/*

 * Copyright 1998-2026 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 *

 * Uses zstd compression library from https://github.com/facebook/zstd

 * Requires version 1.4.x (latest as of this writing is 1.4.5)

 * Using custom free functions require static linking, so that is disabled when

 * using the shared library.

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <openssl/objects.h>

#include "internal/e_os.h"

#include "internal/comp.h"

#include <openssl/err.h>

#include "crypto/cryptlib.h"

#include "internal/bio.h"

#include "internal/thread_once.h"

#include "comp_local.h"

COMP_METHOD *COMP_zstd(void);

#ifdef OPENSSL_NO_ZSTD

#undef ZSTD_SHARED

#else

#ifndef ZSTD_SHARED

#define ZSTD_STATIC_LINKING_ONLY

#endif

#include <zstd.h>

/* Note: There is also a linux zstd.h file in the kernel source */

#ifndef ZSTD_H_235446

#error Wrong (i.e. linux) zstd.h included.

#endif

#if ZSTD_VERSION_MAJOR != 1 || ZSTD_VERSION_MINOR < 4

#error Expecting version 1.4 or greater of ZSTD 1.x

#endif

#ifndef ZSTD_SHARED

/* memory allocations functions for zstd initialisation */

static void *zstd_alloc(void *opaque, size_t size)

{

    return OPENSSL_zalloc(size);

}

static void zstd_free(void *opaque, void *address)

{

    OPENSSL_free(address);

}

static ZSTD_customMem zstd_mem_funcs = {

    zstd_alloc,

    zstd_free,

    NULL

};

#endif

#ifdef ZSTD_SHARED

#include "internal/dso.h"

/* Function pointers */

typedef ZSTD_CStream *(*createCStream_ft)(void);

typedef size_t (*initCStream_ft)(ZSTD_CStream *, int);

typedef size_t (*freeCStream_ft)(ZSTD_CStream *);

typedef size_t (*compressStream2_ft)(ZSTD_CCtx *, ZSTD_outBuffer *, ZSTD_inBuffer *, ZSTD_EndDirective);

typedef size_t (*flushStream_ft)(ZSTD_CStream *, ZSTD_outBuffer *);

typedef size_t (*endStream_ft)(ZSTD_CStream *, ZSTD_outBuffer *);

typedef size_t (*compress_ft)(void *, size_t, const void *, size_t, int);

typedef ZSTD_DStream *(*createDStream_ft)(void);

typedef size_t (*initDStream_ft)(ZSTD_DStream *);

typedef size_t (*freeDStream_ft)(ZSTD_DStream *);

typedef size_t (*decompressStream_ft)(ZSTD_DStream *, ZSTD_outBuffer *, ZSTD_inBuffer *);

typedef size_t (*decompress_ft)(void *, size_t, const void *, size_t);

typedef unsigned (*isError_ft)(size_t);

typedef const char *(*getErrorName_ft)(size_t);

typedef size_t (*DStreamInSize_ft)(void);

typedef size_t (*CStreamInSize_ft)(void);

static createCStream_ft p_createCStream = NULL;

static initCStream_ft p_initCStream = NULL;

static freeCStream_ft p_freeCStream = NULL;

static compressStream2_ft p_compressStream2 = NULL;

static flushStream_ft p_flushStream = NULL;

static endStream_ft p_endStream = NULL;

static compress_ft p_compress = NULL;

static createDStream_ft p_createDStream = NULL;

static initDStream_ft p_initDStream = NULL;

static freeDStream_ft p_freeDStream = NULL;

static decompressStream_ft p_decompressStream = NULL;

static decompress_ft p_decompress = NULL;

static isError_ft p_isError = NULL;

static getErrorName_ft p_getErrorName = NULL;

static DStreamInSize_ft p_DStreamInSize = NULL;

static CStreamInSize_ft p_CStreamInSize = NULL;

static DSO *zstd_dso = NULL;

