libgo/go/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 mutex
  98         mutex sync.Mutex
  99         lines []int // lines contains the offset of the first character for each line (the first entry is always 0)
 100         infos []lineInfo
 101 }
 102
 103 // Name returns the file name of file f as registered with AddFile.
 104 func (f *File) Name() string {
 105         return f.name
 106 }
 107
 108 // Base returns the base offset of file f as registered with AddFile.
 109 func (f *File) Base() int {
 110         return f.base
 111 }
 112
 113 // Size returns the size of file f as registered with AddFile.
 114 func (f *File) Size() int {
 115         return f.size
 116 }
 117
 118 // LineCount returns the number of lines in file f.
 119 func (f *File) LineCount() int {
 120         f.mutex.Lock()
 121         n := len(f.lines)
 122         f.mutex.Unlock()
 123         return n
 124 }
 125
 126 // AddLine adds the line offset for a new line.
 127 // The line offset must be larger than the offset for the previous line
 128 // and smaller than the file size; otherwise the line offset is ignored.
 129 //
 130 func (f *File) AddLine(offset int) {
 131         f.mutex.Lock()
 132         if i := len(f.lines); (i == 0 || f.lines[i-1] < offset) && offset < f.size {
 133                 f.lines = append(f.lines, offset)
 134         }
 135         f.mutex.Unlock()
 136 }
 137
 138 // MergeLine merges a line with the following line. It is akin to replacing
 139 // the newline character at the end of the line with a space (to not change the
 140 // remaining offsets). To obtain the line number, consult e.g. Position.Line.
 141 // MergeLine will panic if given an invalid line number.
 142 //
 143 func (f *File) MergeLine(line int) {
 144         if line <= 0 {
 145                 panic("illegal line number (line numbering starts at 1)")
 146         }
 147         f.mutex.Lock()
 148         defer f.mutex.Unlock()
 149         if line >= len(f.lines) {
 150                 panic("illegal line number")
 151         }
 152         // To merge the line numbered <line> with the line numbered <line+1>,
 153         // we need to remove the entry in lines corresponding to the line
 154         // numbered <line+1>. The entry in lines corresponding to the line
 155         // numbered <line+1> is located at index <line>, since indices in lines
 156         // are 0-based and line numbers are 1-based.
 157         copy(f.lines[line:], f.lines[line+1:])
 158         f.lines = f.lines[:len(f.lines)-1]
 159 }
 160
 161 // SetLines sets the line offsets for a file and reports whether it succeeded.
 162 // The line offsets are the offsets of the first character of each line;
 163 // for instance for the content "ab\nc\n" the line offsets are {0, 3}.
 164 // An empty file has an empty line offset table.
 165 // Each line offset must be larger than the offset for the previous line
 166 // and smaller than the file size; otherwise SetLines fails and returns
 167 // false.
 168 // Callers must not mutate the provided slice after SetLines returns.
 169 //
 170 func (f *File) SetLines(lines []int) bool {
 171         // verify validity of lines table
 172         size := f.size
 173         for i, offset := range lines {
 174                 if i > 0 && offset <= lines[i-1] || size <= offset {
 175                         return false
 176                 }
 177         }
 178
 179         // set lines table
 180         f.mutex.Lock()
 181         f.lines = lines
 182         f.mutex.Unlock()
 183         return true
 184 }
 185
 186 // SetLinesForContent sets the line offsets for the given file content.
 187 // It ignores position-altering //line comments.
 188 func (f *File) SetLinesForContent(content []byte) {
 189         var lines []int
 190         line := 0
 191         for offset, b := range content {
 192                 if line >= 0 {
 193                         lines = append(lines, line)
 194                 }
 195                 line = -1
 196                 if b == '\n' {
 197                         line = offset + 1
 198                 }
 199         }
 200
 201         // set lines table
 202         f.mutex.Lock()
 203         f.lines = lines
 204         f.mutex.Unlock()
 205 }
 206
 207 // A lineInfo object describes alternative file and line number
 208 // information (such as provided via a //line comment in a .go
 209 // file) for a given file offset.
 210 type lineInfo struct {
 211         // fields are exported to make them accessible to gob
 212         Offset   int
 213         Filename string
 214         Line     int
 215 }
 216
 217 // AddLineInfo adds alternative file and line number information for
 218 // a given file offset. The offset must be larger than the offset for
 219 // the previously added alternative line info and smaller than the
 220 // file size; otherwise the information is ignored.
 221 //
 222 // AddLineInfo is typically used to register alternative position
 223 // information for //line filename:line comments in source files.
