root/doc/examples_old/xz_pipe_decomp.c

DEFINITIONS

1. xz_decompress
2. main

/*
 * 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;
}