copy from pytouhou/utils/lzss.py
copy to pytouhou/utils/lzss.pyx
--- a/pytouhou/utils/lzss.py
+++ b/pytouhou/utils/lzss.pyx
@@ -12,12 +12,24 @@
 ## GNU General Public License for more details.
 ##
 
-def decompress(bitstream, size, dictionary_size=0x2000,
-               offset_size=13, length_size=4, minimum_match_length=3):
-    out_data = []
-    dictionary = [0] * dictionary_size
-    dictionary_head = 1
-    while len(out_data) < size:
+from libc.stdlib cimport calloc, malloc, free
+
+
+cpdef bytes decompress(object bitstream,
+                       Py_ssize_t size,
+                       unsigned int dictionary_size=0x2000,
+                       unsigned int offset_size=13,
+                       unsigned int length_size=4,
+                       unsigned int minimum_match_length=3):
+    cdef unsigned int i, ptr, dictionary_head, offset, length
+    cdef unsigned char flag, byte, *out_data, *dictionary
+    cdef bytes _out_data
+
+    out_data = <unsigned char*> malloc(size)
+    dictionary = <unsigned char*> calloc(dictionary_size, 1)
+    dictionary_head, ptr = 1, 0
+
+    while ptr < size:
         flag = bitstream.read_bit()
         if flag:
             # The `flag` bit is set, indicating the upcoming chunk of data is a literal
@@ -25,15 +37,22 @@ def decompress(bitstream, size, dictiona
             byte = bitstream.read(8)
             dictionary[dictionary_head] = byte
             dictionary_head = (dictionary_head + 1) % dictionary_size
-            out_data.append(byte)
+            out_data[ptr] = byte
+            ptr += 1
         else:
             # The `flag` bit is not set, the upcoming chunk is a (offset, length) tuple
             offset = bitstream.read(offset_size)
             length = bitstream.read(length_size) + minimum_match_length
-            if (offset, length) == (0, 0):
+            if offset == 0 and length == 0:
                 break
             for i in range(offset, offset + length):
-                out_data.append(dictionary[i % dictionary_size])
+                out_data[ptr % size] = dictionary[i % dictionary_size]
+                ptr += 1
                 dictionary[dictionary_head] = dictionary[i % dictionary_size]
                 dictionary_head = (dictionary_head + 1) % dictionary_size
-    return b''.join(chr(byte) for byte in out_data)
+
+    _out_data = out_data[:size]
+    free(out_data)
+    free(dictionary)
+    return _out_data
+