Source file src/pkg/exp/eval/func.go

// 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) }