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 // file:line valid position with file name but no column (column == 0) 34 // line:column valid position without file name 35 // line valid position without file name and no column (column == 0) 36 // file invalid position with file name 37 // - invalid position without file name 38 // 39 func (pos Position) String() string { 40 s := pos.Filename 41 if pos.IsValid() { 42 if s != "" { 43 s += ":" 44 } 45 s += fmt.Sprintf("%d", pos.Line) 46 if pos.Column != 0 { 47 s += fmt.Sprintf(":%d", pos.Column) 48 } 49 } 50 if s == "" { 51 s = "-" 52 } 53 return s 54 } 55 56 // Pos is a compact encoding of a source position within a file set. 57 // It can be converted into a Position for a more convenient, but much 58 // larger, representation. 59 // 60 // The Pos value for a given file is a number in the range [base, base+size], 61 // where base and size are specified when a file is added to the file set. 62 // The difference between a Pos value and the corresponding file base 63 // corresponds to the byte offset of that position (represented by the Pos value) 64 // from the beginning of the file. Thus, the file base offset is the Pos value 65 // representing the first byte in the file. 66 // 67 // To create the Pos value for a specific source offset (measured in bytes), 68 // first add the respective file to the current file set using FileSet.AddFile 69 // and then call File.Pos(offset) for that file. Given a Pos value p 70 // for a specific file set fset, the corresponding Position value is 71 // obtained by calling fset.Position(p). 72 // 73 // Pos values can be compared directly with the usual comparison operators: 74 // If two Pos values p and q are in the same file, comparing p and q is 75 // equivalent to comparing the respective source file offsets. If p and q 76 // are in different files, p < q is true if the file implied by p was added 77 // to the respective file set before the file implied by q. 78 // 79 type Pos int 80 81 // The zero value for Pos is NoPos; there is no file and line information 82 // associated with it, and NoPos.IsValid() is false. NoPos is always 83 // smaller than any other Pos value. The corresponding Position value 84 // for NoPos is the zero value for Position. 85 // 86 const NoPos Pos = 0 87 88 // IsValid reports whether the position is valid. 89 func (p Pos) IsValid() bool { 90 return p != NoPos 91 } 92 93 // ----------------------------------------------------------------------------- 94 // File 95 96 // A File is a handle for a file belonging to a FileSet. 97 // A File has a name, size, and line offset table. 98 // 99 type File struct { 100 set *FileSet 101 name string // file name as provided to AddFile 102 base int // Pos value range for this file is [base...base+size] 103 size int // file size as provided to AddFile 104 105 // lines and infos are protected by mutex 106 mutex sync.Mutex 107 lines []int // lines contains the offset of the first character for each line (the first entry is always 0) 108 infos []lineInfo 109 } 110 111 // Name returns the file name of file f as registered with AddFile. 112 func (f *File) Name() string { 113 return f.name 114 } 115 116 // Base returns the base offset of file f as registered with AddFile. 117 func (f *File) Base() int { 118 return f.base 119 } 120 121 // Size returns the size of file f as registered with AddFile. 122 func (f *File) Size() int { 123 return f.size 124 } 125 126 // LineCount returns the number of lines in file f. 127 func (f *File) LineCount() int { 128 f.mutex.Lock() 129 n := len(f.lines) 130 f.mutex.Unlock() 131 return n 132 } 133 134 // AddLine adds the line offset for a new line. 135 // The line offset must be larger than the offset for the previous line 136 // and smaller than the file size; otherwise the line offset is ignored. 137 // 138 func (f *File) AddLine(offset int) { 139 f.mutex.Lock() 140 if i := len(f.lines); (i == 0 || f.lines[i-1] < offset) && offset < f.size { 141 f.lines = append(f.lines, offset) 142 } 143 f.mutex.Unlock() 144 } 145 146 // MergeLine merges a line with the following line. It is akin to replacing 147 // the newline character at the end of the line with a space (to not change the 148 // remaining offsets). To obtain the line number, consult e.g. Position.Line. 149 // MergeLine will panic if given an invalid line number. 