--- /dev/null
+/* Cumulus: Smart Filesystem Backup to Dumb Servers
+ *
+ * Copyright (C) 2006-2008 The Regents of the University of California
+ * Written by Michael Vrable <mvrable@cs.ucsd.edu>
+ *
+ * Much of the code in this file is taken from LBFS, which is
+ * Copyright (C) 1998, 1999 David Mazieres (dm@uun.org)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/* Compute incremental backups at a sub-file level by chopping files up into
+ * blocks in a content-sensitive manner (using Rabin fingerprints). This code
+ * is largely taken from LBFS, primarily the files:
+ * liblbfs/fingerprint.C (fingerprint.C,v 1.1 2001/01/29 22:49:13 benjie Exp)
+ * liblbfs/rabinpoly.h (rabinpoly.h,v 1.4 2002/01/07 21:30:21 athicha Exp)
+ * liblbfs/rabinpoly.C (rabinpoly.C,v 1.1 2001/01/29 22:49:13 benjie Exp)
+ * async/msb.h (msb.h,v 1.6 1998/12/26 18:21:51 dm Exp)
+ * async/msb.C (msb.C,v 1.4 1998/12/26 18:21:51 dm Exp)
+ * but adapted and slimmed down to fit within Cumulus. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <string>
+
+#include "chunk.h"
+
+using std::string;
+
+// Functions/data only needed internally go in a separate namespace. Public
+// interfaces (at the end of the file) are in the global namespace.
+namespace {
+
+#define FINGERPRINT_PT 0xbfe6b8a5bf378d83LL
+#define BREAKMARK_VALUE 0x78
+#define MIN_CHUNK_SIZE 2048
+#define MAX_CHUNK_SIZE 65535
+#define TARGET_CHUNK_SIZE 4096
+
+#define SFS_DEV_RANDOM "/dev/random"
+
+#define INT64(n) n##LL
+#define MSB64 INT64(0x8000000000000000)
+
+template<class R> inline R
+implicit_cast (R r)
+{
+ return r;
+}
+
+/* Highest bit set in a byte */
+static const char bytemsb[0x100] = {
+ 0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5,
+ 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+ 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7,
+ 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+ 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+ 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+};
+
+/* Find last set (most significant bit) */
+static inline u_int fls32 (uint32_t) __attribute__ ((const));
+static inline u_int
+fls32 (u_int32_t v)
+{
+ if (v & 0xffff0000) {
+ if (v & 0xff000000)
+ return 24 + bytemsb[v>>24];
+ else
+ return 16 + bytemsb[v>>16];
+ }
+ if (v & 0x0000ff00)
+ return 8 + bytemsb[v>>8];
+ else
+ return bytemsb[v];
+}
+
+static inline u_int fls64 (u_int64_t) __attribute__ ((const));
+static inline u_int
+fls64 (u_int64_t v)
+{
+ u_int32_t h;
+ if ((h = v >> 32))
+ return 32 + fls32 (h);
+ else
+ return fls32 ((u_int32_t) v);
+}
+
+static uint64_t
+polymod (uint64_t nh, uint64_t nl, uint64_t d)
+{
+ assert (d);
+ int k = fls64 (d) - 1;
+ d <<= 63 - k;
+
+ if (nh) {
+ if (nh & MSB64)
+ nh ^= d;
+ for (int i = 62; i >= 0; i--)
+ if (nh & INT64 (1) << i) {
+ nh ^= d >> 63 - i;
+ nl ^= d << i + 1;
+ }
+ }
+ for (int i = 63; i >= k; i--)
+ if (nl & INT64 (1) << i)
+ nl ^= d >> 63 - i;
+ return nl;
+}
+
+static void
+polymult (uint64_t *php, uint64_t *plp, uint64_t x, uint64_t y)
+{
+ uint64_t ph = 0, pl = 0;
+ if (x & 1)
+ pl = y;
+ for (int i = 1; i < 64; i++)
+ if (x & (INT64 (1) << i)) {
+ ph ^= y >> (64 - i);
+ pl ^= y << i;
+ }
+ if (php)
+ *php = ph;
+ if (plp)
+ *plp = pl;
+}
+
+static uint64_t
+polymmult (uint64_t x, uint64_t y, uint64_t d)
