golang position 代码
文件路径：/src/go/token/position.go
/ Copyright 2010 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 token
import (
"fmt"
"sort"
"sync"
"sync/atomic"
)
/ -----------------------------------------------------------------------------
/ 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)
}
/ 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
/ file:line valid position with file name but no column (column == 0)
/ line:column valid position without file name
/ line valid position without file name and no column (column == 0)
/ 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", pos.Line)
if pos.Column != 0 {
s += fmt.Sprintf(":%d", pos.Column)
}
}
if s == "" {
s = "-"
}
return s
}
/ Pos is a compact encoding of a source position within a file set.
/ It can be converted into a Position for a more convenient, but much
/ larger, representation.
/
/ The Pos value for a given file is a number in the range [base, base+size],
/ where base and size are specified when a file is added to the file set.
/ The difference between a Pos value and the corresponding file base
/ corresponds to the byte offset of that position (represented by the Pos value)
/ from the beginning of the file. Thus, the file base offset is the Pos value
/ representing the first byte in the file.
/
/ To create the Pos value for a specific source offset (measured in bytes),
/ first add the respective file to the current file set using FileSet.AddFile
/ and then call File.Pos(offset) for that file. Given a Pos value p
/ for a specific file set fset, the corresponding Position value is
/ obtained by calling fset.Position(p).
/
/ Pos values can be compared directly with the usual comparison operators:
/ If two Pos values p and q are in the same file, comparing p and q is
/ equivalent to comparing the respective source file offsets. If p and q
/ are in different files, p < q is true if the file implied by p was added
/ to the respective file set before the file implied by q.
type Pos int
/ The zero value for Pos is NoPos; 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.
const NoPos Pos = 0
/ IsValid reports whether the position is valid.
func (p Pos) IsValid() bool {
return p != NoPos
}
/ -----------------------------------------------------------------------------
/ File
/ A File is a handle for a file belonging to a FileSet.
/ A File has a name, size, and line offset table.
type File struct {
name string / file name as provided to AddFile
base int / Pos value range for this file is [base...base+size]
size int / file size as provided to AddFile
/ lines and infos are protected by mutex
mutex sync.Mutex
lines []int / lines contains the offset of the first character for each line (the first entry is always 0)
infos []lineInfo
}
/ 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 f.base
}
/ Size returns the size of file f as registered with AddFile.
func (f *File) Size() int {
return f.size
}
/ LineCount returns the number of lines in file f.
func (f *File) LineCount() int {
f.mutex.Lock()
n := len(f.lines)
f.mutex.Unlock()
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) {
f.mutex.Lock()
if i := len(f.lines); (i == 0 || f.lines[i-1] < offset) && offset < f.size {
f.lines = append(f.lines, offset)
}
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 < 1 {
panic(fmt.Sprintf("invalid line number %d (should be >= 1)", line))
}
f.mutex.Lock()
defer f.mutex.Unlock()
if line >= len(f.lines) {
panic(fmt.Sprintf("invalid line number %d (should be < %d)", line, len(f.lines)))
}
/ 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 <= offset {
return false
}
}
/ set lines table
f.mutex.Lock()
f.lines = lines
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 []int
line := 0
for offset, b := range content {
if line >= 0 {
lines = append(lines, line)
}
line = -1
if b == '\n' {
line = offset + 1
}
}
/ set lines table
f.mutex.Lock()
f.lines = lines
f.mutex.Unlock()
}
/ LineStart returns the Pos value of the start of the specified line.
/ It ignores any alternative positions set using AddLineColumnInfo.
/ LineStart panics if the 1-based line number is invalid.
func (f *File) LineStart(line int) Pos {
if line < 1 {
panic(fmt.Sprintf("invalid line number %d (should be >= 1)", line))
}
f.mutex.Lock()
defer f.mutex.Unlock()
if line > len(f.lines) {
panic(fmt.Sprintf("invalid line number %d (should be < %d)", line, len(f.lines)))
}
return Pos(f.base + f.lines[line-1])
}
/ A lineInfo object describes alternative file, line, and column
/ number information (such as provided via a /line directive)
/ for a given file offset.
type lineInfo struct {
/ fields are exported to make them accessible to gob
Offset int
Filename string
Line, Column int
}
/ AddLineInfo is like AddLineColumnInfo with a column = 1 argument.
