compress_lz4.c

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/*-------------------------------------------------------------------------
 *
 * compress_lz4.c
 *   Routines for archivers to write a LZ4 compressed data stream.
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *     src/bin/pg_dump/compress_lz4.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"
#include <unistd.h>
 
#include "compress_lz4.h"
#include "pg_backup_utils.h"
 
#ifdef USE_LZ4
#include <lz4frame.h>
 
/*
 * LZ4F_HEADER_SIZE_MAX first appeared in v1.7.5 of the library.
 * Redefine it for installations with a lesser version.
 */
#ifndef LZ4F_HEADER_SIZE_MAX
#define LZ4F_HEADER_SIZE_MAX    32
#endif
 
/*---------------------------------
 * Common to both compression APIs
 *---------------------------------
 */
 
/*
 * (de)compression state used by both the Compressor and Stream APIs.
 */
typedef struct LZ4State
{
    /*
     * Used by the Stream API to keep track of the file stream.
     */
    FILE       *fp;
 
    LZ4F_preferences_t prefs;
 
    LZ4F_compressionContext_t ctx;
    LZ4F_decompressionContext_t dtx;
 
    /*
     * Used by the Stream API's lazy initialization.
     */
    bool        inited;
 
    /*
     * Used by the Stream API to distinguish between compression and
     * decompression operations.
     */
    bool        compressing;
 
    /*
     * I/O buffer area.
     */
    char       *buffer;         /* buffer for compressed data */
    size_t      buflen;         /* allocated size of buffer */
    size_t      bufdata;        /* amount of valid data currently in buffer */
    /* These fields are used only while decompressing: */
    size_t      bufnext;        /* next buffer position to decompress */
    char       *outbuf;         /* buffer for decompressed data */
    size_t      outbuflen;      /* allocated size of outbuf */
    size_t      outbufdata;     /* amount of valid data currently in outbuf */
    size_t      outbufnext;     /* next outbuf position to return */
 
    /*
     * Used by both APIs to keep track of error codes.
     */
    size_t      errcode;
} LZ4State;
 
/*
 * LZ4State_compression_init
 *      Initialize the required LZ4State members for compression.
 *
 * Write the LZ4 frame header in a buffer keeping track of its length. Users of
 * this function can choose when and how to write the header to a file stream.
 *
 * Returns true on success. In case of a failure returns false, and stores the
 * error code in state->errcode.
 */
static bool
LZ4State_compression_init(LZ4State *state)
{
    size_t      status;
 
    /*
     * Compute size needed for buffer, assuming we will present at most
     * DEFAULT_IO_BUFFER_SIZE input bytes at a time.
     */
    state->buflen = LZ4F_compressBound(DEFAULT_IO_BUFFER_SIZE, &state->prefs);
 
    /*
     * Add some slop to ensure we're not forced to flush every time.
     *
     * The present slop factor of 50% is chosen so that the typical output
     * block size is about 128K when DEFAULT_IO_BUFFER_SIZE = 128K.  We might
     * need a different slop factor to maintain that equivalence if
     * DEFAULT_IO_BUFFER_SIZE is changed dramatically.
     */
    state->buflen += state->buflen / 2;
 
    /*
     * LZ4F_compressBegin requires a buffer that is greater or equal to
     * LZ4F_HEADER_SIZE_MAX. Verify that the requirement is met.
     */
    if (state->buflen < LZ4F_HEADER_SIZE_MAX)
        state->buflen = LZ4F_HEADER_SIZE_MAX;
 
    status = LZ4F_createCompressionContext(&state->ctx, LZ4F_VERSION);
    if (LZ4F_isError(status))
    {
        state->errcode = status;
        return false;
    }
 
    state->buffer = pg_malloc(state->buflen);
 
    /*
     * Insert LZ4 header into buffer.
     */
    status = LZ4F_compressBegin(state->ctx,
                                state->buffer, state->buflen,
                                &state->prefs);
    if (LZ4F_isError(status))
    {
        state->errcode = status;
        return false;
    }
 
    state->bufdata = status;
 
    return true;
}
 
/*----------------------
 * Compressor API
 *----------------------
 */
 
/* Private routines that support LZ4 compressed data I/O */
 
static void
ReadDataFromArchiveLZ4(ArchiveHandle *AH, CompressorState *cs)
{
    size_t      r;
    size_t      readbuflen;
    char       *outbuf;
    char       *readbuf;
    LZ4F_decompressionContext_t ctx = NULL;
    LZ4F_decompressOptions_t dec_opt;
    LZ4F_errorCode_t status;
 
