ref: 094fc8b15f98807833143e29f1f7d36a1ca4b28c
dir: /sys/src/cmd/python/Extra/mercurial/bdiff.c/
/* bdiff.c - efficient binary diff extension for Mercurial Copyright 2005, 2006 Matt Mackall <[email protected]> This software may be used and distributed according to the terms of the GNU General Public License, incorporated herein by reference. Based roughly on Python difflib */ #include <Python.h> #include <stdlib.h> #include <string.h> #include <limits.h> #if defined __hpux || defined __SUNPRO_C || defined _AIX # define inline #endif #ifdef __linux # define inline __inline #endif #ifdef _WIN32 #ifdef _MSC_VER #define inline __inline typedef unsigned long uint32_t; #else #include <stdint.h> #endif static uint32_t htonl(uint32_t x) { return ((x & 0x000000ffUL) << 24) | ((x & 0x0000ff00UL) << 8) | ((x & 0x00ff0000UL) >> 8) | ((x & 0xff000000UL) >> 24); } #else #include <sys/types.h> #if defined __BEOS__ && !defined __HAIKU__ #include <ByteOrder.h> #else #include <arpa/inet.h> #endif #include <inttypes.h> #endif struct line { int h, len, n, e; const char *l; }; struct pos { int pos, len; }; struct hunk { int a1, a2, b1, b2; }; struct hunklist { struct hunk *base, *head; }; int splitlines(const char *a, int len, struct line **lr) { int h, i; const char *p, *b = a; const char * const plast = a + len - 1; struct line *l; /* count the lines */ i = 1; /* extra line for sentinel */ for (p = a; p < a + len; p++) if (*p == '\n' || p == plast) i++; *lr = l = (struct line *)malloc(sizeof(struct line) * i); if (!l) return -1; /* build the line array and calculate hashes */ h = 0; for (p = a; p < a + len; p++) { /* Leonid Yuriev's hash */ h = (h * 1664525) + *p + 1013904223; if (*p == '\n' || p == plast) { l->h = h; h = 0; l->len = p - b + 1; l->l = b; l->n = INT_MAX; l++; b = p + 1; } } /* set up a sentinel */ l->h = l->len = 0; l->l = a + len; return i - 1; } int inline cmp(struct line *a, struct line *b) { return a->h != b->h || a->len != b->len || memcmp(a->l, b->l, a->len); } static int equatelines(struct line *a, int an, struct line *b, int bn) { int i, j, buckets = 1, t, scale; struct pos *h = NULL; /* build a hash table of the next highest power of 2 */ while (buckets < bn + 1) buckets *= 2; /* try to allocate a large hash table to avoid collisions */ for (scale = 4; scale; scale /= 2) { h = (struct pos *)malloc(scale * buckets * sizeof(struct pos)); if (h) break; } if (!h) return 0; buckets = buckets * scale - 1; /* clear the hash table */ for (i = 0; i <= buckets; i++) { h[i].pos = INT_MAX; h[i].len = 0; } /* add lines to the hash table chains */ for (i = bn - 1; i >= 0; i--) { /* find the equivalence class */ for (j = b[i].h & buckets; h[j].pos != INT_MAX; j = (j + 1) & buckets) if (!cmp(b + i, b + h[j].pos)) break; /* add to the head of the equivalence class */ b[i].n = h[j].pos; b[i].e = j; h[j].pos = i; h[j].len++; /* keep track of popularity */ } /* compute popularity threshold */ t = (bn >= 4000) ? bn / 1000 : bn + 1; /* match items in a to their equivalence class in b */ for (i = 0; i < an; i++) { /* find the equivalence class */ for (j = a[i].h & buckets; h[j].pos != INT_MAX; j = (j + 1) & buckets) if (!cmp(a + i, b + h[j].pos)) break; a[i].e = j; /* use equivalence class for quick compare */ if (h[j].len <= t) a[i].n = h[j].pos; /* point to head of match list */ else a[i].n = INT_MAX; /* too popular */ } /* discard hash tables */ free(h); return 1; } static int longest_match(struct line *a, struct line *b, struct pos *pos, int a1, int a2, int b1, int b2, int *omi, int *omj) { int mi = a1, mj = b1, mk = 0, mb = 0, i, j, k; for (i = a1; i < a2; i++) { /* skip things before the current block */ for (j = a[i].n; j < b1; j = b[j].n) ; /* loop through all lines match a[i] in b */ for (; j < b2; j = b[j].n) { /* does this extend an earlier match? */ if (i > a1 && j > b1 && pos[j - 1].pos == i - 1) k = pos[j - 1].len + 1; else k = 1; pos[j].pos = i; pos[j].len = k; /* best match so far? */ if (k > mk) { mi = i; mj = j; mk = k; } } } if (mk) { mi = mi - mk + 1; mj = mj - mk + 1; } /* expand match to