/*
  * Lagarith lossless decoder
  * Copyright (c) 2009 Nathan Caldwell <saintdev (at) gmail.com>
  *
  * 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

  * Lagarith lossless decoder
  * @author Nathan Caldwell
  */
 
 #include "avcodec.h"
 #include "get_bits.h"
 #include "mathops.h"
 #include "dsputil.h"
 #include "lagarithrac.h"
 
 enum LagarithFrameType {
     FRAME_RAW           = 1,    /*!< uncompressed */
     FRAME_U_RGB24       = 2,    /*!< unaligned RGB24 */
     FRAME_ARITH_YUY2    = 3,    /*!< arithmetic coded YUY2 */
     FRAME_ARITH_RGB24   = 4,    /*!< arithmetic coded RGB24 */
     FRAME_SOLID_GRAY    = 5,    /*!< solid grayscale color frame */
     FRAME_SOLID_COLOR   = 6,    /*!< solid non-grayscale color frame */
     FRAME_OLD_ARITH_RGB = 7,    /*!< obsolete arithmetic coded RGB (no longer encoded by upstream since version 1.1.0) */
     FRAME_ARITH_RGBA    = 8,    /*!< arithmetic coded RGBA */
     FRAME_SOLID_RGBA    = 9,    /*!< solid RGBA color frame */
     FRAME_ARITH_YV12    = 10,   /*!< arithmetic coded YV12 */
     FRAME_REDUCED_RES   = 11,   /*!< reduced resolution YV12 frame */
 };
 
 typedef struct LagarithContext {
     AVCodecContext *avctx;
     AVFrame picture;
     DSPContext dsp;
     int zeros;                  /*!< number of consecutive zero bytes encountered */
     int zeros_rem;              /*!< number of zero bytes remaining to output */
 } LagarithContext;
 
 /**
  * Compute the 52bit mantissa of 1/(double)denom.
  * This crazy format uses floats in an entropy coder and we have to match x86
  * rounding exactly, thus ordinary floats aren't portable enough.
  * @param denom denominator
  * @return 52bit mantissa
  * @see softfloat_mul
  */
 static uint64_t softfloat_reciprocal(uint32_t denom)
 {
     int shift = av_log2(denom - 1) + 1;
     uint64_t ret = (1ULL << 52) / denom;
     uint64_t err = (1ULL << 52) - ret * denom;
     ret <<= shift;
     err <<= shift;
     err +=  denom / 2;
     return ret + err / denom;
 }
 
 /**
  * (uint32_t)(x*f), where f has the given mantissa, and exponent 0
  * Used in combination with softfloat_reciprocal computes x/(double)denom.
  * @param x 32bit integer factor
  * @param mantissa mantissa of f with exponent 0
  * @return 32bit integer value (x*f)
  * @see softfloat_reciprocal
  */
 static uint32_t softfloat_mul(uint32_t x, uint64_t mantissa)
 {
     uint64_t l = x * (mantissa & 0xffffffff);
     uint64_t h = x * (mantissa >> 32);
     h += l >> 32;
     l &= 0xffffffff;
     l += 1 << av_log2(h >> 21);
     h += l >> 32;
     return h >> 20;
 }
 
 static uint8_t lag_calc_zero_run(int8_t x)
 {
     return (x << 1) ^ (x >> 7);
 }
 
 static int lag_decode_prob(GetBitContext *gb, uint32_t *value)
 {
     static const uint8_t series[] = { 1, 2, 3, 5, 8, 13, 21 };
     int i;
     int bit     = 0;
     int bits    = 0;
     int prevbit = 0;
     unsigned val;
 
     for (i = 0; i < 7; i++) {
         if (prevbit && bit)
             break;
         prevbit = bit;
         bit = get_bits1(gb);
         if (bit && !prevbit)
             bits += series[i];
     }
     bits--;
     if (bits < 0 || bits > 31) {
         *value = 0;
         return -1;
     } else if (bits == 0) {
         *value = 0;
         return 0;
     }
 
     val  = get_bits_long(gb, bits);
     val |= 1 << bits;
 
