Add libxdiff library

xdiff/xhistogram.c

+/*
+ * Copyright (C) 2010, Google Inc.
+ * and other copyright owners as documented in JGit's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "xinclude.h"
+#include "xtypes.h"
+#include "xdiff.h"
+
+#define MAX_PTR UINT_MAX
+#define MAX_CNT UINT_MAX
+
+#define LINE_END(n) (line##n + count##n - 1)
+#define LINE_END_PTR(n) (*line##n + *count##n - 1)
+
+struct histindex {
+        struct record {
+                unsigned int ptr, cnt;
+                struct record *next;
+        } **records, /* an occurrence */
+          **line_map; /* map of line to record chain */
+        chastore_t rcha;
+        unsigned int *next_ptrs;
+        unsigned int table_bits,
+                     records_size,
+                     line_map_size;
+
+        unsigned int max_chain_length,
+                     key_shift,
+                     ptr_shift;
+
+        unsigned int cnt,
+                     has_common;
+
+        xdfenv_t *env;
+        xpparam_t const *xpp;
+};
+
+struct region {
+        unsigned int begin1, end1;
+        unsigned int begin2, end2;
+};
+
+#define LINE_MAP(i, a) (i->line_map[(a) - i->ptr_shift])
+
+#define NEXT_PTR(index, ptr) \
+        (index->next_ptrs[(ptr) - index->ptr_shift])
+
+#define CNT(index, ptr) \
+        ((LINE_MAP(index, ptr))->cnt)
+
+#define REC(env, s, l) \
+        (env->xdf##s.recs[l - 1])
+
+static int cmp_recs(xpparam_t const *xpp,
+        xrecord_t *r1, xrecord_t *r2)
+{
+        return r1->ha == r2->ha &&
+                xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
+                            xpp->flags);
+}
+
+#define CMP_ENV(xpp, env, s1, l1, s2, l2) \
+        (cmp_recs(xpp, REC(env, s1, l1), REC(env, s2, l2)))
+
+#define CMP(i, s1, l1, s2, l2) \
+        (cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))
+
+#define TABLE_HASH(index, side, line) \
+        XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
+
+static int scanA(struct histindex *index, int line1, int count1)
+{
+        unsigned int ptr, tbl_idx;
+        unsigned int chain_len;
+        struct record **rec_chain, *rec;
+
+        for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
+                tbl_idx = TABLE_HASH(index, 1, ptr);
+                rec_chain = index->records + tbl_idx;
+                rec = *rec_chain;
+
+                chain_len = 0;
+                while (rec) {
+                        if (CMP(index, 1, rec->ptr, 1, ptr)) {
+                                /*
+                                 * ptr is identical to another element. Insert
+                                 * it onto the front of the existing element
+                                 * chain.
+                                 */
+                                NEXT_PTR(index, ptr) = rec->ptr;
+                                rec->ptr = ptr;
+                                /* cap rec->cnt at MAX_CNT */
+                                rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
+                                LINE_MAP(index, ptr) = rec;
+                                goto continue_scan;
+                        }
+
+                        rec = rec->next;
+                        chain_len++;
+                }
+
+                if (chain_len == index->max_chain_length)
+                        return -1;
+
+                /*
+                 * This is the first time we have ever seen this particular
+                 * element in the sequence. Construct a new chain for it.
+                 */
+                if (!(rec = xdl_cha_alloc(&index->rcha)))
+                        return -1;
+                rec->ptr = ptr;
+                rec->cnt = 1;
+                rec->next = *rec_chain;
+                *rec_chain = rec;
+                LINE_MAP(index, ptr) = rec;
+
+continue_scan:
+                ; /* no op */
+        }
+
+        return 0;
+}
+
+static int try_lcs(struct histindex *index, struct region *lcs, int b_ptr,
+        int line1, int count1, int line2, int count2)
+{
+        unsigned int b_next = b_ptr + 1;
+        struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
+        unsigned int as, ae, bs, be, np, rc;
+        int should_break;
+
+        for (; rec; rec = rec->next) {
+                if (rec->cnt > index->cnt) {
+                        if (!index->has_common)
+                                index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
+                        continue;
+                }
+
+                as = rec->ptr;
+                if (!CMP(index, 1, as, 2, b_ptr))
+                        continue;
+
+                index->has_common = 1;
+                for (;;) {
+                        should_break = 0;
+                        np = NEXT_PTR(index, as);
+                        bs = b_ptr;
+                        ae = as;
+                        be = bs;
+                        rc = rec->cnt;
+
+                        while (line1 < as && line2 < bs
+                                && CMP(index, 1, as - 1, 2, bs - 1)) {
+                                as--;
+                                bs--;
+                                if (1 < rc)
+                                        rc = XDL_MIN(rc, CNT(index, as));
+                        }
+                        while (ae < LINE_END(1) && be < LINE_END(2)
+                                && CMP(index, 1, ae + 1, 2, be + 1)) {
+                                ae++;
+                                be++;
+                                if (1 < rc)
