From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 26 Mar 2003 05:11:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 26 Mar 2003 05:11:52 -0500 Received: from smtp5.wanadoo.fr ([193.252.22.29]:50169 "EHLO mwinf0204.wanadoo.fr") by vger.kernel.org with ESMTP id ; Wed, 26 Mar 2003 05:11:37 -0500 From: Duncan Sands To: linux-kernel@vger.kernel.org Subject: [PATCH] backport crc32 library to 2.4 Date: Wed, 26 Mar 2003 11:22:40 +0100 User-Agent: KMail/1.5.1 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200303261122.40277.baldrick@wanadoo.fr> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Just the 2.5 crc32 routines, not the driver changes. The lib/Makefile changes are probably crap: I don't know anything about Makefile syntax, so just slashed and hacked until it seemed to work. Duncan. diff -Nru a/Documentation/Configure.help b/Documentation/Configure.help --- a/Documentation/Configure.help Wed Mar 26 11:14:07 2003 +++ b/Documentation/Configure.help Wed Mar 26 11:14:07 2003 @@ -26462,6 +26462,13 @@ If unsure, say N. +CRC32 functions +CONFIG_CRC32 + This option is provided for the case where no in-kernel-tree + modules require CRC32 functions, but a module built outside the + kernel tree does. Such modules that use library CRC32 functions + require M here. + # # A couple of things I keep forgetting: # capitalize: AppleTalk, Ethernet, DOS, DMA, FAT, FTP, Internet, diff -Nru a/Makefile b/Makefile --- a/Makefile Wed Mar 26 11:14:07 2003 +++ b/Makefile Wed Mar 26 11:14:07 2003 @@ -216,6 +216,8 @@ drivers/scsi/aic7xxx/aicasm/aicdb.h \ drivers/scsi/aic7xxx/aicasm/y.tab.h \ drivers/scsi/53c700_d.h \ + lib/crc32table.h \ + lib/gen_crc32table \ net/khttpd/make_times_h \ net/khttpd/times.h \ submenu* diff -Nru a/include/linux/crc32.h b/include/linux/crc32.h --- a/include/linux/crc32.h Wed Mar 26 11:14:07 2003 +++ b/include/linux/crc32.h Wed Mar 26 11:14:07 2003 @@ -1,49 +1,27 @@ /* - * crc32.h for early Linux 2.4.19pre kernel inclusion - * This defines ether_crc_le() and ether_crc() as inline functions - * This is slated to change to using the library crc32 functions - * as kernel 2.5.2 included at some future date. + * crc32.h + * See linux/lib/crc32.c for license and changes */ #ifndef _LINUX_CRC32_H #define _LINUX_CRC32_H #include -/* The little-endian AUTODIN II ethernet CRC calculation. - N.B. Do not use for bulk data, use a table-based routine instead. - This is common code and should be moved to net/core/crc.c */ -static unsigned const ethernet_polynomial_le = 0xedb88320U; -static inline unsigned ether_crc_le(int length, unsigned char *data) -{ - unsigned int crc = 0xffffffff; /* Initial value. */ - while(--length >= 0) { - unsigned char current_octet = *data++; - int bit; - for (bit = 8; --bit >= 0; current_octet >>= 1) { - if ((crc ^ current_octet) & 1) { - crc >>= 1; - crc ^= ethernet_polynomial_le; - } else - crc >>= 1; - } - } - return crc; -} +extern u32 crc32_le(u32 crc, unsigned char const *p, size_t len); +extern u32 crc32_be(u32 crc, unsigned char const *p, size_t len); +extern u32 bitreverse(u32 in); -static unsigned const ethernet_polynomial = 0x04c11db7U; -static inline u32 ether_crc(int length, unsigned char *data) -{ - int crc = -1; - while (--length >= 0) { - unsigned char current_octet = *data++; - int bit; - for (bit = 0; bit < 8; bit++, current_octet >>= 1) { - crc = (crc << 1) ^ - ((crc < 0) ^ (current_octet & 1) ? - ethernet_polynomial : 0); - } - } - return crc; -} +#define crc32(seed, data, length) crc32_le(seed, (unsigned