cpython/Modules/regexmodule.c

/*
XXX support range parameter on search
XXX support mstop parameter on search
*/

/***********************************************************
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
The Netherlands.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Stichting Mathematisch
Centrum or CWI or Corporation for National Research Initiatives or
CNRI not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.

While CWI is the initial source for this software, a modified version
is made available by the Corporation for National Research Initiatives
(CNRI) at the Internet address ftp://ftp.python.org.

STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.

******************************************************************/

/* Regular expression objects */
/* This uses Tatu Ylonen's copyleft-free reimplementation of
   GNU regular expressions */

#include "Python.h"

#include <ctype.h>

#include "regexpr.h"

static PyObject *RegexError;	/* Exception */	

typedef struct {
	PyObject_HEAD
	struct re_pattern_buffer re_patbuf; /* The compiled expression */
	struct re_registers re_regs; /* The registers from the last match */
	char re_fastmap[256];	/* Storage for fastmap */
	PyObject *re_translate;	/* String object for translate table */
	PyObject *re_lastok;	/* String object last matched/searched */
	PyObject *re_groupindex;	/* Group name to index dictionary */
	PyObject *re_givenpat;	/* Pattern with symbolic groups */
	PyObject *re_realpat;	/* Pattern without symbolic groups */
} regexobject;

/* Regex object methods */

static void
reg_dealloc(re)
	regexobject *re;
{
	PyMem_XDEL(re->re_patbuf.buffer);
	Py_XDECREF(re->re_translate);
	Py_XDECREF(re->re_lastok);
	Py_XDECREF(re->re_groupindex);
	Py_XDECREF(re->re_givenpat);
	Py_XDECREF(re->re_realpat);
	PyMem_DEL(re);
}

static PyObject *
makeresult(regs)
	struct re_registers *regs;
{
	PyObject *v;
	int i;
	static PyObject *filler = NULL;

	if (filler == NULL) {
		filler = Py_BuildValue("(ii)", -1, -1);
		if (filler == NULL)
			return NULL;
	}
	v = PyTuple_New(RE_NREGS);
	if (v == NULL)
		return NULL;

	for (i = 0; i < RE_NREGS; i++) {
		int lo = regs->start[i];
		int hi = regs->end[i];
		PyObject *w;
		if (lo == -1 && hi == -1) {
			w = filler;
			Py_INCREF(w);
		}
		else
			w = Py_BuildValue("(ii)", lo, hi);
		if (w == NULL || PyTuple_SetItem(v, i, w) < 0) {
			Py_DECREF(v);
			return NULL;
		}
	}
	return v;
}

static PyObject *
regobj_match(re, args)
	regexobject *re;
	PyObject *args;
{
	char *buffer;
	int size;
	int offset = 0;
	int result;

	if (!PyArg_ParseTuple(args, "s#|i", &buffer, &size, &offset))
		return NULL;

	if (offset < 0 || offset > size) {
		PyErr_SetString(RegexError, "match offset out of range");
		return NULL;
	}
	Py_XDECREF(re->re_lastok);
	re->re_lastok = NULL;
	result = re_match(&re->re_patbuf, buffer, size, offset, &re->re_regs);
	if (result < -1) {
		/* Failure like stack overflow */
		PyErr_SetString(RegexError, "match failure");
		return NULL;
	}
	if (result >= 0) {
		PyObject* str = PyString_FromStringAndSize(buffer, size);
		if (!str)
			return NULL;
		re->re_lastok = str;
	}
	return PyInt_FromLong((long)result); /* Length of the match or -1 */
}

static PyObject *
regobj_search(re, args)
	regexobject *re;
	PyObject *args;
{
	char *buffer;
	int size;
	int offset = 0;
	int range;
	int result;
	
	if (!PyArg_ParseTuple(args, "s#|i", &buffer, &size, &offset))
		return NULL;

	if (offset < 0 || offset > size) {
		PyErr_SetString(RegexError, "search offset out of range");
		return NULL;
	}
	/* NB: In Emacs 18.57, the documentation for re_search[_2] and
	   the implementation don't match: the documentation states that
	   |range| positions are tried, while the code tries |range|+1
	   positions.  It seems more productive to believe the code! */
	range = size - offset;
	Py_XDECREF(re->re_lastok);
	re->re_lastok = NULL;
	result = re_search(&re->re_patbuf, buffer, size, offset, range,
			   &re->re_regs);
	if (result < -1) {
		/* Failure like stack overflow */
		PyErr_SetString(RegexError, "match failure");
		return NULL;
	}
	if (result >= 0) {
		PyObject* str = PyString_FromStringAndSize(buffer, size);
		if (!str)
			return NULL;
		re->re_lastok = str;
	}
	return PyInt_FromLong((long)result); /* Position of the match or -1 */
}

