python · vstinner · May 2, 2017 · pitrou · Jun 22, 2017 · vstinner
diff --git a/Modules/_io/_iomodule.h b/Modules/_io/_iomodule.h
@@ -1,3 +1,5 @@
+#include "pythread.h"
+
 /*
  * Declarations shared between the different parts of the io module
  */
@@ -183,3 +185,47 @@ extern PyObject *_PyIO_empty_str;
 extern PyObject *_PyIO_empty_bytes;
 
 extern PyTypeObject _PyBytesIOBuffer_Type;
+
+typedef struct {
+    PyObject_HEAD
+
+    PyObject *raw;
+    int ok;    /* Initialized? */
+    int detached;
+    int readable;
+    int writable;
+    char finalizing;
+
+    /* True if this is a vanilla Buffered object (rather than a user derived
+       class) *and* the raw stream is a vanilla FileIO object. */
+    int fast_closed_checks;
+
+    /* Absolute position inside the raw stream (-1 if unknown). */
+    Py_off_t abs_pos;
+
+    /* A static buffer of size `buffer_size` */
+    char *buffer;
+    /* Current logical position in the buffer. */
+    Py_off_t pos;
+    /* Position of the raw stream in the buffer. */
+    Py_off_t raw_pos;
+
+    /* Just after the last buffered byte in the buffer, or -1 if the buffer
+       isn't ready for reading. */
+    Py_off_t read_end;
+
+    /* Just after the last byte actually written */
+    Py_off_t write_pos;
+    /* Just after the last byte waiting to be written, or -1 if the buffer
+       isn't ready for writing. */
+    Py_off_t write_end;
+
+    PyThread_type_lock lock;
+    volatile unsigned long owner;
+
+    Py_ssize_t buffer_size;
+    Py_ssize_t buffer_mask;
+
+    PyObject *dict;
+    PyObject *weakreflist;
+} _PyIO_buffered;
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
@@ -11,7 +11,6 @@
 #include "Python.h"
 #include "internal/pystate.h"
 #include "structmember.h"
-#include "pythread.h"
 #include "_iomodule.h"
 
 /*[clinic input]
@@ -197,49 +196,7 @@ bufferediobase_write(PyObject *self, PyObject *args)
 }
 
 
-typedef struct {
-    PyObject_HEAD
-
-    PyObject *raw;
-    int ok;    /* Initialized? */
-    int detached;
-    int readable;
-    int writable;
-    char finalizing;
-
-    /* True if this is a vanilla Buffered object (rather than a user derived
-       class) *and* the raw stream is a vanilla FileIO object. */
-    int fast_closed_checks;
-
-    /* Absolute position inside the raw stream (-1 if unknown). */
-    Py_off_t abs_pos;
-
-    /* A static buffer of size `buffer_size` */
-    char *buffer;
-    /* Current logical position in the buffer. */
-    Py_off_t pos;
-    /* Position of the raw stream in the buffer. */
-    Py_off_t raw_pos;
-
-    /* Just after the last buffered byte in the buffer, or -1 if the buffer
-       isn't ready for reading. */
-    Py_off_t read_end;
-
-    /* Just after the last byte actually written */
-    Py_off_t write_pos;
-    /* Just after the last byte waiting to be written, or -1 if the buffer
-       isn't ready for writing. */
-    Py_off_t write_end;
-
-    PyThread_type_lock lock;
-    volatile unsigned long owner;
-
-    Py_ssize_t buffer_size;
-    Py_ssize_t buffer_mask;
-
-    PyObject *dict;
-    PyObject *weakreflist;
-} buffered;
+typedef _PyIO_buffered buffered;
 
 /*
     Implementation notes:

diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
@@ -1075,21 +1075,31 @@ _io_TextIOWrapper___init___impl(textio *self, PyObject *buffer,
 
     self->has_read1 = _PyObject_HasAttrId(buffer, &PyId_read1);
 
-    self->encoding_start_of_stream = 0;
     if (self->seekable && self->encoder) {
         PyObject *cookieObj;
         int cmp;
 
         self->encoding_start_of_stream = 1;
 
-        cookieObj = PyObject_CallMethodObjArgs(buffer, _PyIO_str_tell, NULL);
-        if (cookieObj == NULL)
-            goto error;
+        if (Py_TYPE(buffer) == &PyBufferedWriter_Type
+           || Py_TYPE(buffer) == &PyBufferedRandom_Type) {
+            /* Fast-path for _io.BufferedWriter and _io.BufferedRandom:
+               read directly the private abs_pos attribute */
+            _PyIO_buffered *bw = (_PyIO_buffered *)buffer;
+            /* _buffered_init() sets abs_pos (if the file is seekable) */
+            assert(bw->abs_pos >= 0);
+            cmp = (bw->abs_pos == 0);
+        }
+        else {
+            cookieObj = PyObject_CallMethodObjArgs(buffer, _PyIO_str_tell, NULL);
+            if (cookieObj == NULL)
+                goto error;
 
-        cmp = PyObject_RichCompareBool(cookieObj, _PyLong_Zero, Py_EQ);
-        Py_DECREF(cookieObj);
-        if (cmp < 0) {
-            goto error;
+            cmp = PyObject_RichCompareBool(cookieObj, _PyLong_Zero, Py_EQ);
+            Py_DECREF(cookieObj);
+            if (cmp < 0) {
+                goto error;
+            }
         }
 
         if (cmp == 0) {
@@ -1101,6 +1111,9 @@ _io_TextIOWrapper___init___impl(textio *self, PyObject *buffer,
             Py_DECREF(res);
         }
     }
+    else {
+        self->encoding_start_of_stream = 0;
+    }
 
     self->ok = 1;
     return 0;