/* ===========================================================================
      Writes the given null-terminated string to the compressed file, excluding
   the terminating null character.
      gzputs returns the number of characters written, or -1 in case of error.
*/
int ZEXPORT gzputs(file, s)
    gzFile file;
    const char *s;
{
    return gzwrite(file, (char*)s, (unsigned)strlen(s));
}


/* ===========================================================================
     Flushes all pending output into the compressed file. The parameter
   flush is as in the deflate() function.
*/
local int do_flush (file, flush)
    gzFile file;
    int flush;
{
    uInt len;
    int done = 0;
    gz_stream *s = (gz_stream*)file;

    if (s == NULL || s->mode != 'w') return Z_STREAM_ERROR;

    s->stream.avail_in = 0; /* should be zero already anyway */

    for (;;) {
        len = Z_BUFSIZE - s->stream.avail_out;

        if (len != 0) {
            if ((uInt)fwrite(s->outbuf, 1, len, s->file) != len) {
                s->z_err = Z_ERRNO;
                return Z_ERRNO;
            }
            s->stream.next_out = s->outbuf;
            s->stream.avail_out = Z_BUFSIZE;
        }
        if (done) break;
        s->out += s->stream.avail_out;
        s->z_err = deflate(&(s->stream), flush);
        s->out -= s->stream.avail_out;

        /* Ignore the second of two consecutive flushes: */
        if (len == 0 && s->z_err == Z_BUF_ERROR) s->z_err = Z_OK;

        /* deflate has finished flushing only when it hasn't used up
         * all the available space in the output buffer:
         */
        done = (s->stream.avail_out != 0 || s->z_err == Z_STREAM_END);

        if (s->z_err != Z_OK && s->z_err != Z_STREAM_END) break;
    }
    return  s->z_err == Z_STREAM_END ? Z_OK : s->z_err;
}

int ZEXPORT gzflush (file, flush)
     gzFile file;
     int flush;
{
    gz_stream *s = (gz_stream*)file;
    int err = do_flush (file, flush);

    if (err) return err;
    fflush(s->file);
    return  s->z_err == Z_STREAM_END ? Z_OK : s->z_err;
}
#endif /* NO_GZCOMPRESS */

/* ===========================================================================
      Sets the starting position for the next gzread or gzwrite on the given
   compressed file. The offset represents a number of bytes in the
      gzseek returns the resulting offset location as measured in bytes from
   the beginning of the uncompressed stream, or -1 in case of error.
      SEEK_END is not implemented, returns error.
      In this version of the library, gzseek can be extremely slow.
*/
z_off_t ZEXPORT gzseek (file, offset, whence)
    gzFile file;
    z_off_t offset;
    int whence;
{
    gz_stream *s = (gz_stream*)file;

    if (s == NULL || whence == SEEK_END ||
        s->z_err == Z_ERRNO || s->z_err == Z_DATA_ERROR) {
        return -1L;
    }

    if (s->mode == 'w') {
#ifdef NO_GZCOMPRESS
        return -1L;
#else
        if (whence == SEEK_SET) {
            offset -= s->in;
        }
        if (offset < 0) return -1L;

        /* At this point, offset is the number of zero bytes to write. */
        if (s->inbuf == Z_NULL) {
            s->inbuf = (Byte*)ALLOC(Z_BUFSIZE); /* for seeking */
            if (s->inbuf == Z_NULL) return -1L;
            zmemzero(s->inbuf, Z_BUFSIZE);
        }
        while (offset > 0)  {
            uInt size = Z_BUFSIZE;
            if (offset < Z_BUFSIZE) size = (uInt)offset;

            size = gzwrite(file, s->inbuf, size);
            if (size == 0) return -1L;

            offset -= size;
        }
        return s->in;
#endif
    }
    /* Rest of function is for reading only */

    /* compute absolute position */
    if (whence == SEEK_CUR) {
        offset += s->out;
    }
    if (offset < 0) return -1L;

    if (s->transparent) {
        /* map to fseek */
        s->back = EOF;
        s->stream.avail_in = 0;
        s->stream.next_in = s->inbuf;
        if (fseek(s->file, offset, SEEK_SET) < 0) return -1L;

        s->in = s->out = offset;
        return offset;
    }

    /* For a negative seek, rewind and use positive seek */
    if (offset >= s->out) {
        offset -= s->out;
    } else if (gzrewind(file) < 0) {
        return -1L;
    }
    /* offset is now the number of bytes to skip. */

    if (offset != 0 && s->outbuf == Z_NULL) {
        s->outbuf = (Byte*)ALLOC(Z_BUFSIZE);
        if (s->outbuf == Z_NULL) return -1L;
    }
    if (offset && s->back != EOF) {
        s->back = EOF;
        s->out++;
        offset--;
        if (s->last) s->z_err = Z_STREAM_END;
    }
    while (offset > 0)  {
        int size = Z_BUFSIZE;
        if (offset < Z_BUFSIZE) size = (int)offset;

        size = gzread(file, s->outbuf, (uInt)size);
        if (size <= 0) return -1L;
        offset -= size;
    }
    return s->out;
}

