cue/token/position.go - cue - Git at Google

 // Copyright 2018 The CUE Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 package token

 import (
 	"fmt"
 	"sort"
 	"sync"
 )

 // -----------------------------------------------------------------------------
 // Positions

 // Position describes an arbitrary source position
 // including the file, line, and column location.
 // A Position is valid if the line number is > 0.
 type Position struct {
 	Filename string // filename, if any
 	Offset   int    // offset, starting at 0
 	Line     int    // line number, starting at 1
 	Column   int    // column number, starting at 1 (byte count)
 	// RelPos   Pos // relative position information
 }

 // IsValid reports whether the position is valid.
 func (pos *Position) IsValid() bool { return pos.Line > 0 }

 // String returns a string in one of several forms:
 //
 //	file:line:column    valid position with file name
 //	line:column         valid position without file name
 //	file                invalid position with file name
 //	-                   invalid position without file name
 //
 func (pos Position) String() string {
 	s := pos.Filename
 	if pos.IsValid() {
 		if s != "" {
 			s += ":"
 		}
 		s += fmt.Sprintf("%d:%d", pos.Line, pos.Column)
 	}
 	if s == "" {
 		s = "-"
 	}
 	return s
 }

 // Pos is a compact encoding of a source position within a file, as well as
 // relative positioning information. It can be converted into a Position for a
 // more convenient, but much larger, representation.
 //
 type Pos struct {
 	file   *File
 	offset int
 }

 // File returns the file that contains the position p or nil if there is no
 // such file (for instance for p == NoPos).
 //
 func (p Pos) File() *File {
 	if p.index() == 0 {
 		return nil
 	}
 	return p.file
 }

 func (p Pos) Line() int {
 	if p.file == nil {
 		return 0
 	}
 	return p.Position().Line
 }

 func (p Pos) Column() int {
 	if p.file == nil {
 		return 0
 	}
 	return p.Position().Column
 }

 func (p Pos) Filename() string {
 	if p.file == nil {
 		return ""
 	}
 	return p.Position().Filename
 }

 func (p Pos) Position() Position {
 	if p.file == nil {
 		return Position{}
 	}
 	return p.file.Position(p)
 }

 func (p Pos) String() string {
 	return p.Position().String()
 }

 // NoPos is the zero value for Pos; there is no file and line information
 // associated with it, and NoPos().IsValid() is false. NoPos is always
 // smaller than any other Pos value. The corresponding Position value
 // for NoPos is the zero value for Position.
 var NoPos = Pos{}

 // RelPos indicates the relative position of token to the previous token.
 type RelPos int

 const (
 	// NoRelPos indicates no relative position is specified.
 	NoRelPos RelPos = iota

 	// Elided indicates that the token for which this position is defined is
 	// not rendered at all.
 	Elided

 	// NoSpace indicates there is no whitespace after this token.
 	NoSpace

 	// Blank means there is horizontal space after this token.
 	Blank

 	// Newline means there is a single newline after this token.
 	Newline

 	// NewSection means there are two or more newlines after this token.
 	NewSection

 	relMask  = 0xf
 	relShift = 4
 )

 var relNames = []string{
 	"invalid", "elided", "nospace", "blank", "newline", "section",
 }

 func (p RelPos) String() string { return relNames[p] }

 func (p RelPos) Pos() Pos {
 	return Pos{nil, int(p)}
 }

 // HasRelPos repors whether p has a relative position.
 func (p Pos) HasRelPos() bool {
 	return p.offset&relMask != 0

 }

 func (p Pos) Before(q Pos) bool {
 	return p.file == q.file && p.Offset() < q.Offset()
 }

 // Offset reports the byte offset relative to the file.
 func (p Pos) Offset() int {
 	return p.Position().Offset
 }

 // Add creates a new position relative to the p offset by n.
 func (p Pos) Add(n int) Pos {
 	return Pos{p.file, p.offset + toPos(index(n))}
 }

 // IsValid reports whether the position is valid.
 func (p Pos) IsValid() bool {
 	return p != NoPos
 }