include neighboring popular lines */ while (mi - mb > a1 && mj - mb > b1 && a[mi - mb - 1].e == b[mj - mb - 1].e) mb++; while (mi + mk < a2 && mj + mk < b2 && a[mi + mk].e == b[mj + mk].e) mk++; *omi = mi - mb; *omj = mj - mb; return mk + mb; } static void recurse(struct line *a, struct line *b, struct pos *pos, int a1, int a2, int b1, int b2, struct hunklist *l) { int i, j, k; /* find the longest match in this chunk */ k = longest_match(a, b, pos, a1, a2, b1, b2, &i, &j); if (!k) return; /* and recurse on the remaining chunks on either side */ recurse(a, b, pos, a1, i, b1, j, l); l->head->a1 = i; l->head->a2 = i + k; l->head->b1 = j; l->head->b2 = j + k; l->head++; recurse(a, b, pos, i + k, a2, j + k, b2, l); } static struct hunklist diff(struct line *a, int an, struct line *b, int bn) { struct hunklist l; struct hunk *curr; struct pos *pos; int t; /* allocate and fill arrays */ t = equatelines(a, an, b, bn); pos = (struct pos *)calloc(bn ? bn : 1, sizeof(struct pos)); /* we can't have more matches than lines in the shorter file */ l.head = l.base = (struct hunk *)malloc(sizeof(struct hunk) * ((an<bn ? an:bn) + 1)); if (pos && l.base && t) { /* generate the matching block list */ recurse(a, b, pos, 0, an, 0, bn, &l); l.head->a1 = l.head->a2 = an; l.head->b1 = l.head->b2 = bn; l.head++; } free(pos); /* normalize the hunk list, try to push each hunk towards the end */ for (curr = l.base; curr != l.head; curr++) { struct hunk *next = curr+1; int shift = 0; if (next == l.head) break; if (curr->a2 == next->a1) while (curr->a2+shift < an && curr->b2+shift < bn && !cmp(a+curr->a2+shift, b+curr->b2+shift)) shift++; else if (curr->b2 == next->b1) while (curr->b2+shift < bn && curr->a2+shift < an && !cmp(b+curr->b2+shift, a+curr->a2+shift)) shift++; if (!shift) continue; curr->b2 += shift; next->b1 += shift; curr->a2 += shift; next->a1 += shift; } return l; } static PyObject *blocks(PyObject *self, PyObject *args) { PyObject *sa, *sb, *rl = NULL, *m; struct line *a, *b; struct hunklist l = {NULL, NULL}; struct hunk *h; int an, bn, pos = 0; if (!PyArg_ParseTuple(args, "SS:bdiff", &sa, &sb)) return NULL; an = splitlines(PyString_AsString(sa), PyString_Size(sa), &a); bn = splitlines(PyString_AsString(sb), PyString_Size(sb), &b); if (!a || !b) goto nomem; l = diff(a, an, b, bn); rl = PyList_New(l.head - l.base); if (!l.head || !rl) goto nomem; for (h = l.base; h != l.head; h++) { m = Py_BuildValue("iiii", h->a1, h->a2, h->b1, h->b2); PyList_SetItem(rl, pos, m); pos++; } nomem: free(a); free(b); free(l.base); return rl ? rl : PyErr_NoMemory(); } static PyObject *bdiff(PyObject *self, PyObject *args) { char *sa, *sb; PyObject *result = NULL; struct line *al, *bl; struct hunklist l = {NULL, NULL}; struct hunk *h; char encode[12], *rb; int an, bn, len = 0, la, lb; if (!PyArg_ParseTuple(args, "s#s#:bdiff", &sa, &la, &sb, &lb)) return NULL; an = splitlines(sa, la, &al); bn = splitlines(sb, lb, &bl); if (!al || !bl) goto nomem; l = diff(al, an, bl, bn); if (!l.head) goto nomem; /* calculate length of output */ la = lb = 0; for (h = l.base; h != l.head; h++) { if (h->a1 != la || h->b1 != lb) len += 12 + bl[h->b1].l - bl[lb].l; la = h->a2; lb = h->b2; } result = PyString_FromStringAndSize(NULL, len); if (!result) goto nomem; /* build binary patch */ rb = PyString_AsString(result); la = lb = 0; for (h = l.base; h != l.head; h++) { if (h->a1 != la || h->b1 != lb) { len = bl[h->b1].l - bl[lb].l; *(uint32_t *)(encode) = htonl(al[la].l - al->l); *(uint32_t *)(encode + 4) = htonl(al[h->a1].l - al->l); *(uint32_t *)(encode + 8) = htonl(len); memcpy(rb, encode, 12); memcpy(rb + 12, bl[lb].l, len); rb += 12 + len; } la = h->a2; lb = h->b2; } nomem: free(al); free(bl); free(l.base); return result ? result : PyErr_NoMemory(); } static char mdiff_doc[] = "Efficient binary diff."; static PyMethodDef methods[] = { {"bdiff", bdiff, METH_VARARGS, "calculate a binary diff\n"}, {"blocks", blocks, METH_VARARGS, "find a list of matching lines\n"}, {NULL, NULL} }; PyMODINIT_FUNC initbdiff(void) { Py_InitModule3("bdiff", methods, mdiff_doc); }