author | Yuya Nishihara <yuya@tcha.org> |
Sun, 03 Sep 2017 15:32:45 +0900 | |
changeset 34212 | dfd009e5f9f2 |
parent 29749 | 155f0cc3f813 |
child 34633 | 347c0f4232e1 |
permissions | -rw-r--r-- |
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/* |
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mpatch.c - efficient binary patching for Mercurial |
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This implements a patch algorithm that's O(m + nlog n) where m is the |
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size of the output and n is the number of patches. |
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Given a list of binary patches, it unpacks each into a hunk list, |
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then combines the hunk lists with a treewise recursion to form a |
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single hunk list. This hunk list is then applied to the original |
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text. |
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The text (or binary) fragments are copied directly from their source |
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Python objects into a preallocated output string to avoid the |
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allocation of intermediate Python objects. Working memory is about 2x |
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the total number of hunks. |
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Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> |
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This software may be used and distributed according to the terms |
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of the GNU General Public License, incorporated herein by reference. |
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*/ |
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#include <stdlib.h> |
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#include <string.h> |
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#include "bitmanipulation.h" |
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#include "compat.h" |
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#include "mpatch.h" |
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static struct mpatch_flist *lalloc(ssize_t size) |
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{ |
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struct mpatch_flist *a = NULL; |
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if (size < 1) |
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size = 1; |
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a = (struct mpatch_flist *)malloc(sizeof(struct mpatch_flist)); |
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if (a) { |
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a->base = (struct mpatch_frag *)malloc(sizeof(struct mpatch_frag) * size); |
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if (a->base) { |
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a->head = a->tail = a->base; |
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return a; |
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} |
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free(a); |
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} |
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return NULL; |
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} |
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void mpatch_lfree(struct mpatch_flist *a) |
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{ |
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if (a) { |
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free(a->base); |
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free(a); |
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} |
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} |
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static ssize_t lsize(struct mpatch_flist *a) |
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{ |
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return a->tail - a->head; |
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} |
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/* move hunks in source that are less cut to dest, compensating |
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for changes in offset. the last hunk may be split if necessary. |
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*/ |
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static int gather(struct mpatch_flist *dest, struct mpatch_flist *src, int cut, |
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int offset) |
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{ |
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struct mpatch_frag *d = dest->tail, *s = src->head; |
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int postend, c, l; |
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while (s != src->tail) { |
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if (s->start + offset >= cut) |
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break; /* we've gone far enough */ |
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postend = offset + s->start + s->len; |
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if (postend <= cut) { |
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/* save this hunk */ |
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offset += s->start + s->len - s->end; |
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*d++ = *s++; |
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} |
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else { |
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/* break up this hunk */ |
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c = cut - offset; |
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if (s->end < c) |
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c = s->end; |
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l = cut - offset - s->start; |
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if (s->len < l) |
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l = s->len; |
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offset += s->start + l - c; |
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d->start = s->start; |
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d->end = c; |
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d->len = l; |
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d->data = s->data; |
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d++; |
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s->start = c; |
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s->len = s->len - l; |
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s->data = s->data + l; |
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break; |
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} |
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} |
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dest->tail = d; |
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src->head = s; |
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return offset; |
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} |
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/* like gather, but with no output list */ |
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static int discard(struct mpatch_flist *src, int cut, int offset) |
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{ |
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struct mpatch_frag *s = src->head; |
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int postend, c, l; |
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while (s != src->tail) { |
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if (s->start + offset >= cut) |
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break; |
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postend = offset + s->start + s->len; |
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if (postend <= cut) { |
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offset += s->start + s->len - s->end; |
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s++; |
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} |
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else { |
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c = cut - offset; |
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if (s->end < c) |
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c = s->end; |
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l = cut - offset - s->start; |
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if (s->len < l) |
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l = s->len; |
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offset += s->start + l - c; |
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s->start = c; |
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s->len = s->len - l; |
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s->data = s->data + l; |
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break; |
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} |
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} |
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src->head = s; |
