source: MondoRescue/branches/2.2.5/mindi-busybox/archival/libunarchive/check_header_gzip.c@ 1765

/* vi: set sw=4 ts=4: */
/*
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

#include "libbb.h"
#include "unarchive.h" /* for external decl of check_header_gzip_or_die */

void check_header_gzip_or_die(int src_fd)
{
    union {
        unsigned char raw[8];
        struct {
            unsigned char method;
            unsigned char flags;
            unsigned int mtime;
            unsigned char xtra_flags;
            unsigned char os_flags;
        } formatted;
    } header;

    xread(src_fd, header.raw, 8);

    /* Check the compression method */
    if (header.formatted.method != 8) {
        bb_error_msg_and_die("unknown compression method %d",
                          header.formatted.method);
    }

    if (header.formatted.flags & 0x04) {
        /* bit 2 set: extra field present */
        unsigned extra_short;

        extra_short = xread_char(src_fd) + (xread_char(src_fd) << 8);
        while (extra_short > 0) {
            /* Ignore extra field */
            xread_char(src_fd);
            extra_short--;
        }
    }

    /* Discard original name if any */
    if (header.formatted.flags & 0x08) {
        /* bit 3 set: original file name present */
        while (xread_char(src_fd) != 0);
    }

    /* Discard file comment if any */
    if (header.formatted.flags & 0x10) {
        /* bit 4 set: file comment present */
        while (xread_char(src_fd) != 0);
    }

    /* Read the header checksum */
    if (header.formatted.flags & 0x02) {
        xread_char(src_fd);
        xread_char(src_fd);
    }
}