 224 //
 225 func (f *File) AddLineInfo(offset int, filename string, line int) {
 226         f.mutex.Lock()
 227         if i := len(f.infos); i == 0 || f.infos[i-1].Offset < offset && offset < f.size {
 228                 f.infos = append(f.infos, lineInfo{offset, filename, line})
 229         }
 230         f.mutex.Unlock()
 231 }
 232
 233 // Pos returns the Pos value for the given file offset;
 234 // the offset must be <= f.Size().
 235 // f.Pos(f.Offset(p)) == p.
 236 //
 237 func (f *File) Pos(offset int) Pos {
 238         if offset > f.size {
 239                 panic("illegal file offset")
 240         }
 241         return Pos(f.base + offset)
 242 }
 243
 244 // Offset returns the offset for the given file position p;
 245 // p must be a valid Pos value in that file.
 246 // f.Offset(f.Pos(offset)) == offset.
 247 //
 248 func (f *File) Offset(p Pos) int {
 249         if int(p) < f.base || int(p) > f.base+f.size {
 250                 panic("illegal Pos value")
 251         }
 252         return int(p) - f.base
 253 }
 254
 255 // Line returns the line number for the given file position p;
 256 // p must be a Pos value in that file or NoPos.
 257 //
 258 func (f *File) Line(p Pos) int {
 259         return f.Position(p).Line
 260 }
 261
 262 func searchLineInfos(a []lineInfo, x int) int {
 263         return sort.Search(len(a), func(i int) bool { return a[i].Offset > x }) - 1
 264 }
 265
 266 // unpack returns the filename and line and column number for a file offset.
 267 // If adjusted is set, unpack will return the filename and line information
 268 // possibly adjusted by //line comments; otherwise those comments are ignored.
 269 //
 270 func (f *File) unpack(offset int, adjusted bool) (filename string, line, column int) {
 271         f.mutex.Lock()
 272         defer f.mutex.Unlock()
 273         filename = f.name
 274         if i := searchInts(f.lines, offset); i >= 0 {
 275                 line, column = i+1, offset-f.lines[i]+1
 276         }
 277         if adjusted && len(f.infos) > 0 {
 278                 // almost no files have extra line infos
 279                 if i := searchLineInfos(f.infos, offset); i >= 0 {
 280                         alt := &f.infos[i]
 281                         filename = alt.Filename
 282                         if i := searchInts(f.lines, alt.Offset); i >= 0 {
 283                                 line += alt.Line - i - 1
 284                         }
 285                 }
 286         }
 287         return
 288 }
 289
 290 func (f *File) position(p Pos, adjusted bool) (pos Position) {
 291         offset := int(p) - f.base
 292         pos.Offset = offset
 293         pos.Filename, pos.Line, pos.Column = f.unpack(offset, adjusted)
 294         return
 295 }
 296
 297 // PositionFor returns the Position value for the given file position p.
 298 // If adjusted is set, the position may be adjusted by position-altering
 299 // //line comments; otherwise those comments are ignored.
 300 // p must be a Pos value in f or NoPos.
 301 //
 302 func (f *File) PositionFor(p Pos, adjusted bool) (pos Position) {
 303         if p != NoPos {
 304                 if int(p) < f.base || int(p) > f.base+f.size {
 305                         panic("illegal Pos value")
 306                 }
 307                 pos = f.position(p, adjusted)
 308         }
 309         return
 310 }
 311
 312 // Position returns the Position value for the given file position p.
 313 // Calling f.Position(p) is equivalent to calling f.PositionFor(p, true).
 314 //
 315 func (f *File) Position(p Pos) (pos Position) {
 316         return f.PositionFor(p, true)
 317 }
 318
 319 // -----------------------------------------------------------------------------
 320 // FileSet
 321
 322 // A FileSet represents a set of source files.
 323 // Methods of file sets are synchronized; multiple goroutines
 324 // may invoke them concurrently.
 325 //
 326 type FileSet struct {
 327         mutex sync.RWMutex // protects the file set
 328         base  int          // base offset for the next file
 329         files []*File      // list of files in the order added to the set
 330         last  *File        // cache of last file looked up
 331 }
 332
 333 // NewFileSet creates a new file set.
 334 func NewFileSet() *FileSet {
 335         return &FileSet{
 336                 base: 1, // 0 == NoPos
 337         }
 338 }
 339
 340 // Base returns the minimum base offset that must be provided to
 341 // AddFile when adding the next file.
 342 //
 343 func (s *FileSet) Base() int {
 344         s.mutex.RLock()
 345         b := s.base
 346         s.mutex.RUnlock()
 347         return b
 348
 349 }
 350
 351 // AddFile adds a new file with a given filename, base offset, and file size
 352 // to the file set s and returns the file. Multiple files may have the same
 353 // name. The base offset must not be smaller than the FileSet's Base(), and
 354 // size must not be negative. As a special case, if a negative base is provided,
 355 // the current value of the FileSet's Base() is used instead.