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return offset; |
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} |
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/* combine hunk lists a and b, while adjusting b for offset changes in a/ |
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this deletes a and b and returns the resultant list. */ |
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static struct mpatch_flist *combine(struct mpatch_flist *a, |
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struct mpatch_flist *b) |
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{ |
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struct mpatch_flist *c = NULL; |
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struct mpatch_frag *bh, *ct; |
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int offset = 0, post; |
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if (a && b) |
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c = lalloc((lsize(a) + lsize(b)) * 2); |
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if (c) { |
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for (bh = b->head; bh != b->tail; bh++) { |
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/* save old hunks */ |
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offset = gather(c, a, bh->start, offset); |
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/* discard replaced hunks */ |
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post = discard(a, bh->end, offset); |
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/* insert new hunk */ |
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ct = c->tail; |
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ct->start = bh->start - offset; |
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ct->end = bh->end - post; |
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ct->len = bh->len; |
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ct->data = bh->data; |
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c->tail++; |
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offset = post; |
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} |
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/* hold on to tail from a */ |
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memcpy(c->tail, a->head, sizeof(struct mpatch_frag) * lsize(a)); |
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c->tail += lsize(a); |
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} |
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mpatch_lfree(a); |
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mpatch_lfree(b); |
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return c; |
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} |
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/* decode a binary patch into a hunk list */ |
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int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist **res) |
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{ |
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struct mpatch_flist *l; |
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struct mpatch_frag *lt; |
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int pos = 0; |
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/* assume worst case size, we won't have many of these lists */ |
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l = lalloc(len / 12 + 1); |
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if (!l) |
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return MPATCH_ERR_NO_MEM; |
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lt = l->tail; |
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while (pos >= 0 && pos < len) { |
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lt->start = getbe32(bin + pos); |
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lt->end = getbe32(bin + pos + 4); |
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lt->len = getbe32(bin + pos + 8); |
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lt->data = bin + pos + 12; |
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pos += 12 + lt->len; |
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if (lt->start > lt->end || lt->len < 0) |
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break; /* sanity check */ |
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lt++; |
210 |
} |
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if (pos != len) { |
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mpatch_lfree(l); |
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return MPATCH_ERR_CANNOT_BE_DECODED; |
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} |
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l->tail = lt; |
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*res = l; |
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return 0; |
72 | 220 |
} |
221 |
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222 |
/* calculate the size of resultant text */ |
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ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l) |
72 | 224 |
{ |
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ssize_t outlen = 0, last = 0; |
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struct mpatch_frag *f = l->head; |
72 | 227 |
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228 |
while (f != l->tail) { |
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if (f->start < last || f->end > len) { |
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return MPATCH_ERR_INVALID_PATCH; |
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} |
72 | 232 |
outlen += f->start - last; |
233 |
last = f->end; |
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234 |
outlen += f->len; |
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235 |
f++; |
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236 |
} |
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237 |
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238 |
outlen += len - last; |
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239 |
return outlen; |
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240 |
} |
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int mpatch_apply(char *buf, const char *orig, ssize_t len, |
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struct mpatch_flist *l) |
72 | 244 |
{ |
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struct mpatch_frag *f = l->head; |
72 | 246 |
int last = 0; |
247 |
char *p = buf; |
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248 |
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249 |
while (f != l->tail) { |
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if (f->start < last || f->end > len) { |
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return MPATCH_ERR_INVALID_PATCH; |
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} |
72 | 253 |
memcpy(p, orig + last, f->start - last); |
254 |
p += f->start - last; |
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255 |
memcpy(p, f->data, f->len); |
|
256 |
last = f->end; |
|
257 |
p += f->len; |
|
258 |
f++; |
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259 |
} |
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260 |
memcpy(p, orig + last, len - last); |
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55dd12204b8e
mpatch: remove dependency on Python.h in mpatch.c
Maciej Fijalkowski <fijall@gmail.com>
parents:
29693
diff
changeset
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261 |
return 0; |
72 | 262 |
} |
263 |
||
264 |
/* recursively generate a patch of all bins between start and end */ |
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29694
55dd12204b8e
mpatch: remove dependency on Python.h in mpatch.c
Maciej Fijalkowski <fijall@gmail.com>
parents:
29693
diff
changeset
|
265 |
struct mpatch_flist *mpatch_fold(void *bins, |
55dd12204b8e
mpatch: remove dependency on Python.h in mpatch.c
Maciej Fijalkowski <fijall@gmail.com>
parents:
29693
diff
changeset
|
266 |
struct mpatch_flist* (*get_next_item)(void*, ssize_t), |
55dd12204b8e
mpatch: remove dependency on Python.h in mpatch.c
Maciej Fijalkowski <fijall@gmail.com>
parents:
29693
diff
changeset
|
267 |
ssize_t start, ssize_t end) |
72 | 268 |
{ |
29694
55dd12204b8e
mpatch: remove dependency on Python.h in mpatch.c
Maciej Fijalkowski <fijall@gmail.com>
parents:
29693
diff
changeset
|
269 |
ssize_t len; |
72 | 270 |
|
271 |
if (start + 1 == end) { |
|
272 |
/* trivial case, output a decoded list */ |
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29694
55dd12204b8e
mpatch: remove dependency on Python.h in mpatch.c
Maciej Fijalkowski <fijall@gmail.com>
parents:
29693
diff
changeset
|
273 |
return get_next_item(bins, start); |
72 | 274 |
} |
275 |
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276 |
/* divide and conquer, memory management is elsewhere */ |
|
277 |
len = (end - start) / 2; |
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29694
55dd12204b8e
mpatch: remove dependency on Python.h in mpatch.c
Maciej Fijalkowski <fijall@gmail.com>
parents:
29693
diff
changeset
|
278 |
return combine(mpatch_fold(bins, get_next_item, start, start + len), |
55dd12204b8e
mpatch: remove dependency on Python.h in mpatch.c
Maciej Fijalkowski <fijall@gmail.com>
parents:
29693
diff
changeset
|
279 |
mpatch_fold(bins, get_next_item, start + len, end)); |
72 | 280 |
} |