Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

11 files changed, 2020 insertions, 0 deletions

diff --git a/src/zstd/contrib/seekable_format/examples/.gitignore b/src/zstd/contrib/seekable_format/examples/.gitignore
new file mode 100644
index 000000000..0b83f5e11
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/examples/.gitignore
@@ -0,0 +1,5 @@
+seekable_compression
+seekable_decompression
+seekable_decompression_mem
+parallel_processing
+parallel_compression
diff --git a/src/zstd/contrib/seekable_format/examples/Makefile b/src/zstd/contrib/seekable_format/examples/Makefile
new file mode 100644
index 000000000..543780f75
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/examples/Makefile
@@ -0,0 +1,53 @@
+# ################################################################
+# Copyright (c) 2017-present, Facebook, Inc.
+# All rights reserved.
+#
+# This source code is licensed under both the BSD-style license (found in the
+# LICENSE file in the root directory of this source tree) and the GPLv2 (found
+# in the COPYING file in the root directory of this source tree).
+# ################################################################
+
+# This Makefile presumes libzstd is built, using `make` in / or /lib/
+
+ZSTDLIB_PATH = ../../../lib
+ZSTDLIB_NAME = libzstd.a
+ZSTDLIB = $(ZSTDLIB_PATH)/$(ZSTDLIB_NAME)
+
+CPPFLAGS += -I../ -I../../../lib -I../../../lib/common
+
+CFLAGS ?= -O3
+CFLAGS += -g
+
+SEEKABLE_OBJS = ../zstdseek_compress.c ../zstdseek_decompress.c $(ZSTDLIB)
+
+.PHONY: default all clean test
+
+default: all
+
+all: seekable_compression seekable_decompression seekable_decompression_mem \
+	parallel_processing
+
+$(ZSTDLIB):
+	make -C $(ZSTDLIB_PATH) $(ZSTDLIB_NAME)
+
+seekable_compression : seekable_compression.c $(SEEKABLE_OBJS)
+	$(CC) $(CPPFLAGS) $(CFLAGS) $^ $(LDFLAGS) -o $@
+
+seekable_decompression : seekable_decompression.c $(SEEKABLE_OBJS)
+	$(CC) $(CPPFLAGS) $(CFLAGS) $^ $(LDFLAGS) -o $@
+
+seekable_decompression_mem : seekable_decompression_mem.c $(SEEKABLE_OBJS)
+	$(CC) $(CPPFLAGS) $(CFLAGS) $^ $(LDFLAGS) -o $@
+
+parallel_processing : parallel_processing.c $(SEEKABLE_OBJS)
+	$(CC) $(CPPFLAGS) $(CFLAGS) $^ $(LDFLAGS) -o $@ -pthread
+
+parallel_compression : parallel_compression.c $(SEEKABLE_OBJS)
+	$(CC) $(CPPFLAGS) $(CFLAGS) $^ $(LDFLAGS) -o $@ -pthread
+
+clean:
+	@rm -f core *.o tmp* result* *.zst \
+		seekable_compression seekable_decompression \
+		seekable_decompression_mem \
+		parallel_processing parallel_compression
+	@echo Cleaning completed
diff --git a/src/zstd/contrib/seekable_format/examples/parallel_compression.c b/src/zstd/contrib/seekable_format/examples/parallel_compression.c
new file mode 100644
index 000000000..69644d2b3
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/examples/parallel_compression.c
@@ -0,0 +1,215 @@
+/*
+ * Copyright (c) 2017-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
+#include <stdlib.h>    // malloc, free, exit, atoi
+#include <stdio.h>     // fprintf, perror, feof, fopen, etc.
+#include <string.h>    // strlen, memset, strcat
+#define ZSTD_STATIC_LINKING_ONLY
+#include <zstd.h>      // presumes zstd library is installed
+#include <zstd_errors.h>
+#if defined(WIN32) || defined(_WIN32)
+#  include <windows.h>
+#  define SLEEP(x) Sleep(x)
+#else
+#  include <unistd.h>
+#  define SLEEP(x) usleep(x * 1000)
+#endif
+
+#define XXH_NAMESPACE ZSTD_
+#include "xxhash.h"
+
+#include "pool.h"      // use zstd thread pool for demo
+
+#include "zstd_seekable.h"
+
+static void* malloc_orDie(size_t size)
+{
+    void* const buff = malloc(size);
+    if (buff) return buff;
+    /* error */
+    perror("malloc:");
+    exit(1);
+}
+
+static FILE* fopen_orDie(const char *filename, const char *instruction)
+{
+    FILE* const inFile = fopen(filename, instruction);
+    if (inFile) return inFile;
+    /* error */
+    perror(filename);
+    exit(3);
+}
+
+static size_t fread_orDie(void* buffer, size_t sizeToRead, FILE* file)
+{
+    size_t const readSize = fread(buffer, 1, sizeToRead, file);
+    if (readSize == sizeToRead) return readSize;   /* good */
+    if (feof(file)) return readSize;   /* good, reached end of file */
+    /* error */
+    perror("fread");
+    exit(4);
+}
+
+static size_t fwrite_orDie(const void* buffer, size_t sizeToWrite, FILE* file)
+{
+    size_t const writtenSize = fwrite(buffer, 1, sizeToWrite, file);
+    if (writtenSize == sizeToWrite) return sizeToWrite;   /* good */
+    /* error */
+    perror("fwrite");
+    exit(5);
+}
+
+static size_t fclose_orDie(FILE* file)
+{
+    if (!fclose(file)) return 0;
+    /* error */
+    perror("fclose");
+    exit(6);
+}
+
+static void fseek_orDie(FILE* file, long int offset, int origin)
+{
+    if (!fseek(file, offset, origin)) {
+        if (!fflush(file)) return;
+    }
+    /* error */
+    perror("fseek");
+    exit(7);
+}
+
+static long int ftell_orDie(FILE* file)
+{
+    long int off = ftell(file);
+    if (off != -1) return off;
+    /* error */
+    perror("ftell");
+    exit(8);
+}
+
+struct job {
+    const void* src;
+    size_t srcSize;
+    void* dst;
+    size_t dstSize;
+
+    unsigned checksum;
+
+    int compressionLevel;
+    int done;
+};
+
+static void compressFrame(void* opaque)
+{
+    struct job* job = opaque;
+
+    job->checksum = XXH64(job->src, job->srcSize, 0);
+
+    size_t ret = ZSTD_compress(job->dst, job->dstSize, job->src, job->srcSize, job->compressionLevel);
+    if (ZSTD_isError(ret)) {
+        fprintf(stderr, "ZSTD_compress() error : %s \n", ZSTD_getErrorName(ret));
+        exit(20);
+    }
+
+    job->dstSize = ret;
+    job->done = 1;
+}
+
+static void compressFile_orDie(const char* fname, const char* outName, int cLevel, unsigned frameSize, int nbThreads)
+{
+    POOL_ctx* pool = POOL_create(nbThreads, nbThreads);
+    if (pool == NULL) { fprintf(stderr, "POOL_create() error \n"); exit(9); }
+
+    FILE* const fin  = fopen_orDie(fname, "rb");
+    FILE* const fout = fopen_orDie(outName, "wb");
+
+    if (ZSTD_compressBound(frameSize) > 0xFFFFFFFFU) { fprintf(stderr, "Frame size too large \n"); exit(10); }
+    unsigned dstSize = ZSTD_compressBound(frameSize);
+
+
+    fseek_orDie(fin, 0, SEEK_END);
+    long int length = ftell_orDie(fin);
+    fseek_orDie(fin, 0, SEEK_SET);
+
+    size_t numFrames = (length + frameSize - 1) / frameSize;
+
+    struct job* jobs = malloc_orDie(sizeof(struct job) * numFrames);
+
+    size_t i;
+    for(i = 0; i < numFrames; i++) {
+        void* in = malloc_orDie(frameSize);
+        void* out = malloc_orDie(dstSize);
+
+        size_t inSize = fread_orDie(in, frameSize, fin);
+
+        jobs[i].src = in;
+        jobs[i].srcSize = inSize;
+        jobs[i].dst = out;
+        jobs[i].dstSize = dstSize;
+        jobs[i].compressionLevel = cLevel;
+        jobs[i].done = 0;
+        POOL_add(pool, compressFrame, &jobs[i]);
+    }
+
+    ZSTD_frameLog* fl = ZSTD_seekable_createFrameLog(1);
+    if (fl == NULL) { fprintf(stderr, "ZSTD_seekable_createFrameLog() failed \n"); exit(11); }
+    for (i = 0; i < numFrames; i++) {
+        while (!jobs[i].done) SLEEP(5); /* wake up every 5 milliseconds to check */
+        fwrite_orDie(jobs[i].dst, jobs[i].dstSize, fout);
+        free((void*)jobs[i].src);
+        free(jobs[i].dst);
+
+        size_t ret = ZSTD_seekable_logFrame(fl, jobs[i].dstSize, jobs[i].srcSize, jobs[i].checksum);
+        if (ZSTD_isError(ret)) { fprintf(stderr, "ZSTD_seekable_logFrame() error : %s \n", ZSTD_getErrorName(ret)); }
+    }
+
