...
Run Format

Source file src/go/token/position.go

     1	// Copyright 2010 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package token
     6	
     7	import (
     8		"fmt"
     9		"sort"
    10		"sync"
    11	)
    12	
    13	// -----------------------------------------------------------------------------
    14	// Positions
    15	
    16	// Position describes an arbitrary source position
    17	// including the file, line, and column location.
    18	// A Position is valid if the line number is > 0.
    19	//
    20	type Position struct {
    21		Filename string // filename, if any
    22		Offset   int    // offset, starting at 0
    23		Line     int    // line number, starting at 1
    24		Column   int    // column number, starting at 1 (byte count)
    25	}
    26	
    27	// IsValid reports whether the position is valid.
    28	func (pos *Position) IsValid() bool { return pos.Line > 0 }
    29	
    30	// String returns a string in one of several forms:
    31	//
    32	//	file:line:column    valid position with file name
    33	//	line:column         valid position without file name
    34	//	file                invalid position with file name
    35	//	-                   invalid position without file name
    36	//
    37	func (pos Position) String() string {
    38		s := pos.Filename
    39		if pos.IsValid() {
    40			if s != "" {
    41				s += ":"
    42			}
    43			s += fmt.Sprintf("%d:%d", pos.Line, pos.Column)
    44		}
    45		if s == "" {
    46			s = "-"
    47		}
    48		return s
    49	}
    50	
    51	// Pos is a compact encoding of a source position within a file set.
    52	// It can be converted into a Position for a more convenient, but much
    53	// larger, representation.
    54	//
    55	// The Pos value for a given file is a number in the range [base, base+size],
    56	// where base and size are specified when adding the file to the file set via
    57	// AddFile.
    58	//
    59	// To create the Pos value for a specific source offset (measured in bytes),
    60	// first add the respective file to the current file set using FileSet.AddFile
    61	// and then call File.Pos(offset) for that file. Given a Pos value p
    62	// for a specific file set fset, the corresponding Position value is
    63	// obtained by calling fset.Position(p).
    64	//
    65	// Pos values can be compared directly with the usual comparison operators:
    66	// If two Pos values p and q are in the same file, comparing p and q is
    67	// equivalent to comparing the respective source file offsets. If p and q
    68	// are in different files, p < q is true if the file implied by p was added
    69	// to the respective file set before the file implied by q.
    70	//
    71	type Pos int
    72	
    73	// The zero value for Pos is NoPos; there is no file and line information
    74	// associated with it, and NoPos().IsValid() is false. NoPos is always
    75	// smaller than any other Pos value. The corresponding Position value
    76	// for NoPos is the zero value for Position.
    77	//
    78	const NoPos Pos = 0
    79	
    80	// IsValid reports whether the position is valid.
    81	func (p Pos) IsValid() bool {
    82		return p != NoPos
    83	}
    84	
    85	// -----------------------------------------------------------------------------
    86	// File
    87	
    88	// A File is a handle for a file belonging to a FileSet.
    89	// A File has a name, size, and line offset table.
    90	//
    91	type File struct {
    92		set  *FileSet
    93		name string // file name as provided to AddFile
    94		base int    // Pos value range for this file is [base...base+size]
    95		size int    // file size as provided to AddFile
    96	
    97		// lines and infos are protected by set.mutex
    98		lines []int // lines contains the offset of the first character for each line (the first entry is always 0)
    99		infos []lineInfo
   100	}
   101	
   102	// Name returns the file name of file f as registered with AddFile.
   103	func (f *File) Name() string {
   104		return f.name
   105	}
   106	
   107	// Base returns the base offset of file f as registered with AddFile.
   108	func (f *File) Base() int {
   109		return f.base
   110	}
   111	
   112	// Size returns the size of file f as registered with AddFile.
   113	func (f *File) Size() int {
   114		return f.size
   115	}
   116	
   117	// LineCount returns the number of lines in file f.
   118	func (f *File) LineCount() int {
   119		f.set.mutex.RLock()
   120		n := len(f.lines)
   121		f.set.mutex.RUnlock()
   122		return n
   123	}
   124	
   125	// AddLine adds the line offset for a new line.
   126	// The line offset must be larger than the offset for the previous line
   127	// and smaller than the file size; otherwise the line offset is ignored.
