From 5b4d47756871a11621dc4d96e58a9180479704f3 Mon Sep 17 00:00:00 2001
From: Tim Peters <tim.peters@gmail.com>
Date: Tue, 8 May 2001 22:33:50 +0000
Subject: Intern 1-character strings as soon as they're created.  As-is, they
 aren't interned when created, so the cached versions generally aren't ever
 interned.  With the patch, the 		Py_INCREF(t); 		*p =
 t; 		Py_DECREF(s); 		return; indirection block in
 PyString_InternInPlace() is never executed during a full run of the test
 suite, but was executed very many times before.  So I'm trading more work
 when creating one-character strings for doing less work later.  Note that the
 "more work" here can happen at most 256 times per program run, so it's
 trivial.  The same reasoning accounts for the patch's simplification of
 string_item (the new version can call PyString_FromStringAndSize() no more
 than 256 times per run, so there's no point to inlining that stuff -- if we
 were serious about saving time here, we'd pre-initialize the characters
 vector so that no runtime testing at all was needed!).

---
 Objects/stringobject.c | 27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index 87d7c195..afaa054 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -36,7 +36,7 @@ static PyStringObject *nullstring;
 PyObject *
 PyString_FromStringAndSize(const char *str, int size)
 {
-	register PyStringObject *op;
+	PyStringObject *op;
 #ifndef DONT_SHARE_SHORT_STRINGS
 	if (size == 0 && (op = nullstring) != NULL) {
 #ifdef COUNT_ALLOCS
@@ -73,9 +73,11 @@ PyString_FromStringAndSize(const char *str, int size)
 	op->ob_sval[size] = '\0';
 #ifndef DONT_SHARE_SHORT_STRINGS
 	if (size == 0) {
+		PyString_InternInPlace(&(PyObject *)op);
 		nullstring = op;
 		Py_INCREF(op);
 	} else if (size == 1 && str != NULL) {
+		PyString_InternInPlace(&(PyObject *)op);
 		characters[*str & UCHAR_MAX] = op;
 		Py_INCREF(op);
 	}
@@ -87,7 +89,7 @@ PyObject *
 PyString_FromString(const char *str)
 {
 	register size_t size = strlen(str);
-	register PyStringObject *op;
+	PyStringObject *op;
 	if (size > INT_MAX) {
 		PyErr_SetString(PyExc_OverflowError,
 			"string is too long for a Python string");
@@ -125,9 +127,11 @@ PyString_FromString(const char *str)
 	strcpy(op->ob_sval, str);
 #ifndef DONT_SHARE_SHORT_STRINGS
 	if (size == 0) {
+		PyString_InternInPlace(&(PyObject *)op);
 		nullstring = op;
 		Py_INCREF(op);
 	} else if (size == 1) {
+		PyString_InternInPlace(&(PyObject *)op);
 		characters[*str & UCHAR_MAX] = op;
 		Py_INCREF(op);
 	}
@@ -551,24 +555,17 @@ string_item(PyStringObject *a, register int i)
 {
 	int c;
 	PyObject *v;
+	char *pchar;
 	if (i < 0 || i >= a->ob_size) {
 		PyErr_SetString(PyExc_IndexError, "string index out of range");
 		return NULL;
 	}
-	c = a->ob_sval[i] & UCHAR_MAX;
+	pchar = a->ob_sval + i;
+	c = *pchar & UCHAR_MAX;
 	v = (PyObject *) characters[c];
-#ifdef COUNT_ALLOCS
-	if (v != NULL)
-		one_strings++;
-#endif
-	if (v == NULL) {
-		v = PyString_FromStringAndSize((char *)NULL, 1);
-		if (v == NULL)
-			return NULL;
-		characters[c] = (PyStringObject *) v;
-		((PyStringObject *)v)->ob_sval[0] = c;
-	}
-	Py_INCREF(v);
+	if (v == NULL)
+		v = PyString_FromStringAndSize(pchar, 1);
+	Py_XINCREF(v);
 	return v;
 }
 
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