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 Packages that import unsafe may be non-portable and are not protected by the 9 Go 1 compatibility guidelines. 10 */ 11 package unsafe 12 13 // ArbitraryType is here for the purposes of documentation only and is not actually 14 // part of the unsafe package. It represents the type of an arbitrary Go expression. 15 type ArbitraryType int 16 17 // Pointer represents a pointer to an arbitrary type. There are four special operations 18 // available for type Pointer that are not available for other types. 19 // 1) A pointer value of any type can be converted to a Pointer. 20 // 2) A Pointer can be converted to a pointer value of any type. 21 // 3) A uintptr can be converted to a Pointer. 22 // 4) A Pointer can be converted to a uintptr. 23 // Pointer therefore allows a program to defeat the type system and read and write 24 // arbitrary memory. It should be used with extreme care. 25 type Pointer *ArbitraryType 26 27 // Sizeof takes an expression x of any type and returns the size in bytes 28 // of a hypothetical variable v as if v was declared via var v = x. 29 // The size does not include any memory possibly referenced by x. 30 // For instance, if x is a slice, Sizeof returns the size of the slice 31 // descriptor, not the size of the memory referenced by the slice. 32 func Sizeof(x ArbitraryType) uintptr 33 34 // Offsetof returns the offset within the struct of the field represented by x, 35 // which must be of the form structValue.field. In other words, it returns the 36 // number of bytes between the start of the struct and the start of the field. 37 func Offsetof(x ArbitraryType) uintptr 38 39 // Alignof takes an expression x of any type and returns the alignment 40 // of a hypothetical variable v as if v was declared via var v = x. 41 // It is the largest value m such that the address of v is zero mod m. 42 func Alignof(x ArbitraryType) uintptr 43
