written to outSeqs must be a valid parse of the src buffer. Data corruption may
 * occur if the parse is not valid. A parse is defined to be valid if the
 * following conditions hold:
- *   - The sum of matchLengths and literalLengths is equal to srcSize.
- *   - All sequences in the parse have matchLength != 0, except for the final
- *     sequence. matchLength is not constrained for the final sequence.
- *   - All offsets respect the windowSize parameter as specified in
+ *   - The sum of matchLengths and literalLengths must equal srcSize.
+ *   - All sequences in the parse, except for the final sequence, must have
+ *     matchLength >= ZSTD_MINMATCH_MIN. The final sequence must have
+ *     matchLength >= ZSTD_MINMATCH_MIN or matchLength == 0.
+ *   - All offsets must respect the windowSize parameter as specified in
 *     doc/zstd_compression_format.md.
+ *   - If the final sequence has matchLength == 0, it must also have offset == 0.
 *
 * zstd will only validate these conditions (and fail compression if they do not
 * hold) if the ZSTD_c_validateSequences cParam is enabled. Note that sequence
 * validation has a performance cost.
 *
 * If the user-provided function returns an error, zstd will either fall back
- * to an internal matchfinder or fail the compression operation. The user can
- * choose between the two behaviors by setting the
- * ZSTD_c_enableMatchFinderFallback cParam. Fallback compression will follow any
- * other cParam settings, such as compression level, the same as in a normal
- * compression operation.
+ * to an internal sequence producer or fail the compression operation. The user can
+ * choose between the two behaviors by setting the ZSTD_c_enableSeqProducerFallback
+ * cParam. Fallback compression will follow any other cParam settings, such as
+ * compression level, the same as in a normal compression operation.
 *
- * The user shall instruct zstd to use a particular ZSTD_externalMatchFinder_F
- * function by calling ZSTD_registerExternalMatchFinder(cctx, externalMatchState,
- * externalMatchFinder). This setting will persist until the next parameter reset
- * of the CCtx.
+ * The user shall instruct zstd to use a particular ZSTD_sequenceProducer_F
+ * function by calling
+ *         ZSTD_registerSequenceProducer(cctx,
+ *                                       sequenceProducerState,
+ *                                       sequenceProducer)
+ * This setting will persist until the next parameter reset of the CCtx.
 *
- * The externalMatchState must be initialized by the user before calling
- * ZSTD_registerExternalMatchFinder. The user is responsible for destroying the
- * externalMatchState.
+ * The sequenceProducerState must be initialized by the user before calling
+ * ZSTD_registerSequenceProducer(). The user is responsible for destroying the
+ * sequenceProducerState.
 *
 * *** LIMITATIONS ***
- * External matchfinders are compatible with all zstd compression APIs which respect
- * advanced parameters. However, there are three limitations:
+ * This API is compatible with all zstd compression APIs which respect advanced parameters.
+ * However, there are three limitations:
 *
- * First, the ZSTD_c_enableLongDistanceMatching cParam is not supported.
- * COMPRESSION WILL FAIL if it is enabled and the user tries to compress with an
- * external matchfinder.
- *   - Note that ZSTD_c_enableLongDistanceMatching is auto-enabled by default in
- *     some cases (see its documentation for details). Users must explicitly set
- *     ZSTD_c_enableLongDistanceMatching to ZSTD_ps_disable in such cases if an
- *     external matchfinder is registered.
+ * First, the ZSTD_c_enableLongDistanceMatching cParam is not currently supported.
+ * COMPRESSION WILL FAIL if it is enabled and the user tries to compress with a block-level
+ * external sequence producer.
+ *   - Note that ZSTD_c_enableLongDistanceMatching is auto-enabled by default in some
+ *     cases (see its documentation for details). Users must explicitly set
+ *     ZSTD_c_enableLongDistanceMatching to ZSTD_ps_disable in such cases if an external
+ *     sequence producer is registered.
 *   - As of this writing, ZSTD_c_enableLongDistanceMatching is disabled by default
 *     whenever ZSTD_c_windowLog < 128MB, but that's subject to change. Users should
- *     check the docs on ZSTD_c_enableLongDistanceMatching whenever the external
- *     matchfinder API is used in conjunction with advanced settings (like windowLog).
+ *     check the docs on ZSTD_c_enableLongDistanceMatching whenever the Block-Level Sequence
+ *     Producer API is used in conjunction with advanced settings (like ZSTD_c_windowLog).
 *
- * Second, history buffers are not supported. Concretely, zstd will always pass
- * dictSize == 0 to the external matchfinder (for now). This has two implications:
- *   - Dictionaries are not supported. Compression will *not* fail if the user
+ * Second, history buffers are not currently supported. Concretely, zstd will always pass
+ * dictSize == 0 to the external sequence producer (for now). This has two implications:
+ *   - Dictionaries are not currently supported. Compression will *not* fail if the user
 *     references a dictionary, but the dictionary won't have any effect.
- *   - Stream history is not supported. All compression APIs, including streaming
- *     APIs, work with the external matchfinder, but the external matchfinder won't
- *     receive any history from the previous block. Each block is an independent chunk.
+ *   - Stream history is not currently supported. All advanced compression APIs, including
+ *     streaming APIs, work with external sequence producers, but each block is treated as
+ *     an independent chunk without history from previous blocks.
 *
- * Third, multi-threading within a single compression is not supported. In other words,
- * COMPRESSION WILL FAIL if ZSTD_c_nbWorkers > 0 and an external matchfinder is registered.
+ * Third, multi-threading within a single compression is not currently supported. In other words,
+ * COMPRESSION WILL FAIL if ZSTD_c_nbWorkers > 0 and an external sequence producer is registered.
 * Multi-threading across compressions is fine: simply create one CCtx per thread.
 *
 * Long-term, we plan to overcome all three limitations. There is no technical blocker to
 * overcoming them. It is purely a question of engineering effort.
 */