     *value = val - 1;
 
     return 0;
 }
 
 static int lag_read_prob_header(lag_rac *rac, GetBitContext *gb)
 {
     int i, j, scale_factor;
     unsigned prob, cumulative_target;
     unsigned cumul_prob = 0;
     unsigned scaled_cumul_prob = 0;
 
     rac->prob[0] = 0;
     rac->prob[257] = UINT_MAX;
     /* Read probabilities from bitstream */
     for (i = 1; i < 257; i++) {
         if (lag_decode_prob(gb, &rac->prob[i]) < 0) {
             av_log(rac->avctx, AV_LOG_ERROR, "Invalid probability encountered.\n");
             return -1;
         }
         if ((uint64_t)cumul_prob + rac->prob[i] > UINT_MAX) {
             av_log(rac->avctx, AV_LOG_ERROR, "Integer overflow encountered in cumulative probability calculation.\n");
             return -1;
         }
         cumul_prob += rac->prob[i];
         if (!rac->prob[i]) {
             if (lag_decode_prob(gb, &prob)) {
                 av_log(rac->avctx, AV_LOG_ERROR, "Invalid probability run encountered.\n");
                 return -1;
             }
             if (prob > 257 - i)
                 prob = 257 - i;
             for (j = 0; j < prob; j++)
                 rac->prob[++i] = 0;
         }
     }
 
     if (!cumul_prob) {
         av_log(rac->avctx, AV_LOG_ERROR, "All probabilities are 0!\n");
         return -1;
     }
 
     /* Scale probabilities so cumulative probability is an even power of 2. */
     scale_factor = av_log2(cumul_prob);
 
     if (cumul_prob & (cumul_prob - 1)) {
         uint64_t mul = softfloat_reciprocal(cumul_prob);
         for (i = 1; i < 257; i++) {
             rac->prob[i] = softfloat_mul(rac->prob[i], mul);
             scaled_cumul_prob += rac->prob[i];
         }
 
         scale_factor++;
         cumulative_target = 1 << scale_factor;
 
         if (scaled_cumul_prob > cumulative_target) {
             av_log(rac->avctx, AV_LOG_ERROR,
                    "Scaled probabilities are larger than target!\n");
             return -1;
         }
 
         scaled_cumul_prob = cumulative_target - scaled_cumul_prob;
 
         for (i = 1; scaled_cumul_prob; i = (i & 0x7f) + 1) {
             if (rac->prob[i]) {
                 rac->prob[i]++;
                 scaled_cumul_prob--;
             }
             /* Comment from reference source:
              * if (b & 0x80 == 0) {     // order of operations is 'wrong'; it has been left this way
              *                          // since the compression change is negligable and fixing it
              *                          // breaks backwards compatibilty
              *      b =- (signed int)b;
              *      b &= 0xFF;
              * } else {
              *      b++;
              *      b &= 0x7f;
              * }
              */
         }
     }
 
     rac->scale = scale_factor;
 
     /* Fill probability array with cumulative probability for each symbol. */
     for (i = 1; i < 257; i++)
         rac->prob[i] += rac->prob[i - 1];
 
     return 0;
 }
 
 static void add_lag_median_prediction(uint8_t *dst, uint8_t *src1,
                                       uint8_t *diff, int w, int *left,
                                       int *left_top)
 {
     /* This is almost identical to add_hfyu_median_prediction in dsputil.h.
      * However the &0xFF on the gradient predictor yealds incorrect output
      * for lagarith.
      */
     int i;
     uint8_t l, lt;
 
     l  = *left;
     lt = *left_top;
 
     for (i = 0; i < w; i++) {
         l = mid_pred(l, src1[i], l + src1[i] - lt) + diff[i];
         lt = src1[i];
         dst[i] = l;
     }
 
