mirror of https://github.com/YosysHQ/abc.git
95 lines
2.1 KiB
Python
95 lines
2.1 KiB
Python
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"""
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A simple context manager for redirecting streams in Python.
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The streams are redirected at the the C runtime level so that the output of C extensions
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that use stdio will also be redirected.
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null_file : a stream representing the null device (e.g. /dev/null on Unix)
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redirect: a context manager for redirecting streams
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Author: Baruch Sterin (sterin@berkeley.edu)
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"""
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import os
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import sys
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from contextlib import contextmanager
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null_file = open( os.devnull, "w" )
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@contextmanager
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def _dup( f ):
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fd = os.dup( f.fileno() )
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yield fd
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os.close(fd)
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@contextmanager
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def redirect(dst = null_file, src = sys.stdout):
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"""
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Redirect the src stream into dst.
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Example:
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with redirect( open("somefile.txt", sys.stdout ) ):
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do some stuff ...
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"""
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if src.fileno() == dst.fileno():
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yield
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return
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with _dup( src ) as fd_dup_src:
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dst.flush()
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src.flush()
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os.close( src.fileno() )
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os.dup2( dst.fileno(), src.fileno() )
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yield
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src.flush()
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os.close( src.fileno() )
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os.dup2( fd_dup_src, src.fileno() )
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def start_redirect(dst = null_file, src = sys.stdout):
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"""
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Start redirection of src stream into dst. Return the duplicated file handle of the source.
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Example:
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fd = start_redirect( open("somefile.txt"), sys.stdout )
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... do some stuff ...
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end_redirect(sys.stdout, fd)
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"""
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if src.fileno() == dst.fileno():
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return None
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fd_dup_src = os.dup( src.fileno() )
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dst.flush()
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src.flush()
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os.close( src.fileno() )
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os.dup2( dst.fileno(), src.fileno() )
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return fd_dup_src
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def end_redirect(src, fd_dup_src):
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"""
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End redirection of stream src.Redirect the src stream into dst. src is the source stream and fd_dup_src is the value returned by
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start_redirect()
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"""
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if fd_dup_src is None:
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return
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src.flush()
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os.close( src.fileno() )
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os.dup2( fd_dup_src, src.fileno() )
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os.close(fd_dup_src)
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