astreamer_zstd.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * astreamer_zstd.c
 *
 * Archive streamers that deal with data compressed using zstd.
 * astreamer_zstd_compressor applies zstd compression to the input stream,
 * and astreamer_zstd_decompressor does the reverse.
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *        src/fe_utils/astreamer_zstd.c
 *-------------------------------------------------------------------------
 */
 
#include "postgres_fe.h"
 
#include <unistd.h>
 
#ifdef USE_ZSTD
#include <zstd.h>
#endif
 
#include "common/logging.h"
#include "fe_utils/astreamer.h"
 
#ifdef USE_ZSTD
 
typedef struct astreamer_zstd_frame
{
    astreamer   base;
 
    ZSTD_CCtx  *cctx;
    ZSTD_DCtx  *dctx;
    ZSTD_outBuffer zstd_outBuf;
} astreamer_zstd_frame;
 
static void astreamer_zstd_compressor_content(astreamer *streamer,
                                              astreamer_member *member,
                                              const char *data, int len,
                                              astreamer_archive_context context);
static void astreamer_zstd_compressor_finalize(astreamer *streamer);
static void astreamer_zstd_compressor_free(astreamer *streamer);
 
static const astreamer_ops astreamer_zstd_compressor_ops = {
    .content = astreamer_zstd_compressor_content,
    .finalize = astreamer_zstd_compressor_finalize,
    .free = astreamer_zstd_compressor_free
};
 
static void astreamer_zstd_decompressor_content(astreamer *streamer,
                                                astreamer_member *member,
                                                const char *data, int len,
                                                astreamer_archive_context context);
static void astreamer_zstd_decompressor_finalize(astreamer *streamer);
static void astreamer_zstd_decompressor_free(astreamer *streamer);
 
static const astreamer_ops astreamer_zstd_decompressor_ops = {
    .content = astreamer_zstd_decompressor_content,
    .finalize = astreamer_zstd_decompressor_finalize,
    .free = astreamer_zstd_decompressor_free
};
#endif
 
/*
 * Create a new base backup streamer that performs zstd compression of tar
 * blocks.
 */
astreamer *
astreamer_zstd_compressor_new(astreamer *next, pg_compress_specification *compress)
{
#ifdef USE_ZSTD
    astreamer_zstd_frame *streamer;
    size_t      ret;
 
    Assert(next != NULL);
 
    streamer = palloc0_object(astreamer_zstd_frame);
 
    *((const astreamer_ops **) &streamer->base.bbs_ops) =
        &astreamer_zstd_compressor_ops;
 
    streamer->base.bbs_next = next;
    initStringInfo(&streamer->base.bbs_buffer);
    enlargeStringInfo(&streamer->base.bbs_buffer, ZSTD_DStreamOutSize());
 
    streamer->cctx = ZSTD_createCCtx();
    if (!streamer->cctx)
        pg_fatal("could not create zstd compression context");
 
    /* Set compression level */
    ret = ZSTD_CCtx_setParameter(streamer->cctx, ZSTD_c_compressionLevel,
                                 compress->level);
    if (ZSTD_isError(ret))
        pg_fatal("could not set zstd compression level to %d: %s",
                 compress->level, ZSTD_getErrorName(ret));
 
    /* Set # of workers, if specified */
    if ((compress->options & PG_COMPRESSION_OPTION_WORKERS) != 0)
    {
        /*
         * On older versions of libzstd, this option does not exist, and
         * trying to set it will fail. Similarly for newer versions if they
         * are compiled without threading support.
         */
        ret = ZSTD_CCtx_setParameter(streamer->cctx, ZSTD_c_nbWorkers,
                                     compress->workers);
        if (ZSTD_isError(ret))
            pg_fatal("could not set compression worker count to %d: %s",
                     compress->workers, ZSTD_getErrorName(ret));
    }
 
    if ((compress->options & PG_COMPRESSION_OPTION_LONG_DISTANCE) != 0)
    {
        ret = ZSTD_CCtx_setParameter(streamer->cctx,
                                     ZSTD_c_enableLongDistanceMatching,
                                     compress->long_distance);
        if (ZSTD_isError(ret))
            pg_fatal("could not enable long-distance mode: %s",
                     ZSTD_getErrorName(ret));
    }
 
