mercurial/parsers.c

dirstate: C parsing extension

/*
 parsers.c - efficient content parsing

 Copyright 2008 Matt Mackall <[e-mail]> and others

 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 <ctype.h>
#include <string.h>

static int hexdigit(char c)
{
	if (c >= '0' && c <= '9')
		return c - '0';
	if (c >= 'a' && c <= 'f')
		return c - 'a' + 10;
	if (c >= 'A' && c <= 'F')
		return c - 'A' + 10;

	PyErr_SetString(PyExc_ValueError, "input contains non-hex character");
	return 0;
}

/*
 * Turn a hex-encoded string into binary.
 */
static PyObject *unhexlify(const char *str, int len)
{
	PyObject *ret;
	const char *c;
	char *d;

	ret = PyString_FromStringAndSize(NULL, len / 2);
	if (!ret)
		return NULL;

	d = PyString_AS_STRING(ret);
	for (c = str; c < str + len;) {
		int hi = hexdigit(*c++);
		int lo = hexdigit(*c++);
		*d++ = (hi << 4) | lo;
	}

	return ret;
}

/*
 * This code assumes that a manifest is stitched together with newline
 * ('\n') characters.
 */
static PyObject *parse_manifest(PyObject *self, PyObject *args)
{
	PyObject *mfdict, *fdict;
	char *str, *cur, *start, *zero;
	int len;

	if (!PyArg_ParseTuple(args, "O!O!s#:parse_manifest",
			      &PyDict_Type, &mfdict,
			      &PyDict_Type, &fdict,
			      &str, &len))
		goto quit;

	for (start = cur = str, zero = NULL; cur < str + len; cur++) {
		PyObject *file = NULL, *node = NULL;
		PyObject *flags = NULL;
		int nlen;

		if (!*cur) {
			zero = cur;
			continue;
		}
		else if (*cur != '\n')
			continue;

		if (!zero) {
			PyErr_SetString(PyExc_ValueError,
					"manifest entry has no separator");
			goto quit;
		}

		file = PyString_FromStringAndSize(start, zero - start);
		if (!file)
			goto bail;

		nlen = cur - zero - 1;

		node = unhexlify(zero + 1, nlen > 40 ? 40 : nlen);
		if (!node)
			goto bail;

		if (nlen > 40) {
			PyObject *flags;

			flags = PyString_FromStringAndSize(zero + 41,
							   nlen - 40);
			if (!flags)
				goto bail;

			if (PyDict_SetItem(fdict, file, flags) == -1)
				goto bail;
		}

		if (PyDict_SetItem(mfdict, file, node) == -1)
			goto bail;

		start = cur + 1;
		zero = NULL;

		Py_XDECREF(flags);
		Py_XDECREF(node);
		Py_XDECREF(file);
		continue;
	bail:
		Py_XDECREF(flags);
		Py_XDECREF(node);
		Py_XDECREF(file);
		goto quit;
	}

	if (len > 0 && *(cur - 1) != '\n') {
		PyErr_SetString(PyExc_ValueError,
				"manifest contains trailing garbage");
		goto quit;
	}

	Py_INCREF(Py_None);
	return Py_None;
quit:
	return NULL;
}

#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>
# if defined __BEOS__ && !defined __HAIKU__
#  include <ByteOrder.h>
# else
#  include <arpa/inet.h>
# endif
# include <inttypes.h>
#endif

static PyObject *parse_dirstate(PyObject *self, PyObject *args)
{
	PyObject *dmap, *cmap, *parents = NULL, *ret = NULL;
	PyObject *fname = NULL, *cname = NULL, *entry = NULL;
	char *str, *cur, *end, *cpos;
	int state, mode, size, mtime, flen;
	int len;
	char decode[16]; /* for alignment */

	if (!PyArg_ParseTuple(args, "O!O!s#:parse_dirstate",
			      &PyDict_Type, &dmap,
			      &PyDict_Type, &cmap,
			      &str, &len))
		goto quit;

	/* read parents */
	if (len < 40)
		goto quit;

	parents = Py_BuildValue("s#s#", str, 20, str + 20, 20);
	if (!parents)
		goto quit;

	/* read filenames */
	cur = str + 40;
	end = str + len;

	while (cur < end - 17) {
		/* unpack header */
		state = *cur;
		memcpy(decode, cur + 1, 16);
		mode = ntohl(*(uint32_t *)(decode));
		size = ntohl(*(uint32_t *)(decode + 4));
		mtime = ntohl(*(uint32_t *)(decode + 8));
		flen = ntohl(*(uint32_t *)(decode + 12));
		cur += 17;
		if (cur + flen > end)
			goto quit;

		entry = Py_BuildValue("ciii", state, mode, size, mtime);
		PyObject_GC_UnTrack(entry); /* don't waste time with this */
		if (!entry)
			goto quit;

		cpos = memchr(cur, 0, flen);
		if (cpos) {
			fname = PyString_FromStringAndSize(cur, cpos - cur);
			cname = PyString_FromStringAndSize(cpos + 1,
							   flen - (cpos - cur) - 1);
			if (!fname || !cname ||
			    PyDict_SetItem(cmap, fname, cname) == -1 ||
			    PyDict_SetItem(dmap, fname, entry) == -1)
				goto quit;
			Py_DECREF(cname);
		} else {
			fname = PyString_FromStringAndSize(cur, flen);
			if (!fname ||
			    PyDict_SetItem(dmap, fname, entry) == -1)
				goto quit;
		}
		cur += flen;
		Py_DECREF(fname);
		Py_DECREF(entry);
		fname = cname = entry = NULL;
	}

	ret = parents;
	Py_INCREF(ret);
quit:
	Py_XDECREF(fname);
	Py_XDECREF(cname);
	Py_XDECREF(entry);
	Py_XDECREF(parents);
	return ret;
}

static char parsers_doc[] = "Efficient content parsing.";

static PyMethodDef methods[] = {
	{"parse_manifest", parse_manifest, METH_VARARGS, "parse a manifest\n"},
	{"parse_dirstate", parse_dirstate, METH_VARARGS, "parse a dirstate\n"},
	{NULL, NULL}
};

PyMODINIT_FUNC initparsers(void)
{
	Py_InitModule3("parsers", methods, parsers_doc);
}