1 files changed, 75 insertions, 0 deletions
diff --git a/src/libzisp/value/rune.zig b/src/libzisp/value/rune.zig
new file mode 100644
index 0000000..ab251b4
--- /dev/null
+++ b/src/libzisp/value/rune.zig
@@ -0,0 +1,75 @@
+const std = @import("std");
+
+const value = @import("../value.zig");
+
+const Value = value.Value;
+
+// Zig API
+
+pub fn check(v: Value) bool {
+    return v.isOther(.rune);
+}
+
+pub fn assert(v: Value) void {
+    if (!check(v)) {
+        v.dump();
+        @panic("not rune");
+    }
+}
+
+pub fn isValidRune(s: []const u8) bool {
+    if (s.len == 0 or s.len > 6) {
+        return false;
+    }
+    for (s) |c| {
+        switch (c) {
+            'A'...'Z' => {},
+            'a'...'z' => {},
+            else => return false,
+        }
+    }
+    return true;
+}
+
+fn assertValidRune(s: []const u8) void {
+    if (!isValidRune(s)) {
+        std.debug.print("invalid rune: '{s}'\n", .{s});
+        @panic("invalid rune");
+    }
+}
+
+// See sstr.zig which uses equivalent code; probably good to keep in sync.
+
+pub fn pack(s: []const u8) Value {
+    assertValidRune(s);
+    var v = Value{ .rune = .{ .name = 0 } };
+    const dest: [*]u8 = @ptrCast(&v.rune.name);
+    @memcpy(dest, s);
+    return v;
+}
+
+pub fn unpack(v: Value) struct { [6]u8, u3 } {
+    const s: [6]u8 = @bitCast(v.rune.name);
+    inline for (0..6) |i| {
+        if (s[i] == 0) return .{ s, i };
+    }
+    return .{ s, 6 };
+}
+
+// Zisp API
+
+pub fn pred(v: Value) Value {
+    return value.boole.pack(check(v));
+}
+
+pub fn make(v: Value) Value {
+    const s, const l = value.sstr.unpack(v);
+    return pack(s[0..l]);
+}
+
+pub fn getName(v: Value) Value {
+    const s, const l = unpack(v);
+    return value.sstr.pack(s[0..l]);
+}
+
+// TODO: Registering decoders