diff options
| author | Samuel Thibault <samuel.thibault@ens-lyon.org> | 2011-05-08 23:11:02 +0200 |
|---|---|---|
| committer | Samuel Thibault <samuel.thibault@ens-lyon.org> | 2011-05-08 23:11:02 +0200 |
| commit | cded208c7ea6d107dcbfdb2e2d4622daf41c2886 (patch) | |
| tree | a04a03736b0a928c2954382f924aadb105ee39cc /libdde_linux26/contrib/lib/.svn/text-base/crc32.c.svn-base | |
| parent | fc82e00ca1e174cb961dea6ad37622e9b26cd899 (diff) | |
remove .svn directories
Diffstat (limited to 'libdde_linux26/contrib/lib/.svn/text-base/crc32.c.svn-base')
| -rw-r--r-- | libdde_linux26/contrib/lib/.svn/text-base/crc32.c.svn-base | 501 |
1 files changed, 0 insertions, 501 deletions
diff --git a/libdde_linux26/contrib/lib/.svn/text-base/crc32.c.svn-base b/libdde_linux26/contrib/lib/.svn/text-base/crc32.c.svn-base deleted file mode 100644 index 49d1c9e3..00000000 --- a/libdde_linux26/contrib/lib/.svn/text-base/crc32.c.svn-base +++ /dev/null @@ -1,501 +0,0 @@ -/* - * Oct 15, 2000 Matt Domsch <Matt_Domsch@dell.com> - * Nicer crc32 functions/docs submitted by linux@horizon.com. Thanks! - * Code was from the public domain, copyright abandoned. Code was - * subsequently included in the kernel, thus was re-licensed under the - * GNU GPL v2. - * - * Oct 12, 2000 Matt Domsch <Matt_Domsch@dell.com> - * 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. - * - * This source code is licensed under the GNU General Public License, - * Version 2. See the file COPYING for more details. - */ - -#include <linux/crc32.h> -#include <linux/kernel.h> -#include <linux/module.h> -#include <linux/compiler.h> -#include <linux/types.h> -#include <linux/slab.h> -#include <linux/init.h> -#include <asm/atomic.h> -#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" - -MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>"); -MODULE_DESCRIPTION("Ethernet CRC32 calculations"); -MODULE_LICENSE("GPL"); - -/** - * 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 __pure crc32_le(u32 crc, unsigned char const *p, size_t len); - -#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. - */ - -u32 __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 */ - -u32 __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 { - u8 *p = (u8 *)b; - DO_CRC(*p++); - b = (void *)p; - } 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 { - u8 *p = (u8 *)b; - DO_CRC(*p++); - b = (void *)p; - } 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 - -/** - * 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 __pure crc32_be(u32 crc, unsigned char const *p, size_t len); - -#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. - */ - -u32 __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 */ -u32 __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 { - u8 *p = (u8 *)b; - DO_CRC(*p++); - b = (u32 *)p; - } 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 { - u8 *p = (u8 *)b; - DO_CRC(*p++); - b = (void *)p; - } 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 - -EXPORT_SYMBOL(crc32_le); -EXPORT_SYMBOL(crc32_be); - -/* - * 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 multiple 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. - */ - -#ifdef UNITTEST - -#include <stdlib.h> -#include <stdio.h> - -#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 = bitrev8(*buf); - *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 = bitrev32(init); - crc2 = bitrev32(crc1); - if (crc1 != bitrev32(crc2)) - printf("\nBit reversal fail: 0x%08x -> 0x%08x -> 0x%08x\n", - crc1, crc2, bitrev32(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 */ |
