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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 (
"container/vector";
"eval";
)
/*
* Virtual machine
*/
type vm struct {
pc uint;
// The current execution frame. If execution is within a
// block, this may be a child of the original function
// activation frame.
f *Frame;
// The original function activation frame. This is used to
// access function out args.
activation *Frame;
}
type code []func(*vm)
func (i code) exec(fr *Frame) {
v := vm{0, fr, fr};
l := uint(len(i));
for v.pc < l {
pc := v.pc;
v.pc++;
i[pc](&v);
}
}
/*
* Code buffer
*/
type codeBuf struct {
instrs code;
}
func newCodeBuf() *codeBuf {
return &codeBuf{make(code, 0, 16)};
}
func (b *codeBuf) push(instr func(*vm)) {
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 {
sc *Scope;
fr *Frame;
code code;
}
func (f *evalFunc) NewFrame() *Frame {
return f.sc.NewFrame(f.fr);
}
func (f *evalFunc) Call(fr *Frame) {
f.code.exec(fr);
}
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