/*
  * RTJpeg decoding functions
  * Copyright (c) 2006 Reimar Doeffinger
  *

  * 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
  */

 #include "libavutil/common.h"

 #include "get_bits.h"

 #include "dsputil.h"
 #include "rtjpeg.h"
 
 #define PUT_COEFF(c) \
     i = scan[coeff--]; \
     block[i] = (c) * quant[i];
 

 /// aligns the bitstream to the given power of two

 #define ALIGN(a) \
     n = (-get_bits_count(gb)) & (a - 1); \
     if (n) {skip_bits(gb, n);}
 
 /**

  * @brief read one block from stream
  * @param gb contains stream data
  * @param block where data is written to
  * @param scan array containing the mapping stream address -> block position
  * @param quant quantization factors
  * @return 0 means the block is not coded, < 0 means an error occurred.

  *
  * Note: GetBitContext is used to make the code simpler, since all data is
  * aligned this could be done faster in a different way, e.g. as it is done

  * in MPlayer libmpcodecs/native/rtjpegn.c.

  */

 static inline int get_block(GetBitContext *gb, DCTELEM *block, const uint8_t *scan,
                             const uint32_t *quant) {

     int coeff, i, n;
     int8_t ac;
     uint8_t dc = get_bits(gb, 8);
 
     // block not coded
     if (dc == 255)
        return 0;
 
     // number of non-zero coefficients
     coeff = get_bits(gb, 6);

     if (get_bits_left(gb) < (coeff << 1))

         return -1;

     // normally we would only need to clear the (63 - coeff) last values,
     // but since we do not know where they are we just clear the whole block
     memset(block, 0, 64 * sizeof(DCTELEM));
 
     // 2 bits per coefficient
     while (coeff) {
         ac = get_sbits(gb, 2);
         if (ac == -2)
             break; // continue with more bits
         PUT_COEFF(ac);
     }
 
     // 4 bits per coefficient
     ALIGN(4);

     if (get_bits_left(gb) < (coeff << 2))

         return -1;

     while (coeff) {
         ac = get_sbits(gb, 4);
         if (ac == -8)
             break; // continue with more bits
         PUT_COEFF(ac);
     }
 
     // 8 bits per coefficient
     ALIGN(8);

     if (get_bits_left(gb) < (coeff << 3))

         return -1;

     while (coeff) {
         ac = get_sbits(gb, 8);
         PUT_COEFF(ac);
     }
 
     PUT_COEFF(dc);
     return 1;
 }
 
 /**

  * @brief decode one rtjpeg YUV420 frame

  * @param c context, must be initialized via ff_rtjpeg_decode_init

  * @param f AVFrame to place decoded frame into. If parts of the frame

  *          are not coded they are left unchanged, so consider initializing it

  * @param buf buffer containing input data
  * @param buf_size length of input data in bytes
  * @return number of bytes consumed from the input buffer

  */

 int ff_rtjpeg_decode_frame_yuv420(RTJpegContext *c, AVFrame *f,
                                   const uint8_t *buf, int buf_size) {

     GetBitContext gb;
     int w = c->w / 16, h = c->h / 16;
     int x, y;

     uint8_t *y1 = f->data[0], *y2 = f->data[0] + 8 * f->linesize[0];
     uint8_t *u = f->data[1], *v = f->data[2];

     init_get_bits(&gb, buf, buf_size * 8);
     for (y = 0; y < h; y++) {
         for (x = 0; x < w; x++) {

 #define BLOCK(quant, dst, stride) do { \
     int res = get_block(&gb, block, c->scan, quant); \
     if (res < 0) \
         return res; \
     if (res > 0) \
         c->dsp->idct_put(dst, stride, block); \
 } while (0)

             DCTELEM *block = c->block;

             BLOCK(c->lquant, y1, f->linesize[0]);

             y1 += 8;

             BLOCK(c->lquant, y1, f->linesize[0]);

             y1 += 8;

             BLOCK(c->lquant, y2, f->linesize[0]);

             y2 += 8;

             BLOCK(c->lquant, y2, f->linesize[0]);

             y2 += 8;

             BLOCK(c->cquant, u,  f->linesize[1]);

             u += 8;

             BLOCK(c->cquant, v,  f->linesize[2]);

             v += 8;
         }
         y1 += 2 * 8 * (f->linesize[0] - w);
         y2 += 2 * 8 * (f->linesize[0] - w);
         u += 8 * (f->linesize[1] - w);
         v += 8 * (f->linesize[2] - w);
     }
     return get_bits_count(&gb) / 8;
 }
 
 /**

  * @brief initialize an RTJpegContext, may be called multiple times
  * @param c context to initialize
  * @param dsp specifies the idct to use for decoding
  * @param width width of image, will be rounded down to the nearest multiple

  *              of 16 for decoding

  * @param height height of image, will be rounded down to the nearest multiple

  *              of 16 for decoding

  * @param lquant luma quantization table to use
  * @param cquant chroma quantization table to use

  */

 void ff_rtjpeg_decode_init(RTJpegContext *c, DSPContext *dsp,
                            int width, int height,
                            const uint32_t *lquant, const uint32_t *cquant) {

     int i;
     c->dsp = dsp;
     for (i = 0; i < 64; i++) {
         int z = ff_zigzag_direct[i];
         int p = c->dsp->idct_permutation[i];
         z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant
 
         // permute the scan and quantization tables for the chosen idct
         c->scan[i] = c->dsp->idct_permutation[z];
         c->lquant[p] = lquant[i];
         c->cquant[p] = cquant[i];
     }
     c->w = width;
     c->h = height;
 }