Mercurial > hg
view mercurial/mpatch.c @ 30397:564b33acc21f
patch: migrate to util.iterfile
author | Jun Wu <quark@fb.com> |
---|---|
date | Mon, 14 Nov 2016 23:14:06 +0000 |
parents | 155f0cc3f813 |
children | 347c0f4232e1 |
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line source
/* mpatch.c - efficient binary patching for Mercurial This implements a patch algorithm that's O(m + nlog n) where m is the size of the output and n is the number of patches. Given a list of binary patches, it unpacks each into a hunk list, then combines the hunk lists with a treewise recursion to form a single hunk list. This hunk list is then applied to the original text. The text (or binary) fragments are copied directly from their source Python objects into a preallocated output string to avoid the allocation of intermediate Python objects. Working memory is about 2x the total number of hunks. Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> This software may be used and distributed according to the terms of the GNU General Public License, incorporated herein by reference. */ #include <stdlib.h> #include <string.h> #include "bitmanipulation.h" #include "compat.h" #include "mpatch.h" static struct mpatch_flist *lalloc(ssize_t size) { struct mpatch_flist *a = NULL; if (size < 1) size = 1; a = (struct mpatch_flist *)malloc(sizeof(struct mpatch_flist)); if (a) { a->base = (struct mpatch_frag *)malloc(sizeof(struct mpatch_frag) * size); if (a->base) { a->head = a->tail = a->base; return a; } free(a); } return NULL; } void mpatch_lfree(struct mpatch_flist *a) { if (a) { free(a->base); free(a); } } static ssize_t lsize(struct mpatch_flist *a) { return a->tail - a->head; } /* move hunks in source that are less cut to dest, compensating for changes in offset. the last hunk may be split if necessary. */ static int gather(struct mpatch_flist *dest, struct mpatch_flist *src, int cut, int offset) { struct mpatch_frag *d = dest->tail, *s = src->head; int postend, c, l; while (s != src->tail) { if (s->start + offset >= cut) break; /* we've gone far enough */ postend = offset + s->start + s->len; if (postend <= cut) { /* save this hunk */ offset += s->start + s->len - s->end; *d++ = *s++; } else { /* break up this hunk */ c = cut - offset; if (s->end < c) c = s->end; l = cut - offset - s->start; if (s->len < l) l = s->len; offset += s->start + l - c; d->start = s->start; d->end = c; d->len = l; d->data = s->data; d++; s->start = c; s->len = s->len - l; s->data = s->data + l; break; } } dest->tail = d; src->head = s; return offset; } /* like gather, but with no output list */ static int discard(struct mpatch_flist *src, int cut, int offset) { struct mpatch_frag *s = src->head; int postend, c, l; while (s != src->tail) { if (s->start + offset >= cut) break; postend = offset + s->start + s->len; if (postend <= cut) { offset += s->start + s->len - s->end; s++; } else { c = cut - offset; if (s->end < c) c = s->end; l = cut - offset - s->start; if (s->len < l) l = s->len; offset += s->start + l - c; s->start = c; s->len = s->len - l; s->data = s->data + l; break; } } src->head = s; return offset; } /* combine hunk lists a and b, while adjusting b for offset changes in a/ this deletes a and b and returns the resultant list. */ static struct mpatch_flist *combine(struct mpatch_flist *a, struct mpatch_flist *b) { struct mpatch_flist *c = NULL; struct mpatch_frag *bh, *ct; int offset = 0, post; if (a && b) c = lalloc((lsize(a) + lsize(b)) * 2); if (c) { for (bh = b->head; bh != b->tail; bh++) { /* save old hunks */ offset = gather(c, a, bh->start, offset); /* discard replaced hunks */ post = discard(a, bh->end, offset); /* insert new hunk */ ct = c->tail; ct->start = bh->start - offset; ct->end = bh->end - post; ct->len = bh->len; ct->data = bh->data; c->tail++; offset = post; } /* hold on to tail from a */ memcpy(c->tail, a->head, sizeof(struct mpatch_frag) * lsize(a)); c->tail += lsize(a); } mpatch_lfree(a); mpatch_lfree(b); return c; } /* decode a binary patch into a hunk list */ int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist **res) { struct mpatch_flist *l; struct mpatch_frag *lt; int pos = 0; /* assume worst case size, we won't have many of these lists */ l = lalloc(len / 12 + 1); if (!l) return MPATCH_ERR_NO_MEM; lt = l->tail; while (pos >= 0 && pos < len) { lt->start = getbe32(bin + pos); lt->end = getbe32(bin + pos + 4); lt->len = getbe32(bin + pos + 8); lt->data = bin + pos + 12; pos += 12 + lt->len; if (lt->start > lt->end || lt->len < 0) break; /* sanity check */ lt++; } if (pos != len) { mpatch_lfree(l); return MPATCH_ERR_CANNOT_BE_DECODED; } l->tail = lt; *res = l; return 0; } /* calculate the size of resultant text */ ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l) { ssize_t outlen = 0, last = 0; struct mpatch_frag *f = l->head; while (f != l->tail) { if (f->start < last || f->end > len) { return MPATCH_ERR_INVALID_PATCH; } outlen += f->start - last; last = f->end; outlen += f->len; f++; } outlen += len - last; return outlen; } int mpatch_apply(char *buf, const char *orig, ssize_t len, struct mpatch_flist *l) { struct mpatch_frag *f = l->head; int last = 0; char *p = buf; while (f != l->tail) { if (f->start < last || f->end > len) { return MPATCH_ERR_INVALID_PATCH; } memcpy(p, orig + last, f->start - last); p += f->start - last; memcpy(p, f->data, f->len); last = f->end; p += f->len; f++; } memcpy(p, orig + last, len - last); return 0; } /* recursively generate a patch of all bins between start and end */ struct mpatch_flist *mpatch_fold(void *bins, struct mpatch_flist* (*get_next_item)(void*, ssize_t), ssize_t start, ssize_t end) { ssize_t len; if (start + 1 == end) { /* trivial case, output a decoded list */ return get_next_item(bins, start); } /* divide and conquer, memory management is elsewhere */ len = (end - start) / 2; return combine(mpatch_fold(bins, get_next_item, start, start + len), mpatch_fold(bins, get_next_item, start + len, end)); }