121 lines
3.9 KiB
Go
121 lines
3.9 KiB
Go
/*
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* Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package reflect
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import (
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"unsafe"
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"github.com/goplus/llgo/internal/abi"
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)
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// Value is the reflection interface to a Go value.
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//
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// Not all methods apply to all kinds of values. Restrictions,
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// if any, are noted in the documentation for each method.
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// Use the Kind method to find out the kind of value before
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// calling kind-specific methods. Calling a method
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// inappropriate to the kind of type causes a run time panic.
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//
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// The zero Value represents no value.
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// Its IsValid method returns false, its Kind method returns Invalid,
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// its String method returns "<invalid Value>", and all other methods panic.
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// Most functions and methods never return an invalid value.
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// If one does, its documentation states the conditions explicitly.
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//
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// A Value can be used concurrently by multiple goroutines provided that
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// the underlying Go value can be used concurrently for the equivalent
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// direct operations.
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//
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// To compare two Values, compare the results of the Interface method.
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// Using == on two Values does not compare the underlying values
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// they represent.
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type Value struct {
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// typ_ holds the type of the value represented by a Value.
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// Access using the typ method to avoid escape of v.
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typ_ *abi.Type
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// Pointer-valued data or, if flagIndir is set, pointer to data.
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// Valid when either flagIndir is set or typ.pointers() is true.
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ptr unsafe.Pointer
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// flag holds metadata about the value.
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//
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// The lowest five bits give the Kind of the value, mirroring typ.Kind().
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//
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// The next set of bits are flag bits:
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// - flagStickyRO: obtained via unexported not embedded field, so read-only
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// - flagEmbedRO: obtained via unexported embedded field, so read-only
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// - flagIndir: val holds a pointer to the data
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// - flagAddr: v.CanAddr is true (implies flagIndir and ptr is non-nil)
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// - flagMethod: v is a method value.
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// If ifaceIndir(typ), code can assume that flagIndir is set.
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//
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// The remaining 22+ bits give a method number for method values.
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// If flag.kind() != Func, code can assume that flagMethod is unset.
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flag
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// A method value represents a curried method invocation
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// like r.Read for some receiver r. The typ+val+flag bits describe
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// the receiver r, but the flag's Kind bits say Func (methods are
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// functions), and the top bits of the flag give the method number
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// in r's type's method table.
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}
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type flag uintptr
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const (
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flagKindWidth = 5 // there are 27 kinds
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flagKindMask flag = 1<<flagKindWidth - 1
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flagStickyRO flag = 1 << 5
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flagEmbedRO flag = 1 << 6
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flagIndir flag = 1 << 7
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flagAddr flag = 1 << 8
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flagMethod flag = 1 << 9
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flagMethodShift = 10
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flagRO flag = flagStickyRO | flagEmbedRO
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)
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func (f flag) kind() Kind {
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return Kind(f & flagKindMask)
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}
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func (f flag) ro() flag {
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if f&flagRO != 0 {
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return flagStickyRO
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}
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return 0
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}
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// emptyInterface is the header for an interface{} value.
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type emptyInterface struct {
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typ *abi.Type
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word unsafe.Pointer
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}
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// nonEmptyInterface is the header for an interface value with methods.
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type nonEmptyInterface struct {
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// see ../runtime/iface.go:/Itab
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itab *struct {
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ityp *abi.Type // static interface type
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typ *abi.Type // dynamic concrete type
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hash uint32 // copy of typ.hash
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_ [4]byte
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fun [100000]unsafe.Pointer // method table
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}
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word unsafe.Pointer
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}
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