+{
+ uint64_t h, l;
+ polymult (&h, &l, x, y);
+ return polymod (h, l, d);
+}
+
+#if 0
+static uint64_t
+polygcd (uint64_t x, uint64_t y)
+{
+ for (;;) {
+ if (!y)
+ return x;
+ x = polymod (0, x, y);
+ if (!x)
+ return y;
+ y = polymod (0, y, x);
+ }
+}
+
+static bool
+polyirreducible (uint64_t f)
+{
+ uint64_t u = 2;
+ int m = (fls64 (f) - 1) >> 1;
+ for (int i = 0; i < m; i++) {
+ u = polymmult (u, u, f);
+ if (polygcd (f, u ^ 2) != 1)
+ return false;
+ }
+ return true;
+}
+
+static uint64_t
+polygen (u_int degree)
+{
+ assert (degree > 0 && degree < 64);
+ uint64_t msb = INT64 (1) << degree;
+ uint64_t mask = msb - 1;
+ uint64_t f;
+ int rfd = open (SFS_DEV_RANDOM, O_RDONLY);
+ if (rfd < 0) {
+ fprintf (stderr, "%s: %m\n", SFS_DEV_RANDOM);
+ exit(1);
+ }
+ do {
+ if (read (rfd, &f, sizeof (f)) != implicit_cast<ssize_t> (sizeof (f))) {
+ fprintf (stderr, "%s: read failed\n", SFS_DEV_RANDOM);
+ exit(1);
+ }
+ f = (f & mask) | msb;
+ } while (!polyirreducible (f));
+ close (rfd);
+ return f;
+}
+#endif
+
+class rabinpoly {
+ int shift;
+ uint64_t T[256]; // Lookup table for mod
+ void calcT ();
+public:
+ const uint64_t poly; // Actual polynomial
+
+ explicit rabinpoly (uint64_t poly);
+ uint64_t append8 (uint64_t p, uint8_t m) const
+ { return ((p << 8) | m) ^ T[p >> shift]; }
+};
+
+void
+rabinpoly::calcT ()
+{
+ assert (poly >= 0x100);
+ int xshift = fls64 (poly) - 1;
+ shift = xshift - 8;
+ uint64_t T1 = polymod (0, INT64 (1) << xshift, poly);
+ for (int j = 0; j < 256; j++)
+ T[j] = polymmult (j, T1, poly) | ((uint64_t) j << xshift);
+}
+
+rabinpoly::rabinpoly (uint64_t p)
+ : poly (p)
+{
+ calcT ();
+}
+
+class window : public rabinpoly {
+public:
+ enum {size = 48};
+ //enum {size = 24};
+private:
+ uint64_t fingerprint;
+ int bufpos;
+ uint64_t U[256];
+ uint8_t buf[size];
+
+public:
+ window (uint64_t poly);
+ uint64_t slide8 (uint8_t m) {
+ if (++bufpos >= size)
+ bufpos = 0;
+ uint8_t om = buf[bufpos];
+ buf[bufpos] = m;
+ return fingerprint = append8 (fingerprint ^ U[om], m);
+ }
+ void reset () {
+ fingerprint = 0;
+ bzero (buf, sizeof (buf));
+ }
+};
+
+window::window (uint64_t poly)
+ : rabinpoly (poly), fingerprint (0), bufpos (-1)
+{
+ uint64_t sizeshift = 1;
+ for (int i = 1; i < size; i++)
+ sizeshift = append8 (sizeshift, 0);
+ for (int i = 0; i < 256; i++)
+ U[i] = polymmult (i, sizeshift, poly);
+ bzero (buf, sizeof (buf));
+}
+
+} // end anonymous namespace
+
+/* Public interface to this module. */
+int chunk_compute_max_num_breaks(size_t buflen)
+{
+ return (buflen / MIN_CHUNK_SIZE) + 1;
+}
+
+int chunk_compute_breaks(const char *buf, size_t len, size_t *breakpoints)
+{
+ size_t start, pos;
+ window w(FINGERPRINT_PT);
+
+ int i = 0;
+ start = 0;
+ for (pos = 0; pos < len; pos++) {
+ uint64_t sig = w.slide8(buf[pos]);
+ size_t block_len = pos - start + 1;
+ if ((sig % TARGET_CHUNK_SIZE == BREAKMARK_VALUE
+ && block_len >= MIN_CHUNK_SIZE) || block_len >= MAX_CHUNK_SIZE) {
+ breakpoints[i] = pos;
+ start = pos + 1;
+ i++;
+ w.reset();
+ }
+ }
+
+ if (start < len) {
+ breakpoints[i] = len - 1;
+ i++;
+ }
+
+ return i;
+}
+
+string chunk_algorithm_name()
+{
+ char buf[64];
+ sprintf(buf, "%s-%d", "lbfs", TARGET_CHUNK_SIZE);
+ return buf;
+}
projects / cumulus.git / blobdiff