#define ZSTD_createCStream p_createCStream

#define ZSTD_initCStream p_initCStream

#define ZSTD_freeCStream p_freeCStream

#define ZSTD_compressStream2 p_compressStream2

#define ZSTD_flushStream p_flushStream

#define ZSTD_endStream p_endStream

#define ZSTD_compress p_compress

#define ZSTD_createDStream p_createDStream

#define ZSTD_initDStream p_initDStream

#define ZSTD_freeDStream p_freeDStream

#define ZSTD_decompressStream p_decompressStream

#define ZSTD_decompress p_decompress

#define ZSTD_isError p_isError

#define ZSTD_getErrorName p_getErrorName

#define ZSTD_DStreamInSize p_DStreamInSize

#define ZSTD_CStreamInSize p_CStreamInSize

#endif /* ifdef ZSTD_SHARED */

struct zstd_state {

    ZSTD_CStream *compressor;

    ZSTD_DStream *decompressor;

};

static int zstd_stateful_init(COMP_CTX *ctx)

{

    struct zstd_state *state = OPENSSL_zalloc(sizeof(*state));

    if (state == NULL)

        return 0;

#ifdef ZSTD_SHARED

    state->compressor = ZSTD_createCStream();

#else

    state->compressor = ZSTD_createCStream_advanced(zstd_mem_funcs);

#endif

    if (state->compressor == NULL)

        goto err;

    ZSTD_initCStream(state->compressor, ZSTD_CLEVEL_DEFAULT);

#ifdef ZSTD_SHARED

    state->decompressor = ZSTD_createDStream();

#else

    state->decompressor = ZSTD_createDStream_advanced(zstd_mem_funcs);

#endif

    if (state->decompressor == NULL)

        goto err;

    ZSTD_initDStream(state->decompressor);

    ctx->data = state;

    return 1;

err:

    ZSTD_freeCStream(state->compressor);

    ZSTD_freeDStream(state->decompressor);

    OPENSSL_free(state);

    return 0;

}

static void zstd_stateful_finish(COMP_CTX *ctx)

{

    struct zstd_state *state = ctx->data;

    if (state != NULL) {

        ZSTD_freeCStream(state->compressor);

        ZSTD_freeDStream(state->decompressor);

        OPENSSL_free(state);

        ctx->data = NULL;

    }

}

static ossl_ssize_t zstd_stateful_compress_block(COMP_CTX *ctx, unsigned char *out,

    size_t olen, unsigned char *in,

    size_t ilen)

{

    ZSTD_inBuffer inbuf;

    ZSTD_outBuffer outbuf;

    size_t ret;

    ossl_ssize_t fret;

    struct zstd_state *state = ctx->data;

    inbuf.src = in;

    inbuf.size = ilen;

    inbuf.pos = 0;

    outbuf.dst = out;

    outbuf.size = olen;

    outbuf.pos = 0;

    if (state == NULL)

        return -1;

    /* If input length is zero, end the stream/frame ? */

    if (ilen == 0) {

        ret = ZSTD_endStream(state->compressor, &outbuf);

        if (ZSTD_isError(ret))

            return -1;

        goto end;

    }

    /*

     * The finish API does not provide a final output buffer,

     * so each compress operation has to be ended, if all

     * the input data can't be accepted, or there is more output,

     * this has to be considered an error, since there is no more

     * output buffer space.

     */

    do {

        ret = ZSTD_compressStream2(state->compressor, &outbuf, &inbuf, ZSTD_e_continue);

        if (ZSTD_isError(ret))

            return -1;

        /* do I need to check for ret == 0 ? */

    } while (inbuf.pos < inbuf.size);

    /* Did not consume all the data */

    if (inbuf.pos < inbuf.size)

        return -1;

    ret = ZSTD_flushStream(state->compressor, &outbuf);

    if (ZSTD_isError(ret))

        return -1;

end:

    if (outbuf.pos > OSSL_SSIZE_MAX)

        return -1;

    fret = (ossl_ssize_t)outbuf.pos;

    if (fret < 0)

        return -1;

    return fret;

}

static ossl_ssize_t zstd_stateful_expand_block(COMP_CTX *ctx, unsigned char *out,

    size_t olen, unsigned char *in,

    size_t ilen)

{

    ZSTD_inBuffer inbuf;

    ZSTD_outBuffer outbuf;

    size_t ret;

    ossl_ssize_t fret;

    struct zstd_state *state = ctx->data;

    inbuf.src = in;

    inbuf.size = ilen;

    inbuf.pos = 0;

    outbuf.dst = out;

    outbuf.size = olen;

    outbuf.pos = 0;

    if (state == NULL)

        return -1;

    if (ilen == 0)

        return 0;

    do {

        ret = ZSTD_decompressStream(state->decompressor, &outbuf, &inbuf);

        if (ZSTD_isError(ret))

            return -1;

