use reference counting to manage JSON value lifetime

1 files changed, 40 insertions, 0 deletions

diff --git a/src/jv/rc.zig b/src/jv/rc.zig
new file mode 100644
index 0000000..62a4feb
--- /dev/null
+++ b/src/jv/rc.zig
@@ -0,0 +1,40 @@
+const std = @import("std");
+
+pub fn Rc(comptime T: type) type {
+    const Cell = struct {
+        value: T,
+        ref_count: usize,
+    };
+
+    return struct {
+        const Self = @This();
+
+        cell: *Cell,
+
+        pub fn init(allocator: std.mem.Allocator, value: T) std.mem.Allocator.Error!Self {
+            const cell = try allocator.create(Cell);
+            cell.* = .{ .value = value, .ref_count = 1 };
+            return .{ .cell = cell };
+        }
+
+        pub fn release(self: Self, allocator: std.mem.Allocator) void {
+            self.cell.ref_count -= 1;
+            if (self.cell.ref_count == 0) {
+                allocator.destroy(self.cell);
+            }
+        }
+
+        pub fn retain(self: Self) Self {
+            self.cell.ref_count += 1;
+            return .{ .cell = self.cell };
+        }
+
+        pub fn isUnique(self: Self) bool {
+            return self.cell.ref_count == 1;
+        }
+
+        pub fn get(self: Self) *T {
+            return &self.cell.value;
+        }
+    };
+}