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