Mercurial > hg
view mercurial/mpatch.c @ 25018:93e015a3d1ea
commit: add ui.allowemptycommit config option
This adds a config flag that enables a user to make empty commits.
This is useful in a number of cases.
For instance, automation that creates release branches via
bookmarks may want to make empty commits to that release bookmark so that it
can't be fast-forwarded and so it can record information about the release
bookmark's creation. This is already possible with named branches, so making it
possible for bookmarks makes sense.
Another case we've wanted it is for mirroring repositories into Mercurial. We
have automation that syncs commits into hg by running things from the command
line. The ability to produce empty commits is useful for syncing unusual commits
from other VCS's.
In general, allowing the user to create the DAG as they see fit seems useful,
and when I mentioned this in IRC more than one person piped up and said they
were already hacking around this limitation by using mq, import, and
commit-dummy-change-then-amend-the-content-away style solutions.
author | Durham Goode <durham@fb.com> |
---|---|
date | Mon, 11 May 2015 16:18:28 -0700 |
parents | 09e41ac6289d |
children | b6ed2505d6cf |
line wrap: on
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. */ #define PY_SSIZE_T_CLEAN #include <Python.h> #include <stdlib.h> #include <string.h> #include "util.h" static char mpatch_doc[] = "Efficient binary patching."; static PyObject *mpatch_Error; struct frag { int start, end, len; const char *data; }; struct flist { struct frag *base, *head, *tail; }; static struct flist *lalloc(Py_ssize_t 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 Py_ssize_t 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(const char *bin, Py_ssize_t len) { struct flist *l; struct frag *lt; int pos = 0; /* assume worst case size, we won't have many of these lists */ l = lalloc(len / 12); if (!l) return NULL; 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); if (lt->start > lt->end) break; /* sanity check */ lt->data = bin + pos + 12; pos += 12 + lt->len; lt++; } if (pos != len) { 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 Py_ssize_t calcsize(Py_ssize_t len, struct flist *l) { Py_ssize_t 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, const char *orig, Py_ssize_t 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, Py_ssize_t start, Py_ssize_t end) { Py_ssize_t len, blen; const char *buffer; if (start + 1 == end) { /* trivial case, output a decoded list */ PyObject *tmp = PyList_GetItem(bins, start); if (!tmp) return NULL; if (PyObject_AsCharBuffer(tmp, &buffer, &blen)) return NULL; return decode(buffer, blen); } /* 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; const char *in; char *out; Py_ssize_t len, outlen, inlen; if (!PyArg_ParseTuple(args, "OO:mpatch", &text, &bins)) return NULL; len = PyList_Size(bins); if (!len) { /* nothing to do */ Py_INCREF(text); return text; } if (PyObject_AsCharBuffer(text, &in, &inlen)) return NULL; patch = fold(bins, 0, len); if (!patch) return NULL; outlen = calcsize(inlen, patch); if (outlen < 0) { result = NULL; goto cleanup; } result = PyBytes_FromStringAndSize(NULL, outlen); if (!result) { result = NULL; goto cleanup; } out = PyBytes_AsString(result); if (!apply(out, in, inlen, 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, pos = 0; Py_ssize_t patchlen; char *bin; if (!PyArg_ParseTuple(args, "ls#", &orig, &bin, &patchlen)) return NULL; while (pos >= 0 && pos < patchlen) { start = getbe32(bin + pos); end = getbe32(bin + pos + 4); len = getbe32(bin + pos + 8); if (start > end) break; /* sanity check */ pos += 12 + len; outlen += start - last; last = end; outlen += len; } if (pos != patchlen) { 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} }; #ifdef IS_PY3K static struct PyModuleDef mpatch_module = { PyModuleDef_HEAD_INIT, "mpatch", mpatch_doc, -1, methods }; PyMODINIT_FUNC PyInit_mpatch(void) { PyObject *m; m = PyModule_Create(&mpatch_module); if (m == NULL) return NULL; mpatch_Error = PyErr_NewException("mpatch.mpatchError", NULL, NULL); Py_INCREF(mpatch_Error); PyModule_AddObject(m, "mpatchError", mpatch_Error); return m; } #else PyMODINIT_FUNC initmpatch(void) { Py_InitModule3("mpatch", methods, mpatch_doc); mpatch_Error = PyErr_NewException("mpatch.mpatchError", NULL, NULL); } #endif