1 files changed, 89 insertions, 0 deletions
diff --git a/src/pkg/exp/eval/func.go b/src/pkg/exp/eval/func.go
new file mode 100644
index 000000000..3bf52871d
--- /dev/null
+++ b/src/pkg/exp/eval/func.go
@@ -0,0 +1,89 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package eval
+
+import "os"
+
+/*
+ * Virtual machine
+ */
+
+type Thread struct {
+	abort chan os.Error;
+	pc uint;
+	// The execution frame of this function.  This remains the
+	// same throughout a function invocation.
+	f *Frame;
+}
+
+type code []func(*Thread)
+
+func (i code) exec(t *Thread) {
+	opc := t.pc;
+	t.pc = 0;
+	l := uint(len(i));
+	for t.pc < l {
+		pc := t.pc;
+		t.pc++;
+		i[pc](t);
+	}
+	t.pc = opc;
+}
+
+/*
+ * Code buffer
+ */
+
+type codeBuf struct {
+	instrs code;
+}
+
+func newCodeBuf() *codeBuf {
+	return &codeBuf{make(code, 0, 16)};
+}
+
+func (b *codeBuf) push(instr func(*Thread)) {
+	n := len(b.instrs);
+	if n >= cap(b.instrs) {
+		a := make(code, n, n*2);
+		for i := range b.instrs {
+			a[i] = b.instrs[i];
+		}
+		b.instrs = a;
+	}
+	b.instrs = b.instrs[0:n+1];
+	b.instrs[n] = instr;
+}
+
+func (b *codeBuf) nextPC() uint {
+	return uint(len(b.instrs));
+}
+
+func (b *codeBuf) get() code {
+	// Freeze this buffer into an array of exactly the right size
+	a := make(code, len(b.instrs));
+	for i := range b.instrs {
+		a[i] = b.instrs[i];
+	}
+	return code(a);
+}
+
+/*
+ * User-defined functions
+ */
+
+type evalFunc struct {
+	outer *Frame;
+	frameSize int;
+	code code;
+}
+
+func (f *evalFunc) NewFrame() *Frame {
+	return f.outer.child(f.frameSize);
+}
+
+func (f *evalFunc) Call(t *Thread) {
+	f.code.exec(t);
+}