   128	//
   129	func (f *File) AddLine(offset int) {
   130		f.set.mutex.Lock()
   131		if i := len(f.lines); (i == 0 || f.lines[i-1] < offset) && offset < f.size {
   132			f.lines = append(f.lines, offset)
   133		}
   134		f.set.mutex.Unlock()
   135	}
   136	
   137	// MergeLine merges a line with the following line. It is akin to replacing
   138	// the newline character at the end of the line with a space (to not change the
   139	// remaining offsets). To obtain the line number, consult e.g. Position.Line.
   140	// MergeLine will panic if given an invalid line number.
   141	//
   142	func (f *File) MergeLine(line int) {
   143		if line <= 0 {
   144			panic("illegal line number (line numbering starts at 1)")
   145		}
   146		f.set.mutex.Lock()
   147		defer f.set.mutex.Unlock()
   148		if line >= len(f.lines) {
   149			panic("illegal line number")
   150		}
   151		// To merge the line numbered <line> with the line numbered <line+1>,
   152		// we need to remove the entry in lines corresponding to the line
   153		// numbered <line+1>. The entry in lines corresponding to the line
   154		// numbered <line+1> is located at index <line>, since indices in lines
   155		// are 0-based and line numbers are 1-based.
   156		copy(f.lines[line:], f.lines[line+1:])
   157		f.lines = f.lines[:len(f.lines)-1]
   158	}
   159	
   160	// SetLines sets the line offsets for a file and reports whether it succeeded.
   161	// The line offsets are the offsets of the first character of each line;
   162	// for instance for the content "ab\nc\n" the line offsets are {0, 3}.
   163	// An empty file has an empty line offset table.
   164	// Each line offset must be larger than the offset for the previous line
   165	// and smaller than the file size; otherwise SetLines fails and returns
   166	// false.
   167	// Callers must not mutate the provided slice after SetLines returns.
   168	//
   169	func (f *File) SetLines(lines []int) bool {
   170		// verify validity of lines table
   171		size := f.size
   172		for i, offset := range lines {
   173			if i > 0 && offset <= lines[i-1] || size <= offset {
   174				return false
   175			}
   176		}
   177	
   178		// set lines table
   179		f.set.mutex.Lock()
   180		f.lines = lines
   181		f.set.mutex.Unlock()
   182		return true
   183	}
   184	
   185	// SetLinesForContent sets the line offsets for the given file content.
   186	// It ignores position-altering //line comments.
   187	func (f *File) SetLinesForContent(content []byte) {
   188		var lines []int
   189		line := 0
   190		for offset, b := range content {
   191			if line >= 0 {
   192				lines = append(lines, line)
   193			}
   194			line = -1
   195			if b == '\n' {
   196				line = offset + 1
   197			}
   198		}
   199	
   200		// set lines table
   201		f.set.mutex.Lock()
   202		f.lines = lines
   203		f.set.mutex.Unlock()
   204	}
   205	
   206	// A lineInfo object describes alternative file and line number
   207	// information (such as provided via a //line comment in a .go
   208	// file) for a given file offset.
   209	type lineInfo struct {
   210		// fields are exported to make them accessible to gob
   211		Offset   int
   212		Filename string
   213		Line     int
   214	}
   215	
   216	// AddLineInfo adds alternative file and line number information for
   217	// a given file offset. The offset must be larger than the offset for
   218	// the previously added alternative line info and smaller than the
   219	// file size; otherwise the information is ignored.
   220	//
   221	// AddLineInfo is typically used to register alternative position
   222	// information for //line filename:line comments in source files.
   223	//
   224	func (f *File) AddLineInfo(offset int, filename string, line int) {
   225		f.set.mutex.Lock()
   226		if i := len(f.infos); i == 0 || f.infos[i-1].Offset < offset && offset < f.size {
   227			f.infos = append(f.infos, lineInfo{offset, filename, line})
   228		}
   229		f.set.mutex.Unlock()
   230	}
   231	
   232	// Pos returns the Pos value for the given file offset;
   233	// the offset must be <= f.Size().
   234	// f.Pos(f.Offset(p)) == p.
   235	//
   236	func (f *File) Pos(offset int) Pos {
   237		if offset > f.size {
   238			panic("illegal file offset")
   239		}
   240		return Pos(f.base + offset)
   241	}
   242	
   243	// Offset returns the offset for the given file position p;
   244	// p must be a valid Pos value in that file.
   245	// f.Offset(f.Pos(offset)) == offset.
