X-Git-Url: https://wimlib.net/git/?a=blobdiff_plain;f=include%2Fwimlib%2Fdecompress_common.h;h=856c64117c6cf432cbdb3be761a0ea2f3433f70a;hb=7901ba9cde12d96f6e2dcb612fc5c3b361e988ff;hp=ef7ebe953960cd33c2e91efd341c37f4ba717441;hpb=543d8a6b89049aff65fa7eabf5f4b376a196c8d2;p=wimlib

diff --git a/include/wimlib/decompress_common.h b/include/wimlib/decompress_common.h
index ef7ebe95..856c6411 100644
--- a/include/wimlib/decompress_common.h
+++ b/include/wimlib/decompress_common.h
@@ -2,6 +2,9 @@
  * decompress_common.h
  *
  * Header for decompression code shared by multiple compression formats.
+ *
+ * The author dedicates this file to the public domain.
+ * You can do whatever you want with this file.
  */
 
 #ifndef _WIMLIB_DECOMPRESS_COMMON_H
@@ -12,11 +15,6 @@
 #include "wimlib/endianness.h"
 #include "wimlib/types.h"
 
-#ifndef INPUT_IDX_T_DEFINED
-#define INPUT_IDX_T_DEFINED
-typedef u32 input_idx_t;
-#endif
-
 /* Structure to encapsulate a block of in-memory data that is being interpreted
  * as a stream of bits.
  *
@@ -36,13 +34,13 @@ struct input_bitstream {
 	const u8 *data;
 
 	/* Number of bytes of data that are left.  */
-	input_idx_t data_bytes_left;
+	u32 data_bytes_left;
 };
 
 /* Initializes a bitstream to receive its input from @data. */
 static inline void
 init_input_bitstream(struct input_bitstream *istream,
-		     const void *data, input_idx_t num_data_bytes)
+		     const void *data, u32 num_data_bytes)
 {
 	istream->bitbuf          = 0;
 	istream->bitsleft        = 0;
@@ -56,17 +54,38 @@ init_input_bitstream(struct input_bitstream *istream,
  *
  * If the input data is exhausted, any further bits are assumed to be 0.  */
 static inline void
-bitstream_ensure_bits(struct input_bitstream *istream, unsigned num_bits)
+bitstream_ensure_bits(struct input_bitstream *istream, const unsigned num_bits)
 {
-	for (int nbits = num_bits; (int)istream->bitsleft < nbits; nbits -= 16) {
-		u16 nextword;
-		unsigned shift;
+	u16 nextword;
+	unsigned shift;
+
+	/* This currently works for at most 17 bits.  */
+	wimlib_assert2(num_bits <= 17);
+
+	if (istream->bitsleft >= num_bits)
+		return;
 
+	if (unlikely(istream->data_bytes_left < 2)) {
+		istream->bitsleft = num_bits;
+		return;
+	}
+
+	nextword = le16_to_cpu(*(const le16*)istream->data);
+	shift = sizeof(istream->bitbuf) * 8 - 16 - istream->bitsleft;
+	istream->bitbuf |= (u32)nextword << shift;
+	istream->data += 2;
+	istream->bitsleft += 16;
+	istream->data_bytes_left -= 2;
+
+	/* Help the compiler: If it's known at compile-time that num_bits <= 16,
+	 * a second word will never be needed.  */
+	if (!(is_constant(num_bits) && num_bits <= 16) &&
+	    unlikely(istream->bitsleft < num_bits))
+	{
 		if (unlikely(istream->data_bytes_left < 2)) {
 			istream->bitsleft = num_bits;
 			return;
 		}
-
 		nextword = le16_to_cpu(*(const le16*)istream->data);
 		shift = sizeof(istream->bitbuf) * 8 - 16 - istream->bitsleft;
 		istream->bitbuf |= (u32)nextword << shift;
@@ -211,7 +230,7 @@ make_huffman_decode_table(u16 decode_table[], unsigned num_syms,
  * This function won't write any data beyond this position.
  */
 static inline void
-lz_copy(u8 *dst, unsigned length, unsigned offset, const u8 *winend)
+lz_copy(u8 *dst, u32 length, u32 offset, const u8 *winend)
 {
 	const u8 *src = dst - offset;
 #if defined(__x86_64__) || defined(__i386__)