mirror of
https://github.com/golang/go
synced 2024-11-23 04:10:04 -07:00
86 lines
1.3 KiB
Go
86 lines
1.3 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package eval
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/*
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* Virtual machine
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*/
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type vm struct {
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pc uint;
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// The execution frame of this function. This remains the
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// same throughout a function invocation.
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f *Frame;
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}
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type code []func(*vm)
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func (i code) exec(fr *Frame) {
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v := vm{0, fr};
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l := uint(len(i));
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for v.pc < l {
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pc := v.pc;
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v.pc++;
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i[pc](&v);
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}
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}
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/*
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* Code buffer
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*/
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type codeBuf struct {
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instrs code;
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}
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func newCodeBuf() *codeBuf {
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return &codeBuf{make(code, 0, 16)};
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}
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func (b *codeBuf) push(instr func(*vm)) {
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n := len(b.instrs);
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if n >= cap(b.instrs) {
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a := make(code, n, n*2);
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for i := range b.instrs {
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a[i] = b.instrs[i];
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}
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b.instrs = a;
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}
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b.instrs = b.instrs[0:n+1];
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b.instrs[n] = instr;
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}
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func (b *codeBuf) nextPC() uint {
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return uint(len(b.instrs));
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}
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func (b *codeBuf) get() code {
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// Freeze this buffer into an array of exactly the right size
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a := make(code, len(b.instrs));
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for i := range b.instrs {
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a[i] = b.instrs[i];
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}
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return code(a);
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}
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/*
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* User-defined functions
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*/
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type evalFunc struct {
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outer *Frame;
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frameSize int;
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code code;
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}
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func (f *evalFunc) NewFrame() *Frame {
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return f.outer.child(f.frameSize);
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}
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func (f *evalFunc) Call(fr *Frame) {
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f.code.exec(fr);
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}
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