local int gz_head()

in activemq-cpp/src/main/decaf/internal/util/zip/gzread.c [104:223]

• 99 lines of code
• 26 McCabe index (conditional complexity)

local int gz_head(state)
    gz_statep state;
{
    z_streamp strm = &(state->strm);
    int flags;
    unsigned len;

    /* allocate read buffers and inflate memory */
    if (state->size == 0) {
        /* allocate buffers */
        state->in = malloc(state->want);
        state->out = malloc(state->want << 1);
        if (state->in == NULL || state->out == NULL) {
            if (state->out != NULL)
                free(state->out);
            if (state->in != NULL)
                free(state->in);
            gz_error(state, Z_MEM_ERROR, "out of memory");
            return -1;
        }
        state->size = state->want;

        /* allocate inflate memory */
        state->strm.zalloc = Z_NULL;
        state->strm.zfree = Z_NULL;
        state->strm.opaque = Z_NULL;
        state->strm.avail_in = 0;
        state->strm.next_in = Z_NULL;
        if (inflateInit2(&(state->strm), -15) != Z_OK) {    /* raw inflate */
            free(state->out);
            free(state->in);
            state->size = 0;
            gz_error(state, Z_MEM_ERROR, "out of memory");
            return -1;
        }
    }

    /* get some data in the input buffer */
    if (strm->avail_in == 0) {
        if (gz_avail(state) == -1)
            return -1;
        if (strm->avail_in == 0)
            return 0;
    }

    /* look for the gzip magic header bytes 31 and 139 */
    if (strm->next_in[0] == 31) {
        strm->avail_in--;
        strm->next_in++;
        if (strm->avail_in == 0 && gz_avail(state) == -1)
            return -1;
        if (strm->avail_in && strm->next_in[0] == 139) {
            /* we have a gzip header, woo hoo! */
            strm->avail_in--;
            strm->next_in++;

            /* skip rest of header */
            if (NEXT() != 8) {      /* compression method */
                gz_error(state, Z_DATA_ERROR, "unknown compression method");
                return -1;
            }
            flags = NEXT();
            if (flags & 0xe0) {     /* reserved flag bits */
                gz_error(state, Z_DATA_ERROR, "unknown header flags set");
                return -1;
            }
            NEXT();                 /* modification time */
            NEXT();
            NEXT();
            NEXT();
            NEXT();                 /* extra flags */
            NEXT();                 /* operating system */
            if (flags & 4) {        /* extra field */
                len = (unsigned)NEXT();
                len += (unsigned)NEXT() << 8;
                while (len--)
                    if (NEXT() < 0)
                        break;
            }
            if (flags & 8)          /* file name */
                while (NEXT() > 0)
                    ;
            if (flags & 16)         /* comment */
                while (NEXT() > 0)
                    ;
            if (flags & 2) {        /* header crc */
                NEXT();
                NEXT();
            }
            /* an unexpected end of file is not checked for here -- it will be
               noticed on the first request for uncompressed data */

            /* set up for decompression */
            inflateReset(strm);
            strm->adler = crc32(0L, Z_NULL, 0);
            state->how = GZIP;
            state->direct = 0;
            return 0;
        }
        else {
            /* not a gzip file -- save first byte (31) and fall to raw i/o */
            state->out[0] = 31;
            state->have = 1;
        }
    }

    /* doing raw i/o, save start of raw data for seeking, copy any leftover
       input to output -- this assumes that the output buffer is larger than
       the input buffer, which also assures space for gzungetc() */
    state->raw = state->pos;
    state->next = state->out;
    if (strm->avail_in) {
        memcpy(state->next + state->have, strm->next_in, strm->avail_in);
        state->have += strm->avail_in;
        strm->avail_in = 0;
    }
    state->how = COPY;
    state->direct = 1;
    return 0;
}