Mercurial > hg
view mercurial/mpatch.c @ 5195:33015dac5df5
convert: fix mercurial_sink.putcommit
Changeset 4ebc8693ce72 added some code to putcommit to avoid creating a
revision that touches no files, but this can break regular conversions
from some repositories:
- conceptually, since we're converting a repo, we should try to make
the new hg repo as similar as possible to the original repo - we
should create a new changeset, even if the original revision didn't
touch any files (maybe the commit message had some important bit);
- even if a "regular" revision that doesn't touch any file may seem
weird (and maybe even broken), it's completely legitimate for a merge
revision to not touch any file, and, if we just skip it, the
converted repo will end up with wrong history and possibly an extra
head.
As an example, say the crew and main hg repos are sync'ed. Somebody
sends an important patch to the mailing list. Matt quickly applies
and pushes it. But at the same time somebody also applies it to crew
and pushes it. Suppose the commit message ended up being a bit
different (say, there was a typo and somebody didn't fix it) or that
the date ended up being different (because of different patch-applying
scripts): the changeset hashes will be different, but the manifests
will be the same.
Since both changesets were pushed to public repos, it's hard to recall
them. If both are merged, the manifest from the resulting merge
revision will have the exact same contents as its parents - i.e. the
merge revision really doesn't touch any file at all.
To keep the file filtering stuff "working", the generic code was changed
to skip empty revisions if we're filtering the repo, fixing a bug in the
process (we want parents[0] instead of tip).
author | Alexis S. L. Carvalho <alexis@cecm.usp.br> |
---|---|
date | Fri, 17 Aug 2007 20:18:05 -0300 |
parents | 4759da3e4dc8 |
children | a0952e4e52eb |
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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 <Python.h> #include <stdlib.h> #include <string.h> #ifdef _WIN32 # ifdef _MSC_VER /* msvc 6.0 has problems */ # define inline __inline typedef unsigned long uint32_t; # else # include <stdint.h> # endif static uint32_t ntohl(uint32_t x) { return ((x & 0x000000ffUL) << 24) | ((x & 0x0000ff00UL) << 8) | ((x & 0x00ff0000UL) >> 8) | ((x & 0xff000000UL) >> 24); } #else /* not windows */ # include <sys/types.h> # ifdef __BEOS__ # include <ByteOrder.h> # else # include <arpa/inet.h> # endif # include <inttypes.h> #endif static char mpatch_doc[] = "Efficient binary patching."; static PyObject *mpatch_Error; struct frag { int start, end, len; char *data; }; struct flist { struct frag *base, *head, *tail; }; static struct flist *lalloc(int size) { struct flist *a = NULL; if (size < 1) size = 1; a = (struct flist *)malloc(sizeof(struct flist)); if (a) { a->base = (struct frag *)malloc(sizeof(struct frag) * size); if (a->base) { a->head = a->tail = a->base; return a; } free(a); a = NULL; } if (!PyErr_Occurred()) PyErr_NoMemory(); return NULL; } static void lfree(struct flist *a) { if (a) { free(a->base); free(a); } } static int lsize(struct 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 flist *dest, struct flist *src, int cut, int offset) { struct 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 flist *src, int cut, int offset) { struct 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 flist *combine(struct flist *a, struct flist *b) { struct flist *c = NULL; struct 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 frag) * lsize(a)); c->tail += lsize(a); } lfree(a); lfree(b); return c; } /* decode a binary patch into a hunk list */ static struct flist *decode(char *bin, int len) { struct flist *l; struct frag *lt; char *data = bin + 12, *end = bin + len; char decode[12]; /* for dealing with alignment issues */ /* assume worst case size, we won't have many of these lists */ l = lalloc(len / 12); if (!l) return NULL; lt = l->tail; while (data <= end) { memcpy(decode, bin, 12); lt->start = ntohl(*(uint32_t *)decode); lt->end = ntohl(*(uint32_t *)(decode + 4)); lt->len = ntohl(*(uint32_t *)(decode + 8)); if (lt->start > lt->end) break; /* sanity check */ bin = data + lt->len; if (bin < data) break; /* big data + big (bogus) len can wrap around */ lt->data = data; data = bin + 12; lt++; } if (bin != end) { if (!PyErr_Occurred()) PyErr_SetString(mpatch_Error, "patch cannot be decoded"); lfree(l); return NULL; } l->tail = lt; return l; } /* calculate the size of resultant text */ static int calcsize(int len, struct flist *l) { int outlen = 0, last = 0; struct frag *f = l->head; while (f != l->tail) { if (f->start < last || f->end > len) { if (!PyErr_Occurred()) PyErr_SetString(mpatch_Error, "invalid patch"); return -1; } outlen += f->start - last; last = f->end; outlen += f->len; f++; } outlen += len - last; return outlen; } static int apply(char *buf, char *orig, int len, struct flist *l) { struct frag *f = l->head; int last = 0; char *p = buf; while (f != l->tail) { if (f->start < last || f->end > len) { if (!PyErr_Occurred()) PyErr_SetString(mpatch_Error, "invalid patch"); return 0; } 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 1; } /* recursively generate a patch of all bins between start and end */ static struct flist *fold(PyObject *bins, int start, int end) { int len; if (start + 1 == end) { /* trivial case, output a decoded list */ PyObject *tmp = PyList_GetItem(bins, start); if (!tmp) return NULL; return decode(PyString_AsString(tmp), PyString_Size(tmp)); } /* divide and conquer, memory management is elsewhere */ len = (end - start) / 2; return combine(fold(bins, start, start + len), fold(bins, start + len, end)); } static PyObject * patches(PyObject *self, PyObject *args) { PyObject *text, *bins, *result; struct flist *patch; char *in, *out; int len, outlen; if (!PyArg_ParseTuple(args, "SO:mpatch", &text, &bins)) return NULL; len = PyList_Size(bins); if (!len) { /* nothing to do */ Py_INCREF(text); return text; } patch = fold(bins, 0, len); if (!patch) return NULL; outlen = calcsize(PyString_Size(text), patch); if (outlen < 0) { result = NULL; goto cleanup; } result = PyString_FromStringAndSize(NULL, outlen); if (!result) { result = NULL; goto cleanup; } in = PyString_AsString(text); out = PyString_AsString(result); if (!apply(out, in, PyString_Size(text), patch)) { Py_DECREF(result); result = NULL; } cleanup: lfree(patch); return result; } /* calculate size of a patched file directly */ static PyObject * patchedsize(PyObject *self, PyObject *args) { long orig, start, end, len, outlen = 0, last = 0; int patchlen; char *bin, *binend, *data; char decode[12]; /* for dealing with alignment issues */ if (!PyArg_ParseTuple(args, "ls#", &orig, &bin, &patchlen)) return NULL; binend = bin + patchlen; data = bin + 12; while (data <= binend) { memcpy(decode, bin, 12); start = ntohl(*(uint32_t *)decode); end = ntohl(*(uint32_t *)(decode + 4)); len = ntohl(*(uint32_t *)(decode + 8)); if (start > end) break; /* sanity check */ bin = data + len; if (bin < data) break; /* big data + big (bogus) len can wrap around */ data = bin + 12; outlen += start - last; last = end; outlen += len; } if (bin != binend) { if (!PyErr_Occurred()) PyErr_SetString(mpatch_Error, "patch cannot be decoded"); return NULL; } outlen += orig - last; return Py_BuildValue("l", outlen); } static PyMethodDef methods[] = { {"patches", patches, METH_VARARGS, "apply a series of patches\n"}, {"patchedsize", patchedsize, METH_VARARGS, "calculed patched size\n"}, {NULL, NULL} }; PyMODINIT_FUNC initmpatch(void) { Py_InitModule3("mpatch", methods, mpatch_doc); mpatch_Error = PyErr_NewException("mpatch.mpatchError", NULL, NULL); }