X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=bitstream.h;h=4d81fa3b25521053c8cafcf49a4b14542b83e74a;hp=a3393380e5e02801a4312c6f904c1ea25527aad9;hb=66b97974ebba5c6ea967b713f84f62a1b72da8d2;hpb=01a7db579a518a1a03b940a5a42411e49123ac1b

diff --git a/bitstream.h b/bitstream.h
index a3393380..4d81fa3b 100644
--- a/bitstream.h
+++ b/bitstream.h
@@ -13,20 +13,18 @@
 struct getbit_context {
 	/** Start of the internal buffer. */
 	const uint8_t *buffer;
-	/** End of the internal buffer. */
-	const uint8_t *buffer_end;
+	/** Length of buffer in bits (always a multiple of 8). */
+	uint32_t num_bits;
 	/** Bit counter. */
 	int index;
 };
 
-#define VLC_TYPE int16_t
-
 /** A variable length code table. */
 struct vlc {
 	/** Number of bits of the table. */
 	int bits;
 	/** The code and the bits table. */
-	VLC_TYPE(*table)[2];
+	int16_t (*table)[2];
 	/** The size of the table. */
 	int table_size;
 	/** Amount of memory allocated so far. */
@@ -36,8 +34,12 @@ struct vlc {
 static inline uint32_t show_bits(struct getbit_context *gbc, int num)
 {
 	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]);
+	const char *p;
+	uint32_t x;
+
+	assert(idx + num <= gbc->num_bits);
+	p = (const char *)gbc->buffer + (idx >> 3);
+	x = read_u32_be(p);
 	return (x << (idx & 7)) >> (32 - num);
 }
 
@@ -48,12 +50,13 @@ static inline int get_bits_count(struct getbit_context *gbc)
 
 static inline void skip_bits(struct getbit_context *gbc, int n)
 {
+	assert(gbc->index + n <= gbc->num_bits);
 	gbc->index += n;
 }
 
 static inline unsigned int get_bits(struct getbit_context *gbc, int n)
 {
-	unsigned int ret = show_bits(gbc, n);
+	unsigned int ret = show_bits(gbc, n); /* checks n */
 	skip_bits(gbc, n);
 	return ret;
 }
@@ -61,31 +64,36 @@ static inline unsigned int get_bits(struct getbit_context *gbc, int n)
 /* 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)));
+	int idx;
+	uint8_t tmp, mask;
+
+	assert(gbc->index < gbc->num_bits);
+	idx = gbc->index++;
+	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 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 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)
 {
 	gbc->buffer = buffer;
-	gbc->buffer_end = buffer + size;
+	gbc->num_bits = size * 8;
 	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);
-
+int get_vlc(struct getbit_context *gbc, const struct vlc *vlc);