-#define ZSTD_EXTERNAL_MATCHFINDER_ERROR ((size_t)(-1))
+#define ZSTD_SEQUENCE_PRODUCER_ERROR ((size_t)(-1))

-typedef size_t ZSTD_externalMatchFinder_F (
-  void* externalMatchState,
+typedef size_t ZSTD_sequenceProducer_F (
+  void* sequenceProducerState,
  ZSTD_Sequence* outSeqs, size_t outSeqsCapacity,
  const void* src, size_t srcSize,
  const void* dict, size_t dictSize,
@@ -2928,32 +2941,30 @@ typedef size_t ZSTD_externalMatchFinder_F (
  size_t windowSize
 );

-/*! ZSTD_registerExternalMatchFinder() :
- * Instruct zstd to use an external matchfinder function.
+/*! ZSTD_registerSequenceProducer() :
+ * Instruct zstd to use a block-level external sequence producer function.
 *
- * The externalMatchState must be initialized by the caller, and the caller is
+ * The sequenceProducerState must be initialized by the caller, and the caller is
 * responsible for managing its lifetime. This parameter is sticky across
 * compressions. It will remain set until the user explicitly resets compression
 * parameters.
 *
- * External matchfinder registration is considered to be an "advanced parameter",
- * part of the "advanced API". This means it will only have an effect on
- * compression APIs which respect advanced parameters, such as compress2() and
- * compressStream(). Older compression APIs such as compressCCtx(), which predate
- * the introduction of "advanced parameters", will ignore any external matchfinder
- * setting.
+ * Sequence producer registration is considered to be an "advanced parameter",
+ * part of the "advanced API". This means it will only have an effect on compression
+ * APIs which respect advanced parameters, such as compress2() and compressStream2().
+ * Older compression APIs such as compressCCtx(), which predate the introduction of
+ * "advanced parameters", will ignore any external sequence producer setting.
 *
- * The external matchfinder can be "cleared" by registering a NULL external
- * matchfinder function pointer. This removes all limitations described above in
- * the "LIMITATIONS" section of the API docs.
+ * The sequence producer can be "cleared" by registering a NULL function pointer. This
+ * removes all limitations described above in the "LIMITATIONS" section of the API docs.
 *
- * The user is strongly encouraged to read the full API documentation (above)
- * before calling this function. */
+ * The user is strongly encouraged to read the full API documentation (above) before
+ * calling this function. */
 ZSTDLIB_STATIC_API void
-ZSTD_registerExternalMatchFinder(
+ZSTD_registerSequenceProducer(
  ZSTD_CCtx* cctx,
-  void* externalMatchState,
-  ZSTD_externalMatchFinder_F* externalMatchFinder
+  void* sequenceProducerState,
+  ZSTD_sequenceProducer_F* sequenceProducer
 );