/ It is here for backward-compatibility for code prior to Go 1.11.
func (f *File) AddLineInfo(offset int, filename string, line int) {
f.AddLineColumnInfo(offset, filename, line, 1)
}
/ AddLineColumnInfo adds alternative file, line, and column 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.
/
/ AddLineColumnInfo is typically used to register alternative position
/ information for line directives such as /line filename:line:column.
func (f *File) AddLineColumnInfo(offset int, filename string, line, column int) {
f.mutex.Lock()
if i := len(f.infos); i == 0 || f.infos[i-1].Offset < offset && offset < f.size {
f.infos = append(f.infos, lineInfo{offset, filename, line, column})
}
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) Pos {
if offset > f.size {
panic(fmt.Sprintf("invalid file offset %d (should be <= %d)", offset, f.size))
}
return Pos(f.base + offset)
}
/ 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 {
if int(p) < f.base || int(p) > f.base+f.size {
panic(fmt.Sprintf("invalid Pos value %d (should be in [%d, %d])", p, f.base, f.base+f.size))
}
return int(p) - 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 int, adjusted bool) (filename string, line, column int) {
f.mutex.Lock()
defer f.mutex.Unlock()
filename = f.name
if i := searchInts(f.lines, offset); i >= 0 {
line, column = i+1, offset-f.lines[i]+1
}
if adjusted && len(f.infos) > 0 {
/ few files have extra line infos
if i := searchLineInfos(f.infos, offset); i >= 0 {
alt := &f.infos[i]
filename = alt.Filename
if i := searchInts(f.lines, alt.Offset); i >= 0 {
/ i+1 is the line at which the alternative position was recorded
d := line - (i + 1) / line distance from alternative position base
line = alt.Line + d
if alt.Column == 0 {
/ alternative column is unknown => relative column is unknown
/ (the current specification for line directives requires
/ this to apply until the next PosBase/line directive,
/ not just until the new newline)
column = 0
} else if d == 0 {
/ the alternative position base is on the current line
/ => column is relative to alternative column
column = alt.Column + (offset - alt.Offset)
}
}
}
}
return
}
func (f *File) position(p Pos, adjusted bool) (pos Position) {
offset := int(p) - f.base
pos.Offset = 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) {
if p != NoPos {
if int(p) < f.base || int(p) > f.base+f.size {
panic(fmt.Sprintf("invalid Pos value %d (should be in [%d, %d])", p, f.base, f.base+f.size))
}
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)
}
/ -----------------------------------------------------------------------------
/ FileSet
/ A FileSet represents a set of source files.
/ Methods of file sets are synchronized; multiple goroutines
/ may invoke them concurrently.
/
/ The byte offsets for each file in a file set are mapped into
/ distinct (integer) intervals, one interval [base, base+size]
/ per file. Base represents the first byte in the file, and size
/ is the corresponding file size. A Pos value is a value in such
/ an interval. By determining the interval a Pos value belongs
/ to, the file, its file base, and thus the byte offset (position)
/ the Pos value is representing can be computed.
/
/ When adding a new file, a file base must be provided. That can
/ be any integer value that is past the end of any interval of any
/ file already in the file set. For convenience, FileSet.Base provides
/ such a value, which is simply the end of the Pos interval of the most
/ recently added file, plus one. Unless there is a need to extend an
/ interval later, using the FileSet.Base should be used as argument
/ for FileSet.AddFile.
type FileSet struct {
mutex sync.RWMutex / protects the file set
base int / base offset for the next file
files []*File / list of files in the order added to the set
last atomic.Pointer[File] / cache of last file looked up
}
/ NewFileSet creates a new file set.