    /* Initialize the ZSTD output buffer. */
    streamer->zstd_outBuf.dst = streamer->base.bbs_buffer.data;
    streamer->zstd_outBuf.size = streamer->base.bbs_buffer.maxlen;
    streamer->zstd_outBuf.pos = 0;
 
    return &streamer->base;
#else
    pg_fatal("this build does not support compression with %s", "ZSTD");
    return NULL;                /* keep compiler quiet */
#endif
}
 
#ifdef USE_ZSTD
/*
 * Compress the input data to output buffer.
 *
 * Find out the compression bound based on input data length for each
 * invocation to make sure that output buffer has enough capacity to
 * accommodate the compressed data. In case if the output buffer
 * capacity falls short of compression bound then forward the content
 * of output buffer to next streamer and empty the buffer.
 */
static void
astreamer_zstd_compressor_content(astreamer *streamer,
                                  astreamer_member *member,
                                  const char *data, int len,
                                  astreamer_archive_context context)
{
    astreamer_zstd_frame *mystreamer = (astreamer_zstd_frame *) streamer;
    ZSTD_inBuffer inBuf = {data, len, 0};
 
    while (inBuf.pos < inBuf.size)
    {
        size_t      yet_to_flush;
        size_t      max_needed = ZSTD_compressBound(inBuf.size - inBuf.pos);
 
        /*
         * If the output buffer is not left with enough space, send the
         * compressed bytes to the next streamer, and empty the buffer.
         */
        if (mystreamer->zstd_outBuf.size - mystreamer->zstd_outBuf.pos <
            max_needed)
        {
            astreamer_content(mystreamer->base.bbs_next, member,
                              mystreamer->zstd_outBuf.dst,
                              mystreamer->zstd_outBuf.pos,
                              context);
 
            /* Reset the ZSTD output buffer. */
            mystreamer->zstd_outBuf.dst = mystreamer->base.bbs_buffer.data;
            mystreamer->zstd_outBuf.size = mystreamer->base.bbs_buffer.maxlen;
            mystreamer->zstd_outBuf.pos = 0;
        }
 
        yet_to_flush =
            ZSTD_compressStream2(mystreamer->cctx, &mystreamer->zstd_outBuf,
                                 &inBuf, ZSTD_e_continue);
 
        if (ZSTD_isError(yet_to_flush))
            pg_fatal("could not compress data: %s",
                     ZSTD_getErrorName(yet_to_flush));
    }
}
 
/*
 * End-of-stream processing.
 */
static void
astreamer_zstd_compressor_finalize(astreamer *streamer)
{
    astreamer_zstd_frame *mystreamer = (astreamer_zstd_frame *) streamer;
    size_t      yet_to_flush;
 
    do
    {
        ZSTD_inBuffer in = {NULL, 0, 0};
        size_t      max_needed = ZSTD_compressBound(0);
 
        /*
         * If the output buffer is not left with enough space, send the
         * compressed bytes to the next streamer, and empty the buffer.
         */
        if (mystreamer->zstd_outBuf.size - mystreamer->zstd_outBuf.pos <
            max_needed)
        {
            astreamer_content(mystreamer->base.bbs_next, NULL,
                              mystreamer->zstd_outBuf.dst,
                              mystreamer->zstd_outBuf.pos,
                              ASTREAMER_UNKNOWN);
 
            /* Reset the ZSTD output buffer. */
            mystreamer->zstd_outBuf.dst = mystreamer->base.bbs_buffer.data;
            mystreamer->zstd_outBuf.size = mystreamer->base.bbs_buffer.maxlen;
            mystreamer->zstd_outBuf.pos = 0;
        }
 
        yet_to_flush = ZSTD_compressStream2(mystreamer->cctx,
                                            &mystreamer->zstd_outBuf,
                                            &in, ZSTD_e_end);
 
        if (ZSTD_isError(yet_to_flush))
            pg_fatal("could not compress data: %s",
                     ZSTD_getErrorName(yet_to_flush));
 
    } while (yet_to_flush > 0);
 
    /* Make sure to pass any remaining bytes to the next streamer. */
    if (mystreamer->zstd_outBuf.pos > 0)
        astreamer_content(mystreamer->base.bbs_next, NULL,
                          mystreamer->zstd_outBuf.dst,
                          mystreamer->zstd_outBuf.pos,
                          ASTREAMER_UNKNOWN);
 
    astreamer_finalize(mystreamer->base.bbs_next);
}
 
/*
 * Free memory.
 */
static void
astreamer_zstd_compressor_free(astreamer *streamer)
{
    astreamer_zstd_frame *mystreamer = (astreamer_zstd_frame *) streamer;
 
    astreamer_free(streamer->bbs_next);
    ZSTD_freeCCtx(mystreamer->cctx);
    pfree(streamer->bbs_buffer.data);
    pfree(streamer);
}
#endif
 
