LU-1201 checksum: add libcfs crypto hash

[fs/lustre-release.git] / libcfs / libcfs / posix / posix-crc32.c

diff --git a/libcfs/libcfs/posix/posix-crc32.c b/libcfs/libcfs/posix/posix-crc32.c
new file mode 100644 (file)
index 0000000..972c5ff
--- /dev/null
+++ b/libcfs/libcfs/posix/posix-crc32.c
@@ -0,0 +1,78 @@
+/*
+ *      This file contains part of linux kernel implementation of crc32
+ *      kernel version 2.6.32
+ */
+#include <libcfs/libcfs.h>
+#define CRCPOLY_LE      0xedb88320
+#define CRC_LE_BITS     8
+#define LE_TABLE_SIZE   (1 << CRC_LE_BITS)
+
+static unsigned int crc32table_le[LE_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].
+ *
+ */
+void crc32init_le(void)
+{
+       unsigned i, j;
+       unsigned int 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];
+       }
+}
+
+unsigned int crc32_le(unsigned int crc, unsigned char const *p, size_t len)
+{
+       const unsigned int      *b = (unsigned int *)p;
+       const unsigned int      *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 {
+                       unsigned char *p = (unsigned char *)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 {
+                       unsigned char *p = (unsigned char *)b;
+                       DO_CRC(*p++);
+                       b = (void *)p;
+               } while (--len);
+       }
+
+       return le32_to_cpu(crc);
+#undef DO_CRC
+}