forked from jshiffer/matterbridge
60 lines
1.4 KiB
Go
60 lines
1.4 KiB
Go
// Copyright 2023 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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// package tokeninternal provides access to some internal features of the token
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// package.
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package tokeninternal
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import (
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"go/token"
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"sync"
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"unsafe"
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)
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// GetLines returns the table of line-start offsets from a token.File.
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func GetLines(file *token.File) []int {
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// token.File has a Lines method on Go 1.21 and later.
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if file, ok := (interface{})(file).(interface{ Lines() []int }); ok {
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return file.Lines()
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}
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// This declaration must match that of token.File.
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// This creates a risk of dependency skew.
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// For now we check that the size of the two
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// declarations is the same, on the (fragile) assumption
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// that future changes would add fields.
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type tokenFile119 struct {
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_ string
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_ int
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_ int
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mu sync.Mutex // we're not complete monsters
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lines []int
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_ []struct{}
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}
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type tokenFile118 struct {
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_ *token.FileSet // deleted in go1.19
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tokenFile119
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}
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type uP = unsafe.Pointer
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switch unsafe.Sizeof(*file) {
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case unsafe.Sizeof(tokenFile118{}):
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var ptr *tokenFile118
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*(*uP)(uP(&ptr)) = uP(file)
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ptr.mu.Lock()
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defer ptr.mu.Unlock()
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return ptr.lines
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case unsafe.Sizeof(tokenFile119{}):
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var ptr *tokenFile119
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*(*uP)(uP(&ptr)) = uP(file)
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ptr.mu.Lock()
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defer ptr.mu.Unlock()
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return ptr.lines
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default:
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panic("unexpected token.File size")
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}
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}
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