/* crc32.c -- compute the CRC-32 of a data stream
- * Copyright (C) 1995-2006, 2010, 2011, 2012, 2016, 2018 Mark Adler
+ * Copyright (C) 1995-2022 Mark Adler
* For conditions of distribution and use, see copyright notice in zlib.h
*
* This interleaved implementation of a CRC makes use of pipelined multiple
/* Local functions. */
local z_crc_t multmodp OF((z_crc_t a, z_crc_t b));
local z_crc_t x2nmodp OF((z_off64_t n, unsigned k));
-#ifdef W
- local z_word_t byte_swap OF((z_word_t word));
- local z_crc_t crc_word OF((z_word_t data));
- local z_word_t crc_word_big OF((z_word_t data));
-#endif /* W */
+
+/* If available, use the ARM processor CRC32 instruction. */
+#if defined(__aarch64__) && defined(__ARM_FEATURE_CRC32) && W == 8
+# define ARMCRC32
+#endif
+
+#if defined(W) && (!defined(ARMCRC32) || defined(DYNAMIC_CRC_TABLE))
+/*
+ Swap the bytes in a z_word_t to convert between little and big endian. Any
+ self-respecting compiler will optimize this to a single machine byte-swap
+ instruction, if one is available. This assumes that word_t is either 32 bits
+ or 64 bits.
+ */
+local z_word_t byte_swap(word)
+ z_word_t word;
+{
+# if W == 8
+ return
+ (word & 0xff00000000000000) >> 56 |
+ (word & 0xff000000000000) >> 40 |
+ (word & 0xff0000000000) >> 24 |
+ (word & 0xff00000000) >> 8 |
+ (word & 0xff000000) << 8 |
+ (word & 0xff0000) << 24 |
+ (word & 0xff00) << 40 |
+ (word & 0xff) << 56;
+# else /* W == 4 */
+ return
+ (word & 0xff000000) >> 24 |
+ (word & 0xff0000) >> 8 |
+ (word & 0xff00) << 8 |
+ (word & 0xff) << 24;
+# endif
+}
+#endif
/* CRC polynomial. */
#define POLY 0xedb88320 /* p(x) reflected, with x^32 implied */
is just exclusive-or, and multiplying a polynomial by x is a right shift by
one. If we call the above polynomial p, and represent a byte as the
polynomial q, also with the lowest power in the most significant bit (so the
- byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
+ byte 0xb1 is the polynomial x^7+x^3+x^2+1), then the CRC is (q*x^32) mod p,
where a mod b means the remainder after dividing a by b.
This calculation is done using the shift-register method of multiplying and
return p;
}
-#ifdef W
-
-/*
- Swap the bytes in a z_word_t to convert between little and big endian. Any
- self-respecting compiler will optimize this to a single machine byte-swap
- instruction, if one is available. This assumes that word_t is either 32 bits
- or 64 bits.
- */
-local z_word_t byte_swap(word)
- z_word_t word;
-{
-#if W == 8
- return
- (word & 0xff00000000000000) >> 56 |
- (word & 0xff000000000000) >> 40 |
- (word & 0xff0000000000) >> 24 |
- (word & 0xff00000000) >> 8 |
- (word & 0xff000000) << 8 |
- (word & 0xff0000) << 24 |
- (word & 0xff00) << 40 |
- (word & 0xff) << 56;
-#else /* W == 4 */
- return
- (word & 0xff000000) >> 24 |
- (word & 0xff0000) >> 8 |
- (word & 0xff00) << 8 |
- (word & 0xff) << 24;
-#endif
-}
-
-/*
- Return the CRC of the W bytes in the word_t data, taking the
- least-significant byte of the word as the first byte of data, without any pre
- or post conditioning. This is used to combine the CRCs of each braid.
- */
-local z_crc_t crc_word(data)
- z_word_t data;
-{
- int k;
- for (k = 0; k < W; k++)
- data = (data >> 8) ^ crc_table[data & 0xff];
- return (z_crc_t)data;
-}
-
-local z_word_t crc_word_big(data)
- z_word_t data;
-{
- int k;
- for (k = 0; k < W; k++)
- data = (data << 8) ^
- crc_big_table[(data >> ((W - 1) << 3)) & 0xff];
- return data;
-}
-
-#endif /* W */
-
/* =========================================================================
* This function can be used by asm versions of crc32(), and to force the
* generation of the CRC tables in a threaded application.
}
/* =========================================================================
- * Use ARM machine instructions if requested. This will compute the CRC about
+ * Use ARM machine instructions if available. This will compute the CRC about
* ten times faster than the braided calculation. This code does not check for
- * the presence of the CRC instruction. Compile with care.
+ * the presence of the CRC instruction at run time. __ARM_FEATURE_CRC32 will
+ * only be defined if the compilation specifies an ARM processor architecture
+ * that has the instructions. For example, compiling with -march=armv8.1-a or
+ * -march=armv8-a+crc, or -march=native if the compile machine has the crc32
+ * instructions.
*/
-#if defined(Z_ARM_CRC32) && defined(__aarch64__) && W == 8
+#ifdef ARMCRC32
/*
Constants empirically determined to maximize speed. These values are from
#else
+#ifdef W
+
+/*
+ Return the CRC of the W bytes in the word_t data, taking the
+ least-significant byte of the word as the first byte of data, without any pre
+ or post conditioning. This is used to combine the CRCs of each braid.
+ */
+local z_crc_t crc_word(data)
+ z_word_t data;
+{
+ int k;
+ for (k = 0; k < W; k++)
+ data = (data >> 8) ^ crc_table[data & 0xff];
+ return (z_crc_t)data;
+}
+
+local z_word_t crc_word_big(data)
+ z_word_t data;
+{
+ int k;
+ for (k = 0; k < W; k++)
+ data = (data << 8) ^
+ crc_big_table[(data >> ((W - 1) << 3)) & 0xff];
+ return data;
+}
+
+#endif
+
/* ========================================================================= */
unsigned long ZEXPORT crc32_z(crc, buf, len)
unsigned long crc;
projects / zlib.git / blobdiff