Source file src/pkg/unsafe/unsafe.go

     1	// Copyright 2009 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	/*
     6		Package unsafe contains operations that step around the type safety of Go programs.
     7	*/
     8	package unsafe
     9	
    10	// ArbitraryType is here for the purposes of documentation only and is not actually
    11	// part of the unsafe package.  It represents the type of an arbitrary Go expression.
    12	type ArbitraryType int
    13	
    14	// Pointer represents a pointer to an arbitrary type.  There are three special operations
    15	// available for type Pointer that are not available for other types.
    16	//	1) A pointer value of any type can be converted to a Pointer.
    17	//	2) A Pointer can be converted to a pointer value of any type.
    18	//	3) A uintptr can be converted to a Pointer.
    19	//	4) A Pointer can be converted to a uintptr.
    20	// Pointer therefore allows a program to defeat the type system and read and write
    21	// arbitrary memory. It should be used with extreme care.
    22	type Pointer *ArbitraryType
    23	
    24	// Sizeof returns the size in bytes occupied by the value v.  The size is that of the
    25	// "top level" of the value only.  For instance, if v is a slice, it returns the size of
    26	// the slice descriptor, not the size of the memory referenced by the slice.
    27	func Sizeof(v ArbitraryType) uintptr
    28	
    29	// Offsetof returns the offset within the struct of the field represented by v,
    30	// which must be of the form structValue.field.  In other words, it returns the
    31	// number of bytes between the start of the struct and the start of the field.
    32	func Offsetof(v ArbitraryType) uintptr
    33	
    34	// Alignof returns the alignment of the value v.  It is the maximum value m such
    35	// that the address of a variable with the type of v will always always be zero mod m.
    36	// If v is of the form structValue.field, it returns the alignment of field f within struct object obj.
    37	func Alignof(v ArbitraryType) uintptr