github.com/go-darwin/sys@v0.0.0-20220510002607-68fd01f054ca/unsafeheader/unsafeheader_test.go (about)

     1  // Copyright 2020 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package unsafeheader_test
     6  
     7  import (
     8  	"bytes"
     9  	"reflect"
    10  	"testing"
    11  	"unsafe"
    12  
    13  	"github.com/go-darwin/sys/unsafeheader"
    14  )
    15  
    16  // TestTypeMatchesReflectType ensures that the name and layout of the
    17  // unsafeheader types matches the corresponding Header types in the reflect
    18  // package.
    19  func TestTypeMatchesReflectType(t *testing.T) {
    20  	t.Run("Slice", func(t *testing.T) {
    21  		testHeaderMatchesReflect(t, unsafeheader.Slice{}, reflect.SliceHeader{})
    22  	})
    23  
    24  	t.Run("String", func(t *testing.T) {
    25  		testHeaderMatchesReflect(t, unsafeheader.String{}, reflect.StringHeader{})
    26  	})
    27  }
    28  
    29  func testHeaderMatchesReflect(t *testing.T, header, reflectHeader interface{}) {
    30  	h := reflect.TypeOf(header)
    31  	rh := reflect.TypeOf(reflectHeader)
    32  
    33  	for i := 0; i < h.NumField(); i++ {
    34  		f := h.Field(i)
    35  		rf, ok := rh.FieldByName(f.Name)
    36  		if !ok {
    37  			t.Errorf("Field %d of %v is named %s, but no such field exists in %v", i, h, f.Name, rh)
    38  			continue
    39  		}
    40  		if !typeCompatible(f.Type, rf.Type) {
    41  			t.Errorf("%v.%s has type %v, but %v.%s has type %v", h, f.Name, f.Type, rh, rf.Name, rf.Type)
    42  		}
    43  		if f.Offset != rf.Offset {
    44  			t.Errorf("%v.%s has offset %d, but %v.%s has offset %d", h, f.Name, f.Offset, rh, rf.Name, rf.Offset)
    45  		}
    46  	}
    47  
    48  	if h.NumField() != rh.NumField() {
    49  		t.Errorf("%v has %d fields, but %v has %d", h, h.NumField(), rh, rh.NumField())
    50  	}
    51  	if h.Align() != rh.Align() {
    52  		t.Errorf("%v has alignment %d, but %v has alignment %d", h, h.Align(), rh, rh.Align())
    53  	}
    54  }
    55  
    56  var (
    57  	unsafePointerType = reflect.TypeOf(unsafe.Pointer(nil))
    58  	uintptrType       = reflect.TypeOf(uintptr(0))
    59  )
    60  
    61  func typeCompatible(t, rt reflect.Type) bool {
    62  	return t == rt || (t == unsafePointerType && rt == uintptrType)
    63  }
    64  
    65  // TestWriteThroughHeader ensures that the headers in the unsafeheader package
    66  // can successfully mutate variables of the corresponding built-in types.
    67  //
    68  // This test is expected to fail under -race (which implicitly enables
    69  // -d=checkptr) if the runtime views the header types as incompatible with the
    70  // underlying built-in types.
    71  func TestWriteThroughHeader(t *testing.T) {
    72  	t.Run("Slice", func(t *testing.T) {
    73  		s := []byte("Hello, checkptr!")[:5]
    74  
    75  		var alias []byte
    76  		hdr := (*unsafeheader.Slice)(unsafe.Pointer(&alias))
    77  		hdr.Data = unsafe.Pointer(&s[0])
    78  		hdr.Cap = cap(s)
    79  		hdr.Len = len(s)
    80  
    81  		if !bytes.Equal(alias, s) {
    82  			t.Errorf("alias of %T(%q) constructed via Slice = %T(%q)", s, s, alias, alias)
    83  		}
    84  		if cap(alias) != cap(s) {
    85  			t.Errorf("alias of %T with cap %d has cap %d", s, cap(s), cap(alias))
    86  		}
    87  	})
    88  
    89  	t.Run("String", func(t *testing.T) {
    90  		s := "Hello, checkptr!"
    91  
    92  		var alias string
    93  		hdr := (*unsafeheader.String)(unsafe.Pointer(&alias))
    94  		hdr.Data = (*unsafeheader.String)(unsafe.Pointer(&s)).Data
    95  		hdr.Len = len(s)
    96  
    97  		if alias != s {
    98  			t.Errorf("alias of %q constructed via String = %q", s, alias)
    99  		}
   100  	})
   101  }