Always write the session file in UTF-8.

This patch attempts to solve the Python 2 / Python 3 incompatibilities by
introducing a new `encoded_file` abstraction that we use instead of
`io.open()`.  The problem with the builtin implementation of `io.open` is
that `read` and `write` accept and return `unicode` objects, which are not
always convenient to work with in Python 2.  We solve this by making
`encoded_file.open()` return the same object returned by `io.open()` but
with hooked `read()` and `write()` methods.  These hooked methods will
accept binary or text data, and conditionally convert what it gets to a
`unicode` object using the correct encoding.  When calling `read()` it
also does any conversion necessary to convert the output back into the
native `string` type of the running python version.

Differential Revision: http://reviews.llvm.org/D16736

llvm-svn: 259379

1 files changed, 48 insertions, 0 deletions

diff --git a/lldb/packages/Python/lldbsuite/support/encoded_file.py b/lldb/packages/Python/lldbsuite/support/encoded_file.py
new file mode 100644
index 00000000000..7581564f7e3
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/support/encoded_file.py
@@ -0,0 +1,48 @@
+"""
+                     The LLVM Compiler Infrastructure
+
+This file is distributed under the University of Illinois Open Source
+License. See LICENSE.TXT for details.
+
+Prepares language bindings for LLDB build process.  Run with --help
+to see a description of the supported command line arguments.
+"""
+
+# Python modules:
+import io
+
+# Third party modules
+import six
+
+def _encoded_read(old_read, encoding):
+    def impl(size):
+        result = old_read(size)
+        # If this is Python 2 then we need to convert the resulting `unicode` back
+        # into a `str` before returning
+        if six.PY2:
+            result = result.encode(encoding)
+        return result
+    return impl
+
+def _encoded_write(old_write, encoding):
+    def impl(s):
+        # If we were asked to write a `str` (in Py2) or a `bytes` (in Py3) decode it
+        # as unicode before attempting to write.
+        if isinstance(s, six.binary_type):
+            s = s.decode(encoding)
+        return old_write(s)
+    return impl
+
+'''
+Create a Text I/O file object that can be written to with either unicode strings or byte strings
+under Python 2 and Python 3, and automatically encodes and decodes as necessary to return the
+native string type for the current Python version
+'''
+def open(file, encoding, mode='r', buffering=-1, errors=None, newline=None, closefd=True):
+    wrapped_file = io.open(file, mode=mode, buffering=buffering, encoding=encoding,
+                           errors=errors, newline=newline, closefd=closefd)
+    new_read = _encoded_read(getattr(wrapped_file, 'read'), encoding)
+    new_write = _encoded_write(getattr(wrapped_file, 'write'), encoding)
+    setattr(wrapped_file, 'read', new_read)
+    setattr(wrapped_file, 'write', new_write)
+    return wrapped_file