+    {   unsigned char seekTableBuff[1024];
+        ZSTD_outBuffer out = {seekTableBuff, 1024, 0};
+        while (ZSTD_seekable_writeSeekTable(fl, &out) != 0) {
+            fwrite_orDie(seekTableBuff, out.pos, fout);
+            out.pos = 0;
+        }
+        fwrite_orDie(seekTableBuff, out.pos, fout);
+    }
+
+    ZSTD_seekable_freeFrameLog(fl);
+    free(jobs);
+    fclose_orDie(fout);
+    fclose_orDie(fin);
+}
+
+static const char* createOutFilename_orDie(const char* filename)
+{
+    size_t const inL = strlen(filename);
+    size_t const outL = inL + 5;
+    void* outSpace = malloc_orDie(outL);
+    memset(outSpace, 0, outL);
+    strcat(outSpace, filename);
+    strcat(outSpace, ".zst");
+    return (const char*)outSpace;
+}
+
+int main(int argc, const char** argv) {
+    const char* const exeName = argv[0];
+    if (argc!=4) {
+        printf("wrong arguments\n");
+        printf("usage:\n");
+        printf("%s FILE FRAME_SIZE NB_THREADS\n", exeName);
+        return 1;
+    }
+
+    {   const char* const inFileName = argv[1];
+        unsigned const frameSize = (unsigned)atoi(argv[2]);
+        int const nbThreads = atoi(argv[3]);
+
+        const char* const outFileName = createOutFilename_orDie(inFileName);
+        compressFile_orDie(inFileName, outFileName, 5, frameSize, nbThreads);
+    }
+
+    return 0;
+}
diff --git a/src/zstd/contrib/seekable_format/examples/parallel_processing.c b/src/zstd/contrib/seekable_format/examples/parallel_processing.c
new file mode 100644
index 000000000..36226b49f
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/examples/parallel_processing.c
@@ -0,0 +1,194 @@
+/*
+ * Copyright (c) 2017-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
+/*
+ * A simple demo that sums up all the bytes in the file in parallel using
+ * seekable decompression and the zstd thread pool
+ */
+
+#include <stdlib.h>    // malloc, exit
+#include <stdio.h>     // fprintf, perror, feof
+#include <string.h>    // strerror
+#include <errno.h>     // errno
+#define ZSTD_STATIC_LINKING_ONLY
+#include <zstd.h>      // presumes zstd library is installed
+#include <zstd_errors.h>
+#if defined(WIN32) || defined(_WIN32)
+#  include <windows.h>
+#  define SLEEP(x) Sleep(x)
+#else
+#  include <unistd.h>
+#  define SLEEP(x) usleep(x * 1000)
+#endif
+
+#include "pool.h"      // use zstd thread pool for demo
+
+#include "zstd_seekable.h"
+
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
+static void* malloc_orDie(size_t size)
+{
+    void* const buff = malloc(size);
+    if (buff) return buff;
+    /* error */
+    perror("malloc");
+    exit(1);
+}
+
+static void* realloc_orDie(void* ptr, size_t size)
+{
+    ptr = realloc(ptr, size);
+    if (ptr) return ptr;
+    /* error */
+    perror("realloc");
+    exit(1);
+}
+
+static FILE* fopen_orDie(const char *filename, const char *instruction)
+{
+    FILE* const inFile = fopen(filename, instruction);
+    if (inFile) return inFile;
+    /* error */
+    perror(filename);
+    exit(3);
+}
+
+static size_t fread_orDie(void* buffer, size_t sizeToRead, FILE* file)
+{
+    size_t const readSize = fread(buffer, 1, sizeToRead, file);
+    if (readSize == sizeToRead) return readSize;   /* good */
+    if (feof(file)) return readSize;   /* good, reached end of file */
+    /* error */
+    perror("fread");
+    exit(4);
+}
+
+static size_t fwrite_orDie(const void* buffer, size_t sizeToWrite, FILE* file)
+{
+    size_t const writtenSize = fwrite(buffer, 1, sizeToWrite, file);
+    if (writtenSize == sizeToWrite) return sizeToWrite;   /* good */
+    /* error */
+    perror("fwrite");
+    exit(5);
+}
+
+static size_t fclose_orDie(FILE* file)
+{
+    if (!fclose(file)) return 0;
+    /* error */
+    perror("fclose");
+    exit(6);
+}
+
+static void fseek_orDie(FILE* file, long int offset, int origin) {
+    if (!fseek(file, offset, origin)) {
+        if (!fflush(file)) return;
+    }
+    /* error */
+    perror("fseek");
+    exit(7);
+}
+
+struct sum_job {
+    const char* fname;
+    unsigned long long sum;
+    unsigned frameNb;
+    int done;
+};
+
+static void sumFrame(void* opaque)
+{
+    struct sum_job* job = (struct sum_job*)opaque;
+    job->done = 0;
+
+    FILE* const fin = fopen_orDie(job->fname, "rb");
+
+    ZSTD_seekable* const seekable = ZSTD_seekable_create();
+    if (seekable==NULL) { fprintf(stderr, "ZSTD_seekable_create() error \n"); exit(10); }
+
+    size_t const initResult = ZSTD_seekable_initFile(seekable, fin);
+    if (ZSTD_isError(initResult)) { fprintf(stderr, "ZSTD_seekable_init() error : %s \n", ZSTD_getErrorName(initResult)); exit(11); }
+
+    size_t const frameSize = ZSTD_seekable_getFrameDecompressedSize(seekable, job->frameNb);
+    unsigned char* data = malloc_orDie(frameSize);
+
+    size_t result = ZSTD_seekable_decompressFrame(seekable, data, frameSize, job->frameNb);
+    if (ZSTD_isError(result)) { fprintf(stderr, "ZSTD_seekable_decompressFrame() error : %s \n", ZSTD_getErrorName(result)); exit(12); }
+
+    unsigned long long sum = 0;
+    size_t i;
+    for (i = 0; i < frameSize; i++) {
+        sum += data[i];
+    }
+    job->sum = sum;
+    job->done = 1;
+
+    fclose(fin);
+    ZSTD_seekable_free(seekable);
+    free(data);
+}
+
+static void sumFile_orDie(const char* fname, int nbThreads)
+{
+    POOL_ctx* pool = POOL_create(nbThreads, nbThreads);
+    if (pool == NULL) { fprintf(stderr, "POOL_create() error \n"); exit(9); }
+
+    FILE* const fin = fopen_orDie(fname, "rb");
+
+    ZSTD_seekable* const seekable = ZSTD_seekable_create();
+    if (seekable==NULL) { fprintf(stderr, "ZSTD_seekable_create() error \n"); exit(10); }
+
+    size_t const initResult = ZSTD_seekable_initFile(seekable, fin);
+    if (ZSTD_isError(initResult)) { fprintf(stderr, "ZSTD_seekable_init() error : %s \n", ZSTD_getErrorName(initResult)); exit(11); }
+
+    unsigned const numFrames = ZSTD_seekable_getNumFrames(seekable);
+    struct sum_job* jobs = (struct sum_job*)malloc(numFrames * sizeof(struct sum_job));
+
+    unsigned fnb;
+    for (fnb = 0; fnb < numFrames; fnb++) {
+        jobs[fnb] = (struct sum_job){ fname, 0, fnb, 0 };
+        POOL_add(pool, sumFrame, &jobs[fnb]);
+    }
+
+    unsigned long long total = 0;
+
+    for (fnb = 0; fnb < numFrames; fnb++) {
+        while (!jobs[fnb].done) SLEEP(5); /* wake up every 5 milliseconds to check */
+        total += jobs[fnb].sum;
+    }
+
+    printf("Sum: %llu\n", total);
+
+    POOL_free(pool);
+    ZSTD_seekable_free(seekable);
+    fclose(fin);
+    free(jobs);
+}
+
+
+int main(int argc, const char** argv)
+{
+    const char* const exeName = argv[0];
+
+    if (argc!=3) {
+        fprintf(stderr, "wrong arguments\n");
+        fprintf(stderr, "usage:\n");
+        fprintf(stderr, "%s FILE NB_THREADS\n", exeName);
+        return 1;
+    }
+
+    {
+        const char* const inFilename = argv[1];
+        int const nbThreads = atoi(argv[2]);
+        sumFile_orDie(inFilename, nbThreads);
+    }
+
+    return 0;
+}
diff --git a/src/zstd/contrib/seekable_format/examples/seekable_compression.c b/src/zstd/contrib/seekable_format/examples/seekable_compression.c
new file mode 100644
index 000000000..9a331a895
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/examples/seekable_compression.c
@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2017-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
+#include <stdlib.h>    // malloc, free, exit, atoi
+#include <stdio.h>     // fprintf, perror, feof, fopen, etc.
