Author: Armin Rigo <ar...@tunes.org>
Branch:
Changeset: r2822:0782c203b090
Date: 2016-11-28 10:11 +0100
http://bitbucket.org/cffi/cffi/changeset/0782c203b090/
Log: Document should_clear_after_alloc a bit more
diff --git a/doc/source/ref.rst b/doc/source/ref.rst
--- a/doc/source/ref.rst
+++ b/doc/source/ref.rst
@@ -44,6 +44,11 @@
used for a longer time. Be careful about that when copying the
pointer to the memory somewhere else, e.g. into another structure.
+The returned memory is initially cleared (filled with zeroes), before
+the optional initializer is applied. For performance, see
+`ffi.new_allocator()`_ for a way to allocate non-zero-initialized
+memory.
+
ffi.cast()
++++++++++
@@ -471,7 +476,16 @@
If ``should_clear_after_alloc`` is set to False, then the memory
returned by ``alloc()`` is assumed to be already cleared (or you are
-fine with garbage); otherwise CFFI will clear it.
+fine with garbage); otherwise CFFI will clear it. Example: for
+performance, if you are using ``ffi.new()`` to allocate large chunks of
+memory where the initial content can be left uninitialized, you can do::
+
+ # at module level
+ new_nonzero = ffi.new_allocator(should_clear_after_alloc)
+
+ # then replace `p = ffi.new("char[]", bigsize)` with:
+ p = new_nonzero("char[]", bigsize)
+
ffi.init_once()
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