/*
bdiff.c - efficient binary diff extension for Mercurial
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.
Based roughly on Python difflib
*/
#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include "util.h"
struct line {
int hash, n, e;
Py_ssize_t len;
const char *l;
};
struct pos {
int pos, len;
};
struct hunk;
struct hunk {
int a1, a2, b1, b2;
struct hunk *next;
};
static int splitlines(const char *a, Py_ssize_t len, struct line **lr)
{
unsigned hash;
int i;
const char *p, *b = a;
const char * const plast = a + len - 1;
struct line *l;
/* count the lines */
i = 1; /* extra line for sentinel */
for (p = a; p < a + len; p++)
if (*p == '\n' || p == plast)
i++;
*lr = l = (struct line *)malloc(sizeof(struct line) * i);
if (!l)
return -1;
/* build the line array and calculate hashes */
hash = 0;
for (p = a; p < a + len; p++) {
/* Leonid Yuriev's hash */
hash = (hash * 1664525) + (unsigned char)*p + 1013904223;
if (*p == '\n' || p == plast) {
l->hash = hash;
hash = 0;
l->len = p - b + 1;
l->l = b;
l->n = INT_MAX;
l++;
b = p + 1;
}
}
/* set up a sentinel */
l->hash = 0;
l->len = 0;
l->l = a + len;
return i - 1;
}
static inline int cmp(struct line *a, struct line *b)
{
return a->hash != b->hash || a->len != b->len || memcmp(a->l, b->l, a->len);
}
static int equatelines(struct line *a, int an, struct line *b, int bn)
{
int i, j, buckets = 1, t, scale;
struct pos *h = NULL;
/* build a hash table of the next highest power of 2 */
while (buckets < bn + 1)
buckets *= 2;
/* try to allocate a large hash table to avoid collisions */
for (scale = 4; scale; scale /= 2) {
h = (struct pos *)malloc(scale * buckets * sizeof(struct pos));
if (h)
break;
}
if (!h)
return 0;
buckets = buckets * scale - 1;
/* clear the hash table */
for (i = 0; i <= buckets; i++) {
h[i].pos = INT_MAX;
h[i].len = 0;
}
/* add lines to the hash table chains */
for (i = bn - 1; i >= 0; i--) {
/* find the equivalence class */
for (j = b[i].hash & buckets; h[j].pos != INT_MAX;
j = (j + 1) & buckets)
if (!cmp(b + i, b + h[j].pos))
break;
/* add to the head of the equivalence class */
b[i].n = h[j].pos;
b[i].e = j;
h[j].pos = i;
h[j].len++; /* keep track of popularity */
}
/* compute popularity threshold */
t = (bn >= 31000) ? bn / 1000 : 1000000 / (bn + 1);
/* match items in a to their equivalence class in b */
for (i = 0; i < an; i++) {
/* find the equivalence class */
for (j = a[i].hash & buckets; h[j].pos != INT_MAX;
j = (j + 1) & buckets)
if (!cmp(a + i, b + h[j].pos))
break;
a[i].e = j; /* use equivalence class for quick compare */
if (h[j].len <= t)
a[i].n = h[j].pos; /* point to head of match list */
else
a[i].n = INT_MAX; /* too popular */
}
/* discard hash tables */
free(h);
return 1;
}
static int longest_match(struct line *a, struct line *b, struct pos *pos,
int a1, int a2, int b1, int b2, int *omi, int *omj)
{
int mi = a1, mj = b1, mk = 0, mb = 0, i, j, k;
for (i = a1; i < a2; i++) {
/* skip things before the current block */
for (j = a[i].n; j < b1; j = b[j].n)
;
/* loop through all lines match a[i] in b */
