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// Copyright 2019 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 span
import (
"fmt"
"go/token"
"golang.org/x/tools/internal/lsp/bug"
)
// Range represents a source code range in token.Pos form.
// It also carries the FileSet that produced the positions, so that it is
// self contained.
type Range struct {
Start token.Pos
End token.Pos
// TokFile may be nil if Start or End is invalid.
// TODO: Eventually we should guarantee that it is non-nil.
TokFile *token.File
}
// NewRange creates a new Range from a FileSet and two positions.
// To represent a point pass a 0 as the end pos.
func NewRange(fset *token.FileSet, start, end token.Pos) Range {
tf := fset.File(start)
if tf == nil {
bug.Reportf("nil file")
}
return Range{
Start: start,
End: end,
TokFile: tf,
}
}
// NewTokenFile returns a token.File for the given file content.
func NewTokenFile(filename string, content []byte) *token.File {
fset := token.NewFileSet()
f := fset.AddFile(filename, -1, len(content))
f.SetLinesForContent(content)
return f
}
// IsPoint returns true if the range represents a single point.
func (r Range) IsPoint() bool {
return r.Start == r.End
}
// Span converts a Range to a Span that represents the Range.
// It will fill in all the members of the Span, calculating the line and column
// information.
func (r Range) Span() (Span, error) {
return FileSpan(r.TokFile, r.TokFile, r.Start, r.End)
}
// FileSpan returns a span within the file referenced by start and end, using a
// token.File to translate between offsets and positions.
//
// The start and end position must be contained within posFile, though due to
// line directives they may reference positions in another file. If srcFile is
// provided, it is used to map the line:column positions referenced by start
// and end to offsets in the corresponding file.
func FileSpan(posFile, srcFile *token.File, start, end token.Pos) (Span, error) {
if !start.IsValid() {
return Span{}, fmt.Errorf("start pos is not valid")
}
if posFile == nil {
return Span{}, bug.Errorf("missing file association") // should never get here with a nil file
}
var s Span
var err error
var startFilename string
startFilename, s.v.Start.Line, s.v.Start.Column, err = position(posFile, start)
if err != nil {
return Span{}, err
}
s.v.URI = URIFromPath(startFilename)
if end.IsValid() {
var endFilename string
endFilename, s.v.End.Line, s.v.End.Column, err = position(posFile, end)
if err != nil {
return Span{}, err
}
// In the presence of line directives, a single File can have sections from
// multiple file names.
if endFilename != startFilename {
return Span{}, fmt.Errorf("span begins in file %q but ends in %q", startFilename, endFilename)
}
}
s.v.Start.clean()
s.v.End.clean()
s.v.clean()
tf := posFile
if srcFile != nil {
tf = srcFile
}
if startFilename != tf.Name() {
return Span{}, bug.Errorf("must supply Converter for file %q", startFilename)
}
return s.WithOffset(tf)
}
func position(tf *token.File, pos token.Pos) (string, int, int, error) {
off, err := offset(tf, pos)
if err != nil {
return "", 0, 0, err
}
return positionFromOffset(tf, off)
}
func positionFromOffset(tf *token.File, offset int) (string, int, int, error) {
if offset > tf.Size() {
return "", 0, 0, fmt.Errorf("offset %v is past the end of the file %v", offset, tf.Size())
}
pos := tf.Pos(offset)
p := tf.Position(pos)
// TODO(golang/go#41029): Consider returning line, column instead of line+1, 1 if
// the file's last character is not a newline.
if offset == tf.Size() {
return p.Filename, p.Line + 1, 1, nil
}
return p.Filename, p.Line, p.Column, nil
}
// offset is a copy of the Offset function in go/token, but with the adjustment
// that it does not panic on invalid positions.
func offset(tf *token.File, pos token.Pos) (int, error) {
if int(pos) < tf.Base() || int(pos) > tf.Base()+tf.Size() {
return 0, fmt.Errorf("invalid pos: %d not in [%d, %d]", pos, tf.Base(), tf.Base()+tf.Size())
}
return int(pos) - tf.Base(), nil
}
// Range converts a Span to a Range that represents the Span for the supplied
// File.
func (s Span) Range(tf *token.File) (Range, error) {
s, err := s.WithOffset(tf)
if err != nil {
return Range{}, err
}
// go/token will panic if the offset is larger than the file's size,
// so check here to avoid panicking.
if s.Start().Offset() > tf.Size() {
return Range{}, bug.Errorf("start offset %v is past the end of the file %v", s.Start(), tf.Size())
}
if s.End().Offset() > tf.Size() {
return Range{}, bug.Errorf("end offset %v is past the end of the file %v", s.End(), tf.Size())
}
return Range{
Start: tf.Pos(s.Start().Offset()),
End: tf.Pos(s.End().Offset()),
TokFile: tf,
}, nil
}
// ToPosition converts a byte offset in the file corresponding to tf into
// 1-based line and utf-8 column indexes.
func ToPosition(tf *token.File, offset int) (int, int, error) {
_, line, col, err := positionFromOffset(tf, offset)
return line, col, err
}
// ToOffset converts a 1-base line and utf-8 column index into a byte offset in
// the file corresponding to tf.
func ToOffset(tf *token.File, line, col int) (int, error) {
if line < 0 {
return -1, fmt.Errorf("line is not valid")
}
lineMax := tf.LineCount() + 1
if line > lineMax {
return -1, fmt.Errorf("line is beyond end of file %v", lineMax)
} else if line == lineMax {
if col > 1 {
return -1, fmt.Errorf("column is beyond end of file")
}
// at the end of the file, allowing for a trailing eol
return tf.Size(), nil
}
pos := tf.LineStart(line)
if !pos.IsValid() {
return -1, fmt.Errorf("line is not in file")
}
// we assume that column is in bytes here, and that the first byte of a
// line is at column 1
pos += token.Pos(col - 1)
return offset(tf, pos)
}