        /* If we completed a frame, and there's more data, try again */

    } while (ret == 0 && inbuf.pos < inbuf.size);

    /* Did not consume all the data */

    if (inbuf.pos < inbuf.size)

        return -1;

    if (outbuf.pos > OSSL_SSIZE_MAX)

        return -1;

    fret = (ossl_ssize_t)outbuf.pos;

    if (fret < 0)

        return -1;

    return fret;

}

static COMP_METHOD zstd_stateful_method = {

    NID_zstd,

    LN_zstd,

    zstd_stateful_init,

    zstd_stateful_finish,

    zstd_stateful_compress_block,

    zstd_stateful_expand_block

};

static int zstd_oneshot_init(COMP_CTX *ctx)

{

    return 1;

}

static void zstd_oneshot_finish(COMP_CTX *ctx)

{

}

static ossl_ssize_t zstd_oneshot_compress_block(COMP_CTX *ctx, unsigned char *out,

    size_t olen, unsigned char *in,

    size_t ilen)

{

    size_t out_size;

    ossl_ssize_t ret;

    if (ilen == 0)

        return 0;

    /* Note: uses STDLIB memory allocators */

    out_size = ZSTD_compress(out, olen, in, ilen, ZSTD_CLEVEL_DEFAULT);

    if (ZSTD_isError(out_size))

        return -1;

    if (out_size > OSSL_SSIZE_MAX)

        return -1;

    ret = (ossl_ssize_t)out_size;

    if (ret < 0)

        return -1;

    return ret;

}

static ossl_ssize_t zstd_oneshot_expand_block(COMP_CTX *ctx, unsigned char *out,

    size_t olen, unsigned char *in,

    size_t ilen)

{

    size_t out_size;

    ossl_ssize_t ret;

    if (ilen == 0)

        return 0;

    /* Note: uses STDLIB memory allocators */

    out_size = ZSTD_decompress(out, olen, in, ilen);

    if (ZSTD_isError(out_size))

        return -1;

    if (out_size > OSSL_SSIZE_MAX)

        return -1;

    ret = (ossl_ssize_t)out_size;

    if (ret < 0)

        return -1;

    return ret;

}

static COMP_METHOD zstd_oneshot_method = {

    NID_zstd,

    LN_zstd,

    zstd_oneshot_init,

    zstd_oneshot_finish,

    zstd_oneshot_compress_block,

    zstd_oneshot_expand_block

};

static CRYPTO_ONCE zstd_once = CRYPTO_ONCE_STATIC_INIT;

DEFINE_RUN_ONCE_STATIC(ossl_comp_zstd_init)

{

#ifdef ZSTD_SHARED

#if defined(OPENSSL_SYS_WINDOWS) || defined(OPENSSL_SYS_WIN32)

#define LIBZSTD "LIBZSTD"

#else

#define LIBZSTD "zstd"

#endif

    ERR_set_mark();

    zstd_dso = DSO_load(NULL, LIBZSTD, NULL, 0);

    if (zstd_dso != NULL) {

        p_createCStream = (createCStream_ft)DSO_bind_func(zstd_dso, "ZSTD_createCStream");

        p_initCStream = (initCStream_ft)DSO_bind_func(zstd_dso, "ZSTD_initCStream");

        p_freeCStream = (freeCStream_ft)DSO_bind_func(zstd_dso, "ZSTD_freeCStream");

        p_compressStream2 = (compressStream2_ft)DSO_bind_func(zstd_dso, "ZSTD_compressStream2");

        p_flushStream = (flushStream_ft)DSO_bind_func(zstd_dso, "ZSTD_flushStream");

        p_endStream = (endStream_ft)DSO_bind_func(zstd_dso, "ZSTD_endStream");

        p_compress = (compress_ft)DSO_bind_func(zstd_dso, "ZSTD_compress");

        p_createDStream = (createDStream_ft)DSO_bind_func(zstd_dso, "ZSTD_createDStream");

        p_initDStream = (initDStream_ft)DSO_bind_func(zstd_dso, "ZSTD_initDStream");

        p_freeDStream = (freeDStream_ft)DSO_bind_func(zstd_dso, "ZSTD_freeDStream");