 // IsNewline reports whether the relative information suggests this node should
 // be printed on a new lien.
 func (p Pos) IsNewline() bool {
 	return p.RelPos() >= Newline
 }

 func (p Pos) WithRel(rel RelPos) Pos {
 	return Pos{p.file, p.offset&^relMask | int(rel)}
 }

 func (p Pos) RelPos() RelPos {
 	return RelPos(p.offset & relMask)
 }

 func (p Pos) index() index {
 	return index(p.offset) >> relShift
 }

 func toPos(x index) int {
 	return (int(x) << relShift)
 }

 // -----------------------------------------------------------------------------
 // File

 type index int

 // A File has a name, size, and line offset table.
 type File struct {
 	mutex sync.RWMutex
 	name  string // file name as provided to AddFile
 	base  index  // Pos index range for this file is [base...base+size]
 	size  index  // file size as provided to AddFile

 	// lines and infos are protected by set.mutex
 	lines []index // lines contains the offset of the first character for each line (the first entry is always 0)
 	infos []lineInfo
 }

 // NewFile returns a new file.
 func NewFile(filename string, base, size int) *File {
 	if base < 0 {
 		base = 1
 	}
 	return &File{sync.RWMutex{}, filename, index(base), index(size), []index{0}, nil}
 }

 // Name returns the file name of file f as registered with AddFile.
 func (f *File) Name() string {
 	return f.name
 }

 // Base returns the base offset of file f as registered with AddFile.
 func (f *File) Base() int {
 	return int(f.base)
 }

 // Size returns the size of file f as registered with AddFile.
 func (f *File) Size() int {
 	return int(f.size)
 }

 // LineCount returns the number of lines in file f.
 func (f *File) LineCount() int {
 	f.mutex.RLock()
 	n := len(f.lines)
 	f.mutex.RUnlock()
 	return n
 }

 // AddLine adds the line offset for a new line.
 // The line offset must be larger than the offset for the previous line
 // and smaller than the file size; otherwise the line offset is ignored.
 //
 func (f *File) AddLine(offset int) {
 	x := index(offset)
 	f.mutex.Lock()
 	if i := len(f.lines); (i == 0 || f.lines[i-1] < x) && x < f.size {
 		f.lines = append(f.lines, x)
 	}
 	f.mutex.Unlock()
 }

 // MergeLine merges a line with the following line. It is akin to replacing
 // the newline character at the end of the line with a space (to not change the
 // remaining offsets). To obtain the line number, consult e.g. Position.Line.
 // MergeLine will panic if given an invalid line number.
 //
 func (f *File) MergeLine(line int) {
 	if line <= 0 {
 		panic("illegal line number (line numbering starts at 1)")
 	}
 	f.mutex.Lock()
 	defer f.mutex.Unlock()
 	if line >= len(f.lines) {
 		panic("illegal line number")
 	}
 	// To merge the line numbered <line> with the line numbered <line+1>,
 	// we need to remove the entry in lines corresponding to the line
 	// numbered <line+1>. The entry in lines corresponding to the line
 	// numbered <line+1> is located at index <line>, since indices in lines
 	// are 0-based and line numbers are 1-based.
 	copy(f.lines[line:], f.lines[line+1:])
 	f.lines = f.lines[:len(f.lines)-1]
 }

 // SetLines sets the line offsets for a file and reports whether it succeeded.
 // The line offsets are the offsets of the first character of each line;
 // for instance for the content "ab\nc\n" the line offsets are {0, 3}.
 // An empty file has an empty line offset table.
 // Each line offset must be larger than the offset for the previous line
 // and smaller than the file size; otherwise SetLines fails and returns
 // false.
 // Callers must not mutate the provided slice after SetLines returns.
 //
 func (f *File) SetLines(lines []int) bool {
 	// verify validity of lines table
 	size := f.size
 	for i, offset := range lines {
 		if i > 0 && offset <= lines[i-1] || size <= index(offset) {
 			return false
 		}
 	}

 	// set lines table
 	f.mutex.Lock()
 	f.lines = f.lines[:0]
 	for _, l := range lines {
 		f.lines = append(f.lines, index(l))
 	}
 	f.mutex.Unlock()
 	return true
 }

 // SetLinesForContent sets the line offsets for the given file content.
 // It ignores position-altering //line comments.
 func (f *File) SetLinesForContent(content []byte) {
 	var lines []index
 	line := index(0)
 	for offset, b := range content {
 		if line >= 0 {
 			lines = append(lines, line)
 		}
 		line = -1
 		if b == '\n' {
 			line = index(offset) + 1
 		}
 	}