150 // 151 func (f *File) MergeLine(line int) { 152 if line < 1 { 153 panic(fmt.Sprintf("invalid line number %d (should be >= 1)", line)) 154 } 155 f.mutex.Lock() 156 defer f.mutex.Unlock() 157 if line >= len(f.lines) { 158 panic(fmt.Sprintf("invalid line number %d (should be < %d)", line, len(f.lines))) 159 } 160 // To merge the line numbered <line> with the line numbered <line+1>, 161 // we need to remove the entry in lines corresponding to the line 162 // numbered <line+1>. The entry in lines corresponding to the line 163 // numbered <line+1> is located at index <line>, since indices in lines 164 // are 0-based and line numbers are 1-based. 165 copy(f.lines[line:], f.lines[line+1:]) 166 f.lines = f.lines[:len(f.lines)-1] 167 } 168 169 // SetLines sets the line offsets for a file and reports whether it succeeded. 170 // The line offsets are the offsets of the first character of each line; 171 // for instance for the content "ab\nc\n" the line offsets are {0, 3}. 172 // An empty file has an empty line offset table. 173 // Each line offset must be larger than the offset for the previous line 174 // and smaller than the file size; otherwise SetLines fails and returns 175 // false. 176 // Callers must not mutate the provided slice after SetLines returns. 177 // 178 func (f *File) SetLines(lines []int) bool { 179 // verify validity of lines table 180 size := f.size 181 for i, offset := range lines { 182 if i > 0 && offset <= lines[i-1] || size <= offset { 183 return false 184 } 185 } 186 187 // set lines table 188 f.mutex.Lock() 189 f.lines = lines 190 f.mutex.Unlock() 191 return true 192 } 193 194 // SetLinesForContent sets the line offsets for the given file content. 195 // It ignores position-altering //line comments. 196 func (f *File) SetLinesForContent(content []byte) { 197 var lines []int 198 line := 0 199 for offset, b := range content { 200 if line >= 0 { 201 lines = append(lines, line) 202 } 203 line = -1 204 if b == '\n' { 205 line = offset + 1 206 } 207 } 208 209 // set lines table 210 f.mutex.Lock() 211 f.lines = lines 212 f.mutex.Unlock() 213 } 214 215 // LineStart returns the Pos value of the start of the specified line. 216 // It ignores any alternative positions set using AddLineColumnInfo. 217 // LineStart panics if the 1-based line number is invalid. 218 func (f *File) LineStart(line int) Pos { 219 if line < 1 { 220 panic(fmt.Sprintf("invalid line number %d (should be >= 1)", line)) 221 } 222 f.mutex.Lock() 223 defer f.mutex.Unlock() 224 if line > len(f.lines) { 225 panic(fmt.Sprintf("invalid line number %d (should be < %d)", line, len(f.lines))) 226 } 227 return Pos(f.base + f.lines[line-1]) 228 } 229 230 // A lineInfo object describes alternative file, line, and column 231 // number information (such as provided via a //line directive) 232 // for a given file offset. 233 type lineInfo struct { 234 // fields are exported to make them accessible to gob 235 Offset int 236 Filename string 237 Line, Column int 238 } 239 240 // AddLineInfo is like AddLineColumnInfo with a column = 1 argument. 241 // It is here for backward-compatibility for code prior to Go 1.11. 242 // 243 func (f *File) AddLineInfo(offset int, filename string, line int) { 244 f.AddLineColumnInfo(offset, filename, line, 1) 245 } 246 247 // AddLineColumnInfo adds alternative file, line, and column number 248 // information for a given file offset. The offset must be larger 249 // than the offset for the previously added alternative line info 250 // and smaller than the file size; otherwise the information is 251 // ignored. 252 // 253 // AddLineColumnInfo is typically used to register alternative position 254 // information for line directives such as //line filename:line:column. 255 // 256 func (f *File) AddLineColumnInfo(offset int, filename string, line, column int) { 257 f.mutex.Lock() 258 if i := len(f.infos); i == 0 || f.infos[i-1].Offset < offset && offset < f.size { 259 f.infos = append(f.infos, lineInfo{offset, filename, line, column}) 260 } 261 f.mutex.Unlock() 262 } 263 264 // Pos returns the Pos value for the given file offset; 265 // the offset must be <= f.Size(). 266 // f.Pos(f.Offset(p)) == p. 267 // 268 func (f *File) Pos(offset int) Pos { 269 if offset > f.size { 270 panic(fmt.Sprintf("invalid file offset %d (should be <= %d)", offset, f.size)) 271 } 272 return Pos(f.base + offset) 273 } 274 275 // Offset returns the offset for the given file position p; 276 // p must be a valid Pos value in that file. 277 // f.Offset(f.Pos(offset)) == offset. 278 // 279 func (f *File) Offset(p Pos) int { 280 if int(p) < f.base || int(p) > f.base+f.size { 281 panic(fmt.Sprintf("invalid Pos value %d (should be in [%d, %d])", p, f.base, f.base+f.size)) 282 } 283 return int(p) - f.base 284 } 285 286 // Line returns the line number for the given file position p; 287 // p must be a Pos value in that file or NoPos. 