char const *)data, length) + +/* + * Helpers for hash table generation of ethernet nics: + * + * Ethernet sends the least significant bit of a byte first, thus crc32_le + * is used. The output of crc32_le is bit reversed [most significant bit + * is in bit nr 0], thus it must be reversed before use. Except for + * nics that bit swap the result internally... + */ +#define ether_crc(length, data) bitreverse(crc32_le(~0, data, length)) +#define ether_crc_le(length, data) crc32_le(~0, data, length) #endif /* _LINUX_CRC32_H */ diff -Nru a/lib/Config.in b/lib/Config.in --- a/lib/Config.in Wed Mar 26 11:14:07 2003 +++ b/lib/Config.in Wed Mar 26 11:14:07 2003 @@ -35,4 +35,17 @@ fi fi +# +# Do we need CRC32 support? +# +if [ ]; then + define_tristate CONFIG_CRC32 y +else + if [ ]; then + define_tristate CONFIG_CRC32 m + else + tristate 'CRC32 functions' CONFIG_CRC32 + fi +fi + endmenu diff -Nru a/lib/Makefile b/lib/Makefile --- a/lib/Makefile Wed Mar 26 11:14:07 2003 +++ b/lib/Makefile Wed Mar 26 11:14:07 2003 @@ -8,7 +8,7 @@ L_TARGET := lib.a -export-objs := cmdline.o dec_and_lock.o rwsem-spinlock.o rwsem.o rbtree.o +export-objs := cmdline.o crc32.o dec_and_lock.o rwsem-spinlock.o rwsem.o rbtree.o obj-y := errno.o ctype.o string.o vsprintf.o brlock.o cmdline.o \ bust_spinlocks.o rbtree.o dump_stack.o @@ -20,6 +20,8 @@ obj-y += dec_and_lock.o endif +obj-$(CONFIG_CRC32) += crc32.o + subdir-$(CONFIG_ZLIB_INFLATE) += zlib_inflate subdir-$(CONFIG_ZLIB_DEFLATE) += zlib_deflate @@ -27,3 +29,11 @@ obj-y += $(join $(subdir-y),$(subdir-y:%=/%.o)) include $(TOPDIR)/Rules.make + +crc32.o: crc32table.h + +crc32table.h: gen_crc32table + ./$< > $@ + +gen_crc32table: + $(HOSTCC) $(HOSTCFLAGS) -o $@ $(@:=.c) diff -Nru a/lib/crc32.c b/lib/crc32.c --- /dev/null Wed Dec 31 16:00:00 1969 +++ b/lib/crc32.c Wed Mar 26 11:14:02 2003 @@ -0,0 +1,528 @@ +/* + * Oct 15, 2000 Matt Domsch + * Nicer crc32 functions/docs submitted by linux@horizon.com. Thanks! + * + * Oct 12, 2000 Matt Domsch + * Same crc32 function was used in 5 other places in the kernel. + * I made one version, and deleted the others. + * There are various incantations of crc32(). Some use a seed of 0 or ~0. + * Some xor at the end with ~0. The generic crc32() function takes + * seed as an argument, and doesn't xor at the end. Then individual + * users can do whatever they need. + * drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0. + * fs/jffs2 uses seed 0, doesn't xor with ~0. + * fs/partitions/efi.c uses seed ~0, xor's with ~0. + * + */ + +#include +#include +#include +#include +#include +#include +#include +#include "crc32defs.h" +#if CRC_LE_BITS == 8 +#define tole(x) __constant_cpu_to_le32(x) +#define tobe(x) __constant_cpu_to_be32(x) +#else +#define tole(x) (x) +#define tobe(x) (x) +#endif +#include "crc32table.h" + +#if __GNUC__ >= 3 /* 2.x has "attribute", but only 3.0 has "pure */ +#define attribute(x) __attribute__(x) +#else +#define attribute(x) +#endif + +/* + * This code is in the public domain; copyright abandoned. + * Liability for non-performance of this code is limited to the amount + * you paid for it. Since it is distributed for free, your refund will + * be very very small. If it breaks, you get to keep both pieces. + */ + +MODULE_AUTHOR("Matt Domsch "); +MODULE_DESCRIPTION("Ethernet CRC32 calculations"); +MODULE_LICENSE("GPL and additional rights"); + +#if CRC_LE_BITS == 1 +/* + * In fact, the table-based code will work in this case, but it can be + * simplified by inlining the table in ?: form. + */ + +/** + * crc32_le() - Calculate bitwise little-endian Ethernet AUTODIN II CRC32 + * @crc - seed value for computation. ~0 for Ethernet, sometimes 0 for + * other uses, or the previous crc32 value if computing incrementally. + * @p - pointer to buffer over which CRC is run + * @len - length of buffer @p + * + */ +u32 attribute((pure)) crc32_le(u32 crc, unsigned char const *p, size_t len) +{ + int i; + while (len--) { + crc ^= *p++; + for (i = 0; i < 8; i++) + crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0); + } + return crc; +} +#else /* Table-based approach */ + +/** + * crc32_le() - Calculate bitwise little-endian Ethernet AUTODIN II CRC32 + * @crc - seed value for computation. ~0 for Ethernet, sometimes 0 for + * other uses, or the previous crc32 value if computing incrementally. + * @p - pointer to buffer over which CRC is run + * @len - length of buffer @p + * + */ +u32 attribute((pure)) crc32_le(u32 crc, unsigned char const *p, size_t len) +{ +# if CRC_LE_BITS == 8 + const u32 *b =(u32 *)p; + const u32 *tab = crc32table_le; + +# ifdef __LITTLE_ENDIAN +# define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8) +# else +# define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8) +# endif + + crc = __cpu_to_le32(crc); + /* Align it */ + if(unlikely(((long)b)&3 && len)){ + do { + DO_CRC(*((u8 *)b)++); + } while ((--len) && ((long)b)&3 ); + } + if(likely(len >= 4)){ + /* load data 32 bits wide, xor data 32 bits wide. */ + size_t save_len = len & 3; + len = len >> 2; + --b; /* use pre increment below(*++b) for speed */ + do { + crc ^= *++b; + DO_CRC(0); + DO_CRC(0); + DO_CRC(0); + DO_CRC(0); + } while (--len); + b++; /* point to next byte(s) */ + len = save_len; + } + /* And the last few bytes */ + if(len){ + do { + DO_CRC(*((u8 *)b)++); + } while (--len); + } + + return __le32_to_cpu(crc); +#undef ENDIAN_SHIFT +#undef DO_CRC + +# elif CRC_LE_BITS == 4 + while (len--) { + crc ^= *p++; + crc = (crc >> 4) ^ crc32table_le[crc & 15]; + crc = (crc >> 4) ^ crc32table_le[crc & 15]; + } + return crc; +# elif CRC_LE_BITS == 2 + while (len--) { + crc ^= *p++; + crc = (crc >> 2) ^ crc32table_le[crc & 3]; + crc = (crc >> 2) ^ crc32table_le[crc & 3]; + crc = (crc >> 2) ^ crc32table_le[crc & 3]; + crc = (crc >> 2) ^ crc32table_le[crc & 3]; + } + return crc; +# endif +} +#endif + +#if CRC_BE_BITS == 1 +/* + * In fact, the table-based code will work in this case, but it can be + * simplified by inlining the table in ?: form. + */ + +/** + * crc32_be() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32 + * @crc - seed value for computation. ~0 for Ethernet, sometimes 0 for + * other uses, or the previous crc32 value if computing incrementally. + * @p - pointer to buffer over which CRC is run + * @len - length of buffer @p + * + */ +u32 attribute((pure)) crc32_be(u32 crc, unsigned char const *p, size_t len) +{ + int i; + while (len--) { + crc ^= *p++ << 24; + for (i = 0; i < 8; i++) + crc = + (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : + 0); + } + return crc; +} + +#else /* Table-based approach */ +/** + * crc32_be() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32 + * @crc - seed value for computation. ~0 for Ethernet, sometimes 0 for + * other uses, or the previous crc32 value if computing incrementally. + * @p - pointer to buffer over which CRC is run + * @len - length of buffer @p + * + */ +u32 attribute((pure)) crc32_be(u32 crc, unsigned char const *p, size_t len) +{ +# if CRC_BE_BITS == 8 + const u32 *b =(u32 *)p; + const u32 *tab = crc32table_be; + +# ifdef __LITTLE_ENDIAN +# define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8) +# else +# define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8) +# endif + + crc = __cpu_to_be32(crc); + /* Align it */ + if(unlikely(((long)b)&3 && len)){ + do { + DO_CRC(*((u8 *)b)++); + } while ((--len) && ((long)b)&3 ); + } + if(likely(len >= 4)){ + /* load data 32 bits wide, xor data 32 bits wide. */ + size_t save_len = len & 3; + len = len >> 2; + --b; /* use pre increment below(*++b) for speed */ + do { + crc ^= *++b; + DO_CRC(0); + DO_CRC(0); + DO_CRC(0); + DO_CRC(0); + } while (--len); + b++; /* point to next byte(s) */ + len = save_len; + } + /* And the last few bytes */ + if(len){ + do { + DO_CRC(*((u8 *)b)++); + } while (--len); + } + return __be32_to_cpu(crc); +#undef ENDIAN_SHIFT +#undef DO_CRC + +# elif CRC_BE_BITS == 4 + while (len--) { + crc ^= *p++ << 24; + crc = (crc << 4) ^ crc32table_be[crc >> 28]; + crc = (crc << 4) ^ crc32table_be[crc >> 28]; + } + return crc; +# elif CRC_BE_BITS == 2 + while (len--) { + crc ^= *p++ << 24; + crc = (crc << 2) ^ crc32table_be[crc >> 30]; + crc = (crc << 2) ^ crc32table_be[crc >> 30]; + crc = (crc << 2) ^ crc32table_be[crc >> 30]; + crc = (crc << 2) ^ crc32table_be[crc >> 30]; + } + return crc; +# endif +} +#endif + +u32 bitreverse(u32 x) +{ + x = (x >> 16) | (x << 16); + x = (x >> 8 & 0x00ff00ff) | (x << 8 & 0xff00ff00); + x = (x >> 4 & 0x0f0f0f0f) | (x << 4 & 0xf0f0f0f0); + x = (x >> 2 & 0x33333333) | (x << 2 & 0xcccccccc); + x = (x >> 1 & 0x55555555) | (x << 1 & 0xaaaaaaaa); + return x; +} + +EXPORT_SYMBOL(crc32_le); +EXPORT_SYMBOL(crc32_be); +EXPORT_SYMBOL(bitreverse); + +/* + * A brief CRC tutorial. + * + * A CRC is a long-division remainder. You add the CRC to the message, + * and the whole thing (message+CRC) is a multiple of the given + * CRC polynomial. To check the CRC, you can either check that the + * CRC matches the recomputed value, *or* you can check that the + * remainder computed on the message+CRC is 0. This latter approach + * is used by a lot of hardware implementations, and is why so many + * protocols put the end-of-frame flag after the CRC. + * + * It's actually the same long division you learned in school, except that + * - We're working in binary, so the digits are only 0 and 1, and + * - When dividing polynomials, there are no carries. Rather than add and + * subtract, we just xor. Thus, we tend to get a bit sloppy about + * the difference between adding and subtracting. + * + * A 32-bit CRC polynomial is actually 33 bits long. But since it's + * 33 bits long, bit 32 is always going to be set, so usually the CRC + * is written in hex with the most significant bit omitted. (If you're + * familiar with the IEEE 754 floating-point format, it's the same idea.) + * + * Note that a CRC is computed over a string of *bits*, so you have + * to decide on the endianness of the bits within each byte. To get + * the best error-detecting properties, this should correspond to the + * order they're actually sent. For example, standard RS-232 serial is + * little-endian; the most significant bit (sometimes used for parity) + * is sent last. And when appending a CRC word to a message, you should + * do it in the right order, matching the endianness. + * + * Just like with ordinary division, the remainder is always smaller than + * the divisor (the CRC polynomial) you're dividing by. Each step of the + * division, you take one more digit (bit) of the dividend