     *left     = l;
     *left_top = lt;
 }
 
 static void lag_pred_line(LagarithContext *l, uint8_t *buf,
                           int width, int stride, int line)
 {
     int L, TL;
 
     if (!line) {
         /* Left prediction only for first line */
         L = l->dsp.add_hfyu_left_prediction(buf + 1, buf + 1,
                                             width - 1, buf[0]);
         return;
     } else if (line == 1) {
         /* Second line, left predict first pixel, the rest of the line is median predicted */
         /* FIXME: In the case of RGB this pixel is top predicted */
         TL = buf[-stride];
     } else {
         /* Top left is 2 rows back, last pixel */
         TL = buf[width - (2 * stride) - 1];
     }
     /* Left pixel is actually prev_row[width] */
     L = buf[width - stride - 1];
 
     add_lag_median_prediction(buf, buf - stride, buf,
                               width, &L, &TL);
 }
 
 static int lag_decode_line(LagarithContext *l, lag_rac *rac,
                            uint8_t *dst, int width, int stride,
                            int esc_count)
 {
     int i = 0;
     int ret = 0;
 
     if (!esc_count)
         esc_count = -1;
 
     /* Output any zeros remaining from the previous run */
 handle_zeros:
     if (l->zeros_rem) {
         int count = FFMIN(l->zeros_rem, width - i);
         memset(dst + i, 0, count);
         i += count;
         l->zeros_rem -= count;
     }
 
     while (i < width) {
         dst[i] = lag_get_rac(rac);
         ret++;
 
         if (dst[i])
             l->zeros = 0;
         else
             l->zeros++;
 
         i++;
         if (l->zeros == esc_count) {
             int index = lag_get_rac(rac);
             ret++;
 
             l->zeros = 0;
 
             l->zeros_rem = lag_calc_zero_run(index);
             goto handle_zeros;
         }
     }
     return ret;
 }
 
 static int lag_decode_zero_run_line(LagarithContext *l, uint8_t *dst,
                                     const uint8_t *src, int width,
                                     int esc_count)
 {
     int i = 0;
     int count;
     uint8_t zero_run = 0;
     const uint8_t *start = src;
     uint8_t mask1 = -(esc_count < 2);
     uint8_t mask2 = -(esc_count < 3);
     uint8_t *end = dst + (width - 2);
 
 output_zeros:
     if (l->zeros_rem) {
         count = FFMIN(l->zeros_rem, width - i);
         memset(dst, 0, count);
         l->zeros_rem -= count;
         dst += count;
     }
 
     while (dst < end) {
         i = 0;
         while (!zero_run && dst + i < end) {
             i++;
             zero_run =
                 !(src[i] | (src[i + 1] & mask1) | (src[i + 2] & mask2));
         }
         if (zero_run) {
             zero_run = 0;
             i += esc_count;
             memcpy(dst, src, i);
             dst += i;
             l->zeros_rem = lag_calc_zero_run(src[i]);
 
             src += i + 1;
             goto output_zeros;
         } else {
             memcpy(dst, src, i);
             src += i;
         }
     }
     return start - src;
 }
 
 
 
 static int lag_decode_arith_plane(LagarithContext *l, uint8_t *dst,
                                   int width, int height, int stride,
                                   const uint8_t *src, int src_size)
 {
     int i = 0;
     int read = 0;
     uint32_t length;
     uint32_t offset = 1;
     int esc_count = src[0];
     GetBitContext gb;
     lag_rac rac;
 
     rac.avctx = l->avctx;
     l->zeros = 0;
 
     if (esc_count < 4) {
         length = width * height;
         if (esc_count && AV_RL32(src + 1) < length) {
             length = AV_RL32(src + 1);
             offset += 4;
         }
 
         init_get_bits(&gb, src + offset, src_size * 8);
 
         if (lag_read_prob_header(&rac, &gb) < 0)
             return -1;
 
         lag_rac_init(&rac, &gb, length - stride);
 
         for (i = 0; i < height; i++)
             read += lag_decode_line(l, &rac, dst + (i * stride), width,
                                     stride, esc_count);
 
         if (read > length)
             av_log(l->avctx, AV_LOG_WARNING,
                    "Output more bytes than length (%d of %d)\n", read,
                    length);
     } else if (esc_count < 8) {
         esc_count -= 4;
         if (esc_count > 0) {
             /* Zero run coding only, no range coding. */
             for (i = 0; i < height; i++)
                 src += lag_decode_zero_run_line(l, dst + (i * stride), src,
                                                 width, esc_count);
         } else {
             /* Plane is stored uncompressed */
             for (i = 0; i < height; i++) {
                 memcpy(dst + (i * stride), src, width);
                 src += width;
             }
         }
     } else if (esc_count == 0xff) {

