From 1fe9d2cb0223ecc21aeb547d80e9429698b92477 Mon Sep 17 00:00:00 2001
From: Joshua Suskalo <joshua@iris.tv>
Date: Thu, 23 Sep 2021 08:15:16 -0500
Subject: [PATCH] Move library loading interop to a java class

---
 build.clj                      | 12 +++++++++-
 deps.edn                       |  2 +-
 src/{ => clj}/coffi/ffi.clj    |  8 +++----
 src/java/coffi/ffi/Loader.java | 43 ++++++++++++++++++++++++++++++++++
 4 files changed, 59 insertions(+), 6 deletions(-)
 rename src/{ => clj}/coffi/ffi.clj (99%)
 create mode 100644 src/java/coffi/ffi/Loader.java

diff --git a/build.clj b/build.clj
index 1597ce4..856d970 100644
--- a/build.clj
+++ b/build.clj
@@ -19,7 +19,8 @@
 (def lib-coord 'org.suskalo/coffi)
 (def version (format "0.1.%s-SNAPSHOT" (b/git-count-revs nil)))
 
-(def source-dirs ["src/"])
+(def source-dirs ["src/clj/"])
+(def java-source-dirs ["src/java/"])
 
 (def c-test-dirs ["test/c/"])
 
@@ -42,6 +43,15 @@
   [& path-components]
   (.exists ^java.io.File (apply io/file path-components)))
 
+(defn compile-java
+  "Compiles java classes required for interop."
+  [opts]
+  (.mkdirs (io/file class-dir))
+  (b/process {:command-args ["javac" "--add-modules=jdk.incubator.foreign"
+                             "src/java/coffi/ffi/Loader.java"
+                             "-d" class-dir]})
+  opts)
+
 (defn- write-pom
   "Writes a pom file if one does not already exist."
   [opts]
diff --git a/deps.edn b/deps.edn
index 35e6310..4e3c4ee 100644
--- a/deps.edn
+++ b/deps.edn
@@ -1,4 +1,4 @@
-{:paths ["src"]
+{:paths ["src" "target/classes"]
  :deps {org.clojure/clojure {:mvn/version "1.10.3"}
         insn/insn {:mvn/version "0.2.1"}}
  :aliases
diff --git a/src/coffi/ffi.clj b/src/clj/coffi/ffi.clj
similarity index 99%
rename from src/coffi/ffi.clj
rename to src/clj/coffi/ffi.clj
index fb5bbc7..70779d8 100644
--- a/src/coffi/ffi.clj
+++ b/src/clj/coffi/ffi.clj
@@ -7,6 +7,7 @@
   (:import
    (clojure.lang
     IDeref IFn IMeta IObj IReference)
+   (coffi.ffi Loader)
    (java.lang.invoke
     MethodHandle
     MethodHandles
@@ -567,19 +568,18 @@
 (defn load-system-library
   "Loads the library named `libname` from the system's load path."
   [libname]
-  (System/loadLibrary (name libname)))
+  (Loader/loadSystemLibrary (name libname)))
 
 (defn load-library
   "Loads the library at `path`."
   [path]
-  (System/load (.getAbsolutePath (io/file path))))
+  (Loader/loadLibrary (.getAbsolutePath (io/file path))))
 
 (defn find-symbol
   "Gets the [[MemoryAddress]] of a symbol from the loaded libraries."
   [sym]
   (let [sym (name sym)]
-    (or (.. (CLinker/systemLookup) (lookup sym) (orElse nil))
-        (.. (SymbolLookup/loaderLookup) (lookup sym) (orElse nil)))))
+    (Loader/findSymbol sym)))
 
 (defn- method-type
   "Gets the [[MethodType]] for a set of `args` and `ret` types."
diff --git a/src/java/coffi/ffi/Loader.java b/src/java/coffi/ffi/Loader.java
new file mode 100644
index 0000000..b06d00f
--- /dev/null
+++ b/src/java/coffi/ffi/Loader.java
@@ -0,0 +1,43 @@
+package coffi.ffi;
+
+import jdk.incubator.foreign.*;
+
+/**
+ * Loading libraries with the {@link System#load} and {@link System#loadLibrary}
+ * relies on the classloader, which Clojure messes with. This class exists to
+ * have a consistent classloader, providing a consistent way to load libraries
+ * and symbols from them.
+ */
+public class Loader {
+
+    /**
+     * Loads a library from a given absolute file path.
+     *
+     * @param filepath The absolute file path of the library to load
+     */
+    public static void loadLibrary(String filepath) {
+        System.load(filepath);
+    }
+
+    /**
+     * Loads a library on the system loadpath with the given name.
+     *
+     * @param libname The library name, stripped of platform-specific prefixes and suffixes.
+     */
+    public static void loadSystemLibrary(String libname) {
+        System.loadLibrary(libname);
+    }
+
+    /**
+     * Load the memory address of a symbol.
+     *
+     * First attempts to load the symbol from system libraries, like libc, and
+     * afterwards attempts to load the symbol from other libraries.
+     *
+     * @param symbol The name of the symbol to load from a library.
+     */
+    public static MemoryAddress findSymbol(String symbol) {
+        return CLinker.systemLookup().lookup(symbol)
+            .orElseGet(() -> SymbolLookup.loaderLookup().lookup(symbol).orElse(null));
+    }
+}