merge

Cython/Compiler/Buffer.py

@@ -113,8 +113,8 @@ class IntroduceBufferAuxiliaryVars(CythonTransform):
 #
 # Analysis
 #
-buffer_options = ("dtype", "ndim", "mode") # ordered!
-buffer_defaults = {"ndim": 1, "mode": "full"}
+buffer_options = ("dtype", "ndim", "mode", "negative_indices", "cast") # ordered!
+buffer_defaults = {"ndim": 1, "mode": "full", "negative_indices": True, "cast": False}
 buffer_positional_options_count = 1 # anything beyond this needs keyword argument
 
 ERR_BUF_OPTION_UNKNOWN = '"%s" is not a buffer option'
@@ -124,6 +124,7 @@ ERR_BUF_MISSING = '"%s" missing'
 ERR_BUF_MODE = 'Only allowed buffer modes are: "c", "fortran", "full", "strided" (as a compile-time string)'
 ERR_BUF_NDIM = 'ndim must be a non-negative integer'
 ERR_BUF_DTYPE = 'dtype must be "object", numeric type or a struct'
+ERR_BUF_BOOL = '"%s" must be a boolean'
 
 def analyse_buffer_options(globalpos, env, posargs, dictargs, defaults=None, need_complete=True):
     """
@@ -178,6 +179,14 @@ def analyse_buffer_options(globalpos, env, posargs, dictargs, defaults=None, nee
     if mode and not (mode in ('full', 'strided', 'c', 'fortran')):
         raise CompileError(globalpos, ERR_BUF_MODE)
 
+    def assert_bool(name):
+        x = options.get(name)
+        if not isinstance(x, bool):
+            raise CompileError(globalpos, ERR_BUF_BOOL % name)
+
+    assert_bool('negative_indices')
+    assert_bool('cast')
+
     return options
     
 
@@ -229,13 +238,15 @@ def put_acquire_arg_buffer(entry, code, pos):
     code.globalstate.use_utility_code(acquire_utility_code)
     buffer_aux = entry.buffer_aux
     getbuffer_cname = get_getbuffer_code(entry.type.dtype, code)
+
     # Acquire any new buffer
-    code.putln(code.error_goto_if("%s((PyObject*)%s, &%s, %s, %d) == -1" % (
+    code.putln(code.error_goto_if("%s((PyObject*)%s, &%s, %s, %d, %d) == -1" % (
         getbuffer_cname,
         entry.cname,
         entry.buffer_aux.buffer_info_var.cname,
         get_flags(buffer_aux, entry.type),
-        entry.type.ndim), pos))
+        entry.type.ndim,
+        int(entry.type.cast)), pos))
     # An exception raised in arg parsing cannot be catched, so no
     # need to care about the buffer then.
     put_unpack_buffer_aux_into_scope(buffer_aux, entry.type.mode, code)
@@ -269,11 +280,12 @@ def put_assign_to_buffer(lhs_cname, rhs_cname, buffer_aux, buffer_type,
     bufstruct = buffer_aux.buffer_info_var.cname
     flags = get_flags(buffer_aux, buffer_type)
 
-    getbuffer = "%s((PyObject*)%%s, &%s, %s, %d)" % (get_getbuffer_code(buffer_type.dtype, code),
+    getbuffer = "%s((PyObject*)%%s, &%s, %s, %d, %d)" % (get_getbuffer_code(buffer_type.dtype, code),
                                           # note: object is filled in later (%%s)
                                           bufstruct,
                                           flags,
-                                          buffer_type.ndim)
+                                          buffer_type.ndim,
+                                          int(buffer_type.cast))
 
     if is_initialized:
         # Release any existing buffer
@@ -336,6 +348,7 @@ def put_buffer_lookup_code(entry, index_signeds, index_cnames, options, pos, cod
     """
     bufaux = entry.buffer_aux
     bufstruct = bufaux.buffer_info_var.cname
+    negative_indices = entry.type.negative_indices
 
