avcodec/get_bits: add cached bitstream reader

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/golomb.h

@@ -54,6 +54,23 @@ static inline int get_ue_golomb(GetBitContext *gb)
 {
     unsigned int buf;
 
+#ifdef CACHED_BITSTREAM_READER
+    buf = show_bits_long(gb, 32);
+
+    if (buf >= (1 << 27)) {
+        buf >>= 32 - 9;
+        skip_bits_long(gb, ff_golomb_vlc_len[buf]);
+
+        return ff_ue_golomb_vlc_code[buf];
+    } else {
+        int log = 2 * av_log2(buf) - 31;
+        buf >>= log;
+        buf--;
+        skip_bits_long(gb, 32 - log);
+
+        return buf;
+    }
+#else
     OPEN_READER(re, gb);
     UPDATE_CACHE(re, gb);
     buf = GET_CACHE(re, gb);
@@ -77,6 +94,7 @@ static inline int get_ue_golomb(GetBitContext *gb)
 
         return buf;
     }
+#endif
 }
 
 /**
@@ -101,6 +119,13 @@ static inline int get_ue_golomb_31(GetBitContext *gb)
 {
     unsigned int buf;
 
+#ifdef CACHED_BITSTREAM_READER
+    buf = show_bits_long(gb, 32);
+
+    buf >>= 32 - 9;
+    skip_bits_long(gb, ff_golomb_vlc_len[buf]);
+#else
+
     OPEN_READER(re, gb);
     UPDATE_CACHE(re, gb);
     buf = GET_CACHE(re, gb);
@@ -108,6 +133,7 @@ static inline int get_ue_golomb_31(GetBitContext *gb)
     buf >>= 32 - 9;
     LAST_SKIP_BITS(re, gb, ff_golomb_vlc_len[buf]);
     CLOSE_READER(re, gb);
+#endif
 
     return ff_ue_golomb_vlc_code[buf];
 }
@@ -116,6 +142,33 @@ static inline unsigned get_interleaved_ue_golomb(GetBitContext *gb)
 {
     uint32_t buf;
 
+#ifdef CACHED_BITSTREAM_READER
+    buf = show_bits_long(gb, 32);
+
+    if (buf & 0xAA800000) {
+        buf >>= 32 - 8;
+        skip_bits_long(gb, ff_interleaved_golomb_vlc_len[buf]);
+
+        return ff_interleaved_ue_golomb_vlc_code[buf];
+    } else {
+        unsigned ret = 1;
+
+        do {
+            buf >>= 32 - 8;
+            skip_bits_long(gb, FFMIN(ff_interleaved_golomb_vlc_len[buf], 8));
+
+            if (ff_interleaved_golomb_vlc_len[buf] != 9) {
+                ret <<= (ff_interleaved_golomb_vlc_len[buf] - 1) >> 1;
+                ret  |= ff_interleaved_dirac_golomb_vlc_code[buf];
+                break;
+            }
+            ret = (ret << 4) | ff_interleaved_dirac_golomb_vlc_code[buf];
+            buf = show_bits_long(gb, 32);
+        } while (get_bits_left(gb) > 0);
+
+        return ret - 1;
+    }
+#else
     OPEN_READER(re, gb);
     UPDATE_CACHE(re, gb);
     buf = GET_CACHE(re, gb);
@@ -147,6 +200,7 @@ static inline unsigned get_interleaved_ue_golomb(GetBitContext *gb)
         CLOSE_READER(re, gb);
         return ret - 1;
     }
+#endif
 }
 
 /**
@@ -184,6 +238,28 @@ static inline int get_se_golomb(GetBitContext *gb)
 {
     unsigned int buf;
 
+#ifdef CACHED_BITSTREAM_READER
+    buf = show_bits_long(gb, 32);
+
+    if (buf >= (1 << 27)) {
+        buf >>= 32 - 9;
+        skip_bits_long(gb, ff_golomb_vlc_len[buf]);
+
+        return ff_se_golomb_vlc_code[buf];
+    } else {
+        int log = 2 * av_log2(buf) - 31;
+        buf >>= log;
+
+        skip_bits_long(gb, 32 - log);
+
+        if (buf & 1)
+            buf = -(buf >> 1);
+        else
+            buf = (buf >> 1);
+
+        return buf;
+    }
+#else
     OPEN_READER(re, gb);
     UPDATE_CACHE(re, gb);
     buf = GET_CACHE(re, gb);
@@ -210,6 +286,7 @@ static inline int get_se_golomb(GetBitContext *gb)
 
         return buf;
     }
+#endif
 }
 
 static inline int get_se_golomb_long(GetBitContext *gb)
@@ -223,6 +300,30 @@ static inline int get_interleaved_se_golomb(GetBitContext *gb)
 {
     unsigned int buf;
 