func NewFileSet() *FileSet {
return &FileSet{
base: 1, / 0 == NoPos
}
}
/ Base returns the minimum base offset that must be provided to
/ AddFile when adding the next file.
func (s *FileSet) Base() int {
s.mutex.RLock()
b := s.base
s.mutex.RUnlock()
return b
}
/ AddFile adds a new file with a given filename, base offset, and file size
/ to the file set s and returns the file. Multiple files may have the same
/ name. The base offset must not be smaller than the FileSet's Base(), and
/ size must not be negative. As a special case, if a negative base is provided,
/ the current value of the FileSet's Base() is used instead.
/
/ Adding the file will set the file set's Base() value to base + size + 1
/ as the minimum base value for the next file. The following relationship
/ exists between a Pos value p for a given file offset offs:
/
/ int(p) = base + offs
/
/ with offs in the range [0, size] and thus p in the range [base, base+size].
/ For convenience, File.Pos may be used to create file-specific position
/ values from a file offset.
func (s *FileSet) AddFile(filename string, base, size int) *File {
/ Allocate f outside the critical section.
f := &File{name: filename, size: size, lines: []int{0}}
s.mutex.Lock()
defer s.mutex.Unlock()
if base < 0 {
base = s.base
}
if base < s.base {
panic(fmt.Sprintf("invalid base %d (should be >= %d)", base, s.base))
}
f.base = base
if size < 0 {
panic(fmt.Sprintf("invalid size %d (should be >= 0)", size))
}
/ base >= s.base && size >= 0
base += size + 1 / +1 because EOF also has a position
if base < 0 {
panic("token.Pos offset overflow (> 2G of source code in file set)")
}
/ add the file to the file set
s.base = base
s.files = append(s.files, f)
s.last.Store(f)
return f
}
/ Iterate calls f for the files in the file set in the order they were added
/ until f returns false.
func (s *FileSet) Iterate(f func(*File) bool) {
for i := 0; ; i++ {
var file *File
s.mutex.RLock()
if i < len(s.files) {
file = s.files[i]
}
s.mutex.RUnlock()
if file == nil || !f(file) {
break
}
}
}
func searchFiles(a []*File, x int) int {
return sort.Search(len(a), func(i int) bool { return a[i].base > x }) - 1
}
func (s *FileSet) file(p Pos) *File {
/ common case: p is in last file.
if f := s.last.Load(); f != nil && f.base <= int(p) && int(p) <= f.base+f.size {
return f
}
s.mutex.RLock()
defer s.mutex.RUnlock()
/ p is not in last file - search all files
if i := searchFiles(s.files, int(p)); i >= 0 {
f := s.files[i]
/ f.base <= int(p) by definition of searchFiles
if int(p) <= f.base+f.size {
/ Update cache of last file. A race is ok,
/ but an exclusive lock causes heavy contention.
s.last.Store(f)
return f
}
}
return nil
}
/ File returns the file that contains the position p.
/ If no such file is found (for instance for p == NoPos),
/ the result is nil.
func (s *FileSet) File(p Pos) (f *File) {
if p != NoPos {
f = s.file(p)
}
return
}
/ PositionFor converts a Pos p in the fileset into a Position value.
/ 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 s or NoPos.
func (s *FileSet) PositionFor(p Pos, adjusted bool) (pos Position) {
if p != NoPos {
if f := s.file(p); f != nil {
return f.position(p, adjusted)
}
}
return
}
/ Position converts a Pos p in the fileset into a Position value.
/ Calling s.Position(p) is equivalent to calling s.PositionFor(p, true).
func (s *FileSet) Position(p Pos) (pos Position) {
return s.PositionFor(p, true)
}
/ -----------------------------------------------------------------------------
/ Helper functions
func searchInts(a []int, x int) 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 := int(uint(i+j) >> 1) / avoid overflow when computing h
/ i ≤ h < j
if a[h] <= x {
i = h + 1
} else {
j = h
}
}
return i - 1
}