X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=bitstream.h;h=98937e89f2b98f126007d795f8070c0b33508598;hp=0c0a1eba609629ed488746906443bb9ed34fabbc;hb=04c16387cc13317ded03ce478b131d94558f585f;hpb=7978ce515fc2c19ffd8fd7d8fe356f5fa628d7ff

diff --git a/bitstream.h b/bitstream.h
index 0c0a1eba..98937e89 100644
--- a/bitstream.h
+++ b/bitstream.h
@@ -3,35 +3,42 @@
  *
  * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
  *
- * Licensed under the GNU Lesser General Public License.
- * For licencing details see COPYING.LIB.
+ * Licensed under the GNU Lesser General Public License, see file COPYING.LIB.
  */
 
 /** \file bitstream.h Bitstream structures and inline functions. */
 
 /** 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. */
-	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;
-	VLC_TYPE(*table)[2];	///< code, bits
-	int table_size, table_allocated;
+	/** The code and the bits table. */
+	int16_t (*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;
-	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);
 }
 
@@ -42,77 +49,50 @@ 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;
 }
 
 /* This is rather hot, we can do better than get_bits(gbc, 1). */
-static inline unsigned int get_bits1(struct getbit_context *gbc)
+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 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)
 {
 	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);
-
-/**
- * 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, const struct vlc *vlc);