 #endif   /* ZSTD_H_ZSTD_STATIC_LINKING_ONLY */
--- a/lib/zstd_errors.h
+++ b/lib/zstd_errors.h
@@ -95,7 +95,7 @@ typedef enum {
  ZSTD_error_seekableIO          = 102,
  ZSTD_error_dstBuffer_wrong     = 104,
  ZSTD_error_srcBuffer_wrong     = 105,
-  ZSTD_error_externalMatchFinder_failed = 106,
+  ZSTD_error_sequenceProducer_failed = 106,
  ZSTD_error_externalSequences_invalid = 107,
  ZSTD_error_maxCode = 120  /* never EVER use this value directly, it can change in future versions! Use ZSTD_isError() instead */
 } ZSTD_ErrorCode;
--- a/tests/external_matchfinder.c
+++ b/tests/external_matchfinder.c
@@ -17,8 +17,8 @@ static U32 const HLOG = 10;
 static U32 const MLS = 4;
 static U32 const BADIDX = 0xffffffff;

-static size_t simpleExternalMatchFinder(
-  void* externalMatchState,
+static size_t simpleSequenceProducer(
+  void* sequenceProducerState,
  ZSTD_Sequence* outSeqs, size_t outSeqsCapacity,
  const void* src, size_t srcSize,
  const void* dict, size_t dictSize,
@@ -32,7 +32,7 @@ static size_t simpleExternalMatchFinder(
    size_t seqCount = 0;
    U32 hashTable[HSIZE];

-    (void)externalMatchState;
+    (void)sequenceProducerState;
    (void)dict;
    (void)dictSize;
    (void)outSeqsCapacity;
@@ -80,15 +80,15 @@ static size_t simpleExternalMatchFinder(
    return seqCount;
 }

-size_t zstreamExternalMatchFinder(
-  void* externalMatchState,
+size_t zstreamSequenceProducer(
+  void* sequenceProducerState,
  ZSTD_Sequence* outSeqs, size_t outSeqsCapacity,
  const void* src, size_t srcSize,
  const void* dict, size_t dictSize,
  int compressionLevel,
  size_t windowSize
 ) {
-    EMF_testCase const testCase = *((EMF_testCase*)externalMatchState);
+    EMF_testCase const testCase = *((EMF_testCase*)sequenceProducerState);
    memset(outSeqs, 0, outSeqsCapacity);

    switch (testCase) {
@@ -100,8 +100,8 @@ size_t zstreamExternalMatchFinder(
            outSeqs[0].litLength = (U32)(srcSize);
            return 1;
         case EMF_LOTS_OF_SEQS:
-            return simpleExternalMatchFinder(
-                externalMatchState,
+            return simpleSequenceProducer(
+                sequenceProducerState,
                outSeqs, outSeqsCapacity,
                src, srcSize,
                dict, dictSize,
@@ -135,6 +135,6 @@ size_t zstreamExternalMatchFinder(
            return outSeqsCapacity + 1;
        case EMF_BIG_ERROR:
        default:
-            return ZSTD_EXTERNAL_MATCHFINDER_ERROR;
+            return ZSTD_SEQUENCE_PRODUCER_ERROR;
    }
 }
--- a/tests/external_matchfinder.h
+++ b/tests/external_matchfinder.h
@@ -27,8 +27,8 @@ typedef enum {
    EMF_INVALID_LAST_LITS = 8
 } EMF_testCase;