 356 //
 357 // Adding the file will set the file set's Base() value to base + size + 1
 358 // as the minimum base value for the next file. The following relationship
 359 // exists between a Pos value p for a given file offset offs:
 360 //
 361 //      int(p) = base + offs
 362 //
 363 // with offs in the range [0, size] and thus p in the range [base, base+size].
 364 // For convenience, File.Pos may be used to create file-specific position
 365 // values from a file offset.
 366 //
 367 func (s *FileSet) AddFile(filename string, base, size int) *File {
 368         s.mutex.Lock()
 369         defer s.mutex.Unlock()
 370         if base < 0 {
 371                 base = s.base
 372         }
 373         if base < s.base || size < 0 {
 374                 panic("illegal base or size")
 375         }
 376         // base >= s.base && size >= 0
 377         f := &File{set: s, name: filename, base: base, size: size, lines: []int{0}}
 378         base += size + 1 // +1 because EOF also has a position
 379         if base < 0 {
 380                 panic("token.Pos offset overflow (> 2G of source code in file set)")
 381         }
 382         // add the file to the file set
 383         s.base = base
 384         s.files = append(s.files, f)
 385         s.last = f
 386         return f
 387 }
 388
 389 // Iterate calls f for the files in the file set in the order they were added
 390 // until f returns false.
 391 //
 392 func (s *FileSet) Iterate(f func(*File) bool) {
 393         for i := 0; ; i++ {
 394                 var file *File
 395                 s.mutex.RLock()
 396                 if i < len(s.files) {
 397                         file = s.files[i]
 398                 }
 399                 s.mutex.RUnlock()
 400                 if file == nil || !f(file) {
 401                         break
 402                 }
 403         }
 404 }
 405
 406 func searchFiles(a []*File, x int) int {
 407         return sort.Search(len(a), func(i int) bool { return a[i].base > x }) - 1
 408 }
 409
 410 func (s *FileSet) file(p Pos) *File {
 411         s.mutex.RLock()
 412         // common case: p is in last file
 413         if f := s.last; f != nil && f.base <= int(p) && int(p) <= f.base+f.size {
 414                 s.mutex.RUnlock()
 415                 return f
 416         }
 417         // p is not in last file - search all files
 418         if i := searchFiles(s.files, int(p)); i >= 0 {
 419                 f := s.files[i]
 420                 // f.base <= int(p) by definition of searchFiles
 421                 if int(p) <= f.base+f.size {
 422                         s.mutex.RUnlock()
 423                         s.mutex.Lock()
 424                         s.last = f // race is ok - s.last is only a cache
 425                         s.mutex.Unlock()
 426                         return f
 427                 }
 428         }
 429         s.mutex.RUnlock()
 430         return nil
 431 }
 432
 433 // File returns the file that contains the position p.
 434 // If no such file is found (for instance for p == NoPos),
 435 // the result is nil.
 436 //
 437 func (s *FileSet) File(p Pos) (f *File) {
 438         if p != NoPos {
 439                 f = s.file(p)
 440         }
 441         return
 442 }
 443
 444 // PositionFor converts a Pos p in the fileset into a Position value.
 445 // If adjusted is set, the position may be adjusted by position-altering
 446 // //line comments; otherwise those comments are ignored.
 447 // p must be a Pos value in s or NoPos.
 448 //
 449 func (s *FileSet) PositionFor(p Pos, adjusted bool) (pos Position) {
 450         if p != NoPos {
 451                 if f := s.file(p); f != nil {
 452                         return f.position(p, adjusted)
 453                 }
 454         }
 455         return
 456 }
 457
 458 // Position converts a Pos p in the fileset into a Position value.
 459 // Calling s.Position(p) is equivalent to calling s.PositionFor(p, true).
 460 //
 461 func (s *FileSet) Position(p Pos) (pos Position) {
 462         return s.PositionFor(p, true)
 463 }
 464
 465 // -----------------------------------------------------------------------------
 466 // Helper functions
 467
 468 func searchInts(a []int, x int) int {
 469         // This function body is a manually inlined version of:
 470         //
 471         //   return sort.Search(len(a), func(i int) bool { return a[i] > x }) - 1
 472         //
 473         // With better compiler optimizations, this may not be needed in the
 474         // future, but at the moment this change improves the go/printer
 475         // benchmark performance by ~30%. This has a direct impact on the
 476         // speed of gofmt and thus seems worthwhile (2011-04-29).
 477         // TODO(gri): Remove this when compilers have caught up.
 478         i, j := 0, len(a)
 479         for i < j {
 480                 h := i + (j-i)/2 // avoid overflow when computing h
 481                 // i ≤ h < j
 482                 if a[h] <= x {
 483                         i = h + 1
 484                 } else {
 485                         j = h
 486                 }
 487         }
 488         return i - 1
 489 }