int ZEXPORT gzread()

in activemq-cpp/src/main/decaf/internal/util/zip/gzread.c [362:450]

• 59 lines of code
• 19 McCabe index (conditional complexity)

int ZEXPORT gzread(file, buf, len)
    gzFile file;
    voidp buf;
    unsigned len;
{
    unsigned got, n;
    gz_statep state;
    z_streamp strm;

    /* get internal structure */
    if (file == NULL)
        return -1;
    state = (gz_statep)file;
    strm = &(state->strm);

    /* check that we're reading and that there's no error */
    if (state->mode != GZ_READ || state->err != Z_OK)
        return -1;

    /* since an int is returned, make sure len fits in one, otherwise return
       with an error (this avoids the flaw in the interface) */
    if ((int)len < 0) {
        gz_error(state, Z_BUF_ERROR, "requested length does not fit in int");
        return -1;
    }

    /* if len is zero, avoid unnecessary operations */
    if (len == 0)
        return 0;

    /* process a skip request */
    if (state->seek) {
        state->seek = 0;
        if (gz_skip(state, state->skip) == -1)
            return -1;
    }

    /* get len bytes to buf, or less than len if at the end */
    got = 0;
    do {
        /* first just try copying data from the output buffer */
        if (state->have) {
            n = state->have > len ? len : state->have;
            memcpy(buf, state->next, n);
            state->next += n;
            state->have -= n;
        }

        /* output buffer empty -- return if we're at the end of the input */
        else if (state->eof && strm->avail_in == 0)
            break;

        /* need output data -- for small len or new stream load up our output
           buffer */
        else if (state->how == LOOK || len < (state->size << 1)) {
            /* get more output, looking for header if required */
            if (gz_make(state) == -1)
                return -1;
            continue;       /* no progress yet -- go back to memcpy() above */
            /* the copy above assures that we will leave with space in the
               output buffer, allowing at least one gzungetc() to succeed */
        }

        /* large len -- read directly into user buffer */
        else if (state->how == COPY) {      /* read directly */
            if (gz_load(state, buf, len, &n) == -1)
                return -1;
        }

        /* large len -- decompress directly into user buffer */
        else {  /* state->how == GZIP */
            strm->avail_out = len;
            strm->next_out = buf;
            if (gz_decomp(state) == -1)
                return -1;
            n = state->have;
            state->have = 0;
        }

        /* update progress */
        len -= n;
        buf = (char *)buf + n;
        got += n;
        state->pos += n;
    } while (len);

    /* return number of bytes read into user buffer (will fit in int) */
    return (int)got;
}