+#include <string.h>    // strlen, memset, strcat
+#define ZSTD_STATIC_LINKING_ONLY
+#include <zstd.h>      // presumes zstd library is installed
+
+#include "zstd_seekable.h"
+
+static void* malloc_orDie(size_t size)
+{
+    void* const buff = malloc(size);
+    if (buff) return buff;
+    /* error */
+    perror("malloc:");
+    exit(1);
+}
+
+static FILE* fopen_orDie(const char *filename, const char *instruction)
+{
+    FILE* const inFile = fopen(filename, instruction);
+    if (inFile) return inFile;
+    /* error */
+    perror(filename);
+    exit(3);
+}
+
+static size_t fread_orDie(void* buffer, size_t sizeToRead, FILE* file)
+{
+    size_t const readSize = fread(buffer, 1, sizeToRead, file);
+    if (readSize == sizeToRead) return readSize;   /* good */
+    if (feof(file)) return readSize;   /* good, reached end of file */
+    /* error */
+    perror("fread");
+    exit(4);
+}
+
+static size_t fwrite_orDie(const void* buffer, size_t sizeToWrite, FILE* file)
+{
+    size_t const writtenSize = fwrite(buffer, 1, sizeToWrite, file);
+    if (writtenSize == sizeToWrite) return sizeToWrite;   /* good */
+    /* error */
+    perror("fwrite");
+    exit(5);
+}
+
+static size_t fclose_orDie(FILE* file)
+{
+    if (!fclose(file)) return 0;
+    /* error */
+    perror("fclose");
+    exit(6);
+}
+
+static void compressFile_orDie(const char* fname, const char* outName, int cLevel, unsigned frameSize)
+{
+    FILE* const fin  = fopen_orDie(fname, "rb");
+    FILE* const fout = fopen_orDie(outName, "wb");
+    size_t const buffInSize = ZSTD_CStreamInSize();    /* can always read one full block */
+    void*  const buffIn  = malloc_orDie(buffInSize);
+    size_t const buffOutSize = ZSTD_CStreamOutSize();  /* can always flush a full block */
+    void*  const buffOut = malloc_orDie(buffOutSize);
+
+    ZSTD_seekable_CStream* const cstream = ZSTD_seekable_createCStream();
+    if (cstream==NULL) { fprintf(stderr, "ZSTD_seekable_createCStream() error \n"); exit(10); }
+    size_t const initResult = ZSTD_seekable_initCStream(cstream, cLevel, 1, frameSize);
+    if (ZSTD_isError(initResult)) { fprintf(stderr, "ZSTD_seekable_initCStream() error : %s \n", ZSTD_getErrorName(initResult)); exit(11); }
+
+    size_t read, toRead = buffInSize;
+    while( (read = fread_orDie(buffIn, toRead, fin)) ) {
+        ZSTD_inBuffer input = { buffIn, read, 0 };
+        while (input.pos < input.size) {
+            ZSTD_outBuffer output = { buffOut, buffOutSize, 0 };
+            toRead = ZSTD_seekable_compressStream(cstream, &output , &input);   /* toRead is guaranteed to be <= ZSTD_CStreamInSize() */
+            if (ZSTD_isError(toRead)) { fprintf(stderr, "ZSTD_seekable_compressStream() error : %s \n", ZSTD_getErrorName(toRead)); exit(12); }
+            if (toRead > buffInSize) toRead = buffInSize;   /* Safely handle case when `buffInSize` is manually changed to a value < ZSTD_CStreamInSize()*/
+            fwrite_orDie(buffOut, output.pos, fout);
+        }
+    }
+
+    while (1) {
+        ZSTD_outBuffer output = { buffOut, buffOutSize, 0 };
+        size_t const remainingToFlush = ZSTD_seekable_endStream(cstream, &output);   /* close stream */
+        if (ZSTD_isError(remainingToFlush)) { fprintf(stderr, "ZSTD_seekable_endStream() error : %s \n", ZSTD_getErrorName(remainingToFlush)); exit(13); }
+        fwrite_orDie(buffOut, output.pos, fout);
+        if (!remainingToFlush) break;
+    }
+
+    ZSTD_seekable_freeCStream(cstream);
+    fclose_orDie(fout);
+    fclose_orDie(fin);
+    free(buffIn);
+    free(buffOut);
+}
+
+static char* createOutFilename_orDie(const char* filename)
+{
+    size_t const inL = strlen(filename);
+    size_t const outL = inL + 5;
+    void* outSpace = malloc_orDie(outL);
+    memset(outSpace, 0, outL);
+    strcat(outSpace, filename);
+    strcat(outSpace, ".zst");
+    return (char*)outSpace;
+}
+
+int main(int argc, const char** argv) {
+    const char* const exeName = argv[0];
+    if (argc!=3) {
+        printf("wrong arguments\n");
+        printf("usage:\n");
+        printf("%s FILE FRAME_SIZE\n", exeName);
+        return 1;
+    }
+
+    {   const char* const inFileName = argv[1];
+        unsigned const frameSize = (unsigned)atoi(argv[2]);
+
+        char* const outFileName = createOutFilename_orDie(inFileName);
+        compressFile_orDie(inFileName, outFileName, 5, frameSize);
+        free(outFileName);
+    }
+
+    return 0;
+}
diff --git a/src/zstd/contrib/seekable_format/examples/seekable_decompression.c b/src/zstd/contrib/seekable_format/examples/seekable_decompression.c
new file mode 100644
index 000000000..7050e0fa5
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/examples/seekable_decompression.c
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2017-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
+
+#include <stdlib.h>    // malloc, exit
+#include <stdio.h>     // fprintf, perror, feof
+#include <string.h>    // strerror
+#include <errno.h>     // errno
+#define ZSTD_STATIC_LINKING_ONLY
+#include <zstd.h>      // presumes zstd library is installed
+#include <zstd_errors.h>
+
+#include "zstd_seekable.h"
+
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
+static void* malloc_orDie(size_t size)
+{
+    void* const buff = malloc(size);
+    if (buff) return buff;
+    /* error */
+    perror("malloc");
+    exit(1);
+}
+
+static void* realloc_orDie(void* ptr, size_t size)
+{
+    ptr = realloc(ptr, size);
+    if (ptr) return ptr;
+    /* error */
+    perror("realloc");
+    exit(1);
+}
+
+static FILE* fopen_orDie(const char *filename, const char *instruction)
+{
+    FILE* const inFile = fopen(filename, instruction);
+    if (inFile) return inFile;
+    /* error */
+    perror(filename);
+    exit(3);
+}
+
+static size_t fread_orDie(void* buffer, size_t sizeToRead, FILE* file)
+{
+    size_t const readSize = fread(buffer, 1, sizeToRead, file);
+    if (readSize == sizeToRead) return readSize;   /* good */
+    if (feof(file)) return readSize;   /* good, reached end of file */
+    /* error */
+    perror("fread");
+    exit(4);
+}
+
+static size_t fwrite_orDie(const void* buffer, size_t sizeToWrite, FILE* file)
+{
+    size_t const writtenSize = fwrite(buffer, 1, sizeToWrite, file);
+    if (writtenSize == sizeToWrite) return sizeToWrite;   /* good */
+    /* error */
+    perror("fwrite");
+    exit(5);
+}
+
+static size_t fclose_orDie(FILE* file)
+{
+    if (!fclose(file)) return 0;
+    /* error */
+    perror("fclose");
+    exit(6);
+}
+
+static void fseek_orDie(FILE* file, long int offset, int origin) {
+    if (!fseek(file, offset, origin)) {
+        if (!fflush(file)) return;
+    }
+    /* error */
+    perror("fseek");
+    exit(7);
+}
+
+
+static void decompressFile_orDie(const char* fname, off_t startOffset, off_t endOffset)
+{
+    FILE* const fin  = fopen_orDie(fname, "rb");
+    FILE* const fout = stdout;
+    size_t const buffOutSize = ZSTD_DStreamOutSize();  /* Guarantee to successfully flush at least one complete compressed block in all circumstances. */
+    void*  const buffOut = malloc_orDie(buffOutSize);
+
+    ZSTD_seekable* const seekable = ZSTD_seekable_create();
+    if (seekable==NULL) { fprintf(stderr, "ZSTD_seekable_create() error \n"); exit(10); }
+
+    size_t const initResult = ZSTD_seekable_initFile(seekable, fin);
+    if (ZSTD_isError(initResult)) { fprintf(stderr, "ZSTD_seekable_init() error : %s \n", ZSTD_getErrorName(initResult)); exit(11); }
+
+    while (startOffset < endOffset) {
+        size_t const result = ZSTD_seekable_decompress(seekable, buffOut, MIN(endOffset - startOffset, buffOutSize), startOffset);
+
+        if (ZSTD_isError(result)) {
+            fprintf(stderr, "ZSTD_seekable_decompress() error : %s \n",
+                    ZSTD_getErrorName(result));
+            exit(12);
+        }
+        fwrite_orDie(buffOut, result, fout);
+        startOffset += result;
+    }
+
+    ZSTD_seekable_free(seekable);
+    fclose_orDie(fin);
+    fclose_orDie(fout);
+    free(buffOut);
+}
+
+
+int main(int argc, const char** argv)
+{
+    const char* const exeName = argv[0];
+
+    if (argc!=4) {
+        fprintf(stderr, "wrong arguments\n");
+        fprintf(stderr, "usage:\n");
+        fprintf(stderr, "%s FILE START END\n", exeName);
+        return 1;
+    }
+
+    {
+        const char* const inFilename = argv[1];
+        off_t const startOffset = atoll(argv[2]);
+        off_t const endOffset = atoll(argv[3]);
+        decompressFile_orDie(inFilename, startOffset, endOffset);
+    }
+
+    return 0;
+}
diff --git a/src/zstd/contrib/seekable_format/examples/seekable_decompression_mem.c b/src/zstd/contrib/seekable_format/examples/seekable_decompression_mem.c
new file mode 100644
index 000000000..c36d2221f
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/examples/seekable_decompression_mem.c
@@ -0,0 +1,144 @@
+/*
+ * Copyright (c) 2017-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
+
+#include <stdlib.h>    // malloc, exit
+#include <stdio.h>     // fprintf, perror, feof
+#include <string.h>    // strerror
+#include <errno.h>     // errno
+#define ZSTD_STATIC_LINKING_ONLY
+#include <zstd.h>      // presumes zstd library is installed
+#include <zstd_errors.h>
+
+#include "zstd_seekable.h"
+
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
+#define MAX_FILE_SIZE (8 * 1024 * 1024)
+
+static void* malloc_orDie(size_t size)
+{
+    void* const buff = malloc(size);
+    if (buff) return buff;
+    /* error */
+    perror("malloc");
+    exit(1);
+}
+
+static void* realloc_orDie(void* ptr, size_t size)
+{
+    ptr = realloc(ptr, size);
+    if (ptr) return ptr;
+    /* error */
+    perror("realloc");
+    exit(1);
+}
+
+static FILE* fopen_orDie(const char *filename, const char *instruction)
+{
+    FILE* const inFile = fopen(filename, instruction);
+    if (inFile) return inFile;
+    /* error */
+    perror(filename);
+    exit(3);
+}
+
+static size_t fread_orDie(void* buffer, size_t sizeToRead, FILE* file)
+{
+    size_t const readSize = fread(buffer, 1, sizeToRead, file);
+    if (readSize == sizeToRead) return readSize;   /* good */
+    if (feof(file)) return readSize;   /* good, reached end of file */
+    /* error */
+    perror("fread");
+    exit(4);
+}
+
+static size_t fwrite_orDie(const void* buffer, size_t sizeToWrite, FILE* file)
+{
+    size_t const writtenSize = fwrite(buffer, 1, sizeToWrite, file);
+    if (writtenSize == sizeToWrite) return sizeToWrite;   /* good */
