test/slicecap.go

   1 // run
   2
   3 // Copyright 2014 The Go Authors. All rights reserved.
   4 // Use of this source code is governed by a BSD-style
   5 // license that can be found in the LICENSE file.
   6
   7 package main
   8
   9 import "unsafe"
  10
  11 var (
  12         hello = "hello"
  13         bytes = []byte{1, 2, 3, 4, 5}
  14         ints  = []int32{1, 2, 3, 4, 5}
  15
  16         five = 5
  17
  18         ok = true
  19 )
  20
  21 func notOK() {
  22         if ok {
  23                 println("BUG:")
  24                 ok = false
  25         }
  26 }
  27
  28 func checkString(desc, s string) {
  29         p1 := *(*uintptr)(unsafe.Pointer(&s))
  30         p2 := *(*uintptr)(unsafe.Pointer(&hello))
  31         if p1-p2 >= 5 {
  32                 notOK()
  33                 println("string", desc, "has invalid base")
  34         }
  35 }
  36
  37 func checkBytes(desc string, s []byte) {
  38         p1 := *(*uintptr)(unsafe.Pointer(&s))
  39         p2 := *(*uintptr)(unsafe.Pointer(&bytes))
  40         if p1-p2 >= 5 {
  41                 println("byte slice", desc, "has invalid base")
  42         }
  43 }
  44
  45 func checkInts(desc string, s []int32) {
  46         p1 := *(*uintptr)(unsafe.Pointer(&s))
  47         p2 := *(*uintptr)(unsafe.Pointer(&ints))
  48         if p1-p2 >= 5*4 {
  49                 println("int slice", desc, "has invalid base")
  50         }
  51 }
  52
  53 func main() {
  54         {
  55                 x := hello
  56                 checkString("x", x)
  57                 checkString("x[5:]", x[5:])
  58                 checkString("x[five:]", x[five:])
  59                 checkString("x[5:five]", x[5:five])
  60                 checkString("x[five:5]", x[five:5])
  61                 checkString("x[five:five]", x[five:five])
  62                 checkString("x[1:][2:][2:]", x[1:][2:][2:])
  63                 y := x[4:]
  64                 checkString("y[1:]", y[1:])
  65         }
  66         {
  67                 x := bytes
  68                 checkBytes("x", x)
  69                 checkBytes("x[5:]", x[5:])
  70                 checkBytes("x[five:]", x[five:])
  71                 checkBytes("x[5:five]", x[5:five])
  72                 checkBytes("x[five:5]", x[five:5])
  73                 checkBytes("x[five:five]", x[five:five])
  74                 checkBytes("x[1:][2:][2:]", x[1:][2:][2:])
  75                 y := x[4:]
  76                 checkBytes("y[1:]", y[1:])
  77         }
  78         {
  79                 x := ints
  80                 checkInts("x", x)
  81                 checkInts("x[5:]", x[5:])
  82                 checkInts("x[five:]", x[five:])
  83                 checkInts("x[5:five]", x[5:five])
  84                 checkInts("x[five:5]", x[five:5])
  85                 checkInts("x[five:five]", x[five:five])
  86                 checkInts("x[1:][2:][2:]", x[1:][2:][2:])
  87                 y := x[4:]
  88                 checkInts("y[1:]", y[1:])
  89         }
  90 }