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// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// package tokeninternal provides access to some internal features of the token
// package.
package tokeninternal
import (
"fmt"
"go/token"
"sort"
"sync"
"unsafe"
)
// GetLines returns the table of line-start offsets from a token.File.
func GetLines(file *token.File) []int {
// token.File has a Lines method on Go 1.21 and later.
if file, ok := (interface{})(file).(interface{ Lines() []int }); ok {
return file.Lines()
}
// This declaration must match that of token.File.
// This creates a risk of dependency skew.
// For now we check that the size of the two
// declarations is the same, on the (fragile) assumption
// that future changes would add fields.
type tokenFile119 struct {
_ string
_ int
_ int
mu sync.Mutex // we're not complete monsters
lines []int
_ []struct{}
}
if unsafe.Sizeof(*file) != unsafe.Sizeof(tokenFile119{}) {
panic("unexpected token.File size")
}
var ptr *tokenFile119
type uP = unsafe.Pointer
*(*uP)(uP(&ptr)) = uP(file)
ptr.mu.Lock()
defer ptr.mu.Unlock()
return ptr.lines
}
// AddExistingFiles adds the specified files to the FileSet if they
// are not already present. It panics if any pair of files in the
// resulting FileSet would overlap.
func AddExistingFiles(fset *token.FileSet, files []*token.File) {
// Punch through the FileSet encapsulation.
type tokenFileSet struct {
// This type remained essentially consistent from go1.16 to go1.21.
mutex sync.RWMutex
base int
files []*token.File
_ *token.File // changed to atomic.Pointer[token.File] in go1.19
}
// If the size of token.FileSet changes, this will fail to compile.
const delta = int64(unsafe.Sizeof(tokenFileSet{})) - int64(unsafe.Sizeof(token.FileSet{}))
var _ [-delta * delta]int
type uP = unsafe.Pointer
var ptr *tokenFileSet
*(*uP)(uP(&ptr)) = uP(fset)
ptr.mutex.Lock()
defer ptr.mutex.Unlock()
// Merge and sort.
newFiles := append(ptr.files, files...)
sort.Slice(newFiles, func(i, j int) bool {
return newFiles[i].Base() < newFiles[j].Base()
})
// Reject overlapping files.
// Discard adjacent identical files.
out := newFiles[:0]
for i, file := range newFiles {
if i > 0 {
prev := newFiles[i-1]
if file == prev {
continue
}
if prev.Base()+prev.Size()+1 > file.Base() {
panic(fmt.Sprintf("file %s (%d-%d) overlaps with file %s (%d-%d)",
prev.Name(), prev.Base(), prev.Base()+prev.Size(),
file.Name(), file.Base(), file.Base()+file.Size()))
}
}
out = append(out, file)
}
newFiles = out
ptr.files = newFiles
// Advance FileSet.Base().
if len(newFiles) > 0 {
last := newFiles[len(newFiles)-1]
newBase := last.Base() + last.Size() + 1
if ptr.base < newBase {
ptr.base = newBase
}
}
}
// FileSetFor returns a new FileSet containing a sequence of new Files with
// the same base, size, and line as the input files, for use in APIs that
// require a FileSet.
//
// Precondition: the input files must be non-overlapping, and sorted in order
// of their Base.
func FileSetFor(files ...*token.File) *token.FileSet {
fset := token.NewFileSet()
for _, f := range files {
f2 := fset.AddFile(f.Name(), f.Base(), f.Size())
lines := GetLines(f)
f2.SetLines(lines)
}
return fset
}
// CloneFileSet creates a new FileSet holding all files in fset. It does not
// create copies of the token.Files in fset: they are added to the resulting
// FileSet unmodified.
func CloneFileSet(fset *token.FileSet) *token.FileSet {
var files []*token.File
fset.Iterate(func(f *token.File) bool {
files = append(files, f)
return true
})
newFileSet := token.NewFileSet()
AddExistingFiles(newFileSet, files)
return newFileSet
}
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