+    /* error */
+    perror("fwrite");
+    exit(5);
+}
+
+static size_t fclose_orDie(FILE* file)
+{
+    if (!fclose(file)) return 0;
+    /* error */
+    perror("fclose");
+    exit(6);
+}
+
+static void fseek_orDie(FILE* file, long int offset, int origin) {
+    if (!fseek(file, offset, origin)) {
+        if (!fflush(file)) return;
+    }
+    /* error */
+    perror("fseek");
+    exit(7);
+}
+
+
+static void decompressFile_orDie(const char* fname, off_t startOffset, off_t endOffset)
+{
+    FILE* const fin  = fopen_orDie(fname, "rb");
+    FILE* const fout = stdout;
+    // Just for demo purposes, assume file is <= MAX_FILE_SIZE
+    void*  const buffIn = malloc_orDie(MAX_FILE_SIZE);
+    size_t const inSize = fread_orDie(buffIn, MAX_FILE_SIZE, fin);
+    size_t const buffOutSize = ZSTD_DStreamOutSize();  /* Guarantee to successfully flush at least one complete compressed block in all circumstances. */
+    void*  const buffOut = malloc_orDie(buffOutSize);
+
+    ZSTD_seekable* const seekable = ZSTD_seekable_create();
+    if (seekable==NULL) { fprintf(stderr, "ZSTD_seekable_create() error \n"); exit(10); }
+
+    size_t const initResult = ZSTD_seekable_initBuff(seekable, buffIn, inSize);
+    if (ZSTD_isError(initResult)) { fprintf(stderr, "ZSTD_seekable_init() error : %s \n", ZSTD_getErrorName(initResult)); exit(11); }
+
+    while (startOffset < endOffset) {
+        size_t const result = ZSTD_seekable_decompress(seekable, buffOut, MIN(endOffset - startOffset, buffOutSize), startOffset);
+
+        if (ZSTD_isError(result)) {
+            fprintf(stderr, "ZSTD_seekable_decompress() error : %s \n",
+                    ZSTD_getErrorName(result));
+            exit(12);
+        }
+        fwrite_orDie(buffOut, result, fout);
+        startOffset += result;
+    }
+
+    ZSTD_seekable_free(seekable);
+    fclose_orDie(fin);
+    fclose_orDie(fout);
+    free(buffIn);
+    free(buffOut);
+}
+
+
+int main(int argc, const char** argv)
+{
+    const char* const exeName = argv[0];
+
+    if (argc!=4) {
+        fprintf(stderr, "wrong arguments\n");
+        fprintf(stderr, "usage:\n");
+        fprintf(stderr, "%s FILE START END\n", exeName);
+        return 1;
+    }
+
+    {
+        const char* const inFilename = argv[1];
+        off_t const startOffset = atoll(argv[2]);
+        off_t const endOffset = atoll(argv[3]);
+        decompressFile_orDie(inFilename, startOffset, endOffset);
+    }
+
+    return 0;
+}
diff --git a/src/zstd/contrib/seekable_format/zstd_seekable.h b/src/zstd/contrib/seekable_format/zstd_seekable.h
new file mode 100644
index 000000000..7ffd1ba0a
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/zstd_seekable.h
@@ -0,0 +1,186 @@
+#ifndef SEEKABLE_H
+#define SEEKABLE_H
+
+#if defined (__cplusplus)
+extern "C" {
+#endif
+
+#include <stdio.h>
+#include "zstd.h"   /* ZSTDLIB_API */
+
+
+#define ZSTD_seekTableFooterSize 9
+
+#define ZSTD_SEEKABLE_MAGICNUMBER 0x8F92EAB1
+
+#define ZSTD_SEEKABLE_MAXFRAMES 0x8000000U
+
+/* Limit the maximum size to avoid any potential issues storing the compressed size */
+#define ZSTD_SEEKABLE_MAX_FRAME_DECOMPRESSED_SIZE 0x80000000U
+
+/*-****************************************************************************
+*  Seekable Format
+*
+*  The seekable format splits the compressed data into a series of "frames",
+*  each compressed individually so that decompression of a section in the
+*  middle of an archive only requires zstd to decompress at most a frame's
+*  worth of extra data, instead of the entire archive.
+******************************************************************************/
+
+typedef struct ZSTD_seekable_CStream_s ZSTD_seekable_CStream;
+typedef struct ZSTD_seekable_s ZSTD_seekable;
+
+/*-****************************************************************************
+*  Seekable compression - HowTo
+*  A ZSTD_seekable_CStream object is required to tracking streaming operation.
+*  Use ZSTD_seekable_createCStream() and ZSTD_seekable_freeCStream() to create/
+*  release resources.
+*
+*  Streaming objects are reusable to avoid allocation and deallocation,
+*  to start a new compression operation call ZSTD_seekable_initCStream() on the
+*  compressor.
+*
+*  Data streamed to the seekable compressor will automatically be split into
+*  frames of size `maxFrameSize` (provided in ZSTD_seekable_initCStream()),
+*  or if none is provided, will be cut off whenever ZSTD_seekable_endFrame() is
+*  called or when the default maximum frame size (2GB) is reached.
+*
+*  Use ZSTD_seekable_initCStream() to initialize a ZSTD_seekable_CStream object
+*  for a new compression operation.
+*  `maxFrameSize` indicates the size at which to automatically start a new
+*  seekable frame.  `maxFrameSize == 0` implies the default maximum size.
+*  `checksumFlag` indicates whether or not the seek table should include frame
+*  checksums on the uncompressed data for verification.
+*  @return : a size hint for input to provide for compression, or an error code
+*            checkable with ZSTD_isError()
+*
+*  Use ZSTD_seekable_compressStream() repetitively to consume input stream.
+*  The function will automatically update both `pos` fields.
+*  Note that it may not consume the entire input, in which case `pos < size`,
+*  and it's up to the caller to present again remaining data.
+*  @return : a size hint, preferred nb of bytes to use as input for next
+*            function call or an error code, which can be tested using
+*            ZSTD_isError().
+*            Note 1 : it's just a hint, to help latency a little, any other
+*                     value will work fine.
+*
+*  At any time, call ZSTD_seekable_endFrame() to end the current frame and
+*  start a new one.
+*
+*  ZSTD_seekable_endStream() will end the current frame, and then write the seek
+*  table so that decompressors can efficiently find compressed frames.
+*  ZSTD_seekable_endStream() may return a number > 0 if it was unable to flush
+*  all the necessary data to `output`.  In this case, it should be called again
+*  until all remaining data is flushed out and 0 is returned.
+******************************************************************************/
+
+/*===== Seekable compressor management =====*/
+ZSTDLIB_API ZSTD_seekable_CStream* ZSTD_seekable_createCStream(void);
+ZSTDLIB_API size_t ZSTD_seekable_freeCStream(ZSTD_seekable_CStream* zcs);
+
+/*===== Seekable compression functions =====*/
+ZSTDLIB_API size_t ZSTD_seekable_initCStream(ZSTD_seekable_CStream* zcs, int compressionLevel, int checksumFlag, unsigned maxFrameSize);
+ZSTDLIB_API size_t ZSTD_seekable_compressStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
+ZSTDLIB_API size_t ZSTD_seekable_endFrame(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output);
+ZSTDLIB_API size_t ZSTD_seekable_endStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output);
+
+/*= Raw seek table API
+ *  These functions allow for the seek table to be constructed directly.
+ *  This table can then be appended to a file of concatenated frames.
+ *  This allows the frames to be compressed independently, even in parallel,
+ *  and compiled together afterward into a seekable archive.
+ *
+ *  Use ZSTD_seekable_createFrameLog() to allocate and initialize a tracking
+ *  structure.
+ *
+ *  Call ZSTD_seekable_logFrame() once for each frame in the archive.
+ *  checksum is optional, and will not be used if checksumFlag was 0 when the
+ *  frame log was created.  If present, it should be the least significant 32
+ *  bits of the XXH64 hash of the uncompressed data.
+ *
+ *  Call ZSTD_seekable_writeSeekTable to serialize the data into a seek table.
+ *  If the entire table was written, the return value will be 0.  Otherwise,
+ *  it will be equal to the number of bytes left to write. */
+typedef struct ZSTD_frameLog_s ZSTD_frameLog;
+ZSTDLIB_API ZSTD_frameLog* ZSTD_seekable_createFrameLog(int checksumFlag);
+ZSTDLIB_API size_t ZSTD_seekable_freeFrameLog(ZSTD_frameLog* fl);
+ZSTDLIB_API size_t ZSTD_seekable_logFrame(ZSTD_frameLog* fl, unsigned compressedSize, unsigned decompressedSize, unsigned checksum);
+ZSTDLIB_API size_t ZSTD_seekable_writeSeekTable(ZSTD_frameLog* fl, ZSTD_outBuffer* output);
+
+/*-****************************************************************************
+*  Seekable decompression - HowTo
+*  A ZSTD_seekable object is required to tracking the seekTable.
+*
+*  Call ZSTD_seekable_init* to initialize a ZSTD_seekable object with the
+*  the seek table provided in the input.
+*  There are three modes for ZSTD_seekable_init:
+*    - ZSTD_seekable_initBuff() : An in-memory API.  The data contained in
+*      `src` should be the entire seekable file, including the seek table.
+*      `src` should be kept alive and unmodified until the ZSTD_seekable object
+*      is freed or reset.
+*    - ZSTD_seekable_initFile() : A simplified file API using stdio.  fread and
+*      fseek will be used to access the required data for building the seek
+*      table and doing decompression operations.  `src` should not be closed
+*      or modified until the ZSTD_seekable object is freed or reset.
+*    - ZSTD_seekable_initAdvanced() : A general API allowing the client to
+*      provide its own read and seek callbacks.
+*        + ZSTD_seekable_read() : read exactly `n` bytes into `buffer`.
+*                                 Premature EOF should be treated as an error.
+*        + ZSTD_seekable_seek() : seek the read head to `offset` from `origin`,
+*                                 where origin is either SEEK_SET (beginning of
+*                                 file), or SEEK_END (end of file).
+*  Both functions should return a non-negative value in case of success, and a
+*  negative value in case of failure.  If implementing using this API and
+*  stdio, be careful with files larger than 4GB and fseek.  All of these
+*  functions return an error code checkable with ZSTD_isError().
+*
+*  Call ZSTD_seekable_decompress to decompress `dstSize` bytes at decompressed
+*  offset `offset`.  ZSTD_seekable_decompress may have to decompress the entire
+*  prefix of the frame before the desired data if it has not already processed
+*  this section. If ZSTD_seekable_decompress is called multiple times for a
+*  consecutive range of data, it will efficiently retain the decompressor object
+*  and avoid redecompressing frame prefixes.  The return value is the number of
+*  bytes decompressed, or an error code checkable with ZSTD_isError().
