/*
  * Copyright (c) 1990 James Ashton - Sydney University
  * Copyright (c) 2012 Stefano Sabatini
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**
  * @file
  * X-Face common definitions.
  */
 
 #include <stdint.h>
 
 /* define the face size - 48x48x1 */
 #define XFACE_WIDTH  48
 #define XFACE_HEIGHT 48
 #define XFACE_PIXELS (XFACE_WIDTH * XFACE_HEIGHT)
 
 /* compressed output uses the full range of printable characters.
  * In ASCII these are in a contiguous block so we just need to know
  * the first and last. The total number of printables is needed too. */
 #define XFACE_FIRST_PRINT '!'
 #define XFACE_LAST_PRINT '~'
 #define XFACE_PRINTS (XFACE_LAST_PRINT - XFACE_FIRST_PRINT + 1)
 
 /*
  * Image is encoded as a big integer, using characters from '~' to
  * '!', for a total of 92 symbols. In order to express 48x48=2304
  * bits, we need a total of 354 digits, as given by:
  * ceil(lg_92(2^2304)) = 354
  */
 #define XFACE_MAX_DIGITS 354
 
 #define XFACE_BITSPERWORD 8
 #define XFACE_WORDCARRY (1 << XFACE_BITSPERWORD)
 #define XFACE_WORDMASK (XFACE_WORDCARRY - 1)
 
 #define XFACE_MAX_WORDS ((XFACE_PIXELS * 2 + XFACE_BITSPERWORD - 1) / XFACE_BITSPERWORD)
 
 /* Portable, very large unsigned integer arithmetic is needed.
  * Implementation uses arrays of WORDs. */
 typedef struct {
     int nb_words;
     uint8_t words[XFACE_MAX_WORDS];
 } BigInt;
 
 /**
  * Add a to b storing the result in b.
  */
 void ff_big_add(BigInt *b, uint8_t a);
 
 /**
  * Divide b by a storing the result in b and the remainder in the word
  * pointed to by r.
  */
 void ff_big_div(BigInt *b, uint8_t a, uint8_t *r);
 
 /**
  * Multiply a by b storing the result in b.
  */
 void ff_big_mul(BigInt *b, uint8_t a);
 
 /* Each face is encoded using 9 octrees of 16x16 each. Each level of the
  * trees has varying probabilities of being white, grey or black.
  * The table below is based on sampling many faces */
 enum XFaceColor { XFACE_COLOR_BLACK = 0, XFACE_COLOR_GREY, XFACE_COLOR_WHITE };
 
 /* Data of varying probabilities are encoded by a value in the range 0 - 255.
  * The probability of the data determines the range of possible encodings.
  * Offset gives the first possible encoding of the range. */
 typedef struct {
     int range;
     int offset;
 } ProbRange;
 
 extern const ProbRange ff_xface_probranges_per_level[4][3];
 
 extern const ProbRange ff_xface_probranges_2x2[16];
 
 void ff_xface_generate_face(uint8_t *dst, uint8_t * const src);