    memset(&dec_opt, 0, sizeof(dec_opt));
    status = LZ4F_createDecompressionContext(&ctx, LZ4F_VERSION);
    if (LZ4F_isError(status))
        pg_fatal("could not create LZ4 decompression context: %s",
                 LZ4F_getErrorName(status));
 
    outbuf = pg_malloc(DEFAULT_IO_BUFFER_SIZE);
    readbuf = pg_malloc(DEFAULT_IO_BUFFER_SIZE);
    readbuflen = DEFAULT_IO_BUFFER_SIZE;
    while ((r = cs->readF(AH, &readbuf, &readbuflen)) > 0)
    {
        char       *readp;
        char       *readend;
 
        /* Process one chunk */
        readp = readbuf;
        readend = readbuf + r;
        while (readp < readend)
        {
            size_t      out_size = DEFAULT_IO_BUFFER_SIZE;
            size_t      read_size = readend - readp;
 
            status = LZ4F_decompress(ctx, outbuf, &out_size,
                                     readp, &read_size, &dec_opt);
            if (LZ4F_isError(status))
                pg_fatal("could not decompress: %s",
                         LZ4F_getErrorName(status));
 
            ahwrite(outbuf, 1, out_size, AH);
            readp += read_size;
        }
    }
 
    pg_free(outbuf);
    pg_free(readbuf);
 
    status = LZ4F_freeDecompressionContext(ctx);
    if (LZ4F_isError(status))
        pg_fatal("could not free LZ4 decompression context: %s",
                 LZ4F_getErrorName(status));
}
 
static void
WriteDataToArchiveLZ4(ArchiveHandle *AH, CompressorState *cs,
                      const void *data, size_t dLen)
{
    LZ4State   *state = (LZ4State *) cs->private_data;
    size_t      remaining = dLen;
 
    while (remaining > 0)
    {
        size_t      chunk;
        size_t      required;
        size_t      status;
 
        /* We don't try to present more than DEFAULT_IO_BUFFER_SIZE bytes */
        chunk = Min(remaining, (size_t) DEFAULT_IO_BUFFER_SIZE);
 
        /* If not enough space, must flush buffer */
        required = LZ4F_compressBound(chunk, &state->prefs);
        if (required > state->buflen - state->bufdata)
        {
            cs->writeF(AH, state->buffer, state->bufdata);
            state->bufdata = 0;
        }
 
        status = LZ4F_compressUpdate(state->ctx,
                                     state->buffer + state->bufdata,
                                     state->buflen - state->bufdata,
                                     data, chunk, NULL);
 
        if (LZ4F_isError(status))
            pg_fatal("could not compress data: %s",
                     LZ4F_getErrorName(status));
 
        state->bufdata += status;
 
        data = ((const char *) data) + chunk;
        remaining -= chunk;
    }
}
 
static void
EndCompressorLZ4(ArchiveHandle *AH, CompressorState *cs)
{
    LZ4State   *state = (LZ4State *) cs->private_data;
    size_t      required;
    size_t      status;
 
    /* Nothing needs to be done */
    if (!state)
        return;
 
    /* We might need to flush the buffer to make room for LZ4F_compressEnd */
    required = LZ4F_compressBound(0, &state->prefs);
    if (required > state->buflen - state->bufdata)
    {
        cs->writeF(AH, state->buffer, state->bufdata);
        state->bufdata = 0;
    }
 
    status = LZ4F_compressEnd(state->ctx,
                              state->buffer + state->bufdata,
                              state->buflen - state->bufdata,
                              NULL);
    if (LZ4F_isError(status))
        pg_fatal("could not end compression: %s",
                 LZ4F_getErrorName(status));
    state->bufdata += status;
 
    /* Write the final bufferload */
    cs->writeF(AH, state->buffer, state->bufdata);
 
    status = LZ4F_freeCompressionContext(state->ctx);
    if (LZ4F_isError(status))
        pg_fatal("could not end compression: %s",
                 LZ4F_getErrorName(status));
 
    pg_free(state->buffer);
    pg_free(state);
 
    cs->private_data = NULL;
}
 
/*
 * Public routines that support LZ4 compressed data I/O
 */
void
InitCompressorLZ4(CompressorState *cs, const pg_compress_specification compression_spec)
{
    LZ4State   *state;
 
    cs->readData = ReadDataFromArchiveLZ4;
    cs->writeData = WriteDataToArchiveLZ4;
    cs->end = EndCompressorLZ4;
 
    cs->compression_spec = compression_spec;
 
