Author: Armin Rigo <[email protected]>
Branch:
Changeset: r614:998ec2787b64
Date: 2012-07-09 17:30 +0200
http://bitbucket.org/cffi/cffi/changeset/998ec2787b64/
Log: Document wchar_t.
diff --git a/doc/source/index.rst b/doc/source/index.rst
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -279,6 +279,8 @@
* intN_t, uintN_t (for N=8,16,32,64), intptr_t, uintptr_t, ptrdiff_t,
size_t, ssize_t
+* wchar_t (if supported by the backend)
+
As we will see on `the verification step`_ below, the declarations can
also contain "``...``" at various places; these are placeholders that will
be completed by a call to ``verify()``.
@@ -419,9 +421,18 @@
The C code's integers and floating-point values are mapped to Python's
regular ``int``, ``long`` and ``float``. Moreover, the C type ``char``
-correspond to single-character strings in Python. (If you want it to
+corresponds to single-character strings in Python. (If you want it to
map to small integers, use either ``signed char`` or ``unsigned char``.)
+Similarly, the C type ``wchar_t`` corresponds to single-character
+unicode strings, if supported by the backend. Note that in some
+situations (a narrow Python build with an underlying 4-bytes wchar_t
+type), a single wchar_t character may correspond to a pair of
+surrogates, which is represented as a unicode string of length 2. If
+you need to convert a wchar_t to an integer, do not use ``ord(x)``,
+because it doesn't accept such unicode strings; use instead
+``int(ffi.cast('int', x))``, which does.
+
Pointers, structures and arrays are more complex: they don't have an
obvious Python equivalent. Thus, they correspond to objects of type
``cdata``, which are printed for example as
@@ -528,6 +539,11 @@
>>> str(x) # interpret 'x' as a regular null-terminated string
'Hello'
+Similarly, arrays of wchar_t can be initialized from a unicode string,
+and calling ``unicode()`` on the cdata object returns the current unicode
+string stored in the wchar_t array (encoding and decoding surrogates as
+needed if necessary).
+
Note that unlike Python lists or tuples, but like C, you *cannot* index in
a C array from the end using negative numbers.
@@ -577,6 +593,12 @@
assert C.strlen("hello") == 5
+So far passing unicode strings as ``wchar_t *`` arguments is not
+implemented. You need to write e.g.::
+
+ >>> C.wcslen(ffi.new("wchar_t[]", u"foo"))
+ 3
+
CFFI supports passing and returning structs to functions and callbacks.
Example (sketch)::
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