288 // 289 func (f *File) Line(p Pos) int { 290 return f.Position(p).Line 291 } 292 293 func searchLineInfos(a []lineInfo, x int) int { 294 return sort.Search(len(a), func(i int) bool { return a[i].Offset > x }) - 1 295 } 296 297 // unpack returns the filename and line and column number for a file offset. 298 // If adjusted is set, unpack will return the filename and line information 299 // possibly adjusted by //line comments; otherwise those comments are ignored. 300 // 301 func (f *File) unpack(offset int, adjusted bool) (filename string, line, column int) { 302 f.mutex.Lock() 303 defer f.mutex.Unlock() 304 filename = f.name 305 if i := searchInts(f.lines, offset); i >= 0 { 306 line, column = i+1, offset-f.lines[i]+1 307 } 308 if adjusted && len(f.infos) > 0 { 309 // few files have extra line infos 310 if i := searchLineInfos(f.infos, offset); i >= 0 { 311 alt := &f.infos[i] 312 filename = alt.Filename 313 if i := searchInts(f.lines, alt.Offset); i >= 0 { 314 // i+1 is the line at which the alternative position was recorded 315 d := line - (i + 1) // line distance from alternative position base 316 line = alt.Line + d 317 if alt.Column == 0 { 318 // alternative column is unknown => relative column is unknown 319 // (the current specification for line directives requires 320 // this to apply until the next PosBase/line directive, 321 // not just until the new newline) 322 column = 0 323 } else if d == 0 { 324 // the alternative position base is on the current line 325 // => column is relative to alternative column 326 column = alt.Column + (offset - alt.Offset) 327 } 328 } 329 } 330 } 331 return 332 } 333 334 func (f *File) position(p Pos, adjusted bool) (pos Position) { 335 offset := int(p) - f.base 336 pos.Offset = offset 337 pos.Filename, pos.Line, pos.Column = f.unpack(offset, adjusted) 338 return 339 } 340 341 // PositionFor returns the Position value for the given file position p. 342 // If adjusted is set, the position may be adjusted by position-altering 343 // //line comments; otherwise those comments are ignored. 344 // p must be a Pos value in f or NoPos. 345 // 346 func (f *File) PositionFor(p Pos, adjusted bool) (pos Position) { 347 if p != NoPos { 348 if int(p) < f.base || int(p) > f.base+f.size { 349 panic(fmt.Sprintf("invalid Pos value %d (should be in [%d, %d])", p, f.base, f.base+f.size)) 350 } 351 pos = f.position(p, adjusted) 352 } 353 return 354 } 355 356 // Position returns the Position value for the given file position p. 357 // Calling f.Position(p) is equivalent to calling f.PositionFor(p, true). 358 // 359 func (f *File) Position(p Pos) (pos Position) { 360 return f.PositionFor(p, true) 361 } 362 363 // ----------------------------------------------------------------------------- 364 // FileSet 365 366 // A FileSet represents a set of source files. 367 // Methods of file sets are synchronized; multiple goroutines 368 // may invoke them concurrently. 369 // 370 // The byte offsets for each file in a file set are mapped into 371 // distinct (integer) intervals, one interval [base, base+size] 372 // per file. Base represents the first byte in the file, and size 373 // is the corresponding file size. A Pos value is a value in such 374 // an interval. By determining the interval a Pos value belongs 375 // to, the file, its file base, and thus the byte offset (position) 376 // the Pos value is representing can be computed. 377 // 378 // When adding a new file, a file base must be provided. That can 379 // be any integer value that is past the end of any interval of any 380 // file already in the file set. For convenience, FileSet.Base provides 381 // such a value, which is simply the end of the Pos interval of the most 382 // recently added file, plus one. Unless there is a need to extend an 383 // interval later, using the FileSet.Base should be used as argument 384 // for FileSet.AddFile. 385 // 386 type FileSet struct { 387 mutex sync.RWMutex // protects the file set 388 base int // base offset for the next file 389 files []*File // list of files in the order added to the set 390 last *File // cache of last file looked up 391 } 392 393 // NewFileSet creates a new file set. 394 func NewFileSet() *FileSet { 395 return &FileSet{ 396 base: 1, // 0 == NoPos 397 } 398 } 399 400 // Base returns the minimum base offset that must be provided to 401 // AddFile when adding the next file. 402 // 403 func (s *FileSet) Base() int { 404 s.mutex.RLock() 405 b := s.base 406 s.mutex.RUnlock() 407 return b 408 409 } 410 411 // AddFile adds a new file with a given filename, base offset, and file size 412 // to the file set s and returns the file. Multiple files may have the same 413 // name. The base offset must not be smaller than the FileSet's Base(), and 414 // size must not be negative. As a special case, if a negative base is provided, 415 // the current value of the FileSet's Base() is used instead. 