Optimized single-character strings gotten from s[i].

diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index 9b11f9279dca1e015335a81526b18d1647ad52a3..68f5c3a7927c193fa04a464d7ae6df23be1e8547 100644 (file)
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -241,28 +241,38 @@ stringslice(a, i, j)
        return newsizedstringobject(a->ob_sval + i, (int) (j-i));
 }
 
+#ifdef __STDC__
+#include <limits.h>
+#else
+#ifndef UCHAR_MAX
+#define UCHAR_MAX 255
+#endif
+#endif
+
+static object *characters[UCHAR_MAX + 1];
+
 static object *
 stringitem(a, i)
        stringobject *a;
        register int i;
 {
-       /* This is optimized since this is a common operation! */
-
-       register stringobject *op;
+       int c;
+       object *v;
        if (i < 0 || i >= a->ob_size) {
                err_setstr(IndexError, "string index out of range");
                return NULL;
        }
-       op = (stringobject *)
-               malloc(sizeof(stringobject) + sizeof(char));
-       if (op == NULL)
-               return err_nomem();
-       NEWREF(op);
-       op->ob_type = &Stringtype;
-       op->ob_size = 1;
-       op->ob_sval[0] = a->ob_sval[i];
-       op->ob_sval[1] = '\0';
-       return (object *) op;
+       c = a->ob_sval[i] & UCHAR_MAX;
+       v = characters[c];
+       if (v == NULL) {
+               v = newsizedstringobject((char *)NULL, 1);
+               if (v == NULL)
+                       return NULL;
+               characters[c] = v;
+               ((stringobject *)v)->ob_sval[0] = c;
+       }
+       INCREF(v);
+       return v;
 }
 
 static int