diff -r 087cdbf49e80 Objects/unicodeobject.c
--- a/Objects/unicodeobject.c	Fri Apr 04 21:05:46 2014 +0200
+++ b/Objects/unicodeobject.c	Sat Apr 05 14:43:23 2014 +0300
@@ -8445,70 +8445,94 @@
     return resunicode;
 }
 
+static PyObject no_mapping_sentinel;
+
+static void
+charmaptranslatecache_init(PyObject *cache[128])
+{
+    memset(cache, 0, 128 * sizeof(PyObject *));
+}
+
+static void
+charmaptranslatecache_free(PyObject *cache[128])
+{
+    int i;
+    for (i = 0; i < 128; i++)
+        if (cache[i] != NULL && cache[i] != &no_mapping_sentinel)
+            Py_DECREF(cache[i]);
+}
+
 /* Lookup the character ch in the mapping and put the result in result,
    which must be decrefed by the caller.
-   Return 0 on success, -1 on error */
-static int
-charmaptranslate_lookup(Py_UCS4 c, PyObject *mapping, PyObject **result)
-{
-    PyObject *w = PyLong_FromLong((long)c);
-    PyObject *x;
-
-    if (w == NULL)
-        return -1;
-    x = PyObject_GetItem(mapping, w);
-    Py_DECREF(w);
-    if (x == NULL) {
-        if (PyErr_ExceptionMatches(PyExc_LookupError)) {
-            /* No mapping found means: use 1:1 mapping. */
-            PyErr_Clear();
-            *result = NULL;
-            return 0;
-        } else
-            return -1;
-    }
-    else if (x == Py_None) {
-        *result = x;
-        return 0;
-    }
-    else if (PyLong_Check(x)) {
-        long value = PyLong_AS_LONG(x);
-        long max = PyUnicode_GetMax();
-        if (value < 0 || value > max) {
-            PyErr_Format(PyExc_TypeError,
-                         "character mapping must be in range(0x%x)", max+1);
+   Return NULL on error */
+static PyObject *
+charmaptranslate_lookup(Py_UCS4 c, PyObject *mapping, PyObject *cache[128])
+{
+    PyObject *x = NULL;
+
+    if (c < 128) {
+        x = cache[c];
+        if (x == &no_mapping_sentinel)
+            return x;
+    }
+    if (x != NULL)
+        Py_INCREF(x);
+    else {
+        PyObject *w = PyLong_FromLong((long)c);
+        if (w == NULL)
+            return NULL;
+        x = PyObject_GetItem(mapping, w);
+        Py_DECREF(w);
+        if (x == NULL) {
+            if (PyErr_ExceptionMatches(PyExc_LookupError)) {
+                /* No mapping found means: use 1:1 mapping. */
+                PyErr_Clear();
+                x = &no_mapping_sentinel;
+                if (c < 128)
+                    cache[c] = x;
+                return x;
+            } else
+                return NULL;
+        }
+        if (x == Py_None || PyUnicode_Check(x)) {
+        }
+        else if (PyLong_Check(x)) {
+            long value = PyLong_AS_LONG(x);
+            long max = PyUnicode_GetMax();
+            if (value < 0 || value > max) {
+                PyErr_Format(PyExc_TypeError,
+                             "character mapping must be in range(0x%x)", max+1);
+                Py_DECREF(x);
+                return NULL;
+            }
+        }
+        else {
+            /* wrong return value */
+            PyErr_SetString(PyExc_TypeError,
+                            "character mapping must return integer, None or str");
             Py_DECREF(x);
-            return -1;
-        }
-        *result = x;
-        return 0;
-    }
-    else if (PyUnicode_Check(x)) {
-        *result = x;
-        return 0;
-    }
-    else {
-        /* wrong return value */
-        PyErr_SetString(PyExc_TypeError,
-                        "character mapping must return integer, None or str");
-        Py_DECREF(x);
-        return -1;
-    }
+            return NULL;
+        }
+        if (c < 128) {
+            Py_INCREF(x);
+            cache[c] = x;
+        }
+    }
+    return x;
 }
 
 /* lookup the character, write the result into the writer.
    Return 1 if the result was written into the writer, return 0 if the mapping
    was undefined, raise an exception return -1 on error. */
 static int
-charmaptranslate_output(Py_UCS4 ch, PyObject *mapping,
+charmaptranslate_output(Py_UCS4 ch, PyObject *mapping, PyObject *cache[128],
                         _PyUnicodeWriter *writer)
 {
-    PyObject *item;
-
-    if (charmaptranslate_lookup(ch, mapping, &item))
-        return -1;
-
-    if (item == NULL) {
+    PyObject *item = charmaptranslate_lookup(ch, mapping, cache);
+    if (item == NULL)
+        return -1;
+
+    if (item == &no_mapping_sentinel) {
         /* not found => default to 1:1 mapping */
         if (_PyUnicodeWriter_WriteCharInline(writer, ch) < 0) {
             return -1;
@@ -8536,7 +8560,18 @@
         return -1;
     }
 
-    if (_PyUnicodeWriter_WriteStr(writer, item) < 0) {
+    if (PyUnicode_GET_SIZE(item) == 1) {
+        ch = PyUnicode_READ_CHAR(item, 0);
+        if (_PyUnicodeWriter_WriteCharInline(writer, ch) < 0) {
+            Py_DECREF(item);
+            return -1;
+        }
+        Py_DECREF(item);
+        return 1;
+    }
+
+    if (PyUnicode_GET_SIZE(item) &&
+        _PyUnicodeWriter_WriteStr(writer, item) < 0) {
         Py_DECREF(item);
         return -1;
     }
@@ -8561,6 +8596,7 @@
     PyObject *errorHandler = NULL;
     PyObject *exc = NULL;
     int ignore;
+    PyObject *cache[128];
 
     if (mapping == NULL) {
         PyErr_BadArgument();
@@ -8585,6 +8621,7 @@
         goto onError;
 
     ignore = (errors != NULL && strcmp(errors, "ignore") == 0);
+    charmaptranslatecache_init(cache);
 
     i = 0;
     while (i<size) {
@@ -8595,11 +8632,10 @@
         /* startpos for collecting untranslatable chars */
         Py_ssize_t collstart;
         Py_ssize_t collend;
-        Py_ssize_t coll;
         Py_UCS4 ch;
 
         ch = PyUnicode_READ(kind, data, i);
-        translate = charmaptranslate_output(ch, mapping, &writer);
+        translate = charmaptranslate_output(ch, mapping, cache, &writer);
         if (translate < 0)
             goto onError;
 
@@ -8617,8 +8653,11 @@
         while (collend < size) {
             PyObject *x;
             ch = PyUnicode_READ(kind, data, collend);
-            if (charmaptranslate_lookup(ch, mapping, &x))
+            x = charmaptranslate_lookup(ch, mapping, cache);
+            if (x == NULL)
                 goto onError;
+            if (x == &no_mapping_sentinel)
+                break;
             Py_XDECREF(x);
             if (x != Py_None)
                 break;
@@ -8642,11 +8681,13 @@
             i = newpos;
         }
     }
+    charmaptranslatecache_free(cache);
     Py_XDECREF(exc);
     Py_XDECREF(errorHandler);
     return _PyUnicodeWriter_Finish(&writer);
 
   onError:
+    charmaptranslatecache_free(cache);
     _PyUnicodeWriter_Dealloc(&writer);
     Py_XDECREF(exc);
     Py_XDECREF(errorHandler);