     if options['boundscheck']:
         # Check bounds and fix negative indices.
@@ -349,9 +362,12 @@ def put_buffer_lookup_code(entry, index_signeds, index_cnames, options, pos, cod
             if signed != 0:
                 # not unsigned, deal with negative index
                 code.putln("if (%s < 0) {" % cname)
-                code.putln("%s += %s;" % (cname, shape.cname))
-                code.putln("if (%s) %s = %d;" % (
-                    code.unlikely("%s < 0" % cname), tmp_cname, dim))
+                if negative_indices:
+                    code.putln("%s += %s;" % (cname, shape.cname))
+                    code.putln("if (%s) %s = %d;" % (
+                        code.unlikely("%s < 0" % cname), tmp_cname, dim))
+                else:
+                    code.putln("%s = %d;" % (tmp_cname, dim))
                 code.put("} else ")
             # check bounds in positive direction
             code.putln("if (%s) %s = %d;" % (
@@ -364,7 +380,7 @@ def put_buffer_lookup_code(entry, index_signeds, index_cnames, options, pos, cod
         code.putln(code.error_goto(pos))
         code.end_block()
         code.funcstate.release_temp(tmp_cname)
-    else:
+    elif negative_indices:
         # Only fix negative indices.
         for signed, cname, shape in zip(index_signeds, index_cnames,
                                         bufaux.shapevars):
@@ -563,10 +579,11 @@ def get_getbuffer_code(dtype, code):
     if not code.globalstate.has_utility_code(name):
         code.globalstate.use_utility_code(acquire_utility_code)
         itemchecker = get_ts_check_item(dtype, code)
+        dtype_cname = dtype.declaration_code("")
         utilcode = [dedent("""
-        static int %s(PyObject* obj, Py_buffer* buf, int flags, int nd); /*proto*/
+        static int %s(PyObject* obj, Py_buffer* buf, int flags, int nd, int cast); /*proto*/
         """) % name, dedent("""
-        static int %(name)s(PyObject* obj, Py_buffer* buf, int flags, int nd) {
+        static int %(name)s(PyObject* obj, Py_buffer* buf, int flags, int nd, int cast) {
           const char* ts;
           if (obj == Py_None) {
             __Pyx_ZeroBuffer(buf);
@@ -578,17 +595,25 @@ def get_getbuffer_code(dtype, code):
             __Pyx_BufferNdimError(buf, nd);
             goto fail;
           }
-          ts = buf->format;
-          ts = __Pyx_ConsumeWhitespace(ts);
-          if (!ts) goto fail;
-          ts = %(itemchecker)s(ts);
-          if (!ts) goto fail;
-          ts = __Pyx_ConsumeWhitespace(ts);
-          if (!ts) goto fail;
-          if (*ts != 0) {
-            PyErr_Format(PyExc_ValueError,
-              "Expected non-struct buffer data type (expected end, got '%%s')", ts);
-            goto fail;
+          if (!cast) {
+            ts = buf->format;
+            ts = __Pyx_ConsumeWhitespace(ts);
+            if (!ts) goto fail;
+            ts = %(itemchecker)s(ts);
+            if (!ts) goto fail;
+            ts = __Pyx_ConsumeWhitespace(ts);
+            if (!ts) goto fail;
+            if (*ts != 0) {
+              PyErr_Format(PyExc_ValueError,
+                "Expected non-struct buffer data type (expected end, got '%%s')", ts);
+              goto fail;
+            }
+          } else {
+            if (buf->itemsize != sizeof(%(dtype_cname)s)) {
+              PyErr_SetString(PyExc_ValueError,
+                "Attempted cast of buffer to datatype of different size.");
+              goto fail;
+            }
           }
           if (buf->suboffsets == NULL) buf->suboffsets = __Pyx_minusones;
           return 0;

Cython/Compiler/PyrexTypes.py

@@ -197,20 +197,24 @@ class BufferType(BaseType):
     #  lookups to the base type. ANYTHING NOT DEFINED
     #  HERE IS DELEGATED!
     
-    # dtype         PyrexType
-    # ndim          int
-    # mode          str
-    # is_buffer     boolean
-    # writable      boolean
+    # dtype            PyrexType
+    # ndim             int
+    # mode             str
+    # negative_indices bool
+    # cast             bool
+    # is_buffer        bool
+    # writable         bool
 
     is_buffer = 1
     writable = True
-    def __init__(self, base, dtype, ndim, mode):
+    def __init__(self, base, dtype, ndim, mode, negative_indices, cast):
         self.base = base
         self.dtype = dtype
         self.ndim = ndim
         self.buffer_ptr_type = CPtrType(dtype)
         self.mode = mode
+        self.negative_indices = negative_indices
+        self.cast = cast
     
     def as_argument_type(self):
         return self

tests/run/bufaccess.pyx

@@ -473,6 +473,25 @@ def list_comprehension(object[int] buf, len):
     cdef int i
     print u"|".join([unicode(buf[i]) for i in range(len)])
 
