Reverse the order of copied bytes on big-endian

Fixes test failures on s390x.

Author: ellert

CHANGELOG.rst

@@ -12,6 +12,8 @@ version develop
 -----------------
 + Use upstream ISA-L version 2.31.1 which includes patches to make 
   installation possible.
++ Fix a bug where bytes were copied in the wrong order on big endian
+  architectures. Fixes test failures on s390x.
 
 version 1.7.1
 -----------------

src/isal/isal_shared.h

@@ -207,8 +207,15 @@ static int bitbuffer_copy(struct inflate_state *state, char *to, size_t n){
     int remainder = bits_in_buffer % 8;
     // Shift the 8-byte bitbuffer read_in so that the bytes are aligned.
     uint64_t remaining_bytes = state->read_in >> remainder;
+    #if PY_BIG_ENDIAN
+    char *remaining_buffer = (char *)&remaining_bytes;
+    for (int i = 0; i < n; ++i) {
+        to[i] = remaining_buffer[7-i];
+    }
+    #else
     // memcpy works because of little-endianness
     memcpy(to, &remaining_bytes, n);
+    #endif
     return 0;
 }