Switch some ints to unsigned (they can only have positive values, this allows

compiler to optimize some math from mul/div to shr/shl). Also add a cast to
uint32_t when calling decodeplane32(), this silences a compiler warning.
Lastly, in decodeplane8/32(), flatten a double-loop into a single-loop and
calculate the length once before entering the loop instead of during every
iteration (since it doesn't change).

Patch by Sebastian Vater <cdgs.basty googlemail com>.

Originally committed as revision 22974 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/iff.c

 /*
  * IFF PBM/ILBM bitmap decoder
  * Copyright (c) 2010 Peter Ross <pross@xvid.org>
+ * Copyright (c) 2010 Sebastian Vater <cdgs.basty@googlemail.com>
  *
  * This file is part of FFmpeg.
  *
@@ -31,7 +32,7 @@
 
 typedef struct {
     AVFrame frame;
-    int planesize;
+    unsigned planesize;
     uint8_t * planebuf;
 } IffContext;
 
@@ -40,7 +41,7 @@ typedef struct {
  */
 int ff_cmap_read_palette(AVCodecContext *avctx, uint32_t *pal)
 {
-    int count, i;
+    unsigned count, i;
 
     if (avctx->bits_per_coded_sample > 8) {
         av_log(avctx, AV_LOG_ERROR, "bit_per_coded_sample > 8 not supported\n");
@@ -71,7 +72,7 @@ static av_cold int decode_init(AVCodecContext *avctx)
         return AVERROR_INVALIDDATA;
     }
 
-    s->planesize = avctx->width / 8;
+    s->planesize = avctx->width >> 3;
     s->planebuf = av_malloc(s->planesize + FF_INPUT_BUFFER_PADDING_SIZE);
     if (!s->planebuf)
         return AVERROR(ENOMEM);
@@ -97,12 +98,11 @@ static av_cold int decode_init(AVCodecContext *avctx)
 static void decodeplane8(uint8_t *dst, const uint8_t *const buf, int buf_size, int bps, int plane)
 {
     GetBitContext gb;
-    int i, b;
+    unsigned int i;
+    const unsigned b = (buf_size * 8) + bps - 1;
     init_get_bits(&gb, buf, buf_size * 8);
-    for(i = 0; i < (buf_size * 8 + bps - 1) / bps; i++) {
-        for (b = 0; b < bps; b++) {
-            dst[ i*bps + b ] |= get_bits1(&gb) << plane;
-        }
+    for(i = 0; i < b; i++) {
+        dst[i] |= get_bits1(&gb) << plane;
     }
 }
 
@@ -117,12 +117,11 @@ static void decodeplane8(uint8_t *dst, const uint8_t *const buf, int buf_size, i
 static void decodeplane32(uint32_t *dst, const uint8_t *const buf, int buf_size, int bps, int plane)
 {
     GetBitContext gb;
-    int i, b;
+    unsigned i;
+    const unsigned b = (buf_size * 8) + bps - 1;
     init_get_bits(&gb, buf, buf_size * 8);
-    for(i = 0; i < (buf_size * 8 + bps - 1) / bps; i++) {
-        for (b = 0; b < bps; b++) {
-            dst[ i*bps + b ] |= get_bits1(&gb) << plane;
-        }
+    for(i = 0; i < b; i++) {
+        dst[i] |= get_bits1(&gb) << plane;
     }
 }
 
@@ -132,9 +131,9 @@ static int decode_frame_ilbm(AVCodecContext *avctx,
 {
     IffContext *s = avctx->priv_data;
     const uint8_t *buf = avpkt->data;
-    int buf_size = avpkt->size;
+    unsigned buf_size = avpkt->size;
     const uint8_t *buf_end = buf+buf_size;
-    int y, plane;
+    unsigned y, plane;
 
     if (avctx->reget_buffer(avctx, &s->frame) < 0){
         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
@@ -148,7 +147,7 @@ static int decode_frame_ilbm(AVCodecContext *avctx,
             if (avctx->pix_fmt == PIX_FMT_PAL8) {
                 decodeplane8(row, buf, FFMIN(s->planesize, buf_end - buf), avctx->bits_per_coded_sample, plane);
             } else { // PIX_FMT_BGR32
-                decodeplane32(row, buf, FFMIN(s->planesize, buf_end - buf), avctx->bits_per_coded_sample, plane);
+                decodeplane32((uint32_t *) row, buf, FFMIN(s->planesize, buf_end - buf), avctx->bits_per_coded_sample, plane);
             }
             buf += s->planesize;
         }
@@ -165,9 +164,9 @@ static int decode_frame_byterun1(AVCodecContext *avctx,
 {
     IffContext *s = avctx->priv_data;
     const uint8_t *buf = avpkt->data;
-    int buf_size = avpkt->size;
+    unsigned buf_size = avpkt->size;
     const uint8_t *buf_end = buf+buf_size;
-    int y, plane, x;
+    unsigned y, plane, x;
 
     if (avctx->reget_buffer(avctx, &s->frame) < 0){
         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
@@ -181,7 +180,7 @@ static int decode_frame_byterun1(AVCodecContext *avctx,
             for (plane = 0; plane < avctx->bits_per_coded_sample; plane++) {
                 for(x = 0; x < s->planesize && buf < buf_end; ) {
                     int8_t value = *buf++;
-                    int length;
+                    unsigned length;
                     if (value >= 0) {
                         length = value + 1;
                         memcpy(s->planebuf + x, buf, FFMIN3(length, s->planesize - x, buf_end - buf));
@@ -197,13 +196,13 @@ static int decode_frame_byterun1(AVCodecContext *avctx,
                 if (avctx->pix_fmt == PIX_FMT_PAL8) {
                     decodeplane8(row, s->planebuf, s->planesize, avctx->bits_per_coded_sample, plane);
                 } else { //PIX_FMT_BGR32
-                    decodeplane32(row, s->planebuf, s->planesize, avctx->bits_per_coded_sample, plane);
+                    decodeplane32((uint32_t *) row, s->planebuf, s->planesize, avctx->bits_per_coded_sample, plane);
                 }
             }
         } else {
             for(x = 0; x < avctx->width && buf < buf_end; ) {
                 int8_t value = *buf++;
-                int length;
+                unsigned length;
                 if (value >= 0) {
                     length = value + 1;
                     memcpy(row + x, buf, FFMIN3(length, buf_end - buf, avctx->width - x));