From d4ff1b908baf6d53e13d2a1c763c004568b4d5f9 Mon Sep 17 00:00:00 2001
From: Barry Warsaw <barry@python.org>
Date: Mon, 6 Jan 1997 22:48:32 +0000
Subject: [PATCH] New strop_joinfields implementation, highly optimized for
 Lists.  All other sequences use the Sequence protocol from the abstract API. 
 The algorithm has changed so that only one pass through the sequences are
 made.

---
 Modules/stropmodule.c | 142 ++++++++++++++++++++++++------------------
 1 file changed, 82 insertions(+), 60 deletions(-)

diff --git a/Modules/stropmodule.c b/Modules/stropmodule.c
index 9251b034b6..cb062ad011 100644
--- a/Modules/stropmodule.c
+++ b/Modules/stropmodule.c
@@ -168,11 +168,13 @@ strop_joinfields(self, args)
 	PyObject *self; /* Not used */
 	PyObject *args;
 {
-	PyObject *seq, *item, *res;
-	char *p, *sep = NULL;
-	int seqlen, reslen, itemlen, i, seplen = 0;
-	int ownrefs = 0;
-	PyObject* (*getitemfunc) Py_PROTO((PyObject*, int));
+	PyObject *seq;
+	char *sep = NULL;
+	int seqlen, seplen = 0;
+	int i, reslen = 0, slen = 0, sz = 100;
+	PyObject *res = NULL;
+	char* p = NULL;
+	intargfunc getitemfunc;
 
 	if (!PyArg_ParseTuple(args, "O|s#", &seq, &sep, &seplen))
 		return NULL;
@@ -180,84 +182,104 @@ strop_joinfields(self, args)
 		sep = " ";
 		seplen = 1;
 	}
-	/* do it this way to optimize for the common cases, but also
-	 * support the more general sequence protocol
-	 */
-	if (PyList_Check(seq)) {
-		getitemfunc = PyList_GetItem;
-		seqlen = PyList_Size(seq);
-	}
-	else if (PyTuple_Check(seq)) {
-		getitemfunc = PyTuple_GetItem;
-		seqlen = PyTuple_Size(seq);
-	}
-	else if (PySequence_Check(seq)) {
-		getitemfunc = PySequence_GetItem;
-		seqlen = PySequence_Length(seq);
-		ownrefs = 1;
-	}
-	else {
-		PyErr_SetString(PyExc_TypeError,
-				"first argument must be a sequence");
-		return NULL;
-	}
+
+	seqlen = PySequence_Length(seq);
 	if (seqlen < 0 && PyErr_Occurred())
 		return NULL;
 
-	reslen = 0;
-	for (i = 0; i < seqlen; i++) {
-		if (!(item = getitemfunc(seq, i)))
-			return NULL;
-
-		if (!PyString_Check(item)) {
-			PyErr_SetString(PyExc_TypeError,
-				 "first argument must be sequence of strings");
-			if (ownrefs)
-				Py_DECREF(item);
-			return NULL;
-		}
-		if (i > 0)
-			reslen += seplen;
-		reslen += PyString_Size(item);
-		if (ownrefs)
-			Py_DECREF(item);
-	}
 	if (seqlen == 1) {
 		/* Optimization if there's only one item */
-		item = getitemfunc(seq, 0);
-		if (!ownrefs)
-			Py_XINCREF(item);
+		PyObject *item = PySequence_GetItem(seq, 0);
+		if (item && !PyString_Check(item))
+			PyErr_SetString(PyExc_TypeError,
+				 "first argument must be sequence of strings");
 		return item;
 	}
 
-	res = PyString_FromStringAndSize((char *)NULL, reslen);
-	if (res == NULL)
+	if (!(res = PyString_FromStringAndSize((char*)NULL, sz)))
 		return NULL;
 	p = PyString_AsString(res);
+
+	/* optimize for lists, since it's the most common case.  all others
+	 * (tuples and arbitrary sequences) just use the sequence abstract
+	 * interface.
+	 */
+	if (PyList_Check(seq)) {
+		for (i = 0; i < seqlen; i++) {
+			PyObject *item = PyList_GET_ITEM(seq, i);
+			if (!PyString_Check(item)) {
+				PyErr_SetString(PyExc_TypeError,
+				"first argument must be sequence of strings");
+				Py_DECREF(res);
+				return NULL;
+			}
+			slen = PyString_GET_SIZE(item);
+			while (reslen + slen + seplen >= sz) {
+				if (_PyString_Resize(&res, sz * 2)) {
+					Py_DECREF(res);
+					return NULL;
+				}
+				sz *= 2;
+				p = PyString_AsString(res) + reslen;
+			}
+			if (i > 0) {
+				memcpy(p, sep, seplen);
+				p += seplen;
+				reslen += seplen;
+			}
+			memcpy(p, PyString_AS_STRING(item), slen);
+			p += slen;
+			reslen += slen;
+		}
+		if (_PyString_Resize(&res, reslen)) {
+			Py_DECREF(res);
+			res = NULL;
+		}
+		return res;
+	}
+	else if (!PySequence_Check(seq)) {
+		PyErr_SetString(PyExc_TypeError,
+				"first argument must be a sequence");
+		return NULL;
+	}
+	/* type safe */
+	getitemfunc = seq->ob_type->tp_as_sequence->sq_item;
 	for (i = 0; i < seqlen; i++) {
-		if (!(item = getitemfunc(seq, i))) {
+		PyObject *item = getitemfunc(seq, i);
+		if (!item || !PyString_Check(item)) {
+			PyErr_SetString(PyExc_TypeError,
+				 "first argument must be sequence of strings");
 			Py_DECREF(res);
+			Py_XDECREF(item);
 			return NULL;
 		}
+		slen = PyString_GET_SIZE(item);
+		while (reslen + slen + seplen >= sz) {
+			if (_PyString_Resize(&res, sz * 2)) {
+				Py_DECREF(res);
+				Py_DECREF(item);
+				return NULL;
+			}
+			sz *= 2;
+			p = PyString_AsString(res) + reslen;
+		}
 		if (i > 0) {
 			memcpy(p, sep, seplen);
 			p += seplen;
+			reslen += seplen;
 		}
-		itemlen = PyString_Size(item);
-		memcpy(p, PyString_AsString(item), itemlen);
-		p += itemlen;
-		if (ownrefs)
-			Py_DECREF(item);
+		memcpy(p, PyString_AS_STRING(item), slen);
+		p += slen;
+		reslen += slen;
+		Py_DECREF(item);
 	}
-	if (p != PyString_AsString(res) + reslen) {
-		PyErr_SetString(PyExc_SystemError,
-                                "strop.joinfields: assertion failed");
-		return NULL;
+	if (_PyString_Resize(&res, reslen)) {
+		Py_DECREF(res);
+		res = NULL;
 	}
 	return res;
 }
 
-
 static PyObject *
 strop_find(self, args)
 	PyObject *self; /* Not used */
-- 
2.50.1