X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=bitstream.h;h=5d6be3be2693a84f8107504f4a086dfa578c817b;hp=186f6376dd089903acca90f0b02dc98492f356ee;hb=f0e41e36c3f1a3a5bb6ff66d92d2814391d8f908;hpb=d0e242668ea2741d10b53e9dd53170180c9f5d24

diff --git a/bitstream.h b/bitstream.h
index 186f6376..5d6be3be 100644
--- a/bitstream.h
+++ b/bitstream.h
@@ -9,13 +9,6 @@
 
 /** \file bitstream.h Bitstream structures and inline functions. */
 
-#define AV_RB32(x)  ((((const uint8_t*)(x))[0] << 24) | \
-                     (((const uint8_t*)(x))[1] << 16) | \
-                     (((const uint8_t*)(x))[2] <<  8) | \
-                      ((const uint8_t*)(x))[3])
-
-#define NEG_USR32(a,s) (((uint32_t)(a))>>(32-(s)))
-
 /** Structure for bistream I/O. */
 struct getbit_context {
 	/* Start of the internal buffer. */
@@ -28,147 +21,71 @@ struct getbit_context {
 
 #define VLC_TYPE int16_t
 
+/** A variable length code table. */
 struct vlc {
+	/** Number of bits of the table. */
 	int bits;
-	VLC_TYPE(*table)[2];	///< code, bits
-	int table_size, table_allocated;
+	/** The code and the bits table. */
+	VLC_TYPE(*table)[2];
+	/** The size of the table. */
+	int table_size;
+	/** Amount of memory allocated so far. */
+	int table_allocated;
 };
 
-/** Load \a gb into local variables. */
-#define OPEN_READER(name, gb)\
-	int name##_index= (gb)->index;\
-	int name##_cache= 0;\
-
-/** Store local vars in gb. */
-#define CLOSE_READER(name, gb)\
-	(gb)->index= name##_index;\
-
-/**
- * Refill the internal cache from the bitstream.
- */
-#define UPDATE_CACHE(name, gb)\
-	name##_cache= AV_RB32( ((gb)->buffer) \
-		+ (name##_index >> 3) ) << (name##_index & 0x07);\
-
-/**
- * Remove the next num bits from the cache.
- *
- * SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER).
- */
-#define SKIP_CACHE(name, gb, num)\
-	name##_cache <<= (num);
-
-/**
- * Increment the internal bit counter.
- *
- * \sa SKIP_CACHE.
- */
-#define SKIP_COUNTER(name, gb, num)\
-	name##_index += (num);\
-
-/** Return the next num bits. */
-#define SHOW_UBITS(name, gb, num)\
-	NEG_USR32(name##_cache, num)
-
-static inline int get_bits_count(struct getbit_context *s)
+static inline uint32_t show_bits(struct getbit_context *gbc, int num)
 {
-	return s->index;
+	int idx = gbc->index;
+	const uint8_t *p = gbc->buffer + (idx >> 3);
+	uint32_t x = ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]);
+	return (x << (idx & 7)) >> (32 - num);
 }
 
-/**
- * Read 1-17 bits.
- */
-static inline unsigned int get_bits(struct getbit_context *s, int n)
+static inline int get_bits_count(struct getbit_context *gbc)
 {
-	register int tmp;
-	OPEN_READER(re, s)
-	UPDATE_CACHE(re, s)
-	tmp = SHOW_UBITS(re, s, n);
-	SKIP_COUNTER(re, s, n)
-	CLOSE_READER(re, s)
-	return tmp;
+	return gbc->index;
 }
 
-static inline void skip_bits(struct getbit_context *s, int n)
+static inline void skip_bits(struct getbit_context *gbc, int n)
 {
-	/* gcc seems to optimize this to s->index+=n for the ALT_READER :)) */
-	OPEN_READER(re, s)
-	UPDATE_CACHE(re, s)
-	SKIP_COUNTER(re, s, n)
-	CLOSE_READER(re, s)
+	gbc->index += n;
 }
 
-static inline unsigned int get_bits1(struct getbit_context *s)
+static inline unsigned int get_bits(struct getbit_context *gbc, int n)
 {
-	int idx = s->index;
-	uint8_t result = s->buffer[idx >> 3];
+	unsigned int ret = show_bits(gbc, n);
+	skip_bits(gbc, n);
+	return ret;
+}
 
-	result <<= (idx & 0x07);
-	result >>= 8 - 1;
-	idx++;
-	s->index = idx;
-	return result;
+/* This is rather hot, we can do better than get_bits(gbc, 1). */
+static inline unsigned int get_bit(struct getbit_context *gbc)
+{
+	int idx = gbc->index++;
+	uint8_t tmp = gbc->buffer[idx >> 3], mask = (1 << (7 - (idx & 7)));
+	return !!(tmp & mask);
 }
 
 /**
  * Initialize a getbit_context structure.
  *
- * \param buffer The bitstream buffer. It must be FF_INPUT_BUFFER_PADDING_SIZE
- * bytes larger then the actual read bits * because some optimized bitstream
- * readers read 32 or 64 bit at once and could read over the end.
+ * \param buffer The bitstream buffer. It must be 4 bytes larger then the
+ * actual read bits because the bitstream reader might read 32 bits at once and
+ * could read over the end.
  *
  * \param bit_size The size of the buffer in bytes.
  */
-static inline void init_get_bits(struct getbit_context *s,
+static inline void init_get_bits(struct getbit_context *gbc,
 		const uint8_t *buffer, int size)
 {
-	s->buffer = buffer;
-	s->buffer_end = buffer + size;
-	s->index = 0;
+	gbc->buffer = buffer;
+	gbc->buffer_end = buffer + size;
+	gbc->index = 0;
 }
 
 void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
 		const void *codes, int codes_size);
-
 void free_vlc(struct vlc *vlc);
+int get_vlc(struct getbit_context *gbc, VLC_TYPE(*table)[2], int bits,
+		int max_depth);
 
-/**
- * Parse a vlc code.
- *
- * \param bits The number of bits which will be read at once, must be
- * identical to nb_bits in init_vlc()
- *
- * \param max_depth The number of times bits bits must be read to completely
- * read the longest vlc code = (max_vlc_length + bits - 1) / bits.
- */
-static inline int get_vlc(struct getbit_context *gb, VLC_TYPE(*table)[2],
-		int bits, int max_depth)
-{
-	int n, idx, nb_bits, code;
-
-	OPEN_READER(re, gb)
-	UPDATE_CACHE(re, gb)
-	idx = SHOW_UBITS(re, gb, bits);
-	code = table[idx][0];
-	n = table[idx][1];
-	if (max_depth > 1 && n < 0) {
-		SKIP_COUNTER(re, gb, bits)
-		UPDATE_CACHE(re, gb)
-		nb_bits = -n;
-		idx = SHOW_UBITS(re, gb, nb_bits) + code;
-		code = table[idx][0];
-		n = table[idx][1];
-		if (max_depth > 2 && n < 0) {
-			SKIP_COUNTER(re, gb, nb_bits)
-			UPDATE_CACHE(re, gb)
-			nb_bits = -n;
-			idx = SHOW_UBITS(re, gb, nb_bits) + code;
-			code = table[idx][0];
-			n = table[idx][1];
-		}
-	}
-	SKIP_CACHE(re, gb, n)
-	SKIP_COUNTER(re, gb, n)
-	CLOSE_READER(re, gb)
-	return code;
-}