Issue #394

Implement ffi.from_buffer(x, require_writable=True)

3 files changed, 29 insertions, 7 deletions

diff --git a/c/_cffi_backend.c b/c/_cffi_backend.c
index dc13c61..c6190e7 100644
--- a/c/_cffi_backend.c
+++ b/c/_cffi_backend.c
@@ -6741,7 +6741,8 @@ static int _my_PyObject_GetContiguousBuffer(PyObject *x, Py_buffer *view,
     return 0;
 }
 
-static PyObject *direct_from_buffer(CTypeDescrObject *ct, PyObject *x)
+static PyObject *direct_from_buffer(CTypeDescrObject *ct, PyObject *x,
+                                    int require_writable)
 {
     CDataObject *cd;
     Py_buffer *view;
@@ -6761,7 +6762,7 @@ static PyObject *direct_from_buffer(CTypeDescrObject *ct, PyObject *x)
         PyErr_NoMemory();
         return NULL;
     }
-    if (_my_PyObject_GetContiguousBuffer(x, view, 0) < 0)
+    if (_my_PyObject_GetContiguousBuffer(x, view, require_writable) < 0)
         goto error1;
 
     cd = (CDataObject *)PyObject_GC_New(CDataObject_owngc_frombuf,
@@ -6789,15 +6790,17 @@ static PyObject *b_from_buffer(PyObject *self, PyObject *args)
 {
     CTypeDescrObject *ct;
     PyObject *x;
+    int require_writable = 0;
 
-    if (!PyArg_ParseTuple(args, "O!O", &CTypeDescr_Type, &ct, &x))
+    if (!PyArg_ParseTuple(args, "O!O|i", &CTypeDescr_Type, &ct, &x,
+                          &require_writable))
         return NULL;
 
     if (!(ct->ct_flags & CT_IS_UNSIZED_CHAR_A)) {
         PyErr_Format(PyExc_TypeError, "needs 'char[]', got '%s'", ct->ct_name);
         return NULL;
     }
-    return direct_from_buffer(ct, x);
+    return direct_from_buffer(ct, x, require_writable);
 }
 
 static int _fetch_as_buffer(PyObject *x, Py_buffer *view, int writable_only)
diff --git a/c/ffi_obj.c b/c/ffi_obj.c
index 9e67466..cc5c715 100644
--- a/c/ffi_obj.c
+++ b/c/ffi_obj.c
@@ -697,9 +697,16 @@ PyDoc_STRVAR(ffi_from_buffer_doc,
 "containing large quantities of raw data in some other format, like\n"
 "'array.array' or numpy arrays.");
 
-static PyObject *ffi_from_buffer(PyObject *self, PyObject *arg)
+static PyObject *ffi_from_buffer(PyObject *self, PyObject *args, PyObject *kwds)
 {
-    return direct_from_buffer(g_ct_chararray, arg);
+    PyObject *arg;
+    int require_writable = 0;
+    static char *keywords[] = {"python_buffer", "require_writable", NULL};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|i:from_buffer", keywords,
+                                     &arg, &require_writable))
+        return NULL;
+    return direct_from_buffer(g_ct_chararray, arg, require_writable);
 }
 
 PyDoc_STRVAR(ffi_gc_doc,
@@ -1072,7 +1079,7 @@ static PyMethodDef ffi_methods[] = {
  {"cast",       (PyCFunction)ffi_cast,       METH_VARARGS, ffi_cast_doc},
  {"dlclose",    (PyCFunction)ffi_dlclose,    METH_VARARGS, ffi_dlclose_doc},
  {"dlopen",     (PyCFunction)ffi_dlopen,     METH_VARARGS, ffi_dlopen_doc},
- {"from_buffer",(PyCFunction)ffi_from_buffer,METH_O,       ffi_from_buffer_doc},
+ {"from_buffer",(PyCFunction)ffi_from_buffer,METH_VKW,     ffi_from_buffer_doc},
  {"from_handle",(PyCFunction)ffi_from_handle,METH_O,       ffi_from_handle_doc},
  {"gc",         (PyCFunction)ffi_gc,         METH_VKW,     ffi_gc_doc},
  {"getctype",   (PyCFunction)ffi_getctype,   METH_VKW,     ffi_getctype_doc},
diff --git a/c/test_c.py b/c/test_c.py
index b83c0aa..b6bb752 100644
--- a/c/test_c.py
+++ b/c/test_c.py
@@ -3741,6 +3741,18 @@ def test_from_buffer_more_cases():
     check(4 | 8,  "CHB", "GTB")
     check(4 | 16, "CHB", "ROB")
 
+def test_from_buffer_require_writable():
+    BChar = new_primitive_type("char")
+    BCharP = new_pointer_type(BChar)
+    BCharA = new_array_type(BCharP, None)
+    p1 = from_buffer(BCharA, b"foo", False)
+    assert p1 == from_buffer(BCharA, b"foo", False)
+    py.test.raises((TypeError, BufferError), from_buffer, BCharA, b"foo", True)
+    ba = bytearray(b"foo")
+    p1 = from_buffer(BCharA, ba, True)
+    p1[0] = b"g"
+    assert ba == b"goo"
+
 def test_memmove():
     Short = new_primitive_type("short")
     ShortA = new_array_type(new_pointer_type(Short), None)