    /*
     * Read operations have access to the whole input. No state needs to be
     * carried between calls.
     */
    if (cs->readF)
        return;
 
    state = pg_malloc0(sizeof(*state));
    if (cs->compression_spec.level >= 0)
        state->prefs.compressionLevel = cs->compression_spec.level;
 
    if (!LZ4State_compression_init(state))
        pg_fatal("could not initialize LZ4 compression: %s",
                 LZ4F_getErrorName(state->errcode));
 
    cs->private_data = state;
}
 
/*----------------------
 * Compress Stream API
 *----------------------
 */
 
 
/*
 * LZ4 equivalent to feof() or gzeof().  Return true iff there is no
 * more buffered data and the end of the input file has been reached.
 */
static bool
LZ4Stream_eof(CompressFileHandle *CFH)
{
    LZ4State   *state = (LZ4State *) CFH->private_data;
 
    return state->outbufnext >= state->outbufdata &&
        state->bufnext >= state->bufdata &&
        feof(state->fp);
}
 
static const char *
LZ4Stream_get_error(CompressFileHandle *CFH)
{
    LZ4State   *state = (LZ4State *) CFH->private_data;
    const char *errmsg;
 
    if (LZ4F_isError(state->errcode))
        errmsg = LZ4F_getErrorName(state->errcode);
    else
        errmsg = strerror(errno);
 
    return errmsg;
}
 
/*
 * Initialize an already alloc'ed LZ4State struct for subsequent calls.
 *
 * Creates the necessary contexts for either compression or decompression. When
 * compressing data (indicated by compressing=true), it additionally writes the
 * LZ4 header in the output buffer.
 *
 * It's expected that a not-yet-initialized LZ4State will be zero-filled.
 *
 * Returns true on success. In case of a failure returns false, and stores the
 * error code in state->errcode.
 */
static bool
LZ4Stream_init(LZ4State *state, bool compressing)
{
    size_t      status;
 
    if (state->inited)
        return true;
 
    state->compressing = compressing;
 
    if (state->compressing)
    {
        if (!LZ4State_compression_init(state))
            return false;
    }
    else
    {
        status = LZ4F_createDecompressionContext(&state->dtx, LZ4F_VERSION);
        if (LZ4F_isError(status))
        {
            state->errcode = status;
            return false;
        }
 
        state->buflen = DEFAULT_IO_BUFFER_SIZE;
        state->buffer = pg_malloc(state->buflen);
        state->outbuflen = DEFAULT_IO_BUFFER_SIZE;
        state->outbuf = pg_malloc(state->outbuflen);
    }
 
    state->inited = true;
    return true;
}
 
/*
 * The workhorse for reading decompressed content out of an LZ4 compressed
 * stream.
 *
 * It will read up to 'ptrsize' decompressed content, or up to the new line
 * char if one is found first when the eol_flag is set.
 *
 * Returns the number of bytes of decompressed data copied into the ptr
 * buffer, or -1 in case of error.
 */
static int
LZ4Stream_read_internal(LZ4State *state, void *ptr, int ptrsize, bool eol_flag)
{
    int         dsize = 0;
    int         remaining = ptrsize;
 
    /* Lazy init */
    if (!LZ4Stream_init(state, false /* decompressing */ ))
    {
        pg_log_error("unable to initialize LZ4 library: %s",
                     LZ4F_getErrorName(state->errcode));
        return -1;
    }
 
    /* Loop until postcondition is satisfied */
    while (remaining > 0)
    {
        /*
         * If we already have some decompressed data, return that.
         */
        if (state->outbufnext < state->outbufdata)
        {
            char       *outptr = state->outbuf + state->outbufnext;
            size_t      readlen = state->outbufdata - state->outbufnext;
            bool        eol_found = false;
 
            if (readlen > remaining)
                readlen = remaining;
            /* If eol_flag is set, don't read beyond a newline */
            if (eol_flag)
            {
                char       *eolptr = memchr(outptr, '\n', readlen);
 
                if (eolptr)
                {
                    readlen = eolptr - outptr + 1;
                    eol_found = true;
                }
            }
            memcpy(ptr, outptr, readlen);
            ptr = ((char *) ptr) + readlen;
            state->outbufnext += readlen;
            dsize += readlen;
            remaining -= readlen;
            if (eol_found || remaining == 0)
                break;
            /* We must have emptied outbuf */
            Assert(state->outbufnext >= state->outbufdata);
        }
 