+*
+*  The seek table access functions can be used to obtain the data contained
+*  in the seek table.  If frameIndex is larger than the value returned by
+*  ZSTD_seekable_getNumFrames(), they will return error codes checkable with
+*  ZSTD_isError().  Note that since the offset access functions return
+*  unsigned long long instead of size_t, in this case they will instead return
+*  the value ZSTD_SEEKABLE_FRAMEINDEX_TOOLARGE.
+******************************************************************************/
+
+/*===== Seekable decompressor management =====*/
+ZSTDLIB_API ZSTD_seekable* ZSTD_seekable_create(void);
+ZSTDLIB_API size_t ZSTD_seekable_free(ZSTD_seekable* zs);
+
+/*===== Seekable decompression functions =====*/
+ZSTDLIB_API size_t ZSTD_seekable_initBuff(ZSTD_seekable* zs, const void* src, size_t srcSize);
+ZSTDLIB_API size_t ZSTD_seekable_initFile(ZSTD_seekable* zs, FILE* src);
+ZSTDLIB_API size_t ZSTD_seekable_decompress(ZSTD_seekable* zs, void* dst, size_t dstSize, unsigned long long offset);
+ZSTDLIB_API size_t ZSTD_seekable_decompressFrame(ZSTD_seekable* zs, void* dst, size_t dstSize, unsigned frameIndex);
+
+#define ZSTD_SEEKABLE_FRAMEINDEX_TOOLARGE (0ULL-2)
+/*===== Seek Table access functions =====*/
+ZSTDLIB_API unsigned ZSTD_seekable_getNumFrames(ZSTD_seekable* const zs);
+ZSTDLIB_API unsigned long long ZSTD_seekable_getFrameCompressedOffset(ZSTD_seekable* const zs, unsigned frameIndex);
+ZSTDLIB_API unsigned long long ZSTD_seekable_getFrameDecompressedOffset(ZSTD_seekable* const zs, unsigned frameIndex);
+ZSTDLIB_API size_t ZSTD_seekable_getFrameCompressedSize(ZSTD_seekable* const zs, unsigned frameIndex);
+ZSTDLIB_API size_t ZSTD_seekable_getFrameDecompressedSize(ZSTD_seekable* const zs, unsigned frameIndex);
+ZSTDLIB_API unsigned ZSTD_seekable_offsetToFrameIndex(ZSTD_seekable* const zs, unsigned long long offset);
+
+/*===== Seekable advanced I/O API =====*/
+typedef int(ZSTD_seekable_read)(void* opaque, void* buffer, size_t n);
+typedef int(ZSTD_seekable_seek)(void* opaque, long long offset, int origin);
+typedef struct {
+    void* opaque;
+    ZSTD_seekable_read* read;
+    ZSTD_seekable_seek* seek;
+} ZSTD_seekable_customFile;
+ZSTDLIB_API size_t ZSTD_seekable_initAdvanced(ZSTD_seekable* zs, ZSTD_seekable_customFile src);
+
+#if defined (__cplusplus)
+}
+#endif
+
+#endif
diff --git a/src/zstd/contrib/seekable_format/zstd_seekable_compression_format.md b/src/zstd/contrib/seekable_format/zstd_seekable_compression_format.md
new file mode 100644
index 000000000..bf3080f7b
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/zstd_seekable_compression_format.md
@@ -0,0 +1,116 @@
+# Zstandard Seekable Format
+
+### Notices
+
+Copyright (c) 2017-present Facebook, Inc.
+
+Permission is granted to copy and distribute this document
+for any purpose and without charge,
+including translations into other languages
+and incorporation into compilations,
+provided that the copyright notice and this notice are preserved,
+and that any substantive changes or deletions from the original
+are clearly marked.
+Distribution of this document is unlimited.
+
+### Version
+0.1.0 (11/04/17)
+
+## Introduction
+This document defines a format for compressed data to be stored so that subranges of the data can be efficiently decompressed without requiring the entire document to be decompressed.
+This is done by splitting up the input data into frames,
+each of which are compressed independently,
+and so can be decompressed independently.
+Decompression then takes advantage of a provided 'seek table', which allows the decompressor to immediately jump to the desired data.  This is done in a way that is compatible with the original Zstandard format by placing the seek table in a Zstandard skippable frame.
+
+### Overall conventions
+In this document:
+- square brackets i.e. `[` and `]` are used to indicate optional fields or parameters.
+- the naming convention for identifiers is `Mixed_Case_With_Underscores`
+- All numeric fields are little-endian unless specified otherwise
+
+## Format
+
+The format consists of a number of frames (Zstandard compressed frames and skippable frames), followed by a final skippable frame at the end containing the seek table.
+
+### Seek Table Format
+The structure of the seek table frame is as follows:
+
+|`Skippable_Magic_Number`|`Frame_Size`|`[Seek_Table_Entries]`|`Seek_Table_Footer`|
+|------------------------|------------|----------------------|-------------------|
+| 4 bytes                | 4 bytes    | 8-12 bytes each      | 9 bytes           |
+
+__`Skippable_Magic_Number`__
+
+Value : 0x184D2A5E.
+This is for compatibility with [Zstandard skippable frames].
+Since it is legal for other Zstandard skippable frames to use the same
+magic number, it is not recommended for a decoder to recognize frames
+solely on this.
+
+__`Frame_Size`__
+
+The total size of the skippable frame, not including the `Skippable_Magic_Number` or `Frame_Size`.
+This is for compatibility with [Zstandard skippable frames].
+
+[Zstandard skippable frames]: https://github.com/facebook/zstd/blob/master/doc/zstd_compression_format.md#skippable-frames
+
+#### `Seek_Table_Footer`
+The seek table footer format is as follows:
+
+|`Number_Of_Frames`|`Seek_Table_Descriptor`|`Seekable_Magic_Number`|
+|------------------|-----------------------|-----------------------|
+| 4 bytes          | 1 byte                | 4 bytes               |
+
+__`Seekable_Magic_Number`__
+
+Value : 0x8F92EAB1.
+This value must be the last bytes present in the compressed file so that decoders
+can efficiently find it and determine if there is an actual seek table present.
+
+__`Number_Of_Frames`__
+
+The number of stored frames in the data.
+
+__`Seek_Table_Descriptor`__
+
+A bitfield describing the format of the seek table.
+
+| Bit number | Field name                |
+| ---------- | ----------                |
+| 7          | `Checksum_Flag`           |
+| 6-2        | `Reserved_Bits`           |
+| 1-0        | `Unused_Bits`             |
+
+While only `Checksum_Flag` currently exists, there are 7 other bits in this field that can be used for future changes to the format,
+for example the addition of inline dictionaries.
+
+__`Checksum_Flag`__
+
+If the checksum flag is set, each of the seek table entries contains a 4 byte checksum of the uncompressed data contained in its frame.
+
+`Reserved_Bits` are not currently used but may be used in the future for breaking changes, so a compliant decoder should ensure they are set to 0.  `Unused_Bits` may be used in the future for non-breaking changes, so a compliant decoder should not interpret these bits.
+
+#### __`Seek_Table_Entries`__
+
+`Seek_Table_Entries` consists of `Number_Of_Frames` (one for each frame in the data, not including the seek table frame) entries of the following form, in sequence:
+
+|`Compressed_Size`|`Decompressed_Size`|`[Checksum]`|
+|-----------------|-------------------|------------|
+| 4 bytes         | 4 bytes           | 4 bytes    |
+
+__`Compressed_Size`__
+
+The compressed size of the frame.
+The cumulative sum of the `Compressed_Size` fields of frames `0` to `i` gives the offset in the compressed file of frame `i+1`.
+
+__`Decompressed_Size`__
+
+The size of the decompressed data contained in the frame.  For skippable or otherwise empty frames, this value is 0.
+
+__`Checksum`__
+
+Only present if `Checksum_Flag` is set in the `Seek_Table_Descriptor`.  Value : the least significant 32 bits of the XXH64 digest of the uncompressed data, stored in little-endian format.