416 // 417 // Adding the file will set the file set's Base() value to base + size + 1 418 // as the minimum base value for the next file. The following relationship 419 // exists between a Pos value p for a given file offset offs: 420 // 421 // int(p) = base + offs 422 // 423 // with offs in the range [0, size] and thus p in the range [base, base+size]. 424 // For convenience, File.Pos may be used to create file-specific position 425 // values from a file offset. 426 // 427 func (s *FileSet) AddFile(filename string, base, size int) *File { 428 s.mutex.Lock() 429 defer s.mutex.Unlock() 430 if base < 0 { 431 base = s.base 432 } 433 if base < s.base { 434 panic(fmt.Sprintf("invalid base %d (should be >= %d)", base, s.base)) 435 } 436 if size < 0 { 437 panic(fmt.Sprintf("invalid size %d (should be >= 0)", size)) 438 } 439 // base >= s.base && size >= 0 440 f := &File{set: s, name: filename, base: base, size: size, lines: []int{0}} 441 base += size + 1 // +1 because EOF also has a position 442 if base < 0 { 443 panic("token.Pos offset overflow (> 2G of source code in file set)") 444 } 445 // add the file to the file set 446 s.base = base 447 s.files = append(s.files, f) 448 s.last = f 449 return f 450 } 451 452 // Iterate calls f for the files in the file set in the order they were added 453 // until f returns false. 454 // 455 func (s *FileSet) Iterate(f func(*File) bool) { 456 for i := 0; ; i++ { 457 var file *File 458 s.mutex.RLock() 459 if i < len(s.files) { 460 file = s.files[i] 461 } 462 s.mutex.RUnlock() 463 if file == nil || !f(file) { 464 break 465 } 466 } 467 } 468 469 func searchFiles(a []*File, x int) int { 470 return sort.Search(len(a), func(i int) bool { return a[i].base > x }) - 1 471 } 472 473 func (s *FileSet) file(p Pos) *File { 474 s.mutex.RLock() 475 // common case: p is in last file 476 if f := s.last; f != nil && f.base <= int(p) && int(p) <= f.base+f.size { 477 s.mutex.RUnlock() 478 return f 479 } 480 // p is not in last file - search all files 481 if i := searchFiles(s.files, int(p)); i >= 0 { 482 f := s.files[i] 483 // f.base <= int(p) by definition of searchFiles 484 if int(p) <= f.base+f.size { 485 s.mutex.RUnlock() 486 s.mutex.Lock() 487 s.last = f // race is ok - s.last is only a cache 488 s.mutex.Unlock() 489 return f 490 } 491 } 492 s.mutex.RUnlock() 493 return nil 494 } 495 496 // File returns the file that contains the position p. 497 // If no such file is found (for instance for p == NoPos), 498 // the result is nil. 499 // 500 func (s *FileSet) File(p Pos) (f *File) { 501 if p != NoPos { 502 f = s.file(p) 503 } 504 return 505 } 506 507 // PositionFor converts a Pos p in the fileset into a Position value. 508 // If adjusted is set, the position may be adjusted by position-altering 509 // //line comments; otherwise those comments are ignored. 510 // p must be a Pos value in s or NoPos. 511 // 512 func (s *FileSet) PositionFor(p Pos, adjusted bool) (pos Position) { 513 if p != NoPos { 514 if f := s.file(p); f != nil { 515 return f.position(p, adjusted) 516 } 517 } 518 return 519 } 520 521 // Position converts a Pos p in the fileset into a Position value. 522 // Calling s.Position(p) is equivalent to calling s.PositionFor(p, true). 523 // 524 func (s *FileSet) Position(p Pos) (pos Position) { 525 return s.PositionFor(p, true) 526 } 527 528 // ----------------------------------------------------------------------------- 529 // Helper functions 530 531 func searchInts(a []int, x int) int { 532 // This function body is a manually inlined version of: 533 // 534 // return sort.Search(len(a), func(i int) bool { return a[i] > x }) - 1 535 // 536 // With better compiler optimizations, this may not be needed in the 537 // future, but at the moment this change improves the go/printer 538 // benchmark performance by ~30%. This has a direct impact on the 539 // speed of gofmt and thus seems worthwhile (2011-04-29). 540 // TODO(gri): Remove this when compilers have caught up. 541 i, j := 0, len(a) 542 for i < j { 543 h := int(uint(i+j) >> 1) // avoid overflow when computing h 544 // i ≤ h < j 545 if a[h] <= x { 546 i = h + 1 547 } else { 548 j = h 549 } 550 } 551 return i - 1 552 } 553