Add apply_delta C implementation.

dulwich/_pack.c

@@ -0,0 +1,130 @@
+/* 
+ * Copyright (C) 2009 Jelmer Vernooij <jelmer@samba.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License or (at your option) a later version.
+ * 
+ * This program 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 General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA  02110-1301, USA.
+ */
+
+#include <Python.h>
+#include <stdint.h>
+
+
+static size_t get_delta_header_size(uint8_t *delta, int *index, int length)
+{
+	size_t size = 0;
+	int i = 0;
+	while ((*index) < length) {
+		uint8_t cmd = delta[*index];
+		(*index)++;
+		size |= (cmd & ~0x80) << i;
+		i += 7;
+		if (!(cmd & 0x80))
+			break;
+	}
+	return size;
+}
+
+
+static PyObject *py_apply_delta(PyObject *self, PyObject *args)
+{
+	uint8_t *src_buf, *delta;
+	int src_buf_len, delta_len;
+	size_t src_size, dest_size;
+	size_t outindex = 0;
+	int index;
+	uint8_t *out;
+	PyObject *ret;
+
+	if (!PyArg_ParseTuple(args, "s#s#", (uint8_t *)&src_buf, &src_buf_len, 
+						  (uint8_t *)&delta, &delta_len))
+		return NULL;
+
+    index = 0;
+    src_size = get_delta_header_size(delta, &index, delta_len);
+    if (src_size != src_buf_len) {
+		PyErr_Format(PyExc_ValueError, 
+			"Unexpected source buffer size: %lu vs %d", src_size, src_buf_len);
+		return NULL;
+	}
+    dest_size = get_delta_header_size(delta, &index, delta_len);
+	ret = PyString_FromStringAndSize(NULL, dest_size);
+	if (ret == NULL) {
+		PyErr_NoMemory();
+		return NULL;
+	}
+	out = (uint8_t *)PyString_AsString(ret);
+    while (index < delta_len) {
+        char cmd = delta[index];
+        index++;
+        if (cmd & 0x80) {
+            size_t cp_off = 0, cp_size = 0;
+			int i;
+            for (i = 0; i < 4; i++) {
+                if (cmd & (1 << i)) {
+                    uint8_t x = delta[index];
+                    index++;
+                    cp_off |= x << (i * 8);
+				}
+			}
+            for (i = 0; i < 3; i++) {
+                if (cmd & (1 << (4+i))) {
+                    uint8_t x = delta[index];
+                    index++;
+                    cp_size |= x << (i * 8);
+				}
+			}
+            if (cp_size == 0)
+                cp_size = 0x10000;
+            if (cp_off + cp_size < cp_size ||
+                cp_off + cp_size > src_size ||
+                cp_size > dest_size)
+                break;
+			memcpy(out+outindex, src_buf+cp_off, cp_size);
+			outindex += cp_size;
+		} else if (cmd != 0) {
+			memcpy(out+outindex, delta+index, cmd);
+			outindex += cmd;
+            index += cmd;
+		} else {
+			PyErr_SetString(PyExc_ValueError, "Invalid opcode 0");
+			return NULL;
+		}
+	}
+    
+    if (index != delta_len) {
+		PyErr_SetString(PyExc_ValueError, "delta not empty");
+		return NULL;
+	}
+
+	if (dest_size != outindex) {
+        PyErr_SetString(PyExc_ValueError, "dest size incorrect");
+		return NULL;
+	}
+
+    return ret;
+}
+
+static PyMethodDef py_pack_methods[] = {
+	{ "apply_delta", (PyCFunction)py_apply_delta, METH_VARARGS, NULL },
+};
+
+void init_pack(void)
+{
+	PyObject *m;
+
+	m = Py_InitModule3("_pack", py_pack_methods, NULL);
+	if (m == NULL)
+		return;
+}

dulwich/pack.py

@@ -915,3 +915,8 @@ def load_packs(path):
         if name.startswith("pack-") and name.endswith(".pack"):
             yield Pack(os.path.join(path, name[:-len(".pack")]))
 
+
+try:
+    from dulwich._pack import apply_delta
+except ImportError:
+    pass

setup.py

@@ -23,5 +23,8 @@ setup(name='dulwich',
       """,
       packages=['dulwich', 'dulwich.tests'],
       scripts=['bin/dulwich', 'bin/dul-daemon'],
-      ext_modules=[Extension('dulwich/_objects', ['dulwich/_objects.c'])],
+      ext_modules=[
+          Extension('dulwich/_objects', ['dulwich/_objects.c']),
+          Extension('dulwich/_pack', ['dulwich/_pack.c']),
+          ],
       )