+
+## Version Changes
+- 0.1.0: initial version
diff --git a/src/zstd/contrib/seekable_format/zstdseek_compress.c b/src/zstd/contrib/seekable_format/zstdseek_compress.c
new file mode 100644
index 000000000..5a75714fa
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/zstdseek_compress.c
@@ -0,0 +1,369 @@
+/*
+ * Copyright (c) 2017-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
+#include <stdlib.h>     /* malloc, free */
+#include <limits.h>     /* UINT_MAX */
+#include <assert.h>
+
+#define XXH_STATIC_LINKING_ONLY
+#define XXH_NAMESPACE ZSTD_
+#include "xxhash.h"
+
+#define ZSTD_STATIC_LINKING_ONLY
+#include "zstd.h"
+#include "zstd_errors.h"
+#include "mem.h"
+#include "zstd_seekable.h"
+
+#define CHECK_Z(f) { size_t const ret = (f); if (ret != 0) return ret; }
+
+#undef ERROR
+#define ERROR(name) ((size_t)-ZSTD_error_##name)
+
+#undef MIN
+#undef MAX
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+
+typedef struct {
+    U32 cSize;
+    U32 dSize;
+    U32 checksum;
+} framelogEntry_t;
+
+struct ZSTD_frameLog_s {
+    framelogEntry_t* entries;
+    U32 size;
+    U32 capacity;
+
+    int checksumFlag;
+
+    /* for use when streaming out the seek table */
+    U32 seekTablePos;
+    U32 seekTableIndex;
+} framelog_t;
+
+struct ZSTD_seekable_CStream_s {
+    ZSTD_CStream* cstream;
+    ZSTD_frameLog framelog;
+
+    U32 frameCSize;
+    U32 frameDSize;
+
+    XXH64_state_t xxhState;
+
+    U32 maxFrameSize;
+
+    int writingSeekTable;
+};
+
+size_t ZSTD_seekable_frameLog_allocVec(ZSTD_frameLog* fl)
+{
+    /* allocate some initial space */
+    size_t const FRAMELOG_STARTING_CAPACITY = 16;
+    fl->entries = (framelogEntry_t*)malloc(
+            sizeof(framelogEntry_t) * FRAMELOG_STARTING_CAPACITY);
+    if (fl->entries == NULL) return ERROR(memory_allocation);
+    fl->capacity = FRAMELOG_STARTING_CAPACITY;
+
+    return 0;
+}
+
+size_t ZSTD_seekable_frameLog_freeVec(ZSTD_frameLog* fl)
+{
+    if (fl != NULL) free(fl->entries);
+    return 0;
+}
+
+ZSTD_frameLog* ZSTD_seekable_createFrameLog(int checksumFlag)
+{
+    ZSTD_frameLog* fl = malloc(sizeof(ZSTD_frameLog));
+    if (fl == NULL) return NULL;
+
+    if (ZSTD_isError(ZSTD_seekable_frameLog_allocVec(fl))) {
+        free(fl);
+        return NULL;
+    }
+
+    fl->checksumFlag = checksumFlag;
+    fl->seekTablePos = 0;
+    fl->seekTableIndex = 0;
+    fl->size = 0;
+
+    return fl;
+}
+
+size_t ZSTD_seekable_freeFrameLog(ZSTD_frameLog* fl)
+{
+    ZSTD_seekable_frameLog_freeVec(fl);
+    free(fl);
+    return 0;
+}
+
+ZSTD_seekable_CStream* ZSTD_seekable_createCStream()
+{
+    ZSTD_seekable_CStream* zcs = malloc(sizeof(ZSTD_seekable_CStream));
+
+    if (zcs == NULL) return NULL;
+
+    memset(zcs, 0, sizeof(*zcs));
+
+    zcs->cstream = ZSTD_createCStream();
+    if (zcs->cstream == NULL) goto failed1;
+
+    if (ZSTD_isError(ZSTD_seekable_frameLog_allocVec(&zcs->framelog))) goto failed2;
+
+    return zcs;
+
+failed2:
+    ZSTD_freeCStream(zcs->cstream);
+failed1:
+    free(zcs);
+    return NULL;
+}
+
+size_t ZSTD_seekable_freeCStream(ZSTD_seekable_CStream* zcs)
+{
+    if (zcs == NULL) return 0; /* support free on null */
+    ZSTD_freeCStream(zcs->cstream);
+    ZSTD_seekable_frameLog_freeVec(&zcs->framelog);
+    free(zcs);
+
+    return 0;
+}
+
+size_t ZSTD_seekable_initCStream(ZSTD_seekable_CStream* zcs,
+                                 int compressionLevel,
+                                 int checksumFlag,
+                                 unsigned maxFrameSize)
+{
+    zcs->framelog.size = 0;
+    zcs->frameCSize = 0;
+    zcs->frameDSize = 0;
+
+    /* make sure maxFrameSize has a reasonable value */
+    if (maxFrameSize > ZSTD_SEEKABLE_MAX_FRAME_DECOMPRESSED_SIZE) {
+        return ERROR(frameParameter_unsupported);
+    }
+
+    zcs->maxFrameSize = maxFrameSize
+                                ? maxFrameSize
+                                : ZSTD_SEEKABLE_MAX_FRAME_DECOMPRESSED_SIZE;
+
+    zcs->framelog.checksumFlag = checksumFlag;
+    if (zcs->framelog.checksumFlag) {
+        XXH64_reset(&zcs->xxhState, 0);
+    }
+
+    zcs->framelog.seekTablePos = 0;
+    zcs->framelog.seekTableIndex = 0;
+    zcs->writingSeekTable = 0;
+
+    return ZSTD_initCStream(zcs->cstream, compressionLevel);
+}
+
+size_t ZSTD_seekable_logFrame(ZSTD_frameLog* fl,
+                              unsigned compressedSize,
+                              unsigned decompressedSize,
+                              unsigned checksum)
+{
+    if (fl->size == ZSTD_SEEKABLE_MAXFRAMES)
+        return ERROR(frameIndex_tooLarge);
+
+    /* grow the buffer if required */
+    if (fl->size == fl->capacity) {
+        /* exponential size increase for constant amortized runtime */
+        size_t const newCapacity = fl->capacity * 2;
+        framelogEntry_t* const newEntries = realloc(fl->entries,
+                sizeof(framelogEntry_t) * newCapacity);
+
+        if (newEntries == NULL) return ERROR(memory_allocation);
+
+        fl->entries = newEntries;
+        assert(newCapacity <= UINT_MAX);
+        fl->capacity = (U32)newCapacity;
+    }
+
+    fl->entries[fl->size] = (framelogEntry_t){
+            compressedSize, decompressedSize, checksum
+    };
+    fl->size++;
+
+    return 0;
+}
+
+size_t ZSTD_seekable_endFrame(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output)
+{
+    size_t const prevOutPos = output->pos;
+    /* end the frame */
+    size_t ret = ZSTD_endStream(zcs->cstream, output);
+
+    zcs->frameCSize += output->pos - prevOutPos;
+
+    /* need to flush before doing the rest */
+    if (ret) return ret;
+
+    /* frame done */
+
+    /* store the frame data for later */
+    ret = ZSTD_seekable_logFrame(
+            &zcs->framelog, zcs->frameCSize, zcs->frameDSize,
+            zcs->framelog.checksumFlag
+                    ? XXH64_digest(&zcs->xxhState) & 0xFFFFFFFFU
+                    : 0);
+    if (ret) return ret;
+
+    /* reset for the next frame */
+    zcs->frameCSize = 0;
+    zcs->frameDSize = 0;
+
+    ZSTD_resetCStream(zcs->cstream, 0);
+    if (zcs->framelog.checksumFlag)
+        XXH64_reset(&zcs->xxhState, 0);
+
+    return 0;
+}
+
+size_t ZSTD_seekable_compressStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input)
+{
+    const BYTE* const inBase = (const BYTE*) input->src + input->pos;
+    size_t inLen = input->size - input->pos;
+
+    inLen = MIN(inLen, (size_t)(zcs->maxFrameSize - zcs->frameDSize));
+
+    /* if we haven't finished flushing the last frame, don't start writing a new one */
+    if (inLen > 0) {
+        ZSTD_inBuffer inTmp = { inBase, inLen, 0 };
+        size_t const prevOutPos = output->pos;
+
+        size_t const ret = ZSTD_compressStream(zcs->cstream, output, &inTmp);
+
+        if (zcs->framelog.checksumFlag) {
+            XXH64_update(&zcs->xxhState, inBase, inTmp.pos);
+        }
+
+        zcs->frameCSize += output->pos - prevOutPos;
+        zcs->frameDSize += inTmp.pos;
+
+        input->pos += inTmp.pos;
+
+        if (ZSTD_isError(ret)) return ret;
+    }
+
+    if (zcs->maxFrameSize == zcs->frameDSize) {
+        /* log the frame and start over */
+        size_t const ret = ZSTD_seekable_endFrame(zcs, output);
+        if (ZSTD_isError(ret)) return ret;
+
+        /* get the client ready for the next frame */
+        return (size_t)zcs->maxFrameSize;
+    }
+
+    return (size_t)(zcs->maxFrameSize - zcs->frameDSize);
+}
+
+static inline size_t ZSTD_seekable_seekTableSize(const ZSTD_frameLog* fl)
+{
+    size_t const sizePerFrame = 8 + (fl->checksumFlag?4:0);
+    size_t const seekTableLen = ZSTD_SKIPPABLEHEADERSIZE +
+                                sizePerFrame * fl->size +
+                                ZSTD_seekTableFooterSize;
+
+    return seekTableLen;
+}
+
+static inline size_t ZSTD_stwrite32(ZSTD_frameLog* fl,
+                                    ZSTD_outBuffer* output, U32 const value,
+                                    U32 const offset)
+{
+    if (fl->seekTablePos < offset + 4) {
+        BYTE tmp[4]; /* so that we can work with buffers too small to write a whole word to */
+        size_t const lenWrite =
+                MIN(output->size - output->pos, offset + 4 - fl->seekTablePos);
+        MEM_writeLE32(tmp, value);
+        memcpy((BYTE*)output->dst + output->pos,
+               tmp + (fl->seekTablePos - offset), lenWrite);
+        output->pos += lenWrite;
+        fl->seekTablePos += lenWrite;
+
+        if (lenWrite < 4) return ZSTD_seekable_seekTableSize(fl) - fl->seekTablePos;
+    }
+    return 0;
+}
+
+size_t ZSTD_seekable_writeSeekTable(ZSTD_frameLog* fl, ZSTD_outBuffer* output)
+{
+    /* seekTableIndex: the current index in the table and
+     * seekTableSize: the amount of the table written so far
+     *
+     * This function is written this way so that if it has to return early
+     * because of a small buffer, it can keep going where it left off.
