avcodec: Remove cumbersome way of checking for amount of bytes left

Several encoders used code like the following to check for the amount of
bytes left in a PutBitContext:
pb->buf_end - pb->buf - (put_bits_count(pb) >> 3)
Besides the fact that using the pointers directly might pose
a maintainence burden in the future this also leads to suboptimal code:
The above code reads all three pointers (buf, buf_ptr and buf_end), but
touching buf is unnecessary and switching to put_bytes_left()
automatically fixes this.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/asvenc.c

@@ -167,7 +167,7 @@ static inline int encode_mb(ASV1Context *a, int16_t block[6][64])
 {
     int i;
 
-    av_assert0(a->pb.buf_end - a->pb.buf - (put_bits_count(&a->pb) >> 3) >= MAX_MB_SIZE);
+    av_assert0(put_bytes_left(&a->pb, 0) >= MAX_MB_SIZE);
 
     if (a->avctx->codec_id == AV_CODEC_ID_ASV1) {
         for (i = 0; i < 6; i++)

libavcodec/ffv1enc_template.c

@@ -37,7 +37,7 @@ static av_always_inline int RENAME(encode_line)(FFV1Context *s, int w,
             return AVERROR_INVALIDDATA;
         }
     } else {
-        if (s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb) >> 3) < w * 4) {
+        if (put_bytes_left(&s->pb, 0) < w * 4) {
             av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
             return AVERROR_INVALIDDATA;
         }

libavcodec/huffyuvenc.c

@@ -443,7 +443,7 @@ static int encode_422_bitstream(HYuvContext *s, int offset, int count)
     const uint8_t *u = s->temp[1] + offset / 2;
     const uint8_t *v = s->temp[2] + offset / 2;
 
-    if (s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb) >> 3) < 2 * 4 * count) {
+    if (put_bytes_left(&s->pb, 0) < 2 * 4 * count) {
         av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
         return -1;
     }
@@ -495,7 +495,7 @@ static int encode_plane_bitstream(HYuvContext *s, int width, int plane)
 {
     int i, count = width/2;
 
-    if (s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb) >> 3) < count * s->bps / 2) {
+    if (put_bytes_left(&s->pb, 0) < count * s->bps / 2) {
         av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
         return -1;
     }
@@ -657,7 +657,7 @@ static int encode_gray_bitstream(HYuvContext *s, int count)
 {
     int i;
 
-    if (s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb) >> 3) < 4 * count) {
+    if (put_bytes_left(&s->pb, 0) < 4 * count) {
         av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
         return -1;
     }
@@ -702,8 +702,7 @@ static inline int encode_bgra_bitstream(HYuvContext *s, int count, int planes)
 {
     int i;
 
-    if (s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb) >> 3) <
-        4 * planes * count) {
+    if (put_bytes_left(&s->pb, 0) < 4 * planes * count) {
         av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
         return -1;
     }

libavcodec/ljpegenc.c

@@ -86,7 +86,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
         const int modified_predictor = y ? s->pred : 1;
         uint8_t *ptr = frame->data[0] + (linesize * y);
 
-        if (pb->buf_end - pb->buf - (put_bits_count(pb) >> 3) < width * 4 * 4) {
+        if (put_bytes_left(pb, 0) < width * 4 * 4) {
             av_log(avctx, AV_LOG_ERROR, "encoded frame too large\n");
             return -1;
         }
@@ -211,7 +211,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
 #endif
 
     for (mb_y = 0; mb_y < mb_height; mb_y++) {
-        if (pb->buf_end - pb->buf - (put_bits_count(pb) >> 3) <
+        if (put_bytes_left(pb, 0) <
             mb_width * 4 * 3 * s->hsample[0] * s->vsample[0]) {
             av_log(avctx, AV_LOG_ERROR, "encoded frame too large\n");
             return -1;

libavcodec/mpegvideo_enc.c

@@ -1993,8 +1993,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
         stuffing_count = ff_vbv_update(s, s->frame_bits);
         s->stuffing_bits = 8*stuffing_count;
         if (stuffing_count) {
-            if (s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb) >> 3) <
-                    stuffing_count + 50) {
+            if (put_bytes_left(&s->pb, 0) < stuffing_count + 50) {
                 av_log(avctx, AV_LOG_ERROR, "stuffing too large\n");
                 return -1;
             }
@@ -2911,7 +2910,7 @@ static void update_mb_info(MpegEncContext *s, int startcode)
 
 int ff_mpv_reallocate_putbitbuffer(MpegEncContext *s, size_t threshold, size_t size_increase)
 {
-    if (   s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb)>>3) < threshold
+    if (put_bytes_left(&s->pb, 0) < threshold
         && s->slice_context_count == 1
         && s->pb.buf == s->avctx->internal->byte_buffer) {
         int lastgob_pos = s->ptr_lastgob - s->pb.buf;
@@ -2940,7 +2939,7 @@ int ff_mpv_reallocate_putbitbuffer(MpegEncContext *s, size_t threshold, size_t s
         s->ptr_lastgob   = s->pb.buf + lastgob_pos;
         s->vbv_delay_ptr = s->pb.buf + vbv_pos;
     }
-    if (s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb)>>3) < threshold)
+    if (put_bytes_left(&s->pb, 0) < threshold)
         return AVERROR(EINVAL);
     return 0;
 }
@@ -3032,13 +3031,13 @@ static int encode_thread(AVCodecContext *c, void *arg){
                                + s->mb_width*MAX_MB_BYTES;
 
             ff_mpv_reallocate_putbitbuffer(s, MAX_MB_BYTES, size_increase);
-            if(s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb)>>3) < MAX_MB_BYTES){
+            if (put_bytes_left(&s->pb, 0) < MAX_MB_BYTES){
                 av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
                 return -1;
             }
             if(s->data_partitioning){
-                if(   s->pb2   .buf_end - s->pb2   .buf - (put_bits_count(&s->    pb2)>>3) < MAX_MB_BYTES
-                   || s->tex_pb.buf_end - s->tex_pb.buf - (put_bits_count(&s->tex_pb )>>3) < MAX_MB_BYTES){
+                if (put_bytes_left(&s->pb2,    0) < MAX_MB_BYTES ||
+                    put_bytes_left(&s->tex_pb, 0) < MAX_MB_BYTES) {
                     av_log(s->avctx, AV_LOG_ERROR, "encoded partitioned frame too large\n");
                     return -1;
                 }

libavcodec/svq1enc.c

@@ -372,8 +372,7 @@ static int svq1_encode_plane(SVQ1EncContext *s, int plane,
             int score[4]     = { 0, 0, 0, 0 }, best;
             uint8_t *temp    = s->scratchbuf;
 
-            if (s->pb.buf_end - s->pb.buf -
-                (put_bits_count(&s->pb) >> 3) < 3000) { // FIXME: check size
+            if (put_bytes_left(&s->pb, 0) < 3000) { // FIXME: check size
                 av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
                 return -1;
             }

libavcodec/xsubenc.c

@@ -63,7 +63,7 @@ static int xsub_encode_rle(PutBitContext *pb, const uint8_t *bitmap,
         x0 = 0;
         while (x0 < w) {
             // Make sure we have enough room for at least one run and padding
-            if (pb->size_in_bits - put_bits_count(pb) < 7*8)
+            if (put_bytes_left(pb, 1) < 7)
                 return AVERROR_BUFFER_TOO_SMALL;
 
             x1 = x0;