Fix Unpacker max_buffer_length handling (#506)

msgpack/_unpacker.pyx

@@ -440,34 +440,30 @@ cdef class Unpacker(object):
         self.buf_size = buf_size
         self.buf_tail = tail + _buf_len
 
-    cdef read_from_file(self):
+    cdef int read_from_file(self) except -1:
-        next_bytes = self.file_like_read(
+        cdef Py_ssize_t remains = self.max_buffer_size - (self.buf_tail - self.buf_head)
-                min(self.read_size,
+        if remains <= 0:
-                    self.max_buffer_size - (self.buf_tail - self.buf_head)
+            raise BufferFull
-                    ))
+
+        next_bytes = self.file_like_read(min(self.read_size, remains))
         if next_bytes:
             self.append_buffer(PyBytes_AsString(next_bytes), PyBytes_Size(next_bytes))
         else:
             self.file_like = None
+        return 0
 
     cdef object _unpack(self, execute_fn execute, bint iter=0):
         cdef int ret
         cdef object obj
         cdef Py_ssize_t prev_head
 
-        if self.buf_head >= self.buf_tail and self.file_like is not None:
-            self.read_from_file()
-
         while 1:
             prev_head = self.buf_head
-            if prev_head >= self.buf_tail:
+            if prev_head < self.buf_tail:
-                if iter:
-                    raise StopIteration("No more data to unpack.")
-                else:
-                    raise OutOfData("No more data to unpack.")
-
                 ret = execute(&self.ctx, self.buf, self.buf_tail, &self.buf_head)
                 self.stream_offset += self.buf_head - prev_head
+            else:
+                ret = 0
 
             if ret == 1:
                 obj = unpack_data(&self.ctx)

msgpack/fallback.py

@@ -423,6 +423,8 @@ class Unpacker(object):
 
         # Read from file
         remain_bytes = -remain_bytes
+        if remain_bytes + len(self._buffer) > self._max_buffer_size:
+            raise BufferFull
         while remain_bytes > 0:
             to_read_bytes = max(self._read_size, remain_bytes)
             read_data = self.file_like.read(to_read_bytes)

test/test_sequnpack.py

@@ -2,7 +2,7 @@
 # coding: utf-8
 import io
 from msgpack import Unpacker, BufferFull
-from msgpack import pack
+from msgpack import pack, packb
 from msgpack.exceptions import OutOfData
 from pytest import raises
 
@@ -78,6 +78,15 @@ def test_maxbuffersize():
     assert ord("b") == next(unpacker)
 
 
+def test_maxbuffersize_file():
+    buff = io.BytesIO(packb(b"a" * 10) + packb([b"a" * 20] * 2))
+    unpacker = Unpacker(buff, read_size=1, max_buffer_size=19, max_bin_len=20)
+    assert unpacker.unpack() == b"a" * 10
+    # assert unpacker.unpack() == [b"a" * 20]*2
+    with raises(BufferFull):
+        print(unpacker.unpack())
+
+
 def test_readbytes():
     unpacker = Unpacker(read_size=3)
     unpacker.feed(b"foobar")