X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=bitstream.h;h=5890d08c89d4033f7fefb9a19be525860a701d77;hp=cc56a83c0207c2abc9c6fd25e9e9fd1aa4c5bb7d;hb=741c19c2a25c5d9e165cb99f7ff512209b7bade6;hpb=1f986e5d3d91283fd8d929599b709d1942e139b0

diff --git a/bitstream.h b/bitstream.h
index cc56a83c..5890d08c 100644
--- a/bitstream.h
+++ b/bitstream.h
@@ -9,16 +9,11 @@
 
 /** \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])
-
 /** Structure for bistream I/O. */
 struct getbit_context {
-	/* Start of the internal buffer. */
+	/** Start of the internal buffer. */
 	const uint8_t *buffer;
-	/* End of the internal buffer. */
+	/** End of the internal buffer. */
 	const uint8_t *buffer_end;
 	/** Bit counter. */
 	int index;
@@ -26,17 +21,24 @@ 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;
 };
 
 static inline uint32_t show_bits(struct getbit_context *gbc, int num)
 {
 	int idx = gbc->index;
-	uint32_t x = AV_RB32(gbc->buffer + (idx >> 3)) << (idx & 7);
-	return x >> (32 - num);
+	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);
 }
 
 static inline int get_bits_count(struct getbit_context *gbc)
@@ -56,26 +58,24 @@ static inline unsigned int get_bits(struct getbit_context *gbc, int n)
 	return ret;
 }
 
-static inline unsigned int get_bits1(struct getbit_context *gbc)
+/* 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 result = gbc->buffer[idx >> 3];
-
-	result <<= (idx & 0x07);
-	result >>= 8 - 1;
-	idx++;
-	gbc->index = idx;
-	return result;
+	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 gbc The structure to initialize.
+ * \param buffer The bitstream buffer.
+ * \param size The size of the buffer in bytes.
  *
- * \param bit_size The size of the buffer in bytes.
+ * The bitstream buffer 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.
  */
 static inline void init_get_bits(struct getbit_context *gbc,
 		const uint8_t *buffer, int size)
@@ -87,40 +87,6 @@ static inline void init_get_bits(struct getbit_context *gbc,
 
 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);
-
-/**
- * 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 *gbc, VLC_TYPE(*table)[2],
-		int bits, int max_depth)
-{
-	int n, idx, nb_bits, code;
-
-	idx = show_bits(gbc, bits);
-	code = table[idx][0];
-	n = table[idx][1];
-	if (max_depth > 1 && n < 0) {
-		skip_bits(gbc, bits);
-		nb_bits = -n;
-		idx = show_bits(gbc, nb_bits) + code;
-		code = table[idx][0];
-		n = table[idx][1];
-		if (max_depth > 2 && n < 0) {
-			skip_bits(gbc, nb_bits);
-			nb_bits = -n;
-			idx = show_bits(gbc, nb_bits) + code;
-			code = table[idx][0];
-			n = table[idx][1];
-		}
-	}
-	skip_bits(gbc, n);
-	return code;
-}
+int get_vlc(struct getbit_context *gbc, VLC_TYPE(*table)[2], int bits,
+		int max_depth);