From 05606c768b55f7dc9689eba586d347e0cec78a16 Mon Sep 17 00:00:00 2001
From: Laurence Tratt <laurie@tratt.net>
Date: Tue, 9 Jun 2020 08:10:31 +0100
Subject: [PATCH] Implement the 'as32Bit[Un]signedValue' primitives.

Java SOM crashes on big integers, so I have defined what I believe to be
appropriate semantics for them which appears to be not to perform sign
extension in the conversion. For example:

  ((1 << 60) - 1) as32BitUnsignedValue

in Java SOM returns 4294967295, which is bigger than a signed 32 bit can
represent. This commit preserves that behaviour.
---
 lang_tests/to32bits.som | 43 +++++++++++++++++++++++++++++++++++++++++
 src/lib/vm/core.rs      | 30 ++++++++++++++++++++++++++--
 2 files changed, 71 insertions(+), 2 deletions(-)
 create mode 100644 lang_tests/to32bits.som

diff --git a/lang_tests/to32bits.som b/lang_tests/to32bits.som
new file mode 100644
index 00000000..c982409a
--- /dev/null
+++ b/lang_tests/to32bits.som
@@ -0,0 +1,43 @@
+"
+VM:
+  status: success
+  stdout:
+    0
+    1
+    4294967295
+    4294967295
+    0
+    4294967295
+    0
+    4294967295
+    0
+    1
+    -1
+    -1
+    0
+    -1
+    0
+    -1
+"
+
+to32bits = (
+    run = (
+        0 as32BitUnsignedValue println.
+        1 as32BitUnsignedValue println.
+        -1 as32BitUnsignedValue println.
+        4294967295 as32BitUnsignedValue println.
+        (1 << 60) as32BitUnsignedValue println.
+        ((1 << 60) - 1) as32BitUnsignedValue println.
+        (1 << 200) as32BitUnsignedValue println.
+        ((1 << 200) - 1) as32BitUnsignedValue println.
+
+        0 as32BitSignedValue println.
+        1 as32BitSignedValue println.
+        -1 as32BitSignedValue println.
+        4294967295 as32BitSignedValue println.
+        (1 << 60) as32BitSignedValue println.
+        ((1 << 60) - 1) as32BitSignedValue println.
+        (1 << 200) as32BitSignedValue println.
+        ((1 << 200) - 1) as32BitSignedValue println.
+    )
+)
diff --git a/src/lib/vm/core.rs b/src/lib/vm/core.rs
index 75ddbeec..9b3d60fd 100644
--- a/src/lib/vm/core.rs
+++ b/src/lib/vm/core.rs
@@ -636,8 +636,34 @@ impl VM {
                 self.stack.push(v);
                 SendReturn::Val
             }
-            Primitive::As32BitSignedValue => todo!(),
-            Primitive::As32BitUnsignedValue => todo!(),
+            Primitive::As32BitSignedValue => {
+                let i = if let Some(i) = rcv.as_isize(self) {
+                    i as i32 as isize
+                } else {
+                    rcv.downcast::<ArbInt>(self)
+                        .unwrap()
+                        .bigint()
+                        .to_u32_digits()
+                        .1[0] as i32 as isize
+                };
+                let v = Val::from_isize(self, i as isize);
+                self.stack.push(v);
+                SendReturn::Val
+            }
+            Primitive::As32BitUnsignedValue => {
+                let i = if let Some(i) = rcv.as_isize(self) {
+                    i as u32
+                } else {
+                    rcv.downcast::<ArbInt>(self)
+                        .unwrap()
+                        .bigint()
+                        .to_u32_digits()
+                        .1[0] as u32
+                };
+                let v = Val::from_isize(self, i as isize);
+                self.stack.push(v);
+                SendReturn::Val
+            }
             Primitive::At => {
                 let rcv_tobj = stry!(rcv.tobj(self));
                 let arr = stry!(rcv_tobj.to_array());