 	// set lines table
 	f.mutex.Lock()
 	f.lines = lines
 	f.mutex.Unlock()
 }

 // A lineInfo object describes alternative file and line number
 // information (such as provided via a //line comment in a .go
 // file) for a given file offset.
 type lineInfo struct {
 	// fields are exported to make them accessible to gob
 	Offset   int
 	Filename string
 	Line     int
 }

 // AddLineInfo adds alternative file and line number information for
 // a given file offset. The offset must be larger than the offset for
 // the previously added alternative line info and smaller than the
 // file size; otherwise the information is ignored.
 //
 // AddLineInfo is typically used to register alternative position
 // information for //line filename:line comments in source files.
 //
 func (f *File) AddLineInfo(offset int, filename string, line int) {
 	x := index(offset)
 	f.mutex.Lock()
 	if i := len(f.infos); i == 0 || index(f.infos[i-1].Offset) < x && x < f.size {
 		f.infos = append(f.infos, lineInfo{offset, filename, line})
 	}
 	f.mutex.Unlock()
 }

 // Pos returns the Pos value for the given file offset;
 // the offset must be <= f.Size().
 // f.Pos(f.Offset(p)) == p.
 //
 func (f *File) Pos(offset int, rel RelPos) Pos {
 	if index(offset) > f.size {
 		panic("illegal file offset")
 	}
 	return Pos{f, toPos(f.base+index(offset)) + int(rel)}
 }

 // Offset returns the offset for the given file position p;
 // p must be a valid Pos value in that file.
 // f.Offset(f.Pos(offset)) == offset.
 //
 func (f *File) Offset(p Pos) int {
 	x := p.index()
 	if x < f.base || x > f.base+index(f.size) {
 		panic("illegal Pos value")
 	}
 	return int(x - f.base)
 }

 // Line returns the line number for the given file position p;
 // p must be a Pos value in that file or NoPos.
 //
 func (f *File) Line(p Pos) int {
 	return f.Position(p).Line
 }

 func searchLineInfos(a []lineInfo, x int) int {
 	return sort.Search(len(a), func(i int) bool { return a[i].Offset > x }) - 1
 }

 // unpack returns the filename and line and column number for a file offset.
 // If adjusted is set, unpack will return the filename and line information
 // possibly adjusted by //line comments; otherwise those comments are ignored.
 //
 func (f *File) unpack(offset index, adjusted bool) (filename string, line, column int) {
 	filename = f.name
 	if i := searchInts(f.lines, offset); i >= 0 {
 		line, column = int(i+1), int(offset-f.lines[i]+1)
 	}
 	if adjusted && len(f.infos) > 0 {
 		// almost no files have extra line infos
 		if i := searchLineInfos(f.infos, int(offset)); i >= 0 {
 			alt := &f.infos[i]
 			filename = alt.Filename
 			if i := searchInts(f.lines, index(alt.Offset)); i >= 0 {
 				line += alt.Line - i - 1
 			}
 		}
 	}
 	return
 }

 func (f *File) position(p Pos, adjusted bool) (pos Position) {
 	offset := p.index() - f.base
 	pos.Offset = int(offset)
 	pos.Filename, pos.Line, pos.Column = f.unpack(offset, adjusted)
 	return
 }

 // PositionFor returns the Position value for the given file position p.
 // If adjusted is set, the position may be adjusted by position-altering
 // //line comments; otherwise those comments are ignored.
 // p must be a Pos value in f or NoPos.
 //
 func (f *File) PositionFor(p Pos, adjusted bool) (pos Position) {
 	x := p.index()
 	if p != NoPos {
 		if x < f.base || x > f.base+f.size {
 			panic("illegal Pos value")
 		}
 		pos = f.position(p, adjusted)
 	}
 	return
 }

 // Position returns the Position value for the given file position p.
 // Calling f.Position(p) is equivalent to calling f.PositionFor(p, true).
 //
 func (f *File) Position(p Pos) (pos Position) {
 	return f.PositionFor(p, true)
 }

 // -----------------------------------------------------------------------------
 // Helper functions

 func searchInts(a []index, x index) int {
 	// This function body is a manually inlined version of:
 	//
 	//   return sort.Search(len(a), func(i int) bool { return a[i] > x }) - 1
 	//
 	// With better compiler optimizations, this may not be needed in the
 	// future, but at the moment this change improves the go/printer
 	// benchmark performance by ~30%. This has a direct impact on the
 	// speed of gofmt and thus seems worthwhile (2011-04-29).
 	// TODO(gri): Remove this when compilers have caught up.
 	i, j := 0, len(a)
 	for i < j {
 		h := i + (j-i)/2 // avoid overflow when computing h
 		// i ≤ h < j
 		if a[h] <= x {
 			i = h + 1
 		} else {
 			j = h
 		}
 	}
 	return i - 1
 }
	// Copyright 2018 The CUE Authors
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	package token

	import (
	"fmt"
	"sort"
	"sync"
	)

