Mercurial > hg
view mercurial/mpatch.c @ 1740:f95654385065
add --daemon option to serve command. for issue 45.
code looks odd because it is portable to windows. windows does not have
os.fork, so have to spawn and use pipe to tell parent ready instead.
author | Vadim Gelfer <vadim.gelfer@gmail.com> |
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date | Fri, 17 Feb 2006 16:29:30 -0800 |
parents | 681c5c211b92 |
children | 299c3e26ee45 |
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/* 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 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 #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 #include <sys/types.h> #include <arpa/inet.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; a = malloc(sizeof(struct flist)); if (a) { a->base = malloc(sizeof(struct frag) * size); if (!a->base) { free(a); a = NULL; } else a->head = a->tail = a->base; return a; } 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 *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 (bin < 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)); lt->data = bin + 12; bin += 12 + lt->len; 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; } static PyMethodDef methods[] = { {"patches", patches, METH_VARARGS, "apply a series of patches\n"}, {NULL, NULL} }; PyMODINIT_FUNC initmpatch(void) { Py_InitModule3("mpatch", methods, mpatch_doc); mpatch_Error = PyErr_NewException("mpatch.mpatchError", NULL, NULL); }