Author: Matti Picus <[email protected]>
Branch:
Changeset: r86910:abbb7cdf30ab
Date: 2016-09-06 21:46 +0300
http://bitbucket.org/pypy/pypy/changeset/abbb7cdf30ab/
Log: remove one more pyobj force, rework documentation
diff --git a/pypy/doc/release-pypy2.7-v5.4.1.rst
b/pypy/doc/release-pypy2.7-v5.4.1.rst
--- a/pypy/doc/release-pypy2.7-v5.4.1.rst
+++ b/pypy/doc/release-pypy2.7-v5.4.1.rst
@@ -21,7 +21,7 @@
* Fix for and issue where `unicode.decode('utf8', 'custom_replace')` messed
up
the last byte of a unicode string sometimes
- * Update built-in cffi_ to the soon-to-be-released 1.8.2 version
+ * Update built-in cffi_ to version 1.8.1
* Explicitly detect that we found as-yet-unsupported OpenSSL 1.1, and crash
translation with a message asking for help porting it
diff --git a/pypy/module/cpyext/bytesobject.py
b/pypy/module/cpyext/bytesobject.py
--- a/pypy/module/cpyext/bytesobject.py
+++ b/pypy/module/cpyext/bytesobject.py
@@ -14,43 +14,31 @@
## Implementation of PyBytesObject
## ================================
##
-## The problem
-## -----------
+## PyBytesObject has its own ob_sval buffer, so we have two copies of a string;
+## one in the PyBytesObject returned from various C-API functions and another
+## in the corresponding RPython object.
##
-## PyString_AsString() must return a (non-movable) pointer to the underlying
-## ob_sval, whereas pypy strings are movable. C code may temporarily store
-## this address and use it, as long as it owns a reference to the PyObject.
-## There is no "release" function to specify that the pointer is not needed
-## any more.
+## The following calls can create a PyBytesObject without a correspoinding
+## RPython object:
+
+## In any of the above PyBytesObject, the ob_sval buffer may be modified as
+## long as the freshly allocated PyBytesObject is not "forced" via a call
+## to any of the more sophisticated C-API functions.
##
-## Also, the pointer may be used to fill the initial value of string. This is
-## valid only when the string was just allocated, and is not used elsewhere.
-##
-## Solution
-## --------
-##
-## PyBytesObject contains two additional members: the ob_size and an array
-## char ob_sval which holds a \x0 terminated string.
-##
-## - A string allocated by pypy will be converted into a PyBytesObject with a
-## buffer holding \x0. The first time PyString_AsString() is called, the
-## PyStringObject is reallocated, and the string copied into the buffer. The
-## ob_size reflects the length of the string.
-##
-## - A string allocated with PyString_FromStringAndSize(NULL, size) will
-## allocate a PyBytesObject structure, and a buffer with the specified
-## size+1, as part of the object. The buffer is then supposed to be
immutable.
-##
-##- A buffer obtained from PyString_AS_STRING() could be mutable iff
-## there is no corresponding pypy object for the string
-##
-## - _PyString_Resize() works only on not-yet-pypy'd strings, and returns a
-## similar object.
-##
-## - PyString_Size() doesn't need to force the object.
+## Care has been taken in implementing the functions below, so that
+## if they are called with a non-forced PyBytesObject, they will not
+## unintentionally force the creation of a RPython object. As long as only
these
+## are used, the ob_sval buffer is still modifiable:
+##
+## PyBytes_AsString / PyString_AsString
+## PyBytes_AS_STRING / PyString_AS_STRING
+## PyBytes_AsStringAndSize / PyString_AsStringAndSize
+## PyBytes_Size / PyString_Size
+## PyBytes_Resize / PyString_Resize
+## _PyBytes_Resize / _PyString_Resize (raises if called with a forced object)
##
## - There could be an (expensive!) check in from_ref() that the buffer still
-## corresponds to the pypy gc-managed string.
+## corresponds to the pypy gc-managed string,
##
PyBytesObjectStruct = lltype.ForwardReference()
@@ -177,9 +165,6 @@
raise oefmt(space.w_TypeError,
"expected string or Unicode object, %T found",
from_ref(space, ref))
- if not pyobj_has_w_obj(ref):
- # force the ref
- bytes_realize(space, ref)
ref_str = rffi.cast(PyBytesObject, ref)
data[0] = ref_str.c_ob_sval
if length:
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