        /*
         * If we don't have any pending compressed data, load more into
         * state->buffer.
         */
        if (state->bufnext >= state->bufdata)
        {
            size_t      rsize;
 
            rsize = fread(state->buffer, 1, state->buflen, state->fp);
            if (rsize < state->buflen && !feof(state->fp))
            {
                pg_log_error("could not read from input file: %m");
                return -1;
            }
            if (rsize == 0)
                break;          /* must be EOF */
            state->bufdata = rsize;
            state->bufnext = 0;
        }
 
        /*
         * Decompress some data into state->outbuf.
         */
        {
            size_t      status;
            size_t      outlen = state->outbuflen;
            size_t      inlen = state->bufdata - state->bufnext;
 
            status = LZ4F_decompress(state->dtx,
                                     state->outbuf, &outlen,
                                     state->buffer + state->bufnext,
                                     &inlen,
                                     NULL);
            if (LZ4F_isError(status))
            {
                state->errcode = status;
                pg_log_error("could not read from input file: %s",
                             LZ4F_getErrorName(state->errcode));
                return -1;
            }
            state->bufnext += inlen;
            state->outbufdata = outlen;
            state->outbufnext = 0;
        }
    }
 
    return dsize;
}
 
/*
 * Compress size bytes from ptr and write them to the stream.
 */
static void
LZ4Stream_write(const void *ptr, size_t size, CompressFileHandle *CFH)
{
    LZ4State   *state = (LZ4State *) CFH->private_data;
    size_t      remaining = size;
 
    /* Lazy init */
    if (!LZ4Stream_init(state, true))
        pg_fatal("unable to initialize LZ4 library: %s",
                 LZ4F_getErrorName(state->errcode));
 
    while (remaining > 0)
    {
        size_t      chunk;
        size_t      required;
        size_t      status;
 
        /* We don't try to present more than DEFAULT_IO_BUFFER_SIZE bytes */
        chunk = Min(remaining, (size_t) DEFAULT_IO_BUFFER_SIZE);
 
        /* If not enough space, must flush buffer */
        required = LZ4F_compressBound(chunk, &state->prefs);
        if (required > state->buflen - state->bufdata)
        {
            errno = 0;
            if (fwrite(state->buffer, 1, state->bufdata, state->fp) != state->bufdata)
            {
                errno = (errno) ? errno : ENOSPC;
                pg_fatal("error during writing: %m");
            }
            state->bufdata = 0;
        }
 
        status = LZ4F_compressUpdate(state->ctx,
                                     state->buffer + state->bufdata,
                                     state->buflen - state->bufdata,
                                     ptr, chunk, NULL);
        if (LZ4F_isError(status))
            pg_fatal("error during writing: %s", LZ4F_getErrorName(status));
        state->bufdata += status;
 
        ptr = ((const char *) ptr) + chunk;
        remaining -= chunk;
    }
}
 
/*
 * fread() equivalent implementation for LZ4 compressed files.
 */
static size_t
LZ4Stream_read(void *ptr, size_t size, CompressFileHandle *CFH)
{
    LZ4State   *state = (LZ4State *) CFH->private_data;
    int         ret;
 
    if ((ret = LZ4Stream_read_internal(state, ptr, size, false)) < 0)
        pg_fatal("could not read from input file: %s", LZ4Stream_get_error(CFH));
 
    return (size_t) ret;
}
 
/*
 * fgetc() equivalent implementation for LZ4 compressed files.
 */
static int
LZ4Stream_getc(CompressFileHandle *CFH)
{
    LZ4State   *state = (LZ4State *) CFH->private_data;
    unsigned char c;
 
    if (LZ4Stream_read_internal(state, &c, 1, false) <= 0)
    {
        if (!LZ4Stream_eof(CFH))
            pg_fatal("could not read from input file: %s", LZ4Stream_get_error(CFH));
        else
            pg_fatal("could not read from input file: end of file");
    }
 
    return c;
}
 
/*
 * fgets() equivalent implementation for LZ4 compressed files.
 */
static char *
LZ4Stream_gets(char *ptr, int size, CompressFileHandle *CFH)
{
    LZ4State   *state = (LZ4State *) CFH->private_data;
    int         ret;
 
    ret = LZ4Stream_read_internal(state, ptr, size - 1, true);
 
    /*
     * LZ4Stream_read_internal returning 0 or -1 means that it was either an
     * EOF or an error, but gets_func is defined to return NULL in either case
     * so we can treat both the same here.
     */
    if (ret <= 0)
        return NULL;
 