for (; j < b2; j = b[j].n) {
/* does this extend an earlier match? */
if (i > a1 && j > b1 && pos[j - 1].pos == i - 1)
k = pos[j - 1].len + 1;
else
k = 1;
pos[j].pos = i;
pos[j].len = k;
/* best match so far? */
if (k > mk) {
mi = i;
mj = j;
mk = k;
}
}
}
if (mk) {
mi = mi - mk + 1;
mj = mj - mk + 1;
}
/* expand match to include neighboring popular lines */
while (mi - mb > a1 && mj - mb > b1 &&
a[mi - mb - 1].e == b[mj - mb - 1].e)
mb++;
while (mi + mk < a2 && mj + mk < b2 &&
a[mi + mk].e == b[mj + mk].e)
mk++;
*omi = mi - mb;
*omj = mj - mb;
return mk + mb;
}
static struct hunk *recurse(struct line *a, struct line *b, struct pos *pos,
int a1, int a2, int b1, int b2, struct hunk *l)
{
int i, j, k;
while (1) {
/* find the longest match in this chunk */
k = longest_match(a, b, pos, a1, a2, b1, b2, &i, &j);
if (!k)
return l;
/* and recurse on the remaining chunks on either side */
l = recurse(a, b, pos, a1, i, b1, j, l);
if (!l)
return NULL;
l->next = (struct hunk *)malloc(sizeof(struct hunk));
if (!l->next)
return NULL;
l = l->next;
l->a1 = i;
l->a2 = i + k;
l->b1 = j;
l->b2 = j + k;
l->next = NULL;
/* tail-recursion didn't happen, so do equivalent iteration */
a1 = i + k;
b1 = j + k;
}
}
static int diff(struct line *a, int an, struct line *b, int bn,
struct hunk *base)
{
struct hunk *curr;
struct pos *pos;
int t, count = 0;
/* allocate and fill arrays */
t = equatelines(a, an, b, bn);
pos = (struct pos *)calloc(bn ? bn : 1, sizeof(struct pos));
if (pos && t) {
/* generate the matching block list */
curr = recurse(a, b, pos, 0, an, 0, bn, base);
if (!curr)
return -1;
/* sentinel end hunk */
curr->next = (struct hunk *)malloc(sizeof(struct hunk));
if (!curr->next)
return -1;
curr = curr->next;
curr->a1 = curr->a2 = an;
curr->b1 = curr->b2 = bn;
curr->next = NULL;
}
free(pos);
/* normalize the hunk list, try to push each hunk towards the end */
for (curr = base->next; curr; curr = curr->next) {
struct hunk *next = curr->next;
int shift = 0;
if (!next)
break;
if (curr->a2 == next->a1)
while (curr->a2 + shift < an && curr->b2 + shift < bn
&& !cmp(a + curr->a2 + shift,
b + curr->b2 + shift))
shift++;
else if (curr->b2 == next->b1)
while (curr->b2 + shift < bn && curr->a2 + shift < an
&& !cmp(b + curr->b2 + shift,
a + curr->a2 + shift))
shift++;
if (!shift)
continue;
curr->b2 += shift;
next->b1 += shift;
curr->a2 += shift;
next->a1 += shift;
}
for (curr = base->next; curr; curr = curr->next)
count++;
return count;
}
static void freehunks(struct hunk *l)
{
struct hunk *n;
for (; l; l = n) {
n = l->next;
free(l);
}
}
static PyObject *blocks(PyObject *self, PyObject *args)
{
PyObject *sa, *sb, *rl = NULL, *m;
struct line *a, *b;
struct hunk l, *h;
int an, bn, count, pos = 0;
if (!PyArg_ParseTuple(args, "SS:bdiff", &sa, &sb))
return NULL;
an = splitlines(PyBytes_AsString(sa), PyBytes_Size(sa), &a);
bn = splitlines(PyBytes_AsString(sb), PyBytes_Size(sb), &b);
if (!a || !b)
goto nomem;
l.next = NULL;
count = diff(a, an, b, bn, &l);
if (count < 0)
goto nomem;
rl = PyList_New(count);
if (!rl)
goto nomem;