        p_decompressStream = (decompressStream_ft)DSO_bind_func(zstd_dso, "ZSTD_decompressStream");

        p_decompress = (decompress_ft)DSO_bind_func(zstd_dso, "ZSTD_decompress");

        p_isError = (isError_ft)DSO_bind_func(zstd_dso, "ZSTD_isError");

        p_getErrorName = (getErrorName_ft)DSO_bind_func(zstd_dso, "ZSTD_getErrorName");

        p_DStreamInSize = (DStreamInSize_ft)DSO_bind_func(zstd_dso, "ZSTD_DStreamInSize");

        p_CStreamInSize = (CStreamInSize_ft)DSO_bind_func(zstd_dso, "ZSTD_CStreamInSize");

    }

    if (p_createCStream == NULL || p_initCStream == NULL || p_freeCStream == NULL

        || p_compressStream2 == NULL || p_flushStream == NULL || p_endStream == NULL

        || p_compress == NULL || p_createDStream == NULL || p_initDStream == NULL

        || p_freeDStream == NULL || p_decompressStream == NULL || p_decompress == NULL

        || p_isError == NULL || p_getErrorName == NULL || p_DStreamInSize == NULL

        || p_CStreamInSize == NULL) {

        ERR_clear_last_mark();

        ossl_comp_zstd_cleanup();

        return 0;

    }

    /* Do not leave errors behind on success. */

    ERR_pop_to_mark();

#endif

    return 1;

}

#endif /* ifndef ZSTD / else */

COMP_METHOD *COMP_zstd(void)

{

    COMP_METHOD *meth = NULL;

#ifndef OPENSSL_NO_ZSTD

    if (RUN_ONCE(&zstd_once, ossl_comp_zstd_init))

        meth = &zstd_stateful_method;

#endif

    return meth;

}

COMP_METHOD *COMP_zstd_oneshot(void)

{

    COMP_METHOD *meth = NULL;

#ifndef OPENSSL_NO_ZSTD

    if (RUN_ONCE(&zstd_once, ossl_comp_zstd_init))

        meth = &zstd_oneshot_method;

#endif

    return meth;

}

/* Also called from OPENSSL_cleanup() */

void ossl_comp_zstd_cleanup(void)

{

#ifdef ZSTD_SHARED

    DSO_free(zstd_dso);

    zstd_dso = NULL;

    p_createCStream = NULL;

    p_initCStream = NULL;

    p_freeCStream = NULL;

    p_compressStream2 = NULL;

    p_flushStream = NULL;

    p_endStream = NULL;

    p_compress = NULL;

    p_createDStream = NULL;

    p_initDStream = NULL;

    p_freeDStream = NULL;

    p_decompressStream = NULL;

    p_decompress = NULL;

    p_isError = NULL;

    p_getErrorName = NULL;

    p_DStreamInSize = NULL;

    p_CStreamInSize = NULL;

#endif

}

#ifndef OPENSSL_NO_ZSTD

/* Zstd-based compression/decompression filter BIO */

typedef struct {

    struct { /* input structure */

        ZSTD_DStream *state;

        ZSTD_inBuffer inbuf; /* has const src */

        size_t bufsize;

        void *buffer;

    } decompress;

    struct { /* output structure */

        ZSTD_CStream *state;

        ZSTD_outBuffer outbuf;

        size_t bufsize;

        size_t write_pos;

    } compress;

} BIO_ZSTD_CTX;

#define ZSTD_DEFAULT_BUFSIZE 1024

static int bio_zstd_new(BIO *bi);

static int bio_zstd_free(BIO *bi);

static int bio_zstd_read(BIO *b, char *out, int outl);

static int bio_zstd_write(BIO *b, const char *in, int inl);

static long bio_zstd_ctrl(BIO *b, int cmd, long num, void *ptr);

static long bio_zstd_callback_ctrl(BIO *b, int cmd, BIO_info_cb *fp);

static const BIO_METHOD bio_meth_zstd = {

    BIO_TYPE_COMP,

    "zstd",

    /* TODO: Convert to new style write function */

    bwrite_conv,

    bio_zstd_write,

    /* TODO: Convert to new style read function */

    bread_conv,

    bio_zstd_read,

    NULL, /* bio_zstd_puts, */

    NULL, /* bio_zstd_gets, */

    bio_zstd_ctrl,

    bio_zstd_new,

    bio_zstd_free,

    bio_zstd_callback_ctrl

};