         /* Plane is a solid run of given value */

         for (i = 0; i < height; i++)

             memset(dst + i * stride, src[1], width);
         /* Do not apply prediction.
            Note: memset to 0 above, setting first value to src[1]
            and applying prediction gives the same result. */
         return 0;

     } else {
         av_log(l->avctx, AV_LOG_ERROR,
                "Invalid zero run escape code! (%#x)\n", esc_count);
         return -1;
     }
 
     for (i = 0; i < height; i++) {
         lag_pred_line(l, dst, width, stride, i);
         dst += stride;
     }
 
     return 0;
 }
 
 /**
  * Decode a frame.
  * @param avctx codec context
  * @param data output AVFrame
  * @param data_size size of output data or 0 if no picture is returned
  * @param avpkt input packet
  * @return number of consumed bytes on success or negative if decode fails
  */
 static int lag_decode_frame(AVCodecContext *avctx,
                             void *data, int *data_size, AVPacket *avpkt)
 {
     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;
     LagarithContext *l = avctx->priv_data;
     AVFrame *const p = &l->picture;
     uint8_t frametype = 0;
     uint32_t offset_gu = 0, offset_bv = 0, offset_ry = 9;
 
     AVFrame *picture = data;
 
     if (p->data[0])
         avctx->release_buffer(avctx, p);
 
     p->reference = 0;
     p->key_frame = 1;
 
     frametype = buf[0];
 
     offset_gu = AV_RL32(buf + 1);
     offset_bv = AV_RL32(buf + 5);
 
     switch (frametype) {
     case FRAME_ARITH_YV12:
         avctx->pix_fmt = PIX_FMT_YUV420P;
 
         if (avctx->get_buffer(avctx, p) < 0) {
             av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
             return -1;
         }
 
         lag_decode_arith_plane(l, p->data[0], avctx->width, avctx->height,
                                p->linesize[0], buf + offset_ry,
                                buf_size);
         lag_decode_arith_plane(l, p->data[2], avctx->width / 2,
                                avctx->height / 2, p->linesize[2],
                                buf + offset_gu, buf_size);
         lag_decode_arith_plane(l, p->data[1], avctx->width / 2,
                                avctx->height / 2, p->linesize[1],
                                buf + offset_bv, buf_size);
         break;
     default:
         av_log(avctx, AV_LOG_ERROR,
                "Unsupported Lagarith frame type: %#x\n", frametype);
         return -1;
     }
 
     *picture = *p;
     *data_size = sizeof(AVFrame);
 
     return buf_size;
 }
 
 static av_cold int lag_decode_init(AVCodecContext *avctx)
 {
     LagarithContext *l = avctx->priv_data;
     l->avctx = avctx;
 
     dsputil_init(&l->dsp, avctx);
 
     return 0;
 }
 
 static av_cold int lag_decode_end(AVCodecContext *avctx)
 {
     LagarithContext *l = avctx->priv_data;
 
     if (l->picture.data[0])
         avctx->release_buffer(avctx, &l->picture);
 
     return 0;
 }
 

 AVCodec ff_lagarith_decoder = {

     "lagarith",

     AVMEDIA_TYPE_VIDEO,

     CODEC_ID_LAGARITH,
     sizeof(LagarithContext),
     lag_decode_init,
     NULL,
     lag_decode_end,
     lag_decode_frame,
     CODEC_CAP_DR1,
     .long_name = NULL_IF_CONFIG_SMALL("Lagarith lossless"),
 };