/* get the group from the regex where index can be a string (group name) or
   an integer index [0 .. 99]
 */
static PyObject*
group_from_index(re, index)
	regexobject *re;
	PyObject *index;
{
	int i, a, b;
	char *v;

	if (PyString_Check(index))
		if (re->re_groupindex == NULL ||
		    !(index = PyDict_GetItem(re->re_groupindex, index)))
		{
			PyErr_SetString(RegexError,
					"group() group name doesn't exist");
			return NULL;
		}

	i = PyInt_AsLong(index);
	if (i == -1 && PyErr_Occurred())
		return NULL;

	if (i < 0 || i >= RE_NREGS) {
		PyErr_SetString(RegexError, "group() index out of range");
		return NULL;
	}
	if (re->re_lastok == NULL) {
		PyErr_SetString(RegexError,
			   "group() only valid after successful match/search");
		return NULL;
	}
	a = re->re_regs.start[i];
	b = re->re_regs.end[i];
	if (a < 0 || b < 0) {
		Py_INCREF(Py_None);
		return Py_None;
	}
	
	if (!(v = PyString_AsString(re->re_lastok)))
		return NULL;

	return PyString_FromStringAndSize(v+a, b-a);
}


static PyObject *
regobj_group(re, args)
	regexobject *re;
	PyObject *args;
{
	int n = PyTuple_Size(args);
	int i;
	PyObject *res = NULL;

	if (n < 0)
		return NULL;
	if (n == 0) {
		PyErr_SetString(PyExc_TypeError, "not enough arguments");
		return NULL;
	}
	if (n == 1) {
		/* return value is a single string */
		PyObject *index = PyTuple_GetItem(args, 0);
		if (!index)
			return NULL;
		
		return group_from_index(re, index);
	}

	/* return value is a tuple */
	if (!(res = PyTuple_New(n)))
		return NULL;

	for (i = 0; i < n; i++) {
		PyObject *index = PyTuple_GetItem(args, i);
		PyObject *group = NULL;

		if (!index)
			goto finally;
		if (!(group = group_from_index(re, index)))
			goto finally;
		if (PyTuple_SetItem(res, i, group) < 0)
			goto finally;
	}
	return res;

  finally:
	Py_DECREF(res);
	return NULL;
}


static struct PyMethodDef reg_methods[] = {
	{"match",	(PyCFunction)regobj_match, 1},
	{"search",	(PyCFunction)regobj_search, 1},
	{"group",	(PyCFunction)regobj_group, 1},
	{NULL,		NULL}		/* sentinel */
};



static char* members[] = {
	"last", "regs", "translate",
	"groupindex", "realpat", "givenpat",
	NULL
};


static PyObject *
regobj_getattr(re, name)
	regexobject *re;
	char *name;
{
	if (strcmp(name, "regs") == 0) {
		if (re->re_lastok == NULL) {
			Py_INCREF(Py_None);
			return Py_None;
		}
		return makeresult(&re->re_regs);
	}
	if (strcmp(name, "last") == 0) {
		if (re->re_lastok == NULL) {
			Py_INCREF(Py_None);
			return Py_None;
		}
		Py_INCREF(re->re_lastok);
		return re->re_lastok;
	}
	if (strcmp(name, "translate") == 0) {
		if (re->re_translate == NULL) {
			Py_INCREF(Py_None);
			return Py_None;
		}
		Py_INCREF(re->re_translate);
		return re->re_translate;
	}
	if (strcmp(name, "groupindex") == 0) {
		if (re->re_groupindex == NULL) {
			Py_INCREF(Py_None);
			return Py_None;
		}
		Py_INCREF(re->re_groupindex);
		return re->re_groupindex;
	}
	if (strcmp(name, "realpat") == 0) {
		if (re->re_realpat == NULL) {
			Py_INCREF(Py_None);
			return Py_None;
		}
		Py_INCREF(re->re_realpat);
		return re->re_realpat;
	}
	if (strcmp(name, "givenpat") == 0) {
		if (re->re_givenpat == NULL) {
			Py_INCREF(Py_None);
			return Py_None;
		}
		Py_INCREF(re->re_givenpat);
		return re->re_givenpat;
	}
	if (strcmp(name, "__members__") == 0) {
		int i = 0;
		PyObject *list = NULL;

