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68add46af7
Reflection is about Pointer, not uintptr. Also clarify that Reflect and Unreflect are indirect. R=rsc CC=golang-dev https://golang.org/cl/4254052
62 lines
3.1 KiB
Go
62 lines
3.1 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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The unsafe package contains operations that step around the type safety of Go programs.
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*/
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package unsafe
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// ArbitraryType is here for the purposes of documentation only and is not actually
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// part of the unsafe package. It represents the type of an arbitrary Go expression.
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type ArbitraryType int
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// Pointer represents a pointer to an arbitrary type. There are three special operations
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// available for type Pointer that are not available for other types.
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// 1) A pointer value of any type can be converted to a Pointer.
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// 2) A Pointer can be converted to a pointer value of any type.
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// 3) A uintptr can be converted to a Pointer.
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// 4) A Pointer can be converted to a uintptr.
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// Pointer therefore allows a program to defeat the type system and read and write
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// arbitrary memory. It should be used with extreme care.
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type Pointer *ArbitraryType
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// Sizeof returns the size in bytes occupied by the value v. The size is that of the
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// "top level" of the value only. For instance, if v is a slice, it returns the size of
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// the slice descriptor, not the size of the memory referenced by the slice.
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func Sizeof(v ArbitraryType) int
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// Offsetof returns the offset within the struct of the field represented by v,
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// which must be of the form struct_value.field. In other words, it returns the
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// number of bytes between the start of the struct and the start of the field.
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func Offsetof(v ArbitraryType) int
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// Alignof returns the alignment of the value v. It is the maximum value m such
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// that the address of a variable with the type of v will always always be zero mod m.
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// If v is of the form obj.f, it returns the alignment of field f within struct object obj.
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func Alignof(v ArbitraryType) int
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// Typeof returns the type of an interface value, a runtime.Type.
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func Typeof(i interface{}) (typ interface{})
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// Reflect unpacks an interface value into its type and the address of a copy of the
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// internal value.
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func Reflect(i interface{}) (typ interface{}, addr Pointer)
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// Unreflect inverts Reflect: Given a type and a pointer to a value, it returns an
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// empty interface value with contents the type and the value (not the pointer to
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// the value). The typ is assumed to contain a pointer to a runtime type; the type
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// information in the interface{} is ignored, so that, for example, both
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// *reflect.StructType and *runtime.StructType can be passed for typ.
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func Unreflect(typ interface{}, addr Pointer) (ret interface{})
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// New allocates and returns a pointer to memory for a new value of the given type.
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// The typ is assumed to hold a pointer to a runtime type.
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// Callers should use reflect.MakeZero instead of invoking unsafe.New directly.
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func New(typ interface{}) Pointer
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// NewArray allocates and returns a pointer to an array of n elements of the given type.
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// The typ is assumed to hold a pointer to a runtime type.
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// Callers should use reflect.MakeSlice instead of invoking unsafe.NewArray directly.
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func NewArray(typ interface{}, n int) Pointer
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