initial commit of public abc

1 files changed, 94 insertions, 0 deletions

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