author | Augie Fackler <augie@google.com> |
Mon, 30 Apr 2018 22:13:42 -0400 | |
branch | stable |
changeset 38190 | 1ec4cb8cbc87 |
parent 38189 | faa924469635 |
child 38191 | b8b253aec953 |
permissions | -rw-r--r-- |
72 | 1 |
/* |
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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 <limits.h> |
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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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/* VC9 doesn't include bool and lacks stdbool.h based on cext/util.h */ |
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#if defined(_MSC_VER) || __STDC_VERSION__ < 199901L |
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#define true 1 |
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#define false 0 |
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typedef unsigned char bool; |
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#else |
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#include <stdbool.h> |
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#endif |
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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( |
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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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/* add helper to add src and *dest iff it won't overflow */ |
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static inline bool safeadd(int src, int *dest) |
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{ |
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if ((src > 0) == (*dest > 0)) { |
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if (*dest > 0) { |
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if (src > (INT_MAX - *dest)) { |
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return false; |
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} |
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} else { |
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if (src < (INT_MIN - *dest)) { |
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return false; |
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} |
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} |
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} |
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*dest += src; |
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return true; |
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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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} 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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} |
131 |
} |
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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; |
143 |
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144 |
while (s != src->tail) { |
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if (s->start + offset >= cut) |
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break; |
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148 |
postend = offset + s->start + s->len; |
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149 |
if (postend <= cut) { |
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150 |
offset += s->start + s->len - s->end; |
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s++; |
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} else { |
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c = cut - offset; |
154 |
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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159 |
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160 |
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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} |
167 |
} |
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169 |
src->head = s; |
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return offset; |
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} |
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173 |
/* 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; |
72 | 180 |
int offset = 0, post; |
181 |
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128 | 182 |
if (a && b) |
183 |
c = lalloc((lsize(a) + lsize(b)) * 2); |
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184 |
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185 |
if (c) { |
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72 | 186 |
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128 | 187 |
for (bh = b->head; bh != b->tail; bh++) { |
188 |
/* save old hunks */ |
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189 |
offset = gather(c, a, bh->start, offset); |
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72 | 190 |
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128 | 191 |
/* discard replaced hunks */ |
192 |
post = discard(a, bh->end, offset); |
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72 | 193 |
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128 | 194 |
/* insert new hunk */ |
195 |
ct = c->tail; |
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196 |
ct->start = bh->start - offset; |
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197 |
ct->end = bh->end - post; |
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198 |
ct->len = bh->len; |
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199 |
ct->data = bh->data; |
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200 |
c->tail++; |
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201 |
offset = post; |
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202 |
} |
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203 |
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204 |
/* hold on to tail from a */ |
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205 |
memcpy(c->tail, a->head, sizeof(struct mpatch_frag) * lsize(a)); |
128 | 206 |
c->tail += lsize(a); |
72 | 207 |
} |
208 |
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209 |
mpatch_lfree(a); |
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210 |
mpatch_lfree(b); |
72 | 211 |
return c; |
212 |
} |
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213 |
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214 |
/* decode a binary patch into a hunk list */ |
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215 |
int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist **res) |
72 | 216 |
{ |
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217 |
struct mpatch_flist *l; |
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218 |
struct mpatch_frag *lt; |
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219 |
int pos = 0; |
72 | 220 |
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221 |
/* assume worst case size, we won't have many of these lists */ |
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222 |
l = lalloc(len / 12 + 1); |
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223 |
if (!l) |
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224 |
return MPATCH_ERR_NO_MEM; |
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225 |
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72 | 226 |
lt = l->tail; |
227 |
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228 |
/* We check against len-11 to ensure we have at least 12 bytes |
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229 |
left in the patch so we can read our three be32s out of it. */ |
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230 |
while (pos >= 0 && pos < (len - 11)) { |
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231 |
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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234 |
lt->data = bin + pos + 12; |
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235 |
pos += 12 + lt->len; |
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236 |
if (lt->start > lt->end || lt->len < 0) |
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237 |
break; /* sanity check */ |
72 | 238 |
lt++; |
239 |
} |
|
240 |
||
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241 |
if (pos != len) { |
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242 |
mpatch_lfree(l); |
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243 |
return MPATCH_ERR_CANNOT_BE_DECODED; |
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244 |
} |
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245 |
|
72 | 246 |
l->tail = lt; |
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247 |
*res = l; |
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248 |
return 0; |
72 | 249 |
} |
250 |
||
251 |
/* calculate the size of resultant text */ |
|
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252 |
ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l) |
72 | 253 |
{ |
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254 |
ssize_t outlen = 0, last = 0; |
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255 |
struct mpatch_frag *f = l->head; |
72 | 256 |
|
257 |
while (f != l->tail) { |
|
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258 |
if (f->start < last || f->end > len) { |
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259 |
return MPATCH_ERR_INVALID_PATCH; |
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260 |
} |
72 | 261 |
outlen += f->start - last; |
262 |
last = f->end; |
|
263 |
outlen += f->len; |
|
264 |
f++; |
|
265 |
} |
|
266 |
||
267 |
outlen += len - last; |
|
268 |
return outlen; |
|
269 |
} |
|
270 |
||
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271 |
int mpatch_apply(char *buf, const char *orig, ssize_t len, |
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272 |
struct mpatch_flist *l) |
72 | 273 |
{ |
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|
274 |
struct mpatch_frag *f = l->head; |
72 | 275 |
int last = 0; |
276 |
char *p = buf; |
|
277 |
||
278 |
while (f != l->tail) { |
|
38189
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|
279 |
if (f->start < last || f->start > len || f->end > len || |
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|
280 |
last < 0) { |
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|
281 |
return MPATCH_ERR_INVALID_PATCH; |
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|
282 |
} |
72 | 283 |
memcpy(p, orig + last, f->start - last); |
284 |
p += f->start - last; |
|
285 |
memcpy(p, f->data, f->len); |
|
286 |
last = f->end; |
|
287 |
p += f->len; |
|
288 |
f++; |
|
289 |
} |
|
38188
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|
290 |
if (last < 0) { |
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|
291 |
return MPATCH_ERR_INVALID_PATCH; |
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|
292 |
} |
72 | 293 |
memcpy(p, orig + last, len - last); |
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|
294 |
return 0; |
72 | 295 |
} |
296 |
||
297 |
/* recursively generate a patch of all bins between start and end */ |
|
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|
298 |
struct mpatch_flist * |
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|
299 |
mpatch_fold(void *bins, struct mpatch_flist *(*get_next_item)(void *, ssize_t), |
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|
300 |
ssize_t start, ssize_t end) |
72 | 301 |
{ |
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changeset
|
302 |
ssize_t len; |
72 | 303 |
|
304 |
if (start + 1 == end) { |
|
305 |
/* trivial case, output a decoded list */ |
|
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parents:
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|
306 |
return get_next_item(bins, start); |
72 | 307 |
} |
308 |
||
309 |
/* divide and conquer, memory management is elsewhere */ |
|
310 |
len = (end - start) / 2; |
|
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|
311 |
return combine(mpatch_fold(bins, get_next_item, start, start + len), |
34801
1f4249c764f1
mpatch: switch alignment of wrapped line from tab to spaces with clang-format
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parents:
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changeset
|
312 |
mpatch_fold(bins, get_next_item, start + len, end)); |
72 | 313 |
} |