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Source file test/chancap.go

Documentation: test

  // run
  
  // 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.
  
  // Test the cap predeclared function applied to channels.
  
  package main
  
  import (
  	"strings"
  	"unsafe"
  )
  
  type T chan int
  
  const ptrSize = unsafe.Sizeof((*byte)(nil))
  
  func main() {
  	c := make(T, 10)
  	if len(c) != 0 || cap(c) != 10 {
  		println("chan len/cap ", len(c), cap(c), " want 0 10")
  		panic("fail")
  	}
  
  	for i := 0; i < 3; i++ {
  		c <- i
  	}
  	if len(c) != 3 || cap(c) != 10 {
  		println("chan len/cap ", len(c), cap(c), " want 3 10")
  		panic("fail")
  	}
  
  	c = make(T)
  	if len(c) != 0 || cap(c) != 0 {
  		println("chan len/cap ", len(c), cap(c), " want 0 0")
  		panic("fail")
  	}
  
  	n := -1
  	shouldPanic("makechan: size out of range", func() { _ = make(T, n) })
  	shouldPanic("makechan: size out of range", func() { _ = make(T, int64(n)) })
  	if ptrSize == 8 {
  		n = 1 << 20
  		n <<= 20
  		shouldPanic("makechan: size out of range", func() { _ = make(T, n) })
  		n <<= 20
  		shouldPanic("makechan: size out of range", func() { _ = make(T, n) })
  	} else {
  		n = 1<<31 - 1
  		shouldPanic("makechan: size out of range", func() { _ = make(T, n) })
  		shouldPanic("makechan: size out of range", func() { _ = make(T, int64(n)) })
  	}
  }
  
  func shouldPanic(str string, f func()) {
  	defer func() {
  		err := recover()
  		if err == nil {
  			panic("did not panic")
  		}
  		s := err.(error).Error()
  		if !strings.Contains(s, str) {
  			panic("got panic " + s + ", want " + str)
  		}
  	}()
  
  	f()
  }
  

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