   246	//
   247	func (f *File) Offset(p Pos) int {
   248		if int(p) < f.base || int(p) > f.base+f.size {
   249			panic("illegal Pos value")
   250		}
   251		return int(p) - f.base
   252	}
   253	
   254	// Line returns the line number for the given file position p;
   255	// p must be a Pos value in that file or NoPos.
   256	//
   257	func (f *File) Line(p Pos) int {
   258		return f.Position(p).Line
   259	}
   260	
   261	func searchLineInfos(a []lineInfo, x int) int {
   262		return sort.Search(len(a), func(i int) bool { return a[i].Offset > x }) - 1
   263	}
   264	
   265	// unpack returns the filename and line and column number for a file offset.
   266	// If adjusted is set, unpack will return the filename and line information
   267	// possibly adjusted by //line comments; otherwise those comments are ignored.
   268	//
   269	func (f *File) unpack(offset int, adjusted bool) (filename string, line, column int) {
   270		filename = f.name
   271		if i := searchInts(f.lines, offset); i >= 0 {
   272			line, column = i+1, offset-f.lines[i]+1
   273		}
   274		if adjusted && len(f.infos) > 0 {
   275			// almost no files have extra line infos
   276			if i := searchLineInfos(f.infos, offset); i >= 0 {
   277				alt := &f.infos[i]
   278				filename = alt.Filename
   279				if i := searchInts(f.lines, alt.Offset); i >= 0 {
   280					line += alt.Line - i - 1
   281				}
   282			}
   283		}
   284		return
   285	}
   286	
   287	func (f *File) position(p Pos, adjusted bool) (pos Position) {
   288		offset := int(p) - f.base
   289		pos.Offset = offset
   290		pos.Filename, pos.Line, pos.Column = f.unpack(offset, adjusted)
   291		return
   292	}
   293	
   294	// PositionFor returns the Position value for the given file position p.
   295	// If adjusted is set, the position may be adjusted by position-altering
   296	// //line comments; otherwise those comments are ignored.
   297	// p must be a Pos value in f or NoPos.
   298	//
   299	func (f *File) PositionFor(p Pos, adjusted bool) (pos Position) {
   300		if p != NoPos {
   301			if int(p) < f.base || int(p) > f.base+f.size {
   302				panic("illegal Pos value")
   303			}
   304			pos = f.position(p, adjusted)
   305		}
   306		return
   307	}
   308	
   309	// Position returns the Position value for the given file position p.
   310	// Calling f.Position(p) is equivalent to calling f.PositionFor(p, true).
   311	//
   312	func (f *File) Position(p Pos) (pos Position) {
   313		return f.PositionFor(p, true)
   314	}
   315	
   316	// -----------------------------------------------------------------------------
   317	// FileSet
   318	
   319	// A FileSet represents a set of source files.
   320	// Methods of file sets are synchronized; multiple goroutines
   321	// may invoke them concurrently.
   322	//
   323	type FileSet struct {
   324		mutex sync.RWMutex // protects the file set
   325		base  int          // base offset for the next file
   326		files []*File      // list of files in the order added to the set
   327		last  *File        // cache of last file looked up
   328	}
   329	
   330	// NewFileSet creates a new file set.
   331	func NewFileSet() *FileSet {
   332		return &FileSet{
   333			base: 1, // 0 == NoPos
   334		}
   335	}
   336	
   337	// Base returns the minimum base offset that must be provided to
   338	// AddFile when adding the next file.
   339	//
   340	func (s *FileSet) Base() int {
   341		s.mutex.RLock()
   342		b := s.base
   343		s.mutex.RUnlock()
   344		return b
   345	
   346	}
   347	
   348	// AddFile adds a new file with a given filename, base offset, and file size
   349	// to the file set s and returns the file. Multiple files may have the same
   350	// name. The base offset must not be smaller than the FileSet's Base(), and
   351	// size must not be negative. As a special case, if a negative base is provided,
   352	// the current value of the FileSet's Base() is used instead.
   353	//
   354	// Adding the file will set the file set's Base() value to base + size + 1
   355	// as the minimum base value for the next file. The following relationship
   356	// exists between a Pos value p for a given file offset offs:
   357	//
   358	//	int(p) = base + offs
   359	//
   360	// with offs in the range [0, size] and thus p in the range [base, base+size].
   361	// For convenience, File.Pos may be used to create file-specific position
   362	// values from a file offset.
