xz_pipe_decomp.c

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/*
 * xz_pipe_decomp.c
 * A simple example of pipe-only xz decompressor implementation.
 * version: 2012-06-14 - by Daniel Mealha Cabrita
 * Not copyrighted -- provided to the public domain.
 *
 * Compiling:
 * Link with liblzma. GCC example:
 * $ gcc -llzma xz_pipe_decomp.c -o xz_pipe_decomp
 *
 * Usage example:
 * $ cat some_file.xz | ./xz_pipe_decomp > some_file
 */
 
#include <stdio.h>
#include <stdint.h>
#include <inttypes.h>
#include <stdbool.h>
#include <lzma.h>
 
 
/* read/write buffer sizes */
#define IN_BUF_MAX  4096
#define OUT_BUF_MAX 4096
 
/* error codes */
#define RET_OK          0
#define RET_ERROR_INIT      1
#define RET_ERROR_INPUT     2
#define RET_ERROR_OUTPUT    3
#define RET_ERROR_DECOMPRESSION 4
 
 
/* note: in_file and out_file must be open already */
int xz_decompress (FILE *in_file, FILE *out_file)
{
    lzma_stream strm = LZMA_STREAM_INIT; /* alloc and init lzma_stream struct */
    const uint32_t flags = LZMA_TELL_UNSUPPORTED_CHECK | LZMA_CONCATENATED;
    const uint64_t memory_limit = UINT64_MAX; /* no memory limit */
    uint8_t in_buf [IN_BUF_MAX];
    uint8_t out_buf [OUT_BUF_MAX];
    size_t in_len;  /* length of useful data in in_buf */
    size_t out_len; /* length of useful data in out_buf */
    bool in_finished = false;
    bool out_finished = false;
    lzma_action action;
    lzma_ret ret_xz;
    int ret;
 
    ret = RET_OK;
 
    /* initialize xz decoder */
    ret_xz = lzma_stream_decoder (&strm, memory_limit, flags);
    if (ret_xz != LZMA_OK) {
        fprintf (stderr, "lzma_stream_decoder error: %d\n", (int) ret_xz);
        return RET_ERROR_INIT;
    }
 
    while ((! in_finished) && (! out_finished)) {
        /* read incoming data */
        in_len = fread (in_buf, 1, IN_BUF_MAX, in_file);
 
        if (feof (in_file)) {
            in_finished = true;
        }
        if (ferror (in_file)) {
            in_finished = true;
            ret = RET_ERROR_INPUT;
        }
 
        strm.next_in = in_buf;
        strm.avail_in = in_len;
 
        /* if no more data from in_buf, flushes the
           internal xz buffers and closes the decompressed data
           with LZMA_FINISH */
        action = in_finished ? LZMA_FINISH : LZMA_RUN;
 
        /* loop until there's no pending decompressed output */
        do {
            /* out_buf is clean at this point */
            strm.next_out = out_buf;
            strm.avail_out = OUT_BUF_MAX;
 
            /* decompress data */
            ret_xz = lzma_code (&strm, action);
 
            if ((ret_xz != LZMA_OK) && (ret_xz != LZMA_STREAM_END)) {
                fprintf (stderr, "lzma_code error: %d\n", (int) ret_xz);
                out_finished = true;
                ret = RET_ERROR_DECOMPRESSION;
            } else {
                /* write decompressed data */
                out_len = OUT_BUF_MAX - strm.avail_out;
                fwrite (out_buf, 1, out_len, out_file);
                if (ferror (out_file)) {
                    out_finished = true;
                    ret = RET_ERROR_OUTPUT;
                }
            }
        } while (strm.avail_out == 0);
    }
 
    /* Bug fix (2012-06-14): If no errors were detected, check
       that the last lzma_code() call returned LZMA_STREAM_END.
       If not, the file is probably truncated. */
    if ((ret == RET_OK) && (ret_xz != LZMA_STREAM_END)) {
        fprintf (stderr, "Input truncated or corrupt\n");
        ret = RET_ERROR_DECOMPRESSION;
    }
 
    lzma_end (&strm);
    return ret;
}
 
int main ()
{
    int ret;
 
    ret = xz_decompress (stdin, stdout);
    return ret;
}