* Add faster encode_int32 and decode_int32 methods

spacy/serialize/huffman.pxd

@@ -4,7 +4,7 @@ from libc.stdint cimport int64_t
 from libc.stdint cimport int32_t
 from libc.stdint cimport uint64_t
 
-from .bits cimport Code
+from .bits cimport BitArray, Code
 
 
 cdef struct Node:
@@ -19,3 +19,6 @@ cdef class HuffmanCodec:
 
     cdef readonly list leaves
     cdef readonly dict _map 
+    
+    cpdef int encode_int32(self, int32_t[:] msg, BitArray bits) except -1
+    cpdef int decode_int32(self, BitArray bits, int32_t[:] msg) except -1

spacy/serialize/huffman.pyx

@@ -61,6 +61,19 @@ cdef class HuffmanCodec:
             bits.extend(self.codes[i].bits, self.codes[i].length)
         return bits
 
+    cpdef int encode_int32(self, int32_t[:] msg, BitArray bits) except -1:
+        cdef int msg_i
+        cdef int leaf_i
+        cdef int length = 0
+        for msg_i in range(msg.shape[0]):
+            leaf_i = self._map.get(msg[msg_i], -1)
+            if leaf_i is -1:
+                return 0
+            code = self.codes[leaf_i]
+            bits.extend(code.bits, code.length)
+            length += code.length
+        return length
+
     def n_bits(self, msg, overhead=0):
         cdef int i
         length = 0
@@ -88,8 +101,39 @@ cdef class HuffmanCodec:
                 if i == n:
                     break
         else:
-            raise Exception(
-                "Buffer exhausted at %d/%d symbols read." % (i, len(msg)))
+            raise Exception("Buffer exhausted at %d/%d symbols read." % (i, len(msg)))
+
+    @cython.boundscheck(False)
+    cpdef int decode_int32(self, BitArray bits, int32_t[:] msg) except -1:
+        cdef Node node = self.root
+        cdef int branch
+
+        cdef int n_msg = msg.shape[0]
+        cdef bytes bytes_ = bits.as_bytes()
+        cdef unsigned char byte
+        cdef int i_msg = 0
+        cdef int i_byte = 0
+        cdef int i_bit = 0
+        cdef unsigned char bit
+        cdef int32_t one = 1
+        while i_msg < n_msg:
+            byte = bytes_[i_byte]
+            for i_bit in range(8):
+                bit = byte & (one << i_bit)
+                branch = node.right if bit else node.left
+                if branch >= 0:
+                    node = self.nodes.at(branch)
+                else:
+                    msg[i_msg] = self.leaves[-(branch + 1)]
+                    node = self.nodes.back()
+                    i_msg += 1
+                    if i_msg == n_msg:
+                        break
+            i_byte += 1
+        else:
+            raise Exception("Buffer exhausted at %d/%d symbols read." % (i_msg, len(msg)))
+
+
 
     property strings:
         @cython.boundscheck(False)