/*
 * The Python Imaging Library.
 * $Id$
 *
 * decoder for XBM hex image data
 *
 * history:
 * 96-04-13 fl Created
 *
 * Copyright (c) Fredrik Lundh 1996.
 * Copyright (c) Secret Labs AB 1997.
 *
 * See the README file for information on usage and redistribution.
 */

#include "Imaging.h"

#define HEX(v)                               \
    ((v >= '0' && v <= '9')   ? v - '0'      \
     : (v >= 'a' && v <= 'f') ? v - 'a' + 10 \
     : (v >= 'A' && v <= 'F') ? v - 'A' + 10 \
                              : 0)

int
ImagingXbmDecode(Imaging im, ImagingCodecState state, UINT8 *buf, Py_ssize_t bytes) {
    enum { BYTE = 1, SKIP };

    UINT8 *ptr;

    if (!state->state) {
        state->state = SKIP;
    }

    ptr = buf;

    for (;;) {
        if (state->state == SKIP) {
            /* Skip forward until next 'x' */

            while (bytes > 0) {
                if (*ptr == 'x') {
                    break;
                }
                ptr++;
                bytes--;
            }

            if (bytes == 0) {
                return ptr - buf;
            }

            state->state = BYTE;
        }

        if (bytes < 3) {
            return ptr - buf;
        }

        state->buffer[state->x] = (HEX(ptr[1]) << 4) + HEX(ptr[2]);

        if (++state->x >= state->bytes) {
            /* Got a full line, unpack it */
            state->shuffle((UINT8 *)im->image[state->y], state->buffer, state->xsize);

            state->x = 0;

            if (++state->y >= state->ysize) {
                /* End of file (errcode = 0) */
                return -1;
            }
        }

        ptr += 3;
        bytes -= 3;

        state->state = SKIP;
    }
}