    /*
     * Our caller expects the return string to be NULL terminated and we know
     * that ret is greater than zero.
     */
    ptr[ret - 1] = '\0';
 
    return ptr;
}
 
/*
 * Finalize (de)compression of a stream. When compressing it will write any
 * remaining content and/or generated footer from the LZ4 API.
 */
static bool
LZ4Stream_close(CompressFileHandle *CFH)
{
    FILE       *fp;
    LZ4State   *state = (LZ4State *) CFH->private_data;
    size_t      required;
    size_t      status;
    int         ret;
 
    fp = state->fp;
    if (state->inited)
    {
        if (state->compressing)
        {
            /* We might need to flush the buffer to make room */
            required = LZ4F_compressBound(0, &state->prefs);
            if (required > state->buflen - state->bufdata)
            {
                errno = 0;
                if (fwrite(state->buffer, 1, state->bufdata, state->fp) != state->bufdata)
                {
                    errno = (errno) ? errno : ENOSPC;
                    pg_log_error("could not write to output file: %m");
                }
                state->bufdata = 0;
            }
 
            status = LZ4F_compressEnd(state->ctx,
                                      state->buffer + state->bufdata,
                                      state->buflen - state->bufdata,
                                      NULL);
            if (LZ4F_isError(status))
            {
                pg_log_error("could not end compression: %s",
                             LZ4F_getErrorName(status));
            }
            else
                state->bufdata += status;
 
            errno = 0;
            if (fwrite(state->buffer, 1, state->bufdata, state->fp) != state->bufdata)
            {
                errno = (errno) ? errno : ENOSPC;
                pg_log_error("could not write to output file: %m");
            }
 
            status = LZ4F_freeCompressionContext(state->ctx);
            if (LZ4F_isError(status))
                pg_log_error("could not end compression: %s",
                             LZ4F_getErrorName(status));
        }
        else
        {
            status = LZ4F_freeDecompressionContext(state->dtx);
            if (LZ4F_isError(status))
                pg_log_error("could not end decompression: %s",
                             LZ4F_getErrorName(status));
            pg_free(state->outbuf);
        }
 
        pg_free(state->buffer);
    }
 
    pg_free(state);
    CFH->private_data = NULL;
 
    errno = 0;
    ret = fclose(fp);
    if (ret != 0)
    {
        pg_log_error("could not close file: %m");
        return false;
    }
 
    return true;
}
 
static bool
LZ4Stream_open(const char *path, int fd, const char *mode,
               CompressFileHandle *CFH)
{
    LZ4State   *state = (LZ4State *) CFH->private_data;
 
    if (fd >= 0)
        state->fp = fdopen(dup(fd), mode);
    else
        state->fp = fopen(path, mode);
    if (state->fp == NULL)
    {
        state->errcode = errno;
        return false;
    }
 
    return true;
}
 
static bool
LZ4Stream_open_write(const char *path, const char *mode, CompressFileHandle *CFH)
{
    char       *fname;
    int         save_errno;
    bool        ret;
 
    fname = psprintf("%s.lz4", path);
    ret = CFH->open_func(fname, -1, mode, CFH);
 
    save_errno = errno;
    pg_free(fname);
    errno = save_errno;
 
    return ret;
}
 
/*
 * Public routines
 */
void
InitCompressFileHandleLZ4(CompressFileHandle *CFH,
                          const pg_compress_specification compression_spec)
{
    LZ4State   *state;
 
    CFH->open_func = LZ4Stream_open;
    CFH->open_write_func = LZ4Stream_open_write;
    CFH->read_func = LZ4Stream_read;
    CFH->write_func = LZ4Stream_write;
    CFH->gets_func = LZ4Stream_gets;
    CFH->getc_func = LZ4Stream_getc;
    CFH->eof_func = LZ4Stream_eof;
    CFH->close_func = LZ4Stream_close;
    CFH->get_error_func = LZ4Stream_get_error;
 
    CFH->compression_spec = compression_spec;
    state = pg_malloc0(sizeof(*state));
    if (CFH->compression_spec.level >= 0)
        state->prefs.compressionLevel = CFH->compression_spec.level;
 
    CFH->private_data = state;
}
#else                           /* USE_LZ4 */
void
InitCompressorLZ4(CompressorState *cs,
                  const pg_compress_specification compression_spec)
{
    pg_fatal("this build does not support compression with %s", "LZ4");
}
 
void
InitCompressFileHandleLZ4(CompressFileHandle *CFH,
                          const pg_compress_specification compression_spec)
{
    pg_fatal("this build does not support compression with %s", "LZ4");
}
#endif                          /* USE_LZ4 */