zlib.c

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// SPDX-License-Identifier: GPL-2.0
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <zlib.h>

#include "util/compress.h"
#include "util/util.h"
#include "util/debug.h"


#define CHUNK_SIZE  16384

int gzip_decompress_to_file(const char *input, int output_fd)
{
    int ret = Z_STREAM_ERROR;
    int input_fd;
    void *ptr;
    int len;
    struct stat stbuf;
    unsigned char buf[CHUNK_SIZE];
    z_stream zs = {
        .zalloc     = Z_NULL,
        .zfree      = Z_NULL,
        .opaque     = Z_NULL,
        .avail_in   = 0,
        .next_in    = Z_NULL,
    };

    input_fd = open(input, O_RDONLY);
    if (input_fd < 0)
        return -1;

    if (fstat(input_fd, &stbuf) < 0)
        goto out_close;

    ptr = mmap(NULL, stbuf.st_size, PROT_READ, MAP_PRIVATE, input_fd, 0);
    if (ptr == MAP_FAILED)
        goto out_close;

    if (inflateInit2(&zs, 16 + MAX_WBITS) != Z_OK)
        goto out_unmap;

    zs.next_in = ptr;
    zs.avail_in = stbuf.st_size;

    do {
        zs.next_out = buf;
        zs.avail_out = CHUNK_SIZE;

        ret = inflate(&zs, Z_NO_FLUSH);
        switch (ret) {
        case Z_NEED_DICT:
            ret = Z_DATA_ERROR;
            /* fall through */
        case Z_DATA_ERROR:
        case Z_MEM_ERROR:
            goto out;
        default:
            break;
        }

        len = CHUNK_SIZE - zs.avail_out;
        if (writen(output_fd, buf, len) != len) {
            ret = Z_DATA_ERROR;
            goto out;
        }

    } while (ret != Z_STREAM_END);

out:
    inflateEnd(&zs);
out_unmap:
    munmap(ptr, stbuf.st_size);
out_close:
    close(input_fd);

    return ret == Z_STREAM_END ? 0 : -1;
}