	// -----------------------------------------------------------------------------
	// Positions

	// Position describes an arbitrary source position
	// including the file, line, and column location.
	// A Position is valid if the line number is > 0.
	type Position struct {
	Filename string // filename, if any
	Offset int // offset, starting at 0
	Line int // line number, starting at 1
	Column int // column number, starting at 1 (byte count)
	// RelPos Pos // relative position information
	}

	// IsValid reports whether the position is valid.
	func (pos *Position) IsValid() bool { return pos.Line > 0 }

	// String returns a string in one of several forms:
	//
	// file:line:column valid position with file name
	// line:column valid position without file name
	// file invalid position with file name
	// - invalid position without file name
	//
	func (pos Position) String() string {
	s := pos.Filename
	if pos.IsValid() {
	if s != "" {
	s += ":"
	}
	s += fmt.Sprintf("%d:%d", pos.Line, pos.Column)
	}
	if s == "" {
	s = "-"
	}
	return s
	}

	// Pos is a compact encoding of a source position within a file, as well as
	// relative positioning information. It can be converted into a Position for a
	// more convenient, but much larger, representation.
	//
	type Pos struct {
	file *File
	offset int
	}

	// File returns the file that contains the position p or nil if there is no
	// such file (for instance for p == NoPos).
	//
	func (p Pos) File() *File {
	if p.index() == 0 {
	return nil
	}
	return p.file
	}

	func (p Pos) Line() int {
	if p.file == nil {
	return 0
	}
	return p.Position().Line
	}

	func (p Pos) Column() int {
	if p.file == nil {
	return 0
	}
	return p.Position().Column
	}

	func (p Pos) Filename() string {
	if p.file == nil {
	return ""
	}
	return p.Position().Filename
	}

	func (p Pos) Position() Position {
	if p.file == nil {
	return Position{}
	}
	return p.file.Position(p)
	}

	func (p Pos) String() string {
	return p.Position().String()
	}

	// NoPos is the zero value for Pos; there is no file and line information
	// associated with it, and NoPos().IsValid() is false. NoPos is always
	// smaller than any other Pos value. The corresponding Position value
	// for NoPos is the zero value for Position.
	var NoPos = Pos{}

	// RelPos indicates the relative position of token to the previous token.
	type RelPos int

	const (
	// NoRelPos indicates no relative position is specified.
	NoRelPos RelPos = iota

	// Elided indicates that the token for which this position is defined is
	// not rendered at all.
	Elided

	// NoSpace indicates there is no whitespace after this token.
	NoSpace

	// Blank means there is horizontal space after this token.
	Blank

	// Newline means there is a single newline after this token.
	Newline

	// NewSection means there are two or more newlines after this token.
	NewSection

	relMask = 0xf
	relShift = 4
	)

	var relNames = []string{
	"invalid", "elided", "nospace", "blank", "newline", "section",
	}

	func (p RelPos) String() string { return relNames[p] }

	func (p RelPos) Pos() Pos {
	return Pos{nil, int(p)}
	}

	// HasRelPos repors whether p has a relative position.
	func (p Pos) HasRelPos() bool {
	return p.offset&relMask != 0

	}

	func (p Pos) Before(q Pos) bool {
	return p.file == q.file && p.Offset() < q.Offset()
	}

	// Offset reports the byte offset relative to the file.
	func (p Pos) Offset() int {
	return p.Position().Offset
	}

	// Add creates a new position relative to the p offset by n.
	func (p Pos) Add(n int) Pos {
	return Pos{p.file, p.offset + toPos(index(n))}
	}

	// IsValid reports whether the position is valid.
	func (p Pos) IsValid() bool {
	return p != NoPos
	}