-size_t zstreamExternalMatchFinder(
-  void* externalMatchState,
+size_t zstreamSequenceProducer(
+  void* sequenceProducerState,
  ZSTD_Sequence* outSeqs, size_t outSeqsCapacity,
  const void* src, size_t srcSize,
  const void* dict, size_t dictSize,
--- a/tests/fuzz/Makefile
+++ b/tests/fuzz/Makefile
@@ -35,8 +35,8 @@ PRGDIR = ../../programs
 CONTRIBDIR = ../../contrib

 # TODO(embg) make it possible to plug in an arbitrary matchfinder as a .o file
-MATCHFINDER_DIR = $(CONTRIBDIR)/externalMatchfinder
-MATCHFINDER_SRC = $(MATCHFINDER_DIR)/matchfinder.c
+MATCHFINDER_DIR = $(CONTRIBDIR)/externalSequenceProducer
+MATCHFINDER_SRC = $(MATCHFINDER_DIR)/sequence_producer.c

 FUZZ_CPPFLAGS := -I$(ZSTDDIR) -I$(ZSTDDIR)/common -I$(ZSTDDIR)/compress \
 	-I$(ZSTDDIR)/dictBuilder -I$(ZSTDDIR)/deprecated -I$(ZSTDDIR)/legacy \
--- a/tests/fuzz/zstd_helpers.c
+++ b/tests/fuzz/zstd_helpers.c
@@ -17,7 +17,7 @@
 #include "fuzz_helpers.h"
 #include "zstd.h"
 #include "zdict.h"
-#include "matchfinder.h"
+#include "sequence_producer.h"

 const int kMinClevel = -3;
 const int kMaxClevel = 19;
@@ -71,13 +71,13 @@ ZSTD_parameters FUZZ_randomParams(size_t srcSize, FUZZ_dataProducer_t *producer)
    return params;
 }

-static void setExternalMatchFinderParams(ZSTD_CCtx *cctx, FUZZ_dataProducer_t *producer) {
-    ZSTD_registerExternalMatchFinder(
+static void setSequenceProducerParams(ZSTD_CCtx *cctx, FUZZ_dataProducer_t *producer) {
+    ZSTD_registerSequenceProducer(
        cctx,
        NULL,
-        simpleExternalMatchFinder
+        simpleSequenceProducer
    );
-    setRand(cctx, ZSTD_c_enableMatchFinderFallback, 0, 1, producer);
+    setRand(cctx, ZSTD_c_enableSeqProducerFallback, 0, 1, producer);
    FUZZ_ZASSERT(ZSTD_CCtx_setParameter(cctx, ZSTD_c_nbWorkers, 0));
    FUZZ_ZASSERT(ZSTD_CCtx_setParameter(cctx, ZSTD_c_enableLongDistanceMatching, ZSTD_ps_disable));
 }
@@ -138,9 +138,9 @@ void FUZZ_setRandomParameters(ZSTD_CCtx *cctx, size_t srcSize, FUZZ_dataProducer
    }

    if (FUZZ_dataProducer_uint32Range(producer, 0, 10) == 1) {
-        setExternalMatchFinderParams(cctx, producer);
+        setSequenceProducerParams(cctx, producer);
    } else {
-        ZSTD_registerExternalMatchFinder(cctx, NULL, NULL);
+        ZSTD_registerSequenceProducer(cctx, NULL, NULL);
    }
 }

--- a/tests/zstreamtest.c
+++ b/tests/zstreamtest.c
@@ -40,7 +40,7 @@
 #include "seqgen.h"
 #include "util.h"
 #include "timefn.h"       /* UTIL_time_t, UTIL_clockSpanMicro, UTIL_getTime */
-#include "external_matchfinder.h"   /* zstreamExternalMatchFinder, EMF_testCase */
+#include "external_matchfinder.h"   /* zstreamSequenceProducer, EMF_testCase */

 /*-************************************
 *  Constants
@@ -1856,14 +1856,14 @@ static int basicUnitTests(U32 seed, double compressibility, int bigTests)
    }
    DISPLAYLEVEL(3, "OK \n");

