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https://github.com/protocolbuffers/protobuf-go.git
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bc534a98a5
The purego tag (see https://golang.org/issue/23172) is a community agreed upon signal that a given build environment does not support unsafe. The appengine environment is supposed to respect this tag, but does not properly do so. Add this tag back in until they fix their environment. Change-Id: I9a70062be4339c2e1a93cac31d387698c561b8aa Reviewed-on: https://go-review.googlesource.com/c/154743 Reviewed-by: Damien Neil <dneil@google.com>
65 lines
1.8 KiB
Go
65 lines
1.8 KiB
Go
// Copyright 2018 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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// +build purego appengine
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package impl
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import (
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"fmt"
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"reflect"
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)
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// offset represents the offset to a struct field, accessible from a pointer.
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// The offset is the field index into a struct.
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type offset []int
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// offsetOf returns a field offset for the struct field.
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func offsetOf(f reflect.StructField) offset {
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if len(f.Index) != 1 {
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panic("embedded structs are not supported")
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}
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return f.Index
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}
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// pointer is an abstract representation of a pointer to a struct or field.
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type pointer struct{ v reflect.Value }
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// pointerOfValue returns v as a pointer.
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func pointerOfValue(v reflect.Value) pointer {
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return pointer{v: v}
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}
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// pointerOfIface returns the pointer portion of an interface.
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func pointerOfIface(v interface{}) pointer {
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return pointer{v: reflect.ValueOf(v)}
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}
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// IsNil reports whether the pointer is nil.
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func (p pointer) IsNil() bool {
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return p.v.IsNil()
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}
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// Apply adds an offset to the pointer to derive a new pointer
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// to a specified field. The current pointer must be pointing at a struct.
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func (p pointer) Apply(f offset) pointer {
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// TODO: Handle unexported fields in an API that hides XXX fields?
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return pointer{v: p.v.Elem().FieldByIndex(f).Addr()}
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}
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// AsValueOf treats p as a pointer to an object of type t and returns the value.
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// It is equivalent to reflect.ValueOf(p.AsIfaceOf(t))
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func (p pointer) AsValueOf(t reflect.Type) reflect.Value {
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if p.v.Type().Elem() != t {
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panic(fmt.Sprintf("invalid type: got %v, want %v", p.v.Type(), t))
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}
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return p.v
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}
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// AsIfaceOf treats p as a pointer to an object of type t and returns the value.
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// It is equivalent to p.AsValueOf(t).Interface()
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func (p pointer) AsIfaceOf(t reflect.Type) interface{} {
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return p.AsValueOf(t).Interface()
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}
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