+#
+# The negative_indices buffer option
+#
+@testcase
+def no_negative_indices(object[int, negative_indices=False] buf, int idx):
+    """
+    The most interesting thing here is to inspect the C source and
+    make sure optimal code is produced.
+    
+    >>> A = IntMockBuffer(None, range(6))
+    >>> no_negative_indices(A, 3)
+    3
+    >>> no_negative_indices(A, -1)
+    Traceback (most recent call last):
+        ...
+    IndexError: Out of bounds on buffer access (axis 0)
+    """
+    return buf[idx]
+
 #
 # Buffer type mismatch examples. Varying the type and access
 # method simultaneously, the odds of an interaction is virtually
@@ -635,7 +654,7 @@ def safe_get(object[int] buf, int idx):
     return buf[idx]
 
 @testcase
-@cython.boundscheck(False)
+@cython.boundscheck(False) # outer decorators should take precedence
 @cython.boundscheck(True)
 def unsafe_get(object[int] buf, int idx):
     """
@@ -650,6 +669,18 @@ def unsafe_get(object[int] buf, int idx):
     """
     return buf[idx]
 
+@testcase
+@cython.boundscheck(False)
+def unsafe_get_nonegative(object[int, negative_indices=False] buf, int idx):
+    """
+    Also inspect the C source to see that it is optimal...
+    
+    >>> A = IntMockBuffer(None, range(10), shape=(3,), offset=5)
+    >>> unsafe_get_nonegative(A, -2)
+    3
+    """
+    return buf[idx]
+
 @testcase
 def mixed_get(object[int] buf, int unsafe_idx, int safe_idx):
     """
@@ -912,7 +943,32 @@ def assign_to_object(object[object] buf, int idx, obj):
     """
     buf[idx] = obj
     
+#
+# cast option
+#
+@testcase
+def buffer_cast(object[unsigned int, cast=True] buf, int idx):
+    """
+    Round-trip a signed int through unsigned int buffer access.
+
+    >>> A = IntMockBuffer(None, [-100])
+    >>> buffer_cast(A, 0)
+    -100
+    """
+    cdef unsigned int data = buf[idx]
+    return <int>data
 
+@testcase
+def buffer_cast_fails(object[char, cast=True] buf):
+    """
+    Cannot cast between datatype of different sizes.
+    
+    >>> buffer_cast_fails(IntMockBuffer(None, [0]))
+    Traceback (most recent call last):
+        ...
+    ValueError: Attempted cast of buffer to datatype of different size.
+    """
+    return buf[0]
 
 
 #
@@ -1070,6 +1126,13 @@ cdef class MockBuffer:
     cdef get_default_format(self):
         print "ERROR, not subclassed", self.__class__
     
+cdef class CharMockBuffer(MockBuffer):
+    cdef int write(self, char* buf, object value) except -1:
+        (<char*>buf)[0] = <int>value
+        return 0
+    cdef get_itemsize(self): return sizeof(char)
+    cdef get_default_format(self): return b"@b"
+
 cdef class IntMockBuffer(MockBuffer):
     cdef int write(self, char* buf, object value) except -1:
         (<int*>buf)[0] = <int>value
@@ -1077,6 +1140,13 @@ cdef class IntMockBuffer(MockBuffer):
     cdef get_itemsize(self): return sizeof(int)
     cdef get_default_format(self): return b"@i"
 
+cdef class UnsignedIntMockBuffer(MockBuffer):
+    cdef int write(self, char* buf, object value) except -1:
+        (<unsigned int*>buf)[0] = <unsigned int>value
+        return 0
+    cdef get_itemsize(self): return sizeof(unsigned int)
+    cdef get_default_format(self): return b"@I"
+
 cdef class ShortMockBuffer(MockBuffer):
     cdef int write(self, char* buf, object value) except -1:
         (<short*>buf)[0] = <short>value

tests/run/numpy_test.pyx

@@ -137,6 +137,13 @@ try:
     Traceback (most recent call last):
        ...
     ValueError: only objects, int and float dtypes supported for ndarray buffer access so far (dtype is 20)
+
+    >>> test_good_cast()
+    True
+    >>> test_bad_cast()
+    Traceback (most recent call last):
+        ...
+    ValueError: Attempted cast of buffer to datatype of different size.
     
 """
 except:
@@ -225,3 +232,15 @@ def test_dtype(dtype, inc1):
     a = np.array([0, 10], dtype=dtype)
     inc1(a)
     if a[1] != 11: print "failed!"
+
+
+def test_good_cast():
+    # Check that a signed int can round-trip through casted unsigned int access
+    cdef np.ndarray[unsigned int, cast=True] arr = np.array([-100], dtype='i')
+    cdef unsigned int data = arr[0]
+    return -100 == <int>data
+
+def test_bad_cast():
+    # This should raise an exception
+    cdef np.ndarray[long, cast=True] arr = np.array([1], dtype='b')
+