/*
 * Create a new base backup streamer that performs decompression of zstd
 * compressed blocks.
 */
astreamer *
astreamer_zstd_decompressor_new(astreamer *next)
{
#ifdef USE_ZSTD
    astreamer_zstd_frame *streamer;
 
    Assert(next != NULL);
 
    streamer = palloc0_object(astreamer_zstd_frame);
    *((const astreamer_ops **) &streamer->base.bbs_ops) =
        &astreamer_zstd_decompressor_ops;
 
    streamer->base.bbs_next = next;
    initStringInfo(&streamer->base.bbs_buffer);
    enlargeStringInfo(&streamer->base.bbs_buffer, ZSTD_DStreamOutSize());
 
    streamer->dctx = ZSTD_createDCtx();
    if (!streamer->dctx)
        pg_fatal("could not create zstd decompression context");
 
    /* Initialize the ZSTD output buffer. */
    streamer->zstd_outBuf.dst = streamer->base.bbs_buffer.data;
    streamer->zstd_outBuf.size = streamer->base.bbs_buffer.maxlen;
    streamer->zstd_outBuf.pos = 0;
 
    return &streamer->base;
#else
    pg_fatal("this build does not support compression with %s", "ZSTD");
    return NULL;                /* keep compiler quiet */
#endif
}
 
#ifdef USE_ZSTD
/*
 * Decompress the input data to output buffer until we run out of input
 * data. Each time the output buffer is full, pass on the decompressed data
 * to the next streamer.
 */
static void
astreamer_zstd_decompressor_content(astreamer *streamer,
                                    astreamer_member *member,
                                    const char *data, int len,
                                    astreamer_archive_context context)
{
    astreamer_zstd_frame *mystreamer = (astreamer_zstd_frame *) streamer;
    ZSTD_inBuffer inBuf = {data, len, 0};
 
    while (inBuf.pos < inBuf.size)
    {
        size_t      ret;
 
        /*
         * If output buffer is full then forward the content to next streamer
         * and update the output buffer.
         */
        if (mystreamer->zstd_outBuf.pos >= mystreamer->zstd_outBuf.size)
        {
            astreamer_content(mystreamer->base.bbs_next, member,
                              mystreamer->zstd_outBuf.dst,
                              mystreamer->zstd_outBuf.pos,
                              context);
 
            /* Reset the ZSTD output buffer. */
            mystreamer->zstd_outBuf.dst = mystreamer->base.bbs_buffer.data;
            mystreamer->zstd_outBuf.size = mystreamer->base.bbs_buffer.maxlen;
            mystreamer->zstd_outBuf.pos = 0;
        }
 
        ret = ZSTD_decompressStream(mystreamer->dctx,
                                    &mystreamer->zstd_outBuf, &inBuf);
 
        if (ZSTD_isError(ret))
            pg_fatal("could not decompress data: %s",
                     ZSTD_getErrorName(ret));
    }
}
 
/*
 * End-of-stream processing.
 */
static void
astreamer_zstd_decompressor_finalize(astreamer *streamer)
{
    astreamer_zstd_frame *mystreamer = (astreamer_zstd_frame *) streamer;
 
    /*
     * End of the stream, if there is some pending data in output buffers then
     * we must forward it to next streamer.
     */
    if (mystreamer->zstd_outBuf.pos > 0)
        astreamer_content(mystreamer->base.bbs_next, NULL,
                          mystreamer->base.bbs_buffer.data,
                          mystreamer->base.bbs_buffer.maxlen,
                          ASTREAMER_UNKNOWN);
 
    astreamer_finalize(mystreamer->base.bbs_next);
}
 
/*
 * Free memory.
 */
static void
astreamer_zstd_decompressor_free(astreamer *streamer)
{
    astreamer_zstd_frame *mystreamer = (astreamer_zstd_frame *) streamer;
 
    astreamer_free(streamer->bbs_next);
    ZSTD_freeDCtx(mystreamer->dctx);
    pfree(streamer->bbs_buffer.data);
    pfree(streamer);
}
#endif