   363	//
   364	func (s *FileSet) AddFile(filename string, base, size int) *File {
   365		s.mutex.Lock()
   366		defer s.mutex.Unlock()
   367		if base < 0 {
   368			base = s.base
   369		}
   370		if base < s.base || size < 0 {
   371			panic("illegal base or size")
   372		}
   373		// base >= s.base && size >= 0
   374		f := &File{s, filename, base, size, []int{0}, nil}
   375		base += size + 1 // +1 because EOF also has a position
   376		if base < 0 {
   377			panic("token.Pos offset overflow (> 2G of source code in file set)")
   378		}
   379		// add the file to the file set
   380		s.base = base
   381		s.files = append(s.files, f)
   382		s.last = f
   383		return f
   384	}
   385	
   386	// Iterate calls f for the files in the file set in the order they were added
   387	// until f returns false.
   388	//
   389	func (s *FileSet) Iterate(f func(*File) bool) {
   390		for i := 0; ; i++ {
   391			var file *File
   392			s.mutex.RLock()
   393			if i < len(s.files) {
   394				file = s.files[i]
   395			}
   396			s.mutex.RUnlock()
   397			if file == nil || !f(file) {
   398				break
   399			}
   400		}
   401	}
   402	
   403	func searchFiles(a []*File, x int) int {
   404		return sort.Search(len(a), func(i int) bool { return a[i].base > x }) - 1
   405	}
   406	
   407	func (s *FileSet) file(p Pos) *File {
   408		s.mutex.RLock()
   409		// common case: p is in last file
   410		if f := s.last; f != nil && f.base <= int(p) && int(p) <= f.base+f.size {
   411			s.mutex.RUnlock()
   412			return f
   413		}
   414		// p is not in last file - search all files
   415		if i := searchFiles(s.files, int(p)); i >= 0 {
   416			f := s.files[i]
   417			// f.base <= int(p) by definition of searchFiles
   418			if int(p) <= f.base+f.size {
   419				s.mutex.RUnlock()
   420				s.mutex.Lock()
   421				s.last = f // race is ok - s.last is only a cache
   422				s.mutex.Unlock()
   423				return f
   424			}
   425		}
   426		s.mutex.RUnlock()
   427		return nil
   428	}
   429	
   430	// File returns the file that contains the position p.
   431	// If no such file is found (for instance for p == NoPos),
   432	// the result is nil.
   433	//
   434	func (s *FileSet) File(p Pos) (f *File) {
   435		if p != NoPos {
   436			f = s.file(p)
   437		}
   438		return
   439	}
   440	
   441	// PositionFor converts a Pos p in the fileset into a Position value.
   442	// If adjusted is set, the position may be adjusted by position-altering
   443	// //line comments; otherwise those comments are ignored.
   444	// p must be a Pos value in s or NoPos.
   445	//
   446	func (s *FileSet) PositionFor(p Pos, adjusted bool) (pos Position) {
   447		if p != NoPos {
   448			if f := s.file(p); f != nil {
   449				pos = f.position(p, adjusted)
   450			}
   451		}
   452		return
   453	}
   454	
   455	// Position converts a Pos p in the fileset into a Position value.
   456	// Calling s.Position(p) is equivalent to calling s.PositionFor(p, true).
   457	//
   458	func (s *FileSet) Position(p Pos) (pos Position) {
   459		return s.PositionFor(p, true)
   460	}
   461	
   462	// -----------------------------------------------------------------------------
   463	// Helper functions
   464	
   465	func searchInts(a []int, x int) int {
   466		// This function body is a manually inlined version of:
   467		//
   468		//   return sort.Search(len(a), func(i int) bool { return a[i] > x }) - 1
   469		//
   470		// With better compiler optimizations, this may not be needed in the
   471		// future, but at the moment this change improves the go/printer
   472		// benchmark performance by ~30%. This has a direct impact on the
   473		// speed of gofmt and thus seems worthwhile (2011-04-29).
   474		// TODO(gri): Remove this when compilers have caught up.
   475		i, j := 0, len(a)
   476		for i < j {
   477			h := i + (j-i)/2 // avoid overflow when computing h
   478			// i ≤ h < j
   479			if a[h] <= x {
   480				i = h + 1
   481			} else {
   482				j = h
   483			}
   484		}
   485		return i - 1
   486	}
   487	

View as plain text