source: MondoRescue/branches/stable/mindi-busybox/archival/libunarchive/check_header_gzip.c@ 821

#include <stdlib.h>
#include <unistd.h>
#include "libbb.h"
#include "unarchive.h" /* for external decl of check_header_gzip */

void check_header_gzip(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;
        } formated;
    } header;

    bb_xread_all(src_fd, header.raw, 8);

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

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

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

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

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

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

    return;
}