	// IsNewline reports whether the relative information suggests this node should
	// be printed on a new lien.
	func (p Pos) IsNewline() bool {
	return p.RelPos() >= Newline
	}

	func (p Pos) WithRel(rel RelPos) Pos {
	return Pos{p.file, p.offset&^relMask \| int(rel)}
	}

	func (p Pos) RelPos() RelPos {
	return RelPos(p.offset & relMask)
	}

	func (p Pos) index() index {
	return index(p.offset) >> relShift
	}

	func toPos(x index) int {
	return (int(x) << relShift)
	}

	// -----------------------------------------------------------------------------
	// File

	type index int

	// A File has a name, size, and line offset table.
	type File struct {
	mutex sync.RWMutex
	name string // file name as provided to AddFile
	base index // Pos index range for this file is [base...base+size]
	size index // file size as provided to AddFile

	// lines and infos are protected by set.mutex
	lines []index // lines contains the offset of the first character for each line (the first entry is always 0)
	infos []lineInfo
	}

	// NewFile returns a new file.
	func NewFile(filename string, base, size int) *File {
	if base < 0 {
	base = 1
	}
	return &File{sync.RWMutex{}, filename, index(base), index(size), []index{0}, nil}
	}

	// Name returns the file name of file f as registered with AddFile.
	func (f *File) Name() string {
	return f.name
	}

	// Base returns the base offset of file f as registered with AddFile.
	func (f *File) Base() int {
	return int(f.base)
	}

	// Size returns the size of file f as registered with AddFile.
	func (f *File) Size() int {
	return int(f.size)
	}

	// LineCount returns the number of lines in file f.
	func (f *File) LineCount() int {
	f.mutex.RLock()
	n := len(f.lines)
	f.mutex.RUnlock()
	return n
	}

	// AddLine adds the line offset for a new line.
	// The line offset must be larger than the offset for the previous line
	// and smaller than the file size; otherwise the line offset is ignored.
	//
	func (f *File) AddLine(offset int) {
	x := index(offset)
	f.mutex.Lock()
	if i := len(f.lines); (i == 0 \|\| f.lines[i-1] < x) && x < f.size {
	f.lines = append(f.lines, x)
	}
	f.mutex.Unlock()
	}

	// MergeLine merges a line with the following line. It is akin to replacing
	// the newline character at the end of the line with a space (to not change the
	// remaining offsets). To obtain the line number, consult e.g. Position.Line.
	// MergeLine will panic if given an invalid line number.
	//
	func (f *File) MergeLine(line int) {
	if line <= 0 {
	panic("illegal line number (line numbering starts at 1)")
	}
	f.mutex.Lock()
	defer f.mutex.Unlock()
	if line >= len(f.lines) {
	panic("illegal line number")
	}
	// To merge the line numbered <line> with the line numbered <line+1>,
	// we need to remove the entry in lines corresponding to the line
	// numbered <line+1>. The entry in lines corresponding to the line
	// numbered <line+1> is located at index <line>, since indices in lines
	// are 0-based and line numbers are 1-based.
	copy(f.lines[line:], f.lines[line+1:])
	f.lines = f.lines[:len(f.lines)-1]
	}

	// SetLines sets the line offsets for a file and reports whether it succeeded.
	// The line offsets are the offsets of the first character of each line;
	// for instance for the content "ab\nc\n" the line offsets are {0, 3}.
	// An empty file has an empty line offset table.
	// Each line offset must be larger than the offset for the previous line
	// and smaller than the file size; otherwise SetLines fails and returns
	// false.
	// Callers must not mutate the provided slice after SetLines returns.
	//
	func (f *File) SetLines(lines []int) bool {
	// verify validity of lines table
	size := f.size
	for i, offset := range lines {
	if i > 0 && offset <= lines[i-1] \|\| size <= index(offset) {
	return false
	}
	}

	// set lines table
	f.mutex.Lock()
	f.lines = f.lines[:0]
	for _, l := range lines {
	f.lines = append(f.lines, index(l))
	}
	f.mutex.Unlock()
	return true
	}

	// SetLinesForContent sets the line offsets for the given file content.
	// It ignores position-altering //line comments.
	func (f *File) SetLinesForContent(content []byte) {
	var lines []index
	line := index(0)
	for offset, b := range content {
	if line >= 0 {
	lines = append(lines, line)
	}
	line = -1
	if b == '\n' {
	line = index(offset) + 1
	}
	}

	// set lines table
	f.mutex.Lock()
	f.lines = lines
	f.mutex.Unlock()
	}

	// A lineInfo object describes alternative file and line number
	// information (such as provided via a //line comment in a .go
	// file) for a given file offset.
	type lineInfo struct {
	// fields are exported to make them accessible to gob
	Offset int
	Filename string
	Line int
	}