/* ===========================================================================
     Rewinds input file.
*/
int ZEXPORT gzrewind (file)
    gzFile file;
{
    gz_stream *s = (gz_stream*)file;

    if (s == NULL || s->mode != 'r') return -1;

    s->z_err = Z_OK;
    s->z_eof = 0;
    s->back = EOF;
    s->stream.avail_in = 0;
    s->stream.next_in = s->inbuf;
    s->crc = crc32(0L, Z_NULL, 0);
    if (!s->transparent) (void)inflateReset(&s->stream);
    s->in = 0;
    s->out = 0;
    return fseek(s->file, s->start, SEEK_SET);
}

/* ===========================================================================
     Returns the starting position for the next gzread or gzwrite on the
   given compressed file. This position represents a number of bytes in the
   uncompressed data stream.
*/
z_off_t ZEXPORT gztell (file)
    gzFile file;
{
    return gzseek(file, 0L, SEEK_CUR);
}

/* ===========================================================================
     Returns 1 when EOF has previously been detected reading the given
   input stream, otherwise zero.
*/
int ZEXPORT gzeof (file)
    gzFile file;
{
    gz_stream *s = (gz_stream*)file;

    /* With concatenated compressed files that can have embedded
     * crc trailers, z_eof is no longer the only/best indicator of EOF
     * on a gz_stream. Handle end-of-stream error explicitly here.
     */
    if (s == NULL || s->mode != 'r') return 0;
    if (s->z_eof) return 1;
    return s->z_err == Z_STREAM_END;
}

/* ===========================================================================
     Returns 1 if reading and doing so transparently, otherwise zero.
*/
int ZEXPORT gzdirect (file)
    gzFile file;
{
    gz_stream *s = (gz_stream*)file;

    if (s == NULL || s->mode != 'r') return 0;
    return s->transparent;
}

/* ===========================================================================
   Outputs a long in LSB order to the given file
*/
local void putLong (file, x)
    FILE *file;
    uLong x;
{
    int n;
    for (n = 0; n < 4; n++) {
        fputc((int)(x & 0xff), file);
        x >>= 8;
    }
}

/* ===========================================================================
   Reads a long in LSB order from the given gz_stream. Sets z_err in case
   of error.
*/
local uLong getLong (s)
    gz_stream *s;
{
    uLong x = (uLong)get_byte(s);
    int c;

    x += ((uLong)get_byte(s))<<8;
    x += ((uLong)get_byte(s))<<16;
    c = get_byte(s);
    if (c == EOF) s->z_err = Z_DATA_ERROR;
    x += ((uLong)c)<<24;
    return x;
}

/* ===========================================================================
     Flushes all pending output if necessary, closes the compressed file
   and deallocates all the (de)compression state.
*/
int ZEXPORT gzclose (file)
    gzFile file;
{
    gz_stream *s = (gz_stream*)file;

    if (s == NULL) return Z_STREAM_ERROR;

    if (s->mode == 'w') {
#ifdef NO_GZCOMPRESS
        return Z_STREAM_ERROR;
#else
        if (do_flush (file, Z_FINISH) != Z_OK)
            return destroy((gz_stream*)file);

        putLong (s->file, s->crc);
        putLong (s->file, (uLong)(s->in & 0xffffffff));
#endif
    }
    return destroy((gz_stream*)file);
}

#ifdef STDC
#  define zstrerror(errnum) strerror(errnum)
#else
#  define zstrerror(errnum) ""
#endif

/* ===========================================================================
     Returns the error message for the last error which occurred on the
   given compressed file. errnum is set to zlib error number. If an
   error occurred in the file system and not in the compression library,
   errnum is set to Z_ERRNO and the application may consult errno
   to get the exact error code.
*/
const char * ZEXPORT gzerror (file, errnum)
    gzFile file;
    int *errnum;
{
    char *m;
    gz_stream *s = (gz_stream*)file;

    if (s == NULL) {
        *errnum = Z_STREAM_ERROR;
        return (const char*)ERR_MSG(Z_STREAM_ERROR);
    }
    *errnum = s->z_err;
    if (*errnum == Z_OK) return (const char*)"";

    m = (char*)(*errnum == Z_ERRNO ? zstrerror(errno) : s->stream.msg);

    if (m == NULL || *m == '\0') m = (char*)ERR_MSG(s->z_err);

    TRYFREE(s->msg);
    s->msg = (char*)ALLOC(strlen(s->path) + strlen(m) + 3);
    if (s->msg == Z_NULL) return (const char*)ERR_MSG(Z_MEM_ERROR);
    strcpy(s->msg, s->path);
    strcat(s->msg, ": ");
    strcat(s->msg, m);
    return (const char*)s->msg;
}

/* ===========================================================================
     Clear the error and end-of-file flags, and do the same for the real file.
*/
void ZEXPORT gzclearerr (file)
    gzFile file;
{
    gz_stream *s = (gz_stream*)file;

    if (s == NULL) return;
    if (s->z_err != Z_STREAM_END) s->z_err = Z_OK;
    s->z_eof = 0;
    clearerr(s->file);
}