Add Packer.buffer() (#320)

msgpack/_packer.pyx

@@ -41,6 +41,9 @@ cdef extern from "pack.h":
     int msgpack_pack_ext(msgpack_packer* pk, char typecode, size_t l)
     int msgpack_pack_unicode(msgpack_packer* pk, object o, long long limit)
 
+cdef extern from "buff_converter.h":
+    object buff_to_buff(char *, Py_ssize_t)
+
 cdef int DEFAULT_RECURSE_LIMIT=511
 cdef long long ITEM_LIMIT = (2**32)-1
 
@@ -349,9 +352,16 @@ cdef class Packer(object):
             return buf
 
     def reset(self):
-        """Clear internal buffer."""
+        """Reset internal buffer.
+
+        This method is usaful only when autoreset=False.
+        """
         self.pk.length = 0
 
     def bytes(self):
-        """Return buffer content."""
+        """Return internal buffer contents as bytes object"""
         return PyBytes_FromStringAndSize(self.pk.buf, self.pk.length)
+
+    def getbuffer(self):
+        """Return view of internal buffer."""
+        return buff_to_buff(self.pk.buf, self.pk.length)

msgpack/buff_converter.h

@@ -0,0 +1,28 @@
+#include "Python.h"
+
+/* cython does not support this preprocessor check => write it in raw C */
+#if PY_MAJOR_VERSION == 2
+static PyObject *
+buff_to_buff(char *buff, Py_ssize_t size)
+{
+    return PyBuffer_FromMemory(buff, size);
+}
+
+#elif (PY_MAJOR_VERSION == 3) && (PY_MINOR_VERSION >= 3)
+static PyObject *
+buff_to_buff(char *buff, Py_ssize_t size)
+{
+    return PyMemoryView_FromMemory(buff, size, PyBUF_READ);
+}
+#else
+static PyObject *
+buff_to_buff(char *buff, Py_ssize_t size)
+{
+    Py_buffer pybuf;
+    if (PyBuffer_FillInfo(&pybuf, NULL, buff, size, 1, PyBUF_FULL_RO) == -1) {
+        return NULL;
+    }
+
+    return PyMemoryView_FromBuffer(&pybuf);
+}
+#endif

msgpack/fallback.py

@@ -860,43 +860,35 @@ class Packer(object):
         except:
             self._buffer = StringIO()  # force reset
             raise
-        ret = self._buffer.getvalue()
         if self._autoreset:
+            ret = self._buffer.getvalue()
             self._buffer = StringIO()
-        elif USING_STRINGBUILDER:
-            self._buffer = StringIO(ret)
-        return ret
+            return ret
 
     def pack_map_pairs(self, pairs):
         self._pack_map_pairs(len(pairs), pairs)
-        ret = self._buffer.getvalue()
         if self._autoreset:
+            ret = self._buffer.getvalue()
             self._buffer = StringIO()
-        elif USING_STRINGBUILDER:
-            self._buffer = StringIO(ret)
-        return ret
+            return ret
 
     def pack_array_header(self, n):
         if n >= 2**32:
             raise PackValueError
         self._pack_array_header(n)
-        ret = self._buffer.getvalue()
         if self._autoreset:
+            ret = self._buffer.getvalue()
             self._buffer = StringIO()
-        elif USING_STRINGBUILDER:
-            self._buffer = StringIO(ret)
-        return ret
+            return ret
 
     def pack_map_header(self, n):
         if n >= 2**32:
             raise PackValueError
         self._pack_map_header(n)
-        ret = self._buffer.getvalue()
         if self._autoreset:
+            ret = self._buffer.getvalue()
             self._buffer = StringIO()
-        elif USING_STRINGBUILDER:
-            self._buffer = StringIO(ret)
-        return ret
+            return ret
 
     def pack_ext_type(self, typecode, data):
         if not isinstance(typecode, int):
@@ -976,7 +968,19 @@ class Packer(object):
             raise PackValueError('Bin is too large')
 
     def bytes(self):
+        """Return internal buffer contents as bytes object"""
         return self._buffer.getvalue()
 
     def reset(self):
+        """Reset internal buffer.
+
+        This method is usaful only when autoreset=False.
+        """
         self._buffer = StringIO()
+
+    def getbuffer(self):
+        """Return view of internal buffer."""
+        if USING_STRINGBUILDER or not PY3:
+            return memoryview(self.bytes())
+        else:
+            return self._buffer.getbuffer()