-    DISPLAYLEVEL(3, "test%3i : External matchfinder API: ", testNb++);
+    DISPLAYLEVEL(3, "test%3i : Block-Level External Sequence Producer API: ", testNb++);
    {
        size_t const dstBufSize = ZSTD_compressBound(CNBufferSize);
        BYTE* const dstBuf = (BYTE*)malloc(ZSTD_compressBound(dstBufSize));
        size_t const checkBufSize = CNBufferSize;
        BYTE* const checkBuf = (BYTE*)malloc(checkBufSize);
        int enableFallback;
-        EMF_testCase externalMatchState;
+        EMF_testCase sequenceProducerState;

        CHECK(dstBuf == NULL || checkBuf == NULL, "allocation failed");

@@ -1871,7 +1871,7 @@ static int basicUnitTests(U32 seed, double compressibility, int bigTests)

        /* Reference external matchfinder outside the test loop to
         * check that the reference is preserved across compressions */
-        ZSTD_registerExternalMatchFinder(zc, &externalMatchState, zstreamExternalMatchFinder);
+        ZSTD_registerSequenceProducer(zc, &sequenceProducerState, zstreamSequenceProducer);

        for (enableFallback = 0; enableFallback <= 1; enableFallback++) {
            size_t testCaseId;
@@ -1892,9 +1892,9 @@ static int basicUnitTests(U32 seed, double compressibility, int bigTests)
            ZSTD_ErrorCode const errorCodes[] = {
                ZSTD_error_no_error,
                ZSTD_error_no_error,
-                ZSTD_error_externalMatchFinder_failed,
-                ZSTD_error_externalMatchFinder_failed,
-                ZSTD_error_externalMatchFinder_failed,
+                ZSTD_error_sequenceProducer_failed,
+                ZSTD_error_sequenceProducer_failed,
+                ZSTD_error_sequenceProducer_failed,
                ZSTD_error_externalSequences_invalid,
                ZSTD_error_externalSequences_invalid,
                ZSTD_error_externalSequences_invalid,
@@ -1906,18 +1906,18 @@ static int basicUnitTests(U32 seed, double compressibility, int bigTests)

                int const compressionShouldSucceed = (
                    (errorCodes[testCaseId] == ZSTD_error_no_error) ||
-                    (enableFallback && errorCodes[testCaseId] == ZSTD_error_externalMatchFinder_failed)
+                    (enableFallback && errorCodes[testCaseId] == ZSTD_error_sequenceProducer_failed)
                );

                int const testWithSequenceValidation = (
                    testCases[testCaseId] == EMF_INVALID_OFFSET
                );

-                externalMatchState = testCases[testCaseId];
+                sequenceProducerState = testCases[testCaseId];

                ZSTD_CCtx_reset(zc, ZSTD_reset_session_only);
                CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_validateSequences, testWithSequenceValidation));
-                CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableMatchFinderFallback, enableFallback));
+                CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableSeqProducerFallback, enableFallback));
                res = ZSTD_compress2(zc, dstBuf, dstBufSize, CNBuffer, CNBufferSize);

                if (compressionShouldSucceed) {
@@ -1936,9 +1936,9 @@ static int basicUnitTests(U32 seed, double compressibility, int bigTests)
            /* Test compression with external matchfinder + empty src buffer */
            {
                size_t res;
-                externalMatchState = EMF_ZERO_SEQS;
+                sequenceProducerState = EMF_ZERO_SEQS;
                ZSTD_CCtx_reset(zc, ZSTD_reset_session_only);
-                CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableMatchFinderFallback, enableFallback));
+                CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableSeqProducerFallback, enableFallback));
                res = ZSTD_compress2(zc, dstBuf, dstBufSize, CNBuffer, 0);
                CHECK(ZSTD_isError(res), "EMF: Compression error: %s", ZSTD_getErrorName(res));
                CHECK(ZSTD_decompress(checkBuf, checkBufSize, dstBuf, res) != 0, "EMF: Empty src round trip failed!");
@@ -1947,30 +1947,30 @@ static int basicUnitTests(U32 seed, double compressibility, int bigTests)

