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revlog: rewrite censoring logic...
revlog: rewrite censoring logic I was able to corrupt a revlog relatively easily with the existing censoring code. The underlying problem is that the existing code doesn't fully take delta chains into account. When copying revisions that occur after the censored revision, the delta base can refer to a censored revision. Then at read time, things blow up due to the revision data not being a compressed delta. This commit rewrites the revlog censoring code to take a higher-level approach. We now create a new revlog instance pointing at temp files. We iterate through each revision in the source revlog and insert those revisions into the new revlog, replacing the censored revision's data along the way. The new implementation isn't as efficient as the old one. This is because it will fully engage delta computation on insertion. But I don't think it matters. The new implementation is a bit hacky because it attempts to reload the revlog instance with a new revlog index/data file. This is fragile. But this is needed because the index (which could be backed by C) would have a cached copy of the old, possibly changed data and that could lead to problems accessing index or revision data later. One benefit of the new approach is that we integrate with the transaction. The old revlog is backed up and if the transaction is rolled back, the original revlog is restored. As part of this, we had to teach the transaction about the store vfs. I'm not super keen about this. But this was the easiest way to hook things up to the transaction. We /could/ just ignore the transaction like we were doing before. But any file mutation should be governed by transaction semantics, including undo during rollback. Differential Revision: https://phab.mercurial-scm.org/D4869

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xutils.c
150 lines | 3.1 KiB | text/x-c | CLexer
/*
* LibXDiff by Davide Libenzi ( File Differential Library )
* Copyright (C) 2003 Davide Libenzi
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see
* <http://www.gnu.org/licenses/>.
*
* Davide Libenzi <davidel@xmailserver.org>
*
*/
#include <limits.h>
#include <assert.h>
#include "xinclude.h"
int64_t xdl_bogosqrt(int64_t n) {
int64_t i;
/*
* Classical integer square root approximation using shifts.
*/
for (i = 1; n > 0; n >>= 2)
i <<= 1;
return i;
}
void *xdl_mmfile_first(mmfile_t *mmf, int64_t *size)
{
*size = mmf->size;
return mmf->ptr;
}
int64_t xdl_mmfile_size(mmfile_t *mmf)
{
return mmf->size;
}
int xdl_cha_init(chastore_t *cha, int64_t isize, int64_t icount) {
cha->head = cha->tail = NULL;
cha->isize = isize;
cha->nsize = icount * isize;
cha->ancur = cha->sncur = NULL;
cha->scurr = 0;
return 0;
}
void xdl_cha_free(chastore_t *cha) {
chanode_t *cur, *tmp;
for (cur = cha->head; (tmp = cur) != NULL;) {
cur = cur->next;
xdl_free(tmp);
}
}
void *xdl_cha_alloc(chastore_t *cha) {
chanode_t *ancur;
void *data;
if (!(ancur = cha->ancur) || ancur->icurr == cha->nsize) {
if (!(ancur = (chanode_t *) xdl_malloc(sizeof(chanode_t) + cha->nsize))) {
return NULL;
}
ancur->icurr = 0;
ancur->next = NULL;
if (cha->tail)
cha->tail->next = ancur;
if (!cha->head)
cha->head = ancur;
cha->tail = ancur;
cha->ancur = ancur;
}
data = (char *) ancur + sizeof(chanode_t) + ancur->icurr;
ancur->icurr += cha->isize;
return data;
}
int64_t xdl_guess_lines(mmfile_t *mf, int64_t sample) {
int64_t nl = 0, size, tsize = 0;
char const *data, *cur, *top;
if ((cur = data = xdl_mmfile_first(mf, &size)) != NULL) {
for (top = data + size; nl < sample && cur < top; ) {
nl++;
if (!(cur = memchr(cur, '\n', top - cur)))
cur = top;
else
cur++;
}
tsize += (long) (cur - data);
}
if (nl && tsize)
nl = xdl_mmfile_size(mf) / (tsize / nl);
return nl + 1;
}
int xdl_recmatch(const char *l1, int64_t s1, const char *l2, int64_t s2)
{
if (s1 == s2 && !memcmp(l1, l2, s1))
return 1;
return 0;
}
uint64_t xdl_hash_record(char const **data, char const *top) {
uint64_t ha = 5381;
char const *ptr = *data;
for (; ptr < top && *ptr != '\n'; ptr++) {
ha += (ha << 5);
ha ^= (unsigned long) *ptr;
}
*data = ptr < top ? ptr + 1: ptr;
return ha;
}
unsigned int xdl_hashbits(int64_t size) {
int64_t val = 1;
unsigned int bits = 0;
for (; val < size && bits < (int64_t) CHAR_BIT * sizeof(unsigned int); val <<= 1, bits++);
return bits ? bits: 1;
}