From 90f212df92dabf006aa02151d74d812e18f9949c Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Sun, 4 Dec 2022 10:27:28 -0600
Subject: [PATCH] Add length method ffi/jitfn abstract values.

---
 CHANGELOG.md               | 4 +++-
 examples/jitfn/jitfn.janet | 1 +
 src/core/ffi.c             | 9 ++++++++-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 37b36cc8..94de5684 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,10 +2,12 @@
 All notable changes to this project will be documented in this file.
 
 ## ??? - Unreleased
+- Add `ffi/jitfn` to allow calling function pointers generated at runtime from machine code.
+  Bring your own assembler, though.
 - Channels can now be marshalled. Pending state is not saved, only items in the channel.
 - Use the new `.length` function pointer on abstract types for lengths. Adding
   a `length` method will still work as well.
-- Support byte views on abstract types with the `bytes` function pointer.
+- Support byte views on abstract types with the `.bytes` function pointer.
 - Add the `u` format specifier to printf family functions.
 - Allow printing 64 integer types in `printf` and `string/format` family functions.
 - Allow importing modules from custom directories more easily with the `@` prefix
diff --git a/examples/jitfn/jitfn.janet b/examples/jitfn/jitfn.janet
index 2c668895..5f786c18 100644
--- a/examples/jitfn/jitfn.janet
+++ b/examples/jitfn/jitfn.janet
@@ -10,3 +10,4 @@
 (def signature (ffi/signature :default :void))
 (ffi/call f signature)
 (print "called a jitted function with FFI!")
+(print "machine code: " (describe (string/slice f)))
diff --git a/src/core/ffi.c b/src/core/ffi.c
index 9794626a..3978154a 100644
--- a/src/core/ffi.c
+++ b/src/core/ffi.c
@@ -244,10 +244,17 @@ static JanetByteView janet_ffijit_getbytes(void *p, size_t s) {
     return bytes;
 }
 
+static size_t janet_ffijit_length(void *p, size_t s) {
+    (void) s;
+    JanetFFIJittedFn *fn = p;
+    return fn->size;
+}
+
 const JanetAbstractType janet_type_ffijit = {
     .name = "ffi/jitfn",
     .gc = janet_ffijit_gc,
-    .bytes = janet_ffijit_getbytes
+    .bytes = janet_ffijit_getbytes,
+    .length = janet_ffijit_length
 };
 
 typedef struct {