		/* okay, so it's unlikely this list will change that often.
		   still, it's easier to change it in just one place.
		 */
		while (members[i])
			i++;
		if (!(list = PyList_New(i)))
			return NULL;

		i = 0;
		while (members[i]) {
			PyObject* v = PyString_FromString(members[i]);
			if (!v || PyList_SetItem(list, i, v) < 0) {
				Py_DECREF(list);
				return NULL;
			}
			i++;
		}
		return list;
	}
	return Py_FindMethod(reg_methods, (PyObject *)re, name);
}

static PyTypeObject Regextype = {
	PyObject_HEAD_INIT(&PyType_Type)
	0,				     /*ob_size*/
	"regex",			     /*tp_name*/
	sizeof(regexobject),		     /*tp_size*/
	0,				     /*tp_itemsize*/
	/* methods */
	(destructor)reg_dealloc,	     /*tp_dealloc*/
	0,				     /*tp_print*/
	(getattrfunc)regobj_getattr,	     /*tp_getattr*/
	0,				     /*tp_setattr*/
	0,				     /*tp_compare*/
	0,				     /*tp_repr*/
};

/* reference counting invariants:
   pattern: borrowed
   translate: borrowed
   givenpat: borrowed
   groupindex: transferred
*/
static PyObject *
newregexobject(pattern, translate, givenpat, groupindex)
	PyObject *pattern;
	PyObject *translate;
	PyObject *givenpat;
	PyObject *groupindex;
{
	regexobject *re;
	char *pat;
	int size;

	if (!PyArg_Parse(pattern, "s#", &pat, &size))
		return NULL;
	
	if (translate != NULL && PyString_Size(translate) != 256) {
		PyErr_SetString(RegexError,
				"translation table must be 256 bytes");
		return NULL;
	}
	re = PyObject_NEW(regexobject, &Regextype);
	if (re != NULL) {
		char *error;
		re->re_patbuf.buffer = NULL;
		re->re_patbuf.allocated = 0;
		re->re_patbuf.fastmap = re->re_fastmap;
		if (translate) {
			re->re_patbuf.translate = PyString_AsString(translate);
			if (!re->re_patbuf.translate)
				goto finally;
			Py_INCREF(translate);
		}
		else
			re->re_patbuf.translate = NULL;
		re->re_translate = translate;
		re->re_lastok = NULL;
		re->re_groupindex = groupindex;
		Py_INCREF(pattern);
		re->re_realpat = pattern;
		Py_INCREF(givenpat);
		re->re_givenpat = givenpat;
		error = re_compile_pattern(pat, size, &re->re_patbuf);
		if (error != NULL) {
			PyErr_SetString(RegexError, error);
			goto finally;
		}
	}
	return (PyObject *)re;
  finally:
	Py_DECREF(re);
	return NULL;
}

static PyObject *
regex_compile(self, args)
	PyObject *self;
	PyObject *args;
{
	PyObject *pat = NULL;
	PyObject *tran = NULL;

	if (!PyArg_ParseTuple(args, "S|S", &pat, &tran))
		return NULL;
	return newregexobject(pat, tran, pat, NULL);
}

static PyObject *
symcomp(pattern, gdict)
	PyObject *pattern;
	PyObject *gdict;
{
	char *opat, *oend, *o, *n, *g, *v;
	int group_count = 0;
	int sz;
	int escaped = 0;
	char name_buf[128];
	PyObject *npattern;
	int require_escape = re_syntax & RE_NO_BK_PARENS ? 0 : 1;

	if (!(opat = PyString_AsString(pattern)))
		return NULL;

	if ((sz = PyString_Size(pattern)) < 0)
		return NULL;

	oend = opat + sz;
	o = opat;

	if (oend == opat) {
		Py_INCREF(pattern);
		return pattern;
	}

	if (!(npattern = PyString_FromStringAndSize((char*)NULL, sz)) ||
	    !(n = PyString_AsString(npattern)))
		return NULL;

	while (o < oend) {
		if (*o == '(' && escaped == require_escape) {
			char *backtrack;
			escaped = 0;
			++group_count;
			*n++ = *o;
			if (++o >= oend || *o != '<')
				continue;
			/* *o == '<' */
			if (o+1 < oend && *(o+1) == '>')
				continue;
			backtrack = o;
			g = name_buf;
			for (++o; o < oend;) {
				if (*o == '>') {
				    PyObject *group_name = NULL;
				    PyObject *group_index = NULL;
				    *g++ = '\0';
				    group_name = PyString_FromString(name_buf);
				    group_index = PyInt_FromLong(group_count);
				    if (group_name == NULL ||
					group_index == NULL ||
					PyDict_SetItem(gdict, group_name,
						       group_index) != 0)
				    {
					    Py_XDECREF(group_name);
					    Py_XDECREF(group_index);
					    Py_XDECREF(npattern);
					    return NULL;
				    }
				    ++o;     /* eat the '>' */
				    break;
				}
				if (!isalnum(Py_CHARMASK(*o)) && *o != '_') {
					o = backtrack;
					break;
				}
				*g++ = *o++;
			}
		}
		else if (*o == '[' && !escaped) {
			*n++ = *o;
			++o;		     /* eat the char following '[' */
			*n++ = *o;
			while (o < oend && *o != ']') {
				++o;
				*n++ = *o;
			}
			if (o < oend)
				++o;
		}
		else if (*o == '\\') {
			escaped = 1;
			*n++ = *o;
			++o;
		}
		else {
			escaped = 0;
			*n++ = *o;
			++o;
		}
	}

	if (!(v = PyString_AsString(npattern))) {
		Py_DECREF(npattern);
		return NULL;
	}
	/* _PyString_Resize() decrements npattern on failure */
	if (_PyString_Resize(&npattern, n - v) == 0)
		return npattern;
	else {
		return NULL;
	}

