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// 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) }
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