#endif

const BIO_METHOD *BIO_f_zstd(void)

{

#ifndef OPENSSL_NO_ZSTD

    if (RUN_ONCE(&zstd_once, ossl_comp_zstd_init))

        return &bio_meth_zstd;

#endif

    return NULL;

}

#ifndef OPENSSL_NO_ZSTD

static int bio_zstd_new(BIO *bi)

{

    BIO_ZSTD_CTX *ctx;

#ifdef ZSTD_SHARED

    (void)COMP_zstd();

    if (zstd_dso == NULL) {

        ERR_raise(ERR_LIB_COMP, COMP_R_ZSTD_NOT_SUPPORTED);

        return 0;

    }

#endif

    ctx = OPENSSL_zalloc(sizeof(*ctx));

    if (ctx == NULL) {

        ERR_raise(ERR_LIB_COMP, ERR_R_MALLOC_FAILURE);

        return 0;

    }

#ifdef ZSTD_SHARED

    ctx->decompress.state = ZSTD_createDStream();

#else

    ctx->decompress.state = ZSTD_createDStream_advanced(zstd_mem_funcs);

#endif

    if (ctx->decompress.state == NULL)

        goto err;

    ZSTD_initDStream(ctx->decompress.state);

    ctx->decompress.bufsize = ZSTD_DStreamInSize();

#ifdef ZSTD_SHARED

    ctx->compress.state = ZSTD_createCStream();

#else

    ctx->compress.state = ZSTD_createCStream_advanced(zstd_mem_funcs);

#endif

    if (ctx->compress.state == NULL)

        goto err;

    ZSTD_initCStream(ctx->compress.state, ZSTD_CLEVEL_DEFAULT);

    ctx->compress.bufsize = ZSTD_CStreamInSize();

    BIO_set_init(bi, 1);

    BIO_set_data(bi, ctx);

    return 1;

err:

    ERR_raise(ERR_LIB_COMP, ERR_R_MALLOC_FAILURE);

    ZSTD_freeDStream(ctx->decompress.state);

    ZSTD_freeCStream(ctx->compress.state);

    OPENSSL_free(ctx);

    return 0;

}

static int bio_zstd_free(BIO *bi)

{

    BIO_ZSTD_CTX *ctx;

    if (bi == NULL)

        return 0;

    ctx = BIO_get_data(bi);

    if (ctx != NULL) {

        ZSTD_freeDStream(ctx->decompress.state);

        OPENSSL_free(ctx->decompress.buffer);

        ZSTD_freeCStream(ctx->compress.state);

        OPENSSL_free(ctx->compress.outbuf.dst);

        OPENSSL_free(ctx);

    }

    BIO_set_data(bi, NULL);

    BIO_set_init(bi, 0);

    return 1;

}

static int bio_zstd_read(BIO *b, char *out, int outl)

{

    BIO_ZSTD_CTX *ctx;

    size_t zret;

    int ret;

    ZSTD_outBuffer outBuf;

    BIO *next = BIO_next(b);

    if (out == NULL) {

        ERR_raise(ERR_LIB_COMP, ERR_R_PASSED_NULL_PARAMETER);

        return -1;

    }

    if (outl <= 0)

        return 0;

    ctx = BIO_get_data(b);

    BIO_clear_retry_flags(b);

    if (ctx->decompress.buffer == NULL) {

        ctx->decompress.buffer = OPENSSL_malloc(ctx->decompress.bufsize);

        if (ctx->decompress.buffer == NULL) {

            ERR_raise(ERR_LIB_COMP, ERR_R_MALLOC_FAILURE);

            return -1;

        }

        ctx->decompress.inbuf.src = ctx->decompress.buffer;

        ctx->decompress.inbuf.size = 0;

        ctx->decompress.inbuf.pos = 0;

    }

    /* Copy output data directly to supplied buffer */

    outBuf.dst = out;

    outBuf.size = (size_t)outl;

    outBuf.pos = 0;

    for (;;) {

        /* Decompress while data available */

        do {

            zret = ZSTD_decompressStream(ctx->decompress.state, &outBuf, &ctx->decompress.inbuf);

            if (ZSTD_isError(zret)) {

                ERR_raise(ERR_LIB_COMP, COMP_R_ZSTD_DECOMPRESS_ERROR);

                ERR_add_error_data(1, ZSTD_getErrorName(zret));

                return -1;

            }

            /* No more output space */

            if (outBuf.pos == outBuf.size)

                return (int)outBuf.pos;

        } while (ctx->decompress.inbuf.pos < ctx->decompress.inbuf.size);

        /*

         * No data in input buffer try to read some in, if an error then

         * return the total data read.