}

static PyObject *
regex_symcomp(self, args)
	PyObject *self;
	PyObject *args;
{
	PyObject *pattern;
	PyObject *tran = NULL;
	PyObject *gdict = NULL;
	PyObject *npattern;

	if (!PyArg_ParseTuple(args, "S|S", &pattern, &tran))
		return NULL;

	gdict = PyDict_New();
	if (gdict == NULL || (npattern = symcomp(pattern, gdict)) == NULL) {
		Py_DECREF(gdict);
		Py_DECREF(pattern);
		return NULL;
	}
	return newregexobject(npattern, tran, pattern, gdict);
}


static PyObject *cache_pat;
static PyObject *cache_prog;

static int
update_cache(pat)
	PyObject *pat;
{
	PyObject *tuple = Py_BuildValue("(O)", pat);
	int status = 0;

	if (!tuple)
		return -1;

	if (pat != cache_pat) {
		Py_XDECREF(cache_pat);
		cache_pat = NULL;
		Py_XDECREF(cache_prog);
		cache_prog = regex_compile((PyObject *)NULL, tuple);
		if (cache_prog == NULL) {
			status = -1;
			goto finally;
		}
		cache_pat = pat;
		Py_INCREF(cache_pat);
	}
  finally:
	Py_DECREF(tuple);
	return status;
}

static PyObject *
regex_match(self, args)
	PyObject *self;
	PyObject *args;
{
	PyObject *pat, *string;
	PyObject *tuple, *v;

	if (!PyArg_Parse(args, "(SS)", &pat, &string))
		return NULL;
	if (update_cache(pat) < 0)
		return NULL;

	if (!(tuple = Py_BuildValue("(S)", string)))
		return NULL;
	v = regobj_match((regexobject *)cache_prog, tuple);
	Py_DECREF(tuple);
	return v;
}

static PyObject *
regex_search(self, args)
	PyObject *self;
	PyObject *args;
{
	PyObject *pat, *string;
	PyObject *tuple, *v;

	if (!PyArg_Parse(args, "(SS)", &pat, &string))
		return NULL;
	if (update_cache(pat) < 0)
		return NULL;

	if (!(tuple = Py_BuildValue("(S)", string)))
		return NULL;
	v = regobj_search((regexobject *)cache_prog, tuple);
	Py_DECREF(tuple);
	return v;
}

static PyObject *
regex_set_syntax(self, args)
	PyObject *self;
	PyObject *args;
{
	int syntax;
	if (!PyArg_Parse(args, "i", &syntax))
		return NULL;
	syntax = re_set_syntax(syntax);
	/* wipe the global pattern cache */
	Py_XDECREF(cache_pat);
	cache_pat = NULL;
	Py_XDECREF(cache_prog);
	cache_prog = NULL;
	return PyInt_FromLong((long)syntax);
}

static struct PyMethodDef regex_global_methods[] = {
	{"compile",	regex_compile, 1},
	{"symcomp",	regex_symcomp, 1},
	{"match",	regex_match, 0},
	{"search",	regex_search, 0},
	{"set_syntax",	regex_set_syntax, 0},
	{NULL,		NULL}		     /* sentinel */
};

void
initregex()
{
	PyObject *m, *d, *v;
	int i;
	char *s;
	
	m = Py_InitModule("regex", regex_global_methods);
	d = PyModule_GetDict(m);
	
	/* Initialize regex.error exception */
	v = RegexError = PyString_FromString("regex.error");
	if (v == NULL || PyDict_SetItemString(d, "error", v) != 0)
		goto finally;
	
	/* Initialize regex.casefold constant */
	if (!(v = PyString_FromStringAndSize((char *)NULL, 256)))
		goto finally;
	
	if (!(s = PyString_AsString(v)))
		goto finally;

	for (i = 0; i < 256; i++) {
		if (isupper(i))
			s[i] = tolower(i);
		else
			s[i] = i;
	}
	if (PyDict_SetItemString(d, "casefold", v) < 0)
		goto finally;
	Py_DECREF(v);

	if (!PyErr_Occurred())
		return;
  finally:
	Py_FatalError("can't initialize regex module");
}