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Source file test/slicecap.go

Documentation: test

  // run
  
  // Copyright 2014 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 main
  
  import "unsafe"
  
  var (
  	hello = "hello"
  	bytes = []byte{1, 2, 3, 4, 5}
  	ints  = []int32{1, 2, 3, 4, 5}
  
  	five = 5
  
  	ok = true
  )
  
  func notOK() {
  	if ok {
  		println("BUG:")
  		ok = false
  	}
  }
  
  func checkString(desc, s string) {
  	p1 := *(*uintptr)(unsafe.Pointer(&s))
  	p2 := *(*uintptr)(unsafe.Pointer(&hello))
  	if p1-p2 >= 5 {
  		notOK()
  		println("string", desc, "has invalid base")
  	}
  }
  
  func checkBytes(desc string, s []byte) {
  	p1 := *(*uintptr)(unsafe.Pointer(&s))
  	p2 := *(*uintptr)(unsafe.Pointer(&bytes))
  	if p1-p2 >= 5 {
  		println("byte slice", desc, "has invalid base")
  	}
  }
  
  func checkInts(desc string, s []int32) {
  	p1 := *(*uintptr)(unsafe.Pointer(&s))
  	p2 := *(*uintptr)(unsafe.Pointer(&ints))
  	if p1-p2 >= 5*4 {
  		println("int slice", desc, "has invalid base")
  	}
  }
  
  func main() {
  	{
  		x := hello
  		checkString("x", x)
  		checkString("x[5:]", x[5:])
  		checkString("x[five:]", x[five:])
  		checkString("x[5:five]", x[5:five])
  		checkString("x[five:5]", x[five:5])
  		checkString("x[five:five]", x[five:five])
  		checkString("x[1:][2:][2:]", x[1:][2:][2:])
  		y := x[4:]
  		checkString("y[1:]", y[1:])
  	}
  	{
  		x := bytes
  		checkBytes("x", x)
  		checkBytes("x[5:]", x[5:])
  		checkBytes("x[five:]", x[five:])
  		checkBytes("x[5:five]", x[5:five])
  		checkBytes("x[five:5]", x[five:5])
  		checkBytes("x[five:five]", x[five:five])
  		checkBytes("x[1:][2:][2:]", x[1:][2:][2:])
  		y := x[4:]
  		checkBytes("y[1:]", y[1:])
  	}
  	{
  		x := ints
  		checkInts("x", x)
  		checkInts("x[5:]", x[5:])
  		checkInts("x[five:]", x[five:])
  		checkInts("x[5:five]", x[5:five])
  		checkInts("x[five:5]", x[five:5])
  		checkInts("x[five:five]", x[five:five])
  		checkInts("x[1:][2:][2:]", x[1:][2:][2:])
  		y := x[4:]
  		checkInts("y[1:]", y[1:])
  	}
  }
  

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