# HG changeset patch
# Parent 800507fb0a7e198f45f82e9d1a8dc595c741e257
Make rawiobase_read() read directly to bytes object instead of copying.

diff -r 800507fb0a7e Modules/_io/iobase.c
--- a/Modules/_io/iobase.c	Sun Sep 09 11:19:17 2012 +0200
+++ b/Modules/_io/iobase.c	Mon Sep 10 12:52:30 2012 +0100
@@ -782,7 +782,7 @@
 rawiobase_read(PyObject *self, PyObject *args)
 {
     Py_ssize_t n = -1;
-    PyObject *b, *res;
+    PyObject *b, *m, *res;
 
     if (!PyArg_ParseTuple(args, "|n:read", &n)) {
         return NULL;
@@ -794,13 +794,21 @@
         return _PyObject_CallMethodId(self, &PyId_readall, NULL);
     }
 
-    /* TODO: allocate a bytes object directly instead and manually construct
-       a writable memoryview pointing to it. */
-    b = PyByteArray_FromStringAndSize(NULL, n);
+    b = PyBytes_FromStringAndSize(NULL, n);
     if (b == NULL)
         return NULL;
 
-    res = PyObject_CallMethodObjArgs(self, _PyIO_str_readinto, b, NULL);
+    if (n == 0)
+        return b;
+
+    m = PyMemoryView_FromMemory(PyBytes_AS_STRING(b), n, PyBUF_WRITE);
+    if (m == 0) {
+        Py_DECREF(b);
+        return NULL;
+    }
+
+    res = PyObject_CallMethodObjArgs(self, _PyIO_str_readinto, m, NULL);
+    Py_DECREF(m);
     if (res == NULL || res == Py_None) {
         Py_DECREF(b);
         return res;
@@ -813,9 +821,10 @@
         return NULL;
     }
 
-    res = PyBytes_FromStringAndSize(PyByteArray_AsString(b), n);
-    Py_DECREF(b);
-    return res;
+    if (n < PyBytes_GET_SIZE(b) && _PyBytes_Resize(&b, n) < 0)
+        return NULL;
+
+    return b;
 }