for (h = l.next; h; h = h->next) {
m = Py_BuildValue("iiii", h->a1, h->a2, h->b1, h->b2);
PyList_SetItem(rl, pos, m);
pos++;
}
nomem:
free(a);
free(b);
freehunks(l.next);
return rl ? rl : PyErr_NoMemory();
}
static PyObject *bdiff(PyObject *self, PyObject *args)
{
char *sa, *sb, *rb;
PyObject *result = NULL;
struct line *al, *bl;
struct hunk l, *h;
int an, bn, count;
Py_ssize_t len = 0, la, lb;
PyThreadState *_save;
if (!PyArg_ParseTuple(args, "s#s#:bdiff", &sa, &la, &sb, &lb))
return NULL;
if (la > UINT_MAX || lb > UINT_MAX) {
PyErr_SetString(PyExc_ValueError, "bdiff inputs too large");
return NULL;
}
_save = PyEval_SaveThread();
an = splitlines(sa, la, &al);
bn = splitlines(sb, lb, &bl);
if (!al || !bl)
goto nomem;
l.next = NULL;
count = diff(al, an, bl, bn, &l);
if (count < 0)
goto nomem;
/* calculate length of output */
la = lb = 0;
for (h = l.next; h; h = h->next) {
if (h->a1 != la || h->b1 != lb)
len += 12 + bl[h->b1].l - bl[lb].l;
la = h->a2;
lb = h->b2;
}
PyEval_RestoreThread(_save);
_save = NULL;
result = PyBytes_FromStringAndSize(NULL, len);
if (!result)
goto nomem;
/* build binary patch */
rb = PyBytes_AsString(result);
la = lb = 0;
for (h = l.next; h; h = h->next) {
if (h->a1 != la || h->b1 != lb) {
len = bl[h->b1].l - bl[lb].l;
putbe32((uint32_t)(al[la].l - al->l), rb);
putbe32((uint32_t)(al[h->a1].l - al->l), rb + 4);
putbe32((uint32_t)len, rb + 8);
memcpy(rb + 12, bl[lb].l, len);
rb += 12 + len;
}
la = h->a2;
lb = h->b2;
}
nomem:
if (_save)
PyEval_RestoreThread(_save);
free(al);
free(bl);
freehunks(l.next);
return result ? result : PyErr_NoMemory();
}
/*
* If allws != 0, remove all whitespace (' ', \t and \r). Otherwise,
* reduce whitespace sequences to a single space and trim remaining whitespace
* from end of lines.
*/
static PyObject *fixws(PyObject *self, PyObject *args)
{
PyObject *s, *result = NULL;
char allws, c;
const char *r;
Py_ssize_t i, rlen, wlen = 0;
char *w;
if (!PyArg_ParseTuple(args, "Sb:fixws", &s, &allws))
return NULL;
r = PyBytes_AsString(s);
rlen = PyBytes_Size(s);
w = (char *)malloc(rlen ? rlen : 1);
if (!w)
goto nomem;
for (i = 0; i != rlen; i++) {
c = r[i];
if (c == ' ' || c == '\t' || c == '\r') {
if (!allws && (wlen == 0 || w[wlen - 1] != ' '))
w[wlen++] = ' ';
} else if (c == '\n' && !allws
&& wlen > 0 && w[wlen - 1] == ' ') {
w[wlen - 1] = '\n';
} else {
w[wlen++] = c;
}
}
result = PyBytes_FromStringAndSize(w, wlen);
nomem:
free(w);
return result ? result : PyErr_NoMemory();
}
static char mdiff_doc[] = "Efficient binary diff.";
static PyMethodDef methods[] = {
{"bdiff", bdiff, METH_VARARGS, "calculate a binary diff\n"},
{"blocks", blocks, METH_VARARGS, "find a list of matching lines\n"},
{"fixws", fixws, METH_VARARGS, "normalize diff whitespaces\n"},
{NULL, NULL}
};
#ifdef IS_PY3K
static struct PyModuleDef bdiff_module = {
PyModuleDef_HEAD_INIT,
"bdiff",
mdiff_doc,
-1,
methods
};
PyMODINIT_FUNC PyInit_bdiff(void)
{
return PyModule_Create(&bdiff_module);
}
#else
PyMODINIT_FUNC initbdiff(void)
{
Py_InitModule3("bdiff", methods, mdiff_doc);
}
#endif