        /* Test that reset clears the external matchfinder */
        CHECK_Z(ZSTD_CCtx_reset(zc, ZSTD_reset_session_and_parameters));
-        externalMatchState = EMF_BIG_ERROR; /* ensure zstd will fail if the matchfinder wasn't cleared */
-        CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableMatchFinderFallback, 0));
+        sequenceProducerState = EMF_BIG_ERROR; /* ensure zstd will fail if the matchfinder wasn't cleared */
+        CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableSeqProducerFallback, 0));
        CHECK_Z(ZSTD_compress2(zc, dstBuf, dstBufSize, CNBuffer, CNBufferSize));

        /* Test that registering mFinder == NULL clears the external matchfinder */
        ZSTD_CCtx_reset(zc, ZSTD_reset_session_and_parameters);
-        ZSTD_registerExternalMatchFinder(zc, &externalMatchState, zstreamExternalMatchFinder);
-        externalMatchState = EMF_BIG_ERROR; /* ensure zstd will fail if the matchfinder wasn't cleared */
-        CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableMatchFinderFallback, 0));
-        ZSTD_registerExternalMatchFinder(zc, NULL, NULL); /* clear the external matchfinder */
+        ZSTD_registerSequenceProducer(zc, &sequenceProducerState, zstreamSequenceProducer);
+        sequenceProducerState = EMF_BIG_ERROR; /* ensure zstd will fail if the matchfinder wasn't cleared */
+        CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableSeqProducerFallback, 0));
+        ZSTD_registerSequenceProducer(zc, NULL, NULL); /* clear the external matchfinder */
        CHECK_Z(ZSTD_compress2(zc, dstBuf, dstBufSize, CNBuffer, CNBufferSize));

        /* Test that external matchfinder doesn't interact with older APIs */
        ZSTD_CCtx_reset(zc, ZSTD_reset_session_and_parameters);
-        ZSTD_registerExternalMatchFinder(zc, &externalMatchState, zstreamExternalMatchFinder);
-        externalMatchState = EMF_BIG_ERROR; /* ensure zstd will fail if the matchfinder is used */
-        CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableMatchFinderFallback, 0));
+        ZSTD_registerSequenceProducer(zc, &sequenceProducerState, zstreamSequenceProducer);
+        sequenceProducerState = EMF_BIG_ERROR; /* ensure zstd will fail if the matchfinder is used */
+        CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableSeqProducerFallback, 0));
        CHECK_Z(ZSTD_compressCCtx(zc, dstBuf, dstBufSize, CNBuffer, CNBufferSize, 3));

        /* Test that compression returns the correct error with LDM */
        CHECK_Z(ZSTD_CCtx_reset(zc, ZSTD_reset_session_and_parameters));
        {
            size_t res;
-            ZSTD_registerExternalMatchFinder(zc, &externalMatchState, zstreamExternalMatchFinder);
+            ZSTD_registerSequenceProducer(zc, &sequenceProducerState, zstreamSequenceProducer);
            CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_enableLongDistanceMatching, ZSTD_ps_enable));
            res = ZSTD_compress2(zc, dstBuf, dstBufSize, CNBuffer, CNBufferSize);
            CHECK(!ZSTD_isError(res), "EMF: Should have raised an error!");
@@ -1985,7 +1985,7 @@ static int basicUnitTests(U32 seed, double compressibility, int bigTests)
        CHECK_Z(ZSTD_CCtx_reset(zc, ZSTD_reset_session_and_parameters));
        {
            size_t res;
-            ZSTD_registerExternalMatchFinder(zc, &externalMatchState, zstreamExternalMatchFinder);
+            ZSTD_registerSequenceProducer(zc, &sequenceProducerState, zstreamSequenceProducer);
            CHECK_Z(ZSTD_CCtx_setParameter(zc, ZSTD_c_nbWorkers, 1));
            res = ZSTD_compress2(zc, dstBuf, dstBufSize, CNBuffer, CNBufferSize);
            CHECK(!ZSTD_isError(res), "EMF: Should have raised an error!");