         */

        ret = BIO_read(next, ctx->decompress.buffer, (int)ctx->decompress.bufsize);

        if (ret <= 0) {

            BIO_copy_next_retry(b);

            if (ret < 0 && outBuf.pos == 0)

                return ret;

            return (int)outBuf.pos;

        }

        ctx->decompress.inbuf.size = ret;

        ctx->decompress.inbuf.pos = 0;

    }

}

static int bio_zstd_write(BIO *b, const char *in, int inl)

{

    BIO_ZSTD_CTX *ctx;

    size_t zret;

    ZSTD_inBuffer inBuf;

    int ret;

    int done = 0;

    BIO *next = BIO_next(b);

    if (in == NULL || inl <= 0)

        return 0;

    ctx = BIO_get_data(b);

    BIO_clear_retry_flags(b);

    if (ctx->compress.outbuf.dst == NULL) {

        ctx->compress.outbuf.dst = OPENSSL_malloc(ctx->compress.bufsize);

        if (ctx->compress.outbuf.dst == NULL) {

            ERR_raise(ERR_LIB_COMP, ERR_R_MALLOC_FAILURE);

            return 0;

        }

        ctx->compress.outbuf.size = ctx->compress.bufsize;

        ctx->compress.outbuf.pos = 0;

        ctx->compress.write_pos = 0;

    }

    /* Obtain input data directly from supplied buffer */

    inBuf.src = in;

    inBuf.size = inl;

    inBuf.pos = 0;

    for (;;) {

        /* If data in output buffer write it first */

        while (ctx->compress.write_pos < ctx->compress.outbuf.pos) {

            ret = BIO_write(next, (unsigned char *)ctx->compress.outbuf.dst + ctx->compress.write_pos,

                (int)(ctx->compress.outbuf.pos - ctx->compress.write_pos));

            if (ret <= 0) {

                BIO_copy_next_retry(b);

                if (ret < 0 && inBuf.pos == 0)

                    return ret;

                return (int)inBuf.pos;

            }

            ctx->compress.write_pos += ret;

        }

        /* Have we consumed all supplied data? */

        if (done)

            return (int)inBuf.pos;

        /* Reset buffer */

        ctx->compress.outbuf.pos = 0;

        ctx->compress.outbuf.size = ctx->compress.bufsize;

        ctx->compress.write_pos = 0;

        /* Compress some more */

        zret = ZSTD_compressStream2(ctx->compress.state, &ctx->compress.outbuf, &inBuf, ZSTD_e_end);

        if (ZSTD_isError(zret)) {

            ERR_raise(ERR_LIB_COMP, COMP_R_ZSTD_COMPRESS_ERROR);

            ERR_add_error_data(1, ZSTD_getErrorName(zret));

            return 0;

        } else if (zret == 0) {

            done = 1;

        }

    }

}

static int bio_zstd_flush(BIO *b)

{

    BIO_ZSTD_CTX *ctx;

    size_t zret;

    int ret;

    BIO *next = BIO_next(b);

    ctx = BIO_get_data(b);

    /* If no data written or already flush show success */

    if (ctx->compress.outbuf.dst == NULL)

        return 1;

    BIO_clear_retry_flags(b);

    /* No more input data */

    ctx->compress.outbuf.pos = 0;

    ctx->compress.outbuf.size = ctx->compress.bufsize;

    ctx->compress.write_pos = 0;

    for (;;) {

        /* If data in output buffer write it first */

        while (ctx->compress.write_pos < ctx->compress.outbuf.pos) {

            ret = BIO_write(next, (unsigned char *)ctx->compress.outbuf.dst + ctx->compress.write_pos,

                (int)(ctx->compress.outbuf.pos - ctx->compress.write_pos));

            if (ret <= 0) {

                BIO_copy_next_retry(b);

                return ret;