+     */
+
+    size_t const sizePerFrame = 8 + (fl->checksumFlag?4:0);
+    size_t const seekTableLen = ZSTD_seekable_seekTableSize(fl);
+
+    CHECK_Z(ZSTD_stwrite32(fl, output, ZSTD_MAGIC_SKIPPABLE_START | 0xE, 0));
+    assert(seekTableLen <= (size_t)UINT_MAX);
+    CHECK_Z(ZSTD_stwrite32(fl, output, (U32)seekTableLen - ZSTD_SKIPPABLEHEADERSIZE, 4));
+
+    while (fl->seekTableIndex < fl->size) {
+        unsigned long long const start = ZSTD_SKIPPABLEHEADERSIZE + sizePerFrame * fl->seekTableIndex;
+        assert(start + 8 <= UINT_MAX);
+        CHECK_Z(ZSTD_stwrite32(fl, output,
+                               fl->entries[fl->seekTableIndex].cSize,
+                               (U32)start + 0));
+
+        CHECK_Z(ZSTD_stwrite32(fl, output,
+                               fl->entries[fl->seekTableIndex].dSize,
+                               (U32)start + 4));
+
+        if (fl->checksumFlag) {
+            CHECK_Z(ZSTD_stwrite32(
+                    fl, output, fl->entries[fl->seekTableIndex].checksum,
+                    (U32)start + 8));
+        }
+
+        fl->seekTableIndex++;
+    }
+
+    assert(seekTableLen <= UINT_MAX);
+    CHECK_Z(ZSTD_stwrite32(fl, output, fl->size,
+                           (U32)seekTableLen - ZSTD_seekTableFooterSize));
+
+    if (output->size - output->pos < 1) return seekTableLen - fl->seekTablePos;
+    if (fl->seekTablePos < seekTableLen - 4) {
+        BYTE sfd = 0;
+        sfd |= (fl->checksumFlag) << 7;
+
+        ((BYTE*)output->dst)[output->pos] = sfd;
+        output->pos++;
+        fl->seekTablePos++;
+    }
+
+    CHECK_Z(ZSTD_stwrite32(fl, output, ZSTD_SEEKABLE_MAGICNUMBER,
+                           (U32)seekTableLen - 4));
+
+    if (fl->seekTablePos != seekTableLen) return ERROR(GENERIC);
+    return 0;
+}
+
+size_t ZSTD_seekable_endStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output)
+{
+    if (!zcs->writingSeekTable && zcs->frameDSize) {
+        const size_t endFrame = ZSTD_seekable_endFrame(zcs, output);
+        if (ZSTD_isError(endFrame)) return endFrame;
+        /* return an accurate size hint */
+        if (endFrame) return endFrame + ZSTD_seekable_seekTableSize(&zcs->framelog);
+    }
+
+    zcs->writingSeekTable = 1;
+
+    return ZSTD_seekable_writeSeekTable(&zcs->framelog, output);
+}
diff --git a/src/zstd/contrib/seekable_format/zstdseek_decompress.c b/src/zstd/contrib/seekable_format/zstdseek_decompress.c
new file mode 100644
index 000000000..abfd1e902
--- /dev/null
+++ b/src/zstd/contrib/seekable_format/zstdseek_decompress.c
@@ -0,0 +1,467 @@
+/*
+ * Copyright (c) 2017-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ * You may select, at your option, one of the above-listed licenses.
+ */
+
+/* *********************************************************
+*  Turn on Large Files support (>4GB) for 32-bit Linux/Unix
+***********************************************************/
+#if !defined(__64BIT__) || defined(__MINGW32__)       /* No point defining Large file for 64 bit but MinGW-w64 requires it */
+#  if !defined(_FILE_OFFSET_BITS)
+#    define _FILE_OFFSET_BITS 64                      /* turn off_t into a 64-bit type for ftello, fseeko */
+#  endif
+#  if !defined(_LARGEFILE_SOURCE)                     /* obsolete macro, replaced with _FILE_OFFSET_BITS */
+#    define _LARGEFILE_SOURCE 1                       /* Large File Support extension (LFS) - fseeko, ftello */
+#  endif
+#  if defined(_AIX) || defined(__hpux)
+#    define _LARGE_FILES                              /* Large file support on 32-bits AIX and HP-UX */
+#  endif
+#endif
+
+/* ************************************************************
+* Avoid fseek()'s 2GiB barrier with MSVC, macOS, *BSD, MinGW
+***************************************************************/
+#if defined(_MSC_VER) && _MSC_VER >= 1400
+#   define LONG_SEEK _fseeki64
+#elif !defined(__64BIT__) && (PLATFORM_POSIX_VERSION >= 200112L) /* No point defining Large file for 64 bit */
+#  define LONG_SEEK fseeko
+#elif defined(__MINGW32__) && !defined(__STRICT_ANSI__) && !defined(__NO_MINGW_LFS) && defined(__MSVCRT__)
+#   define LONG_SEEK fseeko64
+#elif defined(_WIN32) && !defined(__DJGPP__)
+#   include <windows.h>
+    static int LONG_SEEK(FILE* file, __int64 offset, int origin) {
+        LARGE_INTEGER off;
+        DWORD method;
+        off.QuadPart = offset;
+        if (origin == SEEK_END)
+            method = FILE_END;
+        else if (origin == SEEK_CUR)
+            method = FILE_CURRENT;
+        else
+            method = FILE_BEGIN;
+
+        if (SetFilePointerEx((HANDLE) _get_osfhandle(_fileno(file)), off, NULL, method))
+            return 0;
+        else
+            return -1;
+    }
+#else
+#   define LONG_SEEK fseek
+#endif
+
+#include <stdlib.h>  /* malloc, free */
+#include <stdio.h>   /* FILE* */
+#include <limits.h>  /* UNIT_MAX */
+#include <assert.h>
+
+#define XXH_STATIC_LINKING_ONLY
+#define XXH_NAMESPACE ZSTD_
+#include "xxhash.h"
+
+#define ZSTD_STATIC_LINKING_ONLY
+#include "zstd.h"
+#include "zstd_errors.h"
+#include "mem.h"
+#include "zstd_seekable.h"
+
+#undef ERROR
+#define ERROR(name) ((size_t)-ZSTD_error_##name)
+
+#define CHECK_IO(f) { int const errcod = (f); if (errcod < 0) return ERROR(seekableIO); }
+
+#undef MIN
+#undef MAX
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+
+/* Special-case callbacks for FILE* and in-memory modes, so that we can treat
+ * them the same way as the advanced API */
+static int ZSTD_seekable_read_FILE(void* opaque, void* buffer, size_t n)
+{
+    size_t const result = fread(buffer, 1, n, (FILE*)opaque);
+    if (result != n) {
+        return -1;
+    }
+    return 0;
+}
+
+static int ZSTD_seekable_seek_FILE(void* opaque, long long offset, int origin)
+{
+    int const ret = LONG_SEEK((FILE*)opaque, offset, origin);
+    if (ret) return ret;
+    return fflush((FILE*)opaque);
+}
+
+typedef struct {
+    const void *ptr;
+    size_t size;
+    size_t pos;
+} buffWrapper_t;
+
+static int ZSTD_seekable_read_buff(void* opaque, void* buffer, size_t n)
+{
+    buffWrapper_t* buff = (buffWrapper_t*) opaque;
+    if (buff->pos + n > buff->size) return -1;
+    memcpy(buffer, (const BYTE*)buff->ptr + buff->pos, n);
+    buff->pos += n;
+    return 0;
+}
+
+static int ZSTD_seekable_seek_buff(void* opaque, long long offset, int origin)
+{
+    buffWrapper_t* const buff = (buffWrapper_t*) opaque;
+    unsigned long long newOffset;
+    switch (origin) {
+    case SEEK_SET:
+        newOffset = offset;
+        break;
+    case SEEK_CUR:
+        newOffset = (unsigned long long)buff->pos + offset;
+        break;
+    case SEEK_END:
+        newOffset = (unsigned long long)buff->size + offset;
+        break;
+    default:
+        assert(0);  /* not possible */
+    }
+    if (newOffset > buff->size) {
+        return -1;
+    }
+    buff->pos = newOffset;
+    return 0;
+}
+
+typedef struct {
+    U64 cOffset;
+    U64 dOffset;
+    U32 checksum;
+} seekEntry_t;
+
+typedef struct {
+    seekEntry_t* entries;
+    size_t tableLen;
+
+    int checksumFlag;
+} seekTable_t;
+
+#define SEEKABLE_BUFF_SIZE ZSTD_BLOCKSIZE_MAX
+
+struct ZSTD_seekable_s {
+    ZSTD_DStream* dstream;
+    seekTable_t seekTable;
+    ZSTD_seekable_customFile src;
+
+    U64 decompressedOffset;
+    U32 curFrame;
+
+    BYTE inBuff[SEEKABLE_BUFF_SIZE]; /* need to do our own input buffering */
+    BYTE outBuff[SEEKABLE_BUFF_SIZE]; /* so we can efficiently decompress the
+                                         starts of chunks before we get to the
+                                         desired section */
+    ZSTD_inBuffer in; /* maintain continuity across ZSTD_seekable_decompress operations */
+    buffWrapper_t buffWrapper; /* for `src.opaque` in in-memory mode */
+
+    XXH64_state_t xxhState;
+};
+
+ZSTD_seekable* ZSTD_seekable_create(void)
+{
+    ZSTD_seekable* zs = malloc(sizeof(ZSTD_seekable));
+
+    if (zs == NULL) return NULL;
+
+    /* also initializes stage to zsds_init */
+    memset(zs, 0, sizeof(*zs));
+
+    zs->dstream = ZSTD_createDStream();
+    if (zs->dstream == NULL) {
+        free(zs);
+        return NULL;
+    }
+
+    return zs;
+}
+
+size_t ZSTD_seekable_free(ZSTD_seekable* zs)
+{
+    if (zs == NULL) return 0; /* support free on null */
+    ZSTD_freeDStream(zs->dstream);
+    free(zs->seekTable.entries);
+    free(zs);
+
+    return 0;
+}
+
+/** ZSTD_seekable_offsetToFrameIndex() :
+ *  Performs a binary search to find the last frame with a decompressed offset
+ *  <= pos
+ *  @return : the frame's index */
+unsigned ZSTD_seekable_offsetToFrameIndex(ZSTD_seekable* const zs, unsigned long long pos)
+{
+    U32 lo = 0;
+    U32 hi = (U32)zs->seekTable.tableLen;
+    assert(zs->seekTable.tableLen <= UINT_MAX);
+
+    if (pos >= zs->seekTable.entries[zs->seekTable.tableLen].dOffset) {
+        return (U32)zs->seekTable.tableLen;
+    }
+
+    while (lo + 1 < hi) {
+        U32 const mid = lo + ((hi - lo) >> 1);
+        if (zs->seekTable.entries[mid].dOffset <= pos) {
+            lo = mid;
+        } else {
+            hi = mid;
+        }
+    }
+    return lo;
+}
+
+unsigned ZSTD_seekable_getNumFrames(ZSTD_seekable* const zs)
+{
+    assert(zs->seekTable.tableLen <= UINT_MAX);