+                                        rc = XDL_MIN(rc, CNT(index, ae));
+                        }
+
+                        if (b_next <= be)
+                                b_next = be + 1;
+                        if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
+                                lcs->begin1 = as;
+                                lcs->begin2 = bs;
+                                lcs->end1 = ae;
+                                lcs->end2 = be;
+                                index->cnt = rc;
+                        }
+
+                        if (np == 0)
+                                break;
+
+                        while (np <= ae) {
+                                np = NEXT_PTR(index, np);
+                                if (np == 0) {
+                                        should_break = 1;
+                                        break;
+                                }
+                        }
+
+                        if (should_break)
+                                break;
+
+                        as = np;
+                }
+        }
+        return b_next;
+}
+
+static int find_lcs(struct histindex *index, struct region *lcs,
+        int line1, int count1, int line2, int count2) {
+        int b_ptr;
+
+        if (scanA(index, line1, count1))
+                return -1;
+
+        index->cnt = index->max_chain_length + 1;
+
+        for (b_ptr = line2; b_ptr <= LINE_END(2); )
+                b_ptr = try_lcs(index, lcs, b_ptr, line1, count1, line2, count2);
+
+        return index->has_common && index->max_chain_length < index->cnt;
+}
+
+static int fall_back_to_classic_diff(struct histindex *index,
+                int line1, int count1, int line2, int count2)
+{
+        xpparam_t xpp;
+        xpp.flags = index->xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
+
+        return xdl_fall_back_diff(index->env, &xpp,
+                                  line1, count1, line2, count2);
+}
+
+static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env,
+        int line1, int count1, int line2, int count2)
+{
+        struct histindex index;
+        struct region lcs;
+        int sz;
+        int result = -1;
+
+        if (count1 <= 0 && count2 <= 0)
+                return 0;
+
+        if (LINE_END(1) >= MAX_PTR)
+                return -1;
+
+        if (!count1) {
+                while(count2--)
+                        env->xdf2.rchg[line2++ - 1] = 1;
+                return 0;
+        } else if (!count2) {
+                while(count1--)
+                        env->xdf1.rchg[line1++ - 1] = 1;
+                return 0;
+        }
+
+        memset(&index, 0, sizeof(index));
+
+        index.env = env;
+        index.xpp = xpp;
+
+        index.records = NULL;
+        index.line_map = NULL;
+        /* in case of early xdl_cha_free() */
+        index.rcha.head = NULL;
+
+        index.table_bits = xdl_hashbits(count1);
+        sz = index.records_size = 1 << index.table_bits;
+        sz *= sizeof(struct record *);
+        if (!(index.records = (struct record **) xdl_malloc(sz)))
+                goto cleanup;
+        memset(index.records, 0, sz);
+
+        sz = index.line_map_size = count1;
+        sz *= sizeof(struct record *);
+        if (!(index.line_map = (struct record **) xdl_malloc(sz)))
+                goto cleanup;
+        memset(index.line_map, 0, sz);
+
+        sz = index.line_map_size;
+        sz *= sizeof(unsigned int);
+        if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
+                goto cleanup;
+        memset(index.next_ptrs, 0, sz);
+
+        /* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
+        if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
+                goto cleanup;
+
+        index.ptr_shift = line1;
+        index.max_chain_length = 64;
+
+        memset(&lcs, 0, sizeof(lcs));
+        if (find_lcs(&index, &lcs, line1, count1, line2, count2))
+                result = fall_back_to_classic_diff(&index, line1, count1, line2, count2);
+        else {
+                if (lcs.begin1 == 0 && lcs.begin2 == 0) {
+                        while (count1--)
+                                env->xdf1.rchg[line1++ - 1] = 1;
+                        while (count2--)
+                                env->xdf2.rchg[line2++ - 1] = 1;
+                        result = 0;
+                } else {
+                        result = histogram_diff(xpp, env,
+                                                line1, lcs.begin1 - line1,
+                                                line2, lcs.begin2 - line2);
+                        if (result)
+                                goto cleanup;
+                        result = histogram_diff(xpp, env,
+                                                lcs.end1 + 1, LINE_END(1) - lcs.end1,
+                                                lcs.end2 + 1, LINE_END(2) - lcs.end2);
+                        if (result)
+                                goto cleanup;
+                }
+        }
+
+cleanup:
+        xdl_free(index.records);
+        xdl_free(index.line_map);
+        xdl_free(index.next_ptrs);
+        xdl_cha_free(&index.rcha);
+
+        return result;
+}
+
+int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
+        xpparam_t const *xpp, xdfenv_t *env)
+{
+        if (xdl_prepare_env(file1, file2, xpp, env) < 0)
+                return -1;
+
+        return histogram_diff(xpp, env,
+                env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
+                env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
+}