From 8f7450e33d9edcab790d5b2ad303cbb81a86536e Mon Sep 17 00:00:00 2001
From: Ben Beasley <code@musicinmybrain.net>
Date: Wed, 26 Jun 2024 15:21:31 -0400
Subject: [PATCH] Fix 128-bit int regression on big-endian with Python <3.13
 (#4291)

Fixes #4290.
---
 newsfragments/4291.fixed.md |  1 +
 src/conversions/std/num.rs  | 23 +++++++++++++----------
 2 files changed, 14 insertions(+), 10 deletions(-)
 create mode 100644 newsfragments/4291.fixed.md

diff --git a/newsfragments/4291.fixed.md b/newsfragments/4291.fixed.md
new file mode 100644
index 00000000..38242ff7
--- /dev/null
+++ b/newsfragments/4291.fixed.md
@@ -0,0 +1 @@
+Fix 128-bit int regression on big-endian platforms with Python <3.13
diff --git a/src/conversions/std/num.rs b/src/conversions/std/num.rs
index effe7c7c..1304e73e 100644
--- a/src/conversions/std/num.rs
+++ b/src/conversions/std/num.rs
@@ -238,15 +238,18 @@ mod fast_128bit_int_conversion {
                         unsafe { ffi::PyNumber_Index(ob.as_ptr()).assume_owned_or_err(ob.py())? };
                     let mut buffer = [0u8; std::mem::size_of::<$rust_type>()];
                     #[cfg(not(Py_3_13))]
-                    crate::err::error_on_minusone(ob.py(), unsafe {
-                        ffi::_PyLong_AsByteArray(
-                            num.as_ptr() as *mut ffi::PyLongObject,
-                            buffer.as_mut_ptr(),
-                            buffer.len(),
-                            1,
-                            $is_signed.into(),
-                        )
-                    })?;
+                    {
+                        crate::err::error_on_minusone(ob.py(), unsafe {
+                            ffi::_PyLong_AsByteArray(
+                                num.as_ptr() as *mut ffi::PyLongObject,
+                                buffer.as_mut_ptr(),
+                                buffer.len(),
+                                1,
+                                $is_signed.into(),
+                            )
+                        })?;
+                        Ok(<$rust_type>::from_le_bytes(buffer))
+                    }
                     #[cfg(Py_3_13)]
                     {
                         let mut flags = ffi::Py_ASNATIVEBYTES_NATIVE_ENDIAN;
@@ -272,8 +275,8 @@ mod fast_128bit_int_conversion {
                                 "Python int larger than 128 bits",
                             ));
                         }
+                        Ok(<$rust_type>::from_ne_bytes(buffer))
                     }
-                    Ok(<$rust_type>::from_ne_bytes(buffer))
                 }
 
                 #[cfg(feature = "experimental-inspect")]