+#ifdef CACHED_BITSTREAM_READER
+    buf = show_bits_long(gb, 32);
+
+    if (buf & 0xAA800000) {
+        buf >>= 32 - 8;
+        skip_bits_long(gb, ff_interleaved_golomb_vlc_len[buf]);
+
+        return ff_interleaved_se_golomb_vlc_code[buf];
+    } else {
+        int log;
+        skip_bits(gb, 8);
+        buf |= 1 | show_bits_long(gb, 24);
+
+        if ((buf & 0xAAAAAAAA) == 0)
+            return INVALID_VLC;
+
+        for (log = 31; (buf & 0x80000000) == 0; log--)
+            buf = (buf << 2) - ((buf << log) >> (log - 1)) + (buf >> 30);
+
+        skip_bits_long(gb, 63 - 2 * log - 8);
+
+        return (signed) (((((buf << log) >> log) - 1) ^ -(buf & 0x1)) + 1) >> 1;
+    }
+#else
     OPEN_READER(re, gb);
     UPDATE_CACHE(re, gb);
     buf = GET_CACHE(re, gb);
@@ -250,6 +351,7 @@ static inline int get_interleaved_se_golomb(GetBitContext *gb)
 
         return (signed) (((((buf << log) >> log) - 1) ^ -(buf & 0x1)) + 1) >> 1;
     }
+#endif
 }
 
 static inline int dirac_get_se_golomb(GetBitContext *gb)
@@ -273,6 +375,24 @@ static inline int get_ur_golomb(GetBitContext *gb, int k, int limit,
     unsigned int buf;
     int log;
 
+#ifdef CACHED_BITSTREAM_READER
+    buf = show_bits_long(gb, 32);
+
+    log = av_log2(buf);
+
+    if (log > 31 - limit) {
+        buf >>= log - k;
+        buf  += (30 - log) << k;
+        skip_bits_long(gb, 32 + k - log);
+
+        return buf;
+    } else {
+        skip_bits_long(gb, limit);
+        buf = get_bits_long(gb, esc_len);
+
+        return buf + limit - 1;
+    }
+#else
     OPEN_READER(re, gb);
     UPDATE_CACHE(re, gb);
     buf = GET_CACHE(re, gb);
@@ -297,6 +417,7 @@ static inline int get_ur_golomb(GetBitContext *gb, int k, int limit,
 
         return buf + limit - 1;
     }
+#endif
 }
 
 /**
@@ -308,6 +429,35 @@ static inline int get_ur_golomb_jpegls(GetBitContext *gb, int k, int limit,
     unsigned int buf;
     int log;
 
+#ifdef CACHED_BITSTREAM_READER
+    buf = show_bits_long(gb, 32);
+
+    log = av_log2(buf);
+
+    if (log - k >= 1 && 32 - log < limit) {
+        buf >>= log - k;
+        buf  += (30 - log) << k;
+        skip_bits_long(gb, 32 + k - log);
+
+        return buf;
+    } else {
+        int i;
+        for (i = 0;
+             i < limit && get_bits1(gb) == 0 && get_bits_left(gb) > 0;
+             i++);
+
+        if (i < limit - 1) {
+            buf = get_bits_long(gb, k);
+
+            return buf + (i << k);
+        } else if (i == limit - 1) {
+            buf = get_bits_long(gb, esc_len);
+
+            return buf + 1;
+        } else
+            return -1;
+    }
+#else
     OPEN_READER(re, gb);
     UPDATE_CACHE(re, gb);
     buf = GET_CACHE(re, gb);
@@ -364,6 +514,7 @@ static inline int get_ur_golomb_jpegls(GetBitContext *gb, int k, int limit,
         CLOSE_READER(re, gb);
         return buf;
     }
+#endif
 }
 
 /**