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https://github.com/gopl-zh/gopl-zh.github.com.git
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41 lines
831 B
Go
41 lines
831 B
Go
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// See page 146.
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// The trace program uses defer to add entry/exit diagnostics to a function.
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package main
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import (
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"log"
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"time"
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)
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//!+main
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func bigSlowOperation() {
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defer trace("bigSlowOperation")() // don't forget the extra parentheses
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// ...lots of work...
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time.Sleep(10 * time.Second) // simulate slow operation by sleeping
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}
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func trace(msg string) func() {
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start := time.Now()
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log.Printf("enter %s", msg)
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return func() { log.Printf("exit %s (%s)", msg, time.Since(start)) }
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}
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//!-main
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func main() {
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bigSlowOperation()
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}
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/*
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!+output
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$ go build gopl.io/ch5/trace
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$ ./trace
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2015/11/18 09:53:26 enter bigSlowOperation
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2015/11/18 09:53:36 exit bigSlowOperation (10.000589217s)
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!-output
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*/
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