From 42b6f9d23ab0f94744a90edb6fd74450f589ca14 Mon Sep 17 00:00:00 2001
From: Johannes Stoelp <johannes.stoelp@gmail.com>
Date: Wed, 18 Dec 2024 23:13:12 +0100
Subject: interface: minimal example for a runtime dispatch

---
 example-interface/Makefile |  2 ++
 example-interface/main.zig | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100644 example-interface/Makefile
 create mode 100644 example-interface/main.zig

(limited to 'example-interface')

diff --git a/example-interface/Makefile b/example-interface/Makefile
new file mode 100644
index 0000000..6576ece
--- /dev/null
+++ b/example-interface/Makefile
@@ -0,0 +1,2 @@
+run:
+	zig run main.zig
diff --git a/example-interface/main.zig b/example-interface/main.zig
new file mode 100644
index 0000000..085aa82
--- /dev/null
+++ b/example-interface/main.zig
@@ -0,0 +1,45 @@
+const std = @import("std");
+
+/// Interface type, holding a pointer to the object and the interface function pointers.
+const Iter = struct {
+    ptr: *anyopaque,
+    next_fn: *const fn (*anyopaque) ?i32,
+
+    /// Convenience wrapper to call vtable function.
+    pub fn next(self: Iter) ?i32 {
+        return self.next_fn(self.ptr);
+    }
+};
+
+const UpIter = struct {
+    end: i32,
+    now: i32 = 0,
+
+    /// Create an Inter interface object from UpIter.
+    pub fn iter(self: *UpIter) Iter {
+        return Iter{ .ptr = self, .next_fn = next };
+    }
+
+    pub fn next(ptr: *anyopaque) ?i32 {
+        const self: *UpIter = @alignCast(@ptrCast(ptr));
+        if (self.now < self.end) {
+            self.now += 1;
+            return self.now;
+        } else {
+            return null;
+        }
+    }
+};
+
+/// Function example taking an Iter interface object.
+fn run_iter(iter: Iter) void {
+    while (iter.next()) |v| {
+        std.debug.print("{},", .{v});
+    }
+    std.debug.print("\n", .{});
+}
+
+pub fn main() void {
+    var uit = UpIter{ .end = 10 };
+    run_iter(uit.iter());
+}
-- 
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