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Boxiang Sun
cython
Commits
04780910
Commit
04780910
authored
Jun 20, 2018
by
scoder
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GitHub
Jun 20, 2018
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Merge pull request #2381 from gabrieldemarmiesse/test_string_7
Adding tests for "Unicode and passing strings" part 7
parents
4a29c094
50cdd869
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docs/examples/tutorial/string/const.pyx
docs/examples/tutorial/string/const.pyx
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docs/examples/tutorial/string/someheader.h
docs/examples/tutorial/string/someheader.h
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docs/src/tutorial/strings.rst
docs/src/tutorial/strings.rst
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docs/examples/tutorial/string/const.pyx
0 → 100644
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04780910
cdef
extern
from
"someheader.h"
:
ctypedef
const
char
specialChar
int
process_string
(
const
char
*
s
)
const
unsigned
char
*
look_up_cached_string
(
const
unsigned
char
*
key
)
docs/examples/tutorial/string/someheader.h
0 → 100644
View file @
04780910
typedef
const
char
specialChar
;
int
process_string
(
const
char
*
s
);
const
unsigned
char
*
look_up_cached_string
(
const
unsigned
char
*
key
);
docs/src/tutorial/strings.rst
View file @
04780910
...
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@@ -264,52 +264,13 @@ Many C libraries use the ``const`` modifier in their API to declare
that they will not modify a string, or to require that users must
not modify a string they return, for example:
.. code-block:: c
typedef const char specialChar;
int process_string(const char* s);
const unsigned char* look_up_cached_string(const unsigned char* key);
.. literalinclude:: ../../examples/tutorial/string/someheader.h
Since version 0.18, Cython has support for the ``const`` modifier in
the language, so you can declare the above functions straight away as
follows::
cdef extern from "someheader.h":
ctypedef const char specialChar
int process_string(const char* s)
const unsigned char* look_up_cached_string(const unsigned char* key)
Previous versions required users to make the necessary declarations
at a textual level. If you need to support older Cython versions,
you can use the following approach.
In general, for arguments of external C functions, the ``const``
modifier does not matter and can be left out in the Cython
declaration (e.g. in a .pxd file). The C compiler will still do
the right thing, even if you declare this to Cython::
cdef extern from "someheader.h":
int process_string(char* s) # note: looses API information!
However, in most other situations, such as for return values and
variables that use specifically typedef-ed API types, it does matter
and the C compiler will emit at least a warning if used incorrectly.
To help with this, you can use the type definitions in the
``libc.string`` module, e.g.::
from libc.string cimport const_char, const_uchar
cdef extern from "someheader.h":
ctypedef const_char specialChar
int process_string(const_char* s)
const_uchar* look_up_cached_string(const_uchar* key)
Note: even if the API only uses ``const`` for function arguments,
it is still preferable to properly declare them using these
provided :c:type:`const_char` types in order to simplify adaptations.
In Cython 0.18, these standard declarations have been changed to
use the correct ``const`` modifier, so your code will automatically
benefit from the new ``const`` support if it uses them.
follows:
.. literalinclude:: ../../examples/tutorial/string/const.pyx
Decoding bytes to text
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