	// AddLineInfo adds alternative file and line number information for
	// a given file offset. The offset must be larger than the offset for
	// the previously added alternative line info and smaller than the
	// file size; otherwise the information is ignored.
	//
	// AddLineInfo is typically used to register alternative position
	// information for //line filename:line comments in source files.
	//
	func (f *File) AddLineInfo(offset int, filename string, line int) {
	x := index(offset)
	f.mutex.Lock()
	if i := len(f.infos); i == 0 \|\| index(f.infos[i-1].Offset) < x && x < f.size {
	f.infos = append(f.infos, lineInfo{offset, filename, line})
	}
	f.mutex.Unlock()
	}

	// Pos returns the Pos value for the given file offset;
	// the offset must be <= f.Size().
	// f.Pos(f.Offset(p)) == p.
	//
	func (f *File) Pos(offset int, rel RelPos) Pos {
	if index(offset) > f.size {
	panic("illegal file offset")
	}
	return Pos{f, toPos(f.base+index(offset)) + int(rel)}
	}

	// Offset returns the offset for the given file position p;
	// p must be a valid Pos value in that file.
	// f.Offset(f.Pos(offset)) == offset.
	//
	func (f *File) Offset(p Pos) int {
	x := p.index()
	if x < f.base \|\| x > f.base+index(f.size) {
	panic("illegal Pos value")
	}
	return int(x - f.base)
	}

	// Line returns the line number for the given file position p;
	// p must be a Pos value in that file or NoPos.
	//
	func (f *File) Line(p Pos) int {
	return f.Position(p).Line
	}

	func searchLineInfos(a []lineInfo, x int) int {
	return sort.Search(len(a), func(i int) bool { return a[i].Offset > x }) - 1
	}

	// unpack returns the filename and line and column number for a file offset.
	// If adjusted is set, unpack will return the filename and line information
	// possibly adjusted by //line comments; otherwise those comments are ignored.
	//
	func (f *File) unpack(offset index, adjusted bool) (filename string, line, column int) {
	filename = f.name
	if i := searchInts(f.lines, offset); i >= 0 {
	line, column = int(i+1), int(offset-f.lines[i]+1)
	}
	if adjusted && len(f.infos) > 0 {
	// almost no files have extra line infos
	if i := searchLineInfos(f.infos, int(offset)); i >= 0 {
	alt := &f.infos[i]
	filename = alt.Filename
	if i := searchInts(f.lines, index(alt.Offset)); i >= 0 {
	line += alt.Line - i - 1
	}
	}
	}
	return
	}

	func (f *File) position(p Pos, adjusted bool) (pos Position) {
	offset := p.index() - f.base
	pos.Offset = int(offset)
	pos.Filename, pos.Line, pos.Column = f.unpack(offset, adjusted)
	return
	}

	// PositionFor returns the Position value for the given file position p.
	// If adjusted is set, the position may be adjusted by position-altering
	// //line comments; otherwise those comments are ignored.
	// p must be a Pos value in f or NoPos.
	//
	func (f *File) PositionFor(p Pos, adjusted bool) (pos Position) {
	x := p.index()
	if p != NoPos {
	if x < f.base \|\| x > f.base+f.size {
	panic("illegal Pos value")
	}
	pos = f.position(p, adjusted)
	}
	return
	}

	// Position returns the Position value for the given file position p.
	// Calling f.Position(p) is equivalent to calling f.PositionFor(p, true).
	//
	func (f *File) Position(p Pos) (pos Position) {
	return f.PositionFor(p, true)
	}

	// -----------------------------------------------------------------------------
	// Helper functions

	func searchInts(a []index, x index) int {
	// This function body is a manually inlined version of:
	//
	// return sort.Search(len(a), func(i int) bool { return a[i] > x }) - 1
	//
	// With better compiler optimizations, this may not be needed in the
	// future, but at the moment this change improves the go/printer
	// benchmark performance by ~30%. This has a direct impact on the
	// speed of gofmt and thus seems worthwhile (2011-04-29).
	// TODO(gri): Remove this when compilers have caught up.
	i, j := 0, len(a)
	for i < j {
	h := i + (j-i)/2 // avoid overflow when computing h
	// i ≤ h < j
	if a[h] <= x {
	i = h + 1
	} else {
	j = h
	}
	}
	return i - 1
	}