and append it + * to the current remainder. Then you figure out the appropriate multiple + * of the divisor to subtract to being the remainder back into range. + * In binary, it's easy - it has to be either 0 or 1, and to make the + * XOR cancel, it's just a copy of bit 32 of the remainder. + * + * When computing a CRC, we don't care about the quotient, so we can + * throw the quotient bit away, but subtract the appropriate multiple of + * the polynomial from the remainder and we're back to where we started, + * ready to process the next bit. + * + * A big-endian CRC written this way would be coded like: + * for (i = 0; i < input_bits; i++) { + * multiple = remainder & 0x80000000 ? CRCPOLY : 0; + * remainder = (remainder << 1 | next_input_bit()) ^ multiple; + * } + * Notice how, to get at bit 32 of the shifted remainder, we look + * at bit 31 of the remainder *before* shifting it. + * + * But also notice how the next_input_bit() bits we're shifting into + * the remainder don't actually affect any decision-making until + * 32 bits later. Thus, the first 32 cycles of this are pretty boring. + * Also, to add the CRC to a message, we need a 32-bit-long hole for it at + * the end, so we have to add 32 extra cycles shifting in zeros at the + * end of every message, + * + * So the standard trick is to rearrage merging in the next_input_bit() + * until the moment it's needed. Then the first 32 cycles can be precomputed, + * and merging in the final 32 zero bits to make room for the CRC can be + * skipped entirely. + * This changes the code to: + * for (i = 0; i < input_bits; i++) { + * remainder ^= next_input_bit() << 31; + * multiple = (remainder & 0x80000000) ? CRCPOLY : 0; + * remainder = (remainder << 1) ^ multiple; + * } + * With this optimization, the little-endian code is simpler: + * for (i = 0; i < input_bits; i++) { + * remainder ^= next_input_bit(); + * multiple = (remainder & 1) ? CRCPOLY : 0; + * remainder = (remainder >> 1) ^ multiple; + * } + * + * Note that the other details of endianness have been hidden in CRCPOLY + * (which must be bit-reversed) and next_input_bit(). + * + * However, as long as next_input_bit is returning the bits in a sensible + * order, we can actually do the merging 8 or more bits at a time rather + * than one bit at a time: + * for (i = 0; i < input_bytes; i++) { + * remainder ^= next_input_byte() << 24; + * for (j = 0; j < 8; j++) { + * multiple = (remainder & 0x80000000) ? CRCPOLY : 0; + * remainder = (remainder << 1) ^ multiple; + * } + * } + * Or in little-endian: + * for (i = 0; i < input_bytes; i++) { + * remainder ^= next_input_byte(); + * for (j = 0; j < 8; j++) { + * multiple = (remainder & 1) ? CRCPOLY : 0; + * remainder = (remainder << 1) ^ multiple; + * } + * } + * If the input is a multiple of 32 bits, you can even XOR in a 32-bit + * word at a time and increase the inner loop count to 32. + * + * You can also mix and match the two loop styles, for example doing the + * bulk of a message byte-at-a-time and adding bit-at-a-time processing + * for any fractional bytes at the end. + * + * The only remaining optimization is to the byte-at-a-time table method. + * Here, rather than just shifting one bit of the remainder to decide + * in the correct multiple to subtract, we can shift a byte at a time. + * This produces a 40-bit (rather than a 33-bit) intermediate remainder, + * but again the multiple of the polynomial to subtract depends only on + * the high bits, the high 8 bits in this case. + * + * The multile