            }

            ctx->compress.write_pos += ret;

        }

        /* Reset buffer */

        ctx->compress.outbuf.pos = 0;

        ctx->compress.outbuf.size = ctx->compress.bufsize;

        ctx->compress.write_pos = 0;

        /* Compress some more */

        zret = ZSTD_flushStream(ctx->compress.state, &ctx->compress.outbuf);

        if (ZSTD_isError(zret)) {

            ERR_raise(ERR_LIB_COMP, COMP_R_ZSTD_COMPRESS_ERROR);

            ERR_add_error_data(1, ZSTD_getErrorName(zret));

            return 0;

        }

        if (zret == 0)

            return 1;

    }

}

static long bio_zstd_ctrl(BIO *b, int cmd, long num, void *ptr)

{

    BIO_ZSTD_CTX *ctx;

    int ret = 0, *ip;

    size_t ibs, obs;

    unsigned char *tmp;

    BIO *next = BIO_next(b);

    if (next == NULL)

        return 0;

    ctx = BIO_get_data(b);

    switch (cmd) {

    case BIO_CTRL_RESET:

        /* reset decompressor */

        ctx->decompress.inbuf.size = 0;

        ctx->decompress.inbuf.pos = 0;

        if (ctx->decompress.state != NULL)

            ZSTD_initDStream(ctx->decompress.state);

        /* reset compressor */

        ctx->compress.write_pos = 0;

        ctx->compress.outbuf.pos = 0;

        if (ctx->compress.state != NULL)

            ZSTD_initCStream(ctx->compress.state, ZSTD_CLEVEL_DEFAULT);

        /* keep existing bufsize, do not set it to 0 */

        ret = 1;

        break;

    case BIO_CTRL_FLUSH:

        ret = bio_zstd_flush(b);

        if (ret > 0) {

            ret = BIO_flush(next);

            BIO_copy_next_retry(b);

        }

        break;

    case BIO_C_SET_BUFF_SIZE:

        ibs = ctx->decompress.bufsize;

        obs = ctx->compress.bufsize;

        if (ptr != NULL) {

            ip = ptr;

            if (*ip == 0)

                ibs = (size_t)num;

            else

                obs = (size_t)num;

        } else {

            obs = ibs = (size_t)num;

        }

        if (ibs > 0 && ibs != ctx->decompress.bufsize) {

            if (ctx->decompress.buffer != NULL) {

                tmp = OPENSSL_realloc(ctx->decompress.buffer, ibs);

                if (tmp == NULL)

                    return 0;

                if (ctx->decompress.inbuf.src == ctx->decompress.buffer)

                    ctx->decompress.inbuf.src = tmp;

                ctx->decompress.buffer = tmp;

            }

            ctx->decompress.bufsize = ibs;

        }

        if (obs > 0 && obs != ctx->compress.bufsize) {

            if (ctx->compress.outbuf.dst != NULL) {

                tmp = OPENSSL_realloc(ctx->compress.outbuf.dst, obs);

                if (tmp == NULL)

                    return 0;

                ctx->compress.outbuf.dst = tmp;

            }

            ctx->compress.bufsize = obs;

        }

        ret = 1;

        break;

    case BIO_C_DO_STATE_MACHINE:

        BIO_clear_retry_flags(b);

        ret = BIO_ctrl(next, cmd, num, ptr);

        BIO_copy_next_retry(b);

        break;

    case BIO_CTRL_WPENDING:

        if (ctx->compress.outbuf.pos < ctx->compress.outbuf.size)

            ret = 1;

        else

            ret = BIO_ctrl(next, cmd, num, ptr);

        break;

    case BIO_CTRL_PENDING:

        if (ctx->decompress.inbuf.pos < ctx->decompress.inbuf.size)

            ret = 1;

        else

            ret = BIO_ctrl(next, cmd, num, ptr);

        break;

    default:

        ret = BIO_ctrl(next, cmd, num, ptr);

        break;

    }

    return ret;

}

static long bio_zstd_callback_ctrl(BIO *b, int cmd, BIO_info_cb *fp)

{

    BIO *next = BIO_next(b);

    if (next == NULL)

        return 0;

    return BIO_callback_ctrl(next, cmd, fp);

}

#endif