+    return (unsigned)zs->seekTable.tableLen;
+}
+
+unsigned long long ZSTD_seekable_getFrameCompressedOffset(ZSTD_seekable* const zs, unsigned frameIndex)
+{
+    if (frameIndex >= zs->seekTable.tableLen) return ZSTD_SEEKABLE_FRAMEINDEX_TOOLARGE;
+    return zs->seekTable.entries[frameIndex].cOffset;
+}
+
+unsigned long long ZSTD_seekable_getFrameDecompressedOffset(ZSTD_seekable* const zs, unsigned frameIndex)
+{
+    if (frameIndex >= zs->seekTable.tableLen) return ZSTD_SEEKABLE_FRAMEINDEX_TOOLARGE;
+    return zs->seekTable.entries[frameIndex].dOffset;
+}
+
+size_t ZSTD_seekable_getFrameCompressedSize(ZSTD_seekable* const zs, unsigned frameIndex)
+{
+    if (frameIndex >= zs->seekTable.tableLen) return ERROR(frameIndex_tooLarge);
+    return zs->seekTable.entries[frameIndex + 1].cOffset -
+           zs->seekTable.entries[frameIndex].cOffset;
+}
+
+size_t ZSTD_seekable_getFrameDecompressedSize(ZSTD_seekable* const zs, unsigned frameIndex)
+{
+    if (frameIndex > zs->seekTable.tableLen) return ERROR(frameIndex_tooLarge);
+    return zs->seekTable.entries[frameIndex + 1].dOffset -
+           zs->seekTable.entries[frameIndex].dOffset;
+}
+
+static size_t ZSTD_seekable_loadSeekTable(ZSTD_seekable* zs)
+{
+    int checksumFlag;
+    ZSTD_seekable_customFile src = zs->src;
+    /* read the footer, fixed size */
+    CHECK_IO(src.seek(src.opaque, -(int)ZSTD_seekTableFooterSize, SEEK_END));
+    CHECK_IO(src.read(src.opaque, zs->inBuff, ZSTD_seekTableFooterSize));
+
+    if (MEM_readLE32(zs->inBuff + 5) != ZSTD_SEEKABLE_MAGICNUMBER) {
+        return ERROR(prefix_unknown);
+    }
+
+    {   BYTE const sfd = zs->inBuff[4];
+        checksumFlag = sfd >> 7;
+
+        /* check reserved bits */
+        if ((checksumFlag >> 2) & 0x1f) {
+            return ERROR(corruption_detected);
+        }
+    }
+
+    {   U32 const numFrames = MEM_readLE32(zs->inBuff);
+        U32 const sizePerEntry = 8 + (checksumFlag?4:0);
+        U32 const tableSize = sizePerEntry * numFrames;
+        U32 const frameSize = tableSize + ZSTD_seekTableFooterSize + ZSTD_SKIPPABLEHEADERSIZE;
+
+        U32 remaining = frameSize - ZSTD_seekTableFooterSize; /* don't need to re-read footer */
+        {
+            U32 const toRead = MIN(remaining, SEEKABLE_BUFF_SIZE);
+
+            CHECK_IO(src.seek(src.opaque, -(S64)frameSize, SEEK_END));
+            CHECK_IO(src.read(src.opaque, zs->inBuff, toRead));
+
+            remaining -= toRead;
+        }
+
+        if (MEM_readLE32(zs->inBuff) != (ZSTD_MAGIC_SKIPPABLE_START | 0xE)) {
+            return ERROR(prefix_unknown);
+        }
+        if (MEM_readLE32(zs->inBuff+4) + ZSTD_SKIPPABLEHEADERSIZE != frameSize) {
+            return ERROR(prefix_unknown);
+        }
+
+        {   /* Allocate an extra entry at the end so that we can do size
+             * computations on the last element without special case */
+            seekEntry_t* entries = (seekEntry_t*)malloc(sizeof(seekEntry_t) * (numFrames + 1));
+
+            U32 idx = 0;
+            U32 pos = 8;
+
+
+            U64 cOffset = 0;
+            U64 dOffset = 0;
+
+            if (!entries) {
+                free(entries);
+                return ERROR(memory_allocation);
+            }
+
+            /* compute cumulative positions */
+            for (; idx < numFrames; idx++) {
+                if (pos + sizePerEntry > SEEKABLE_BUFF_SIZE) {
+                    U32 const offset = SEEKABLE_BUFF_SIZE - pos;
+                    U32 const toRead = MIN(remaining, SEEKABLE_BUFF_SIZE - offset);
+                    memmove(zs->inBuff, zs->inBuff + pos, offset); /* move any data we haven't read yet */
+                    CHECK_IO(src.read(src.opaque, zs->inBuff+offset, toRead));
+                    remaining -= toRead;
+                    pos = 0;
+                }
+                entries[idx].cOffset = cOffset;
+                entries[idx].dOffset = dOffset;
+
+                cOffset += MEM_readLE32(zs->inBuff + pos);
+                pos += 4;
+                dOffset += MEM_readLE32(zs->inBuff + pos);
+                pos += 4;
+                if (checksumFlag) {
+                    entries[idx].checksum = MEM_readLE32(zs->inBuff + pos);
+                    pos += 4;
+                }
+            }
+            entries[numFrames].cOffset = cOffset;
+            entries[numFrames].dOffset = dOffset;
+
+            zs->seekTable.entries = entries;
+            zs->seekTable.tableLen = numFrames;
+            zs->seekTable.checksumFlag = checksumFlag;
+            return 0;
+        }
+    }
+}
+
+size_t ZSTD_seekable_initBuff(ZSTD_seekable* zs, const void* src, size_t srcSize)
+{
+    zs->buffWrapper = (buffWrapper_t){src, srcSize, 0};
+    {   ZSTD_seekable_customFile srcFile = {&zs->buffWrapper,
+                                            &ZSTD_seekable_read_buff,
+                                            &ZSTD_seekable_seek_buff};
+        return ZSTD_seekable_initAdvanced(zs, srcFile); }
+}
+
+size_t ZSTD_seekable_initFile(ZSTD_seekable* zs, FILE* src)
+{
+    ZSTD_seekable_customFile srcFile = {src, &ZSTD_seekable_read_FILE,
+                                        &ZSTD_seekable_seek_FILE};
+    return ZSTD_seekable_initAdvanced(zs, srcFile);
+}
+
+size_t ZSTD_seekable_initAdvanced(ZSTD_seekable* zs, ZSTD_seekable_customFile src)
+{
+    zs->src = src;
+
+    {   const size_t seekTableInit = ZSTD_seekable_loadSeekTable(zs);
+        if (ZSTD_isError(seekTableInit)) return seekTableInit; }
+
+    zs->decompressedOffset = (U64)-1;
+    zs->curFrame = (U32)-1;
+
+    {   const size_t dstreamInit = ZSTD_initDStream(zs->dstream);
+        if (ZSTD_isError(dstreamInit)) return dstreamInit; }
+    return 0;
+}
+
+size_t ZSTD_seekable_decompress(ZSTD_seekable* zs, void* dst, size_t len, unsigned long long offset)
+{
+    U32 targetFrame = ZSTD_seekable_offsetToFrameIndex(zs, offset);
+    do {
+        /* check if we can continue from a previous decompress job */
+        if (targetFrame != zs->curFrame || offset != zs->decompressedOffset) {
+            zs->decompressedOffset = zs->seekTable.entries[targetFrame].dOffset;
+            zs->curFrame = targetFrame;
+
+            CHECK_IO(zs->src.seek(zs->src.opaque,
+                                  zs->seekTable.entries[targetFrame].cOffset,
+                                  SEEK_SET));
+            zs->in = (ZSTD_inBuffer){zs->inBuff, 0, 0};
+            XXH64_reset(&zs->xxhState, 0);
+            ZSTD_resetDStream(zs->dstream);
+        }
+
+        while (zs->decompressedOffset < offset + len) {
+            size_t toRead;
+            ZSTD_outBuffer outTmp;
+            size_t prevOutPos;
+            if (zs->decompressedOffset < offset) {
+                /* dummy decompressions until we get to the target offset */
+                outTmp = (ZSTD_outBuffer){zs->outBuff, MIN(SEEKABLE_BUFF_SIZE, offset - zs->decompressedOffset), 0};
+            } else {
+                outTmp = (ZSTD_outBuffer){dst, len, zs->decompressedOffset - offset};
+            }
+
+            prevOutPos = outTmp.pos;
+            toRead = ZSTD_decompressStream(zs->dstream, &outTmp, &zs->in);
+            if (ZSTD_isError(toRead)) {
+                return toRead;
+            }
+
+            if (zs->seekTable.checksumFlag) {
+                XXH64_update(&zs->xxhState, (BYTE*)outTmp.dst + prevOutPos,
+                             outTmp.pos - prevOutPos);
+            }
+            zs->decompressedOffset += outTmp.pos - prevOutPos;
+
+            if (toRead == 0) {
+                /* frame complete */
+
+                /* verify checksum */
+                if (zs->seekTable.checksumFlag &&
+                    (XXH64_digest(&zs->xxhState) & 0xFFFFFFFFU) !=
+                            zs->seekTable.entries[targetFrame].checksum) {
+                    return ERROR(corruption_detected);
+                }
+
+                if (zs->decompressedOffset < offset + len) {
+                    /* go back to the start and force a reset of the stream */
+                    targetFrame = ZSTD_seekable_offsetToFrameIndex(zs, zs->decompressedOffset);
+                }
+                break;
+            }
+
+            /* read in more data if we're done with this buffer */
+            if (zs->in.pos == zs->in.size) {
+                toRead = MIN(toRead, SEEKABLE_BUFF_SIZE);
+                CHECK_IO(zs->src.read(zs->src.opaque, zs->inBuff, toRead));
+                zs->in.size = toRead;
+                zs->in.pos = 0;
+            }
+        }
+    } while (zs->decompressedOffset != offset + len);
+
+    return len;
+}
+
+size_t ZSTD_seekable_decompressFrame(ZSTD_seekable* zs, void* dst, size_t dstSize, unsigned frameIndex)
+{
+    if (frameIndex >= zs->seekTable.tableLen) {
+        return ERROR(frameIndex_tooLarge);
+    }
+
+    {
+        size_t const decompressedSize =
+                zs->seekTable.entries[frameIndex + 1].dOffset -
+                zs->seekTable.entries[frameIndex].dOffset;
+        if (dstSize < decompressedSize) {
+            return ERROR(dstSize_tooSmall);
+        }
+        return ZSTD_seekable_decompress(
+                zs, dst, decompressedSize,
+                zs->seekTable.entries[frameIndex].dOffset);
+    }
+}