we need in that case is the low 32 bits of a 40-bit + * value whose high 8 bits are given, and which is a multiple of the + * generator polynomial. This is simply the CRC-32 of the given + * one-byte message. + * + * Two more details: normally, appending zero bits to a message which + * is already a multiple of a polynomial produces a larger multiple of that + * polynomial. To enable a CRC to detect this condition, it's common to + * invert the CRC before appending it. This makes the remainder of the + * message+crc come out not as zero, but some fixed non-zero value. + * + * The same problem applies to zero bits prepended to the message, and + * a similar solution is used. Instead of starting with a remainder of + * 0, an initial remainder of all ones is used. As long as you start + * the same way on decoding, it doesn't make a difference. + */ + +#if UNITTEST + +#include +#include + +#if 0 /*Not used at present */ +static void +buf_dump(char const *prefix, unsigned char const *buf, size_t len) +{ + fputs(prefix, stdout); + while (len--) + printf(" %02x", *buf++); + putchar('\n'); + +} +#endif + +static void bytereverse(unsigned char *buf, size_t len) +{ + while (len--) { + unsigned char x = *buf; + x = (x >> 4) | (x << 4); + x = (x >> 2 & 0x33) | (x << 2 & 0xcc); + x = (x >> 1 & 0x55) | (x << 1 & 0xaa); + *buf++ = x; + } +} + +static void random_garbage(unsigned char *buf, size_t len) +{ + while (len--) + *buf++ = (unsigned char) random(); +} + +#if 0 /* Not used at present */ +static void store_le(u32 x, unsigned char *buf) +{ + buf[0] = (unsigned char) x; + buf[1] = (unsigned char) (x >> 8); + buf[2] = (unsigned char) (x >> 16); + buf[3] = (unsigned char) (x >> 24); +} +#endif + +static void store_be(u32 x, unsigned char *buf) +{ + buf[0] = (unsigned char) (x >> 24); + buf[1] = (unsigned char) (x >> 16); + buf[2] = (unsigned char) (x >> 8); + buf[3] = (unsigned char) x; +} + +/* + * This checks that CRC(buf + CRC(buf)) = 0, and that + * CRC commutes with bit-reversal. This has the side effect + * of bytewise bit-reversing the input buffer, and returns + * the CRC of the reversed buffer. + */ +static u32 test_step(u32 init, unsigned char *buf, size_t len) +{ + u32 crc1, crc2; + size_t i; + + crc1 = crc32_be(init, buf, len); + store_be(crc1, buf + len); + crc2 = crc32_be(init, buf, len + 4); + if (crc2) + printf("\nCRC cancellation fail: 0x%08x should be 0\n", + crc2); + + for (i = 0; i <= len + 4; i++) { + crc2 = crc32_be(init, buf, i); + crc2 = crc32_be(crc2, buf + i, len + 4 - i); + if (crc2) + printf("\nCRC split fail: 0x%08x\n", crc2); + } + + /* Now swap it around for the other test */ + + bytereverse(buf, len + 4); + init = bitreverse(init); + crc2 = bitreverse(crc1); + if (crc1 != bitreverse(crc2)) + printf("\nBit reversal fail: 0x%08x -> %0x08x -> 0x%08x\n", + crc1, crc2, bitreverse(crc2)); + crc1 = crc32_le(init, buf, len); + if (crc1 != crc2) + printf("\nCRC endianness fail: 0x%08x != 0x%08x\n", crc1, + crc2); + crc2 = crc32_le(init, buf, len + 4); + if (crc2) + printf("\nCRC cancellation fail: 0x%08x should be 0\n", + crc2); + + for (i = 0; i <= len + 4; i++) { + crc2 = crc32_le(init, buf, i); + crc2 = crc32_le(crc2, buf + i, len + 4 - i); + if (crc2) + printf("\nCRC split fail: 0x%08x\n", crc2); + } + + return crc1; +} + +#define SIZE 64 +#define INIT1 0 +#define INIT2 0 + +int main(void) +{ + unsigned char buf1[SIZE + 4]; + unsigned char buf2[SIZE + 4]; + unsigned char buf3[SIZE + 4]; + int i, j; + u32 crc1, crc2, crc3; + + for (i = 0; i <= SIZE; i++) { + printf("\rTesting length %d...", i); + fflush(stdout); + random_garbage(buf1, i); + random_garbage(buf2, i); + for (j = 0; j < i; j++) + buf3[j] = buf1[j] ^ buf2[j]; + + crc1 = test_step(INIT1, buf1, i); + crc2 = test_step(INIT2, buf2, i); + /* Now check that CRC(buf1 ^ buf2) = CRC(buf1) ^ CRC(buf2) */ + crc3 = test_step(INIT1 ^ INIT2, buf3, i); + if (crc3 != (crc1 ^ crc2)) + printf("CRC XOR fail: 0x%08x != 0x%08x ^ 0x%08x\n", + crc3, crc1, crc2); + } + printf("\nAll test complete. No failures expected.\n"); + return 0; +} + +#endif /* UNITTEST */ diff -Nru a/lib/crc32defs.h b/lib/crc32defs.h --- /dev/null Wed Dec 31 16:00:00 1969 +++ b/lib/crc32defs.h Wed Mar 26 11:14:02 2003 @@ -0,0 +1,32 @@ +/* + * There are multiple 16-bit CRC polynomials in common use, but this is + * *the* standard CRC-32 polynomial, first popularized by Ethernet. + * x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+x^0 + */ +#define CRCPOLY_LE 0xedb88320 +#define CRCPOLY_BE 0x04c11db7 + +/* How many bits at a time to use. Requires a table of 4< 8 || CRC_LE_BITS < 1 || CRC_LE_BITS & CRC_LE_BITS-1 +# error CRC_LE_BITS must be a power of 2 between 1 and 8 +#endif + +/* + * Big-endian CRC computation. Used with serial bit streams sent + * msbit-first. Be sure to use cpu_to_be32() to append the computed CRC. + */ +#if CRC_BE_BITS > 8 || CRC_BE_BITS < 1 || CRC_BE_BITS & CRC_BE_BITS-1 +# error CRC_BE_BITS must be a power of 2 between 1 and 8 +#endif diff -Nru a/lib/gen_crc32table.c b/lib/gen_crc32table.c --- /dev/null Wed Dec 31 16:00:00 1969 +++ b/lib/gen_crc32table.c Wed Mar 26 11:14:02 2003 @@ -0,0 +1,82 @@ +#include +#include "crc32defs.h" +#include + +#define ENTRIES_PER_LINE 4 + +#define LE_TABLE_SIZE (1 << CRC_LE_BITS) +#define BE_TABLE_SIZE (1 << CRC_BE_BITS) + +static u_int32_t crc32table_le[LE_TABLE_SIZE]; +static u_int32_t crc32table_be[BE_TABLE_SIZE]; + +/** + * crc32init_le() - allocate and initialize LE table data + * + * crc is the crc of the byte i; other entries are filled in based on the + * fact that crctable[i^j] = crctable[i] ^ crctable[j]. + * + */ +static void crc32init_le(void) +{ + unsigned i, j; + u_int32_t crc = 1; + + crc32table_le[0] = 0; + + for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) { + crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0); + for (j = 0; j < LE_TABLE_SIZE; j += 2 * i) + crc32table_le[i + j] = crc ^ crc32table_le[j]; + } +} + +/** + * crc32init_be() - allocate and initialize BE table data + */ +static void crc32init_be(void) +{ + unsigned i, j; + u_int32_t crc = 0x80000000; + + crc32table_be[0] = 0; + + for (i = 1; i < BE_TABLE_SIZE; i <<= 1) { + crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0); + for (j = 0; j < i; j++) + crc32table_be[i + j] = crc ^ crc32table_be[j]; + } +} + +static void output_table(u_int32_t table[], int len, char *trans) +{ + int i; + + for (i = 0; i < len - 1; i++) { + if (i % ENTRIES_PER_LINE == 0) + printf("\n"); + printf("%s(0x%8.8xL), ", trans, table[i]); + } + printf("%s(0x%8.8xL)\n", trans, table[len - 1]); +} + +int main(int argc, char** argv) +{ + printf("/* this file is generated - do not edit */\n\n"); + + if (CRC_LE_BITS > 1) { + crc32init_le(); + printf("static const u32 crc32table_le[] = {"); + output_table(crc32table_le, LE_TABLE_SIZE, "tole"); + printf("};\n"); + } + + if (CRC_BE_BITS > 1) { + crc32init_be(); + printf("static const u32 crc32table_be[] = {"); + output_table(crc32table_be, BE_TABLE_SIZE, "tobe"); + printf("};\n"); + } + + return 0; +}