#!/usr/bin/env python3
# ----------------------------------------------------------------------
# Copyright (C) 2024 Tristan Hoellinger
# Distributed under the GNU General Public License v3.0 (GPLv3).
# See the LICENSE file in the root directory for details.
# SPDX-License-Identifier: GPL-3.0-or-later
# ----------------------------------------------------------------------
__author__ = "Tristan Hoellinger"
__version__ = "0.1.0"
__date__ = "2024"
__license__ = "GPLv3"
"""
Tools to deal with low-level operations such as redirecting stdout from
C code.
"""
from contextlib import contextmanager
import platform
import ctypes
import io
import os, sys
import tempfile
libc = ctypes.CDLL(None)
if platform.system() == "Darwin": # macOS
stdout_symbol = "__stdoutp"
stderr_symbol = "__stderrp"
else:
stdout_symbol = "stdout"
stderr_symbol = "stderr"
c_stdout = ctypes.c_void_p.in_dll(libc, stdout_symbol)
c_stderr = ctypes.c_void_p.in_dll(libc, stderr_symbol)
# Taken from:
# https://eli.thegreenplace.net/2015/redirecting-all-kinds-of-stdout-in-python/
[docs]
@contextmanager
def stdout_redirector(stream):
"""A context manager that redirects stdout to the given stream. For
instance, this can be used to redirect C code stdout to None (to
avoid cluttering the log, e.g., when using tqdm).
Args:
stream (file-like object): The stream to which stdout should be
redirected.
Example:
>>> with stdout_redirector(stream):
>>> print("Hello world!") # Will be printed to stream
>>> # instead of stdout.
"""
# The original fd stdout points to. Usually 1 on POSIX systems.
original_stdout_fd = sys.stdout.fileno()
def _redirect_stdout(to_fd):
"""Redirect stdout to the given file descriptor."""
# Flush the C-level buffer stdout
libc.fflush(c_stdout)
# Flush and close sys.stdout - also closes the file descriptor (fd)
sys.stdout.close()
# Make original_stdout_fd point to the same file as to_fd
os.dup2(to_fd, original_stdout_fd)
# Create a new sys.stdout that points to the redirected fd
sys.stdout = io.TextIOWrapper(os.fdopen(original_stdout_fd, "wb"))
# Save a copy of the original stdout fd in saved_stdout_fd
saved_stdout_fd = os.dup(original_stdout_fd)
try:
# Create a temporary file and redirect stdout to it
tfile = tempfile.TemporaryFile(mode="w+b")
_redirect_stdout(tfile.fileno())
# Yield to caller, then redirect stdout back to the saved fd
yield
_redirect_stdout(saved_stdout_fd)
# Copy contents of temporary file to the given stream
tfile.flush()
tfile.seek(0, io.SEEK_SET)
stream.write(tfile.read())
finally:
tfile.close()
os.close(saved_stdout_fd)
# Adapted from:
# https://eli.thegreenplace.net/2015/redirecting-all-kinds-of-stdout-in-python/
[docs]
@contextmanager
def stderr_redirector(stream):
"""A context manager that redirects stderr to the given stream.
For instance, this can be used to redirect C code stderr to None (to
avoid cluttering the log, e.g., when using tqdm).
Use with caution.
Args:
stream (file-like object): The stream to which stdout should be
redirected.
"""
# The original fd stdout points to. Usually 1 on POSIX systems.
original_stderr_fd = sys.stderr.fileno()
def _redirect_stderr(to_fd):
"""Redirect stderr to the given file descriptor."""
# Flush the C-level buffer stderr
libc.fflush(c_stderr)
# Flush and close sys.stderr - also closes the file descriptor (fd)
sys.stderr.close()
# Make original_stderr_fd point to the same file as to_fd
os.dup2(to_fd, original_stderr_fd)
# Create a new sys.stderr that points to the redirected fd
sys.stderr = io.TextIOWrapper(os.fdopen(original_stderr_fd, "wb"))
# Save a copy of the original stdout fd in saved_stdout_fd
saved_stderr_fd = os.dup(original_stderr_fd)
try:
# Create a temporary file and redirect stdout to it
tfile = tempfile.TemporaryFile(mode="w+b")
_redirect_stderr(tfile.fileno())
# Yield to caller, then redirect stdout back to the saved fd
yield
_redirect_stderr(saved_stderr_fd)
# Copy contents of temporary file to the given stream
tfile.flush()
tfile.seek(0, io.SEEK_SET)
stream.write(tfile.read())
finally:
tfile.close()
os.close(saved_stderr_fd)