From 29bf4e44f6392e402f15512e80295750691d436a Mon Sep 17 00:00:00 2001
From: Andrew McNamara <andrewm@object-craft.com.au>
Date: Tue, 11 Jan 2005 04:49:53 +0000
Subject: Now that internal dialect type is immutable, and the dialect registry
 only contains instances of the dialect type, we can refer directly to the
 dialect instances rather than creating new ones. In other words, if the
 dialect comes from the registry, and we apply no further modifications, the
 reader/writer can use the dialect object directly.

---
 Modules/_csv.c | 69 ++++++++++++++++++++++++++++++++++------------------------
 1 file changed, 40 insertions(+), 29 deletions(-)

diff --git a/Modules/_csv.c b/Modules/_csv.c
index 34870fc..e70e001 100644
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -301,11 +301,12 @@ static char *dialect_kws[] = {
 	NULL
 };
 
-static int
-dialect_init(DialectObj * self, PyObject * args, PyObject * kwargs)
+static PyObject *
+dialect_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
 {
-	int ret = -1;
-        PyObject *dialect = NULL;
+	DialectObj *self;
+	PyObject *ret = NULL;
+	PyObject *dialect = NULL;
 	PyObject *delimiter = NULL;
 	PyObject *doublequote = NULL;
 	PyObject *escapechar = NULL;
@@ -326,7 +327,35 @@ dialect_init(DialectObj * self, PyObject * args, PyObject * kwargs)
 					 &quoting,
 					 &skipinitialspace,
 					 &strict))
-                return -1;
+		return NULL;
+
+	if (dialect != NULL) {
+		if (IS_BASESTRING(dialect)) {
+			dialect = get_dialect_from_registry(dialect);
+			if (dialect == NULL)
+				return NULL;
+		}
+		else
+			Py_INCREF(dialect);
+		/* Can we reuse this instance? */
+		if (PyObject_TypeCheck(dialect, &Dialect_Type) &&
+		    delimiter == 0 &&
+		    doublequote == 0 &&
+		    escapechar == 0 &&
+		    lineterminator == 0 &&
+		    quotechar == 0 &&
+		    quoting == 0 &&
+		    skipinitialspace == 0 &&
+		    strict == 0)
+			return dialect;
+	}
+
+	self = (DialectObj *)type->tp_alloc(type, 0);
+	if (self == NULL) {
+		Py_XDECREF(dialect);
+		return NULL;
+	}
+	self->lineterminator = NULL;
 
 	Py_XINCREF(delimiter);
 	Py_XINCREF(doublequote);
@@ -337,16 +366,9 @@ dialect_init(DialectObj * self, PyObject * args, PyObject * kwargs)
 	Py_XINCREF(skipinitialspace);
 	Py_XINCREF(strict);
 	if (dialect != NULL) {
-		if (IS_BASESTRING(dialect)) {
-			dialect = get_dialect_from_registry(dialect);
-			if (dialect == NULL)
-				goto err;
-		} else
-			Py_INCREF(dialect);
 #define DIALECT_GETATTR(v, n) \
 		if (v == NULL) \
 			v = PyObject_GetAttrString(dialect, n)
-
 		DIALECT_GETATTR(delimiter, "delimiter");
 		DIALECT_GETATTR(doublequote, "doublequote");
 		DIALECT_GETATTR(escapechar, "escapechar");
@@ -356,7 +378,6 @@ dialect_init(DialectObj * self, PyObject * args, PyObject * kwargs)
 		DIALECT_GETATTR(skipinitialspace, "skipinitialspace");
 		DIALECT_GETATTR(strict, "strict");
 		PyErr_Clear();
-		Py_DECREF(dialect);
 	}
 
 	/* check types and convert to C values */
@@ -387,12 +408,13 @@ dialect_init(DialectObj * self, PyObject * args, PyObject * kwargs)
 		goto err;
 	}
 	if (self->lineterminator == 0) {
-                PyErr_SetString(PyExc_TypeError, "lineterminator must be set");
+		PyErr_SetString(PyExc_TypeError, "lineterminator must be set");
 		goto err;
 	}
 
-	ret = 0;
+	ret = (PyObject *)self;
 err:
+	Py_XDECREF(dialect);
 	Py_XDECREF(delimiter);
 	Py_XDECREF(doublequote);
 	Py_XDECREF(escapechar);
@@ -401,18 +423,7 @@ err:
 	Py_XDECREF(quoting);
 	Py_XDECREF(skipinitialspace);
 	Py_XDECREF(strict);
-        return ret;
-}
-
-static PyObject *
-dialect_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
-{
-        DialectObj *self;
-        self = (DialectObj *)type->tp_alloc(type, 0);
-        if (self != NULL) {
-                self->lineterminator = NULL;
-        }
-        return (PyObject *)self;
+	return ret;
 }
 
 
@@ -459,8 +470,8 @@ static PyTypeObject Dialect_Type = {
 	0,					/* tp_descr_get */
 	0,					/* tp_descr_set */
 	0,					/* tp_dictoffset */
-	(initproc)dialect_init,			/* tp_init */
-	PyType_GenericAlloc,	                /* tp_alloc */
+	0,					/* tp_init */
+	0,					/* tp_alloc */
 	dialect_new,			        /* tp_new */
 	0,                           		/* tp_free */
 };
-- 
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