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Diffstat (limited to 'src/go/token/position.go')
| -rw-r--r-- | src/go/token/position.go | 485 |
1 files changed, 485 insertions, 0 deletions
diff --git a/src/go/token/position.go b/src/go/token/position.go new file mode 100644 index 000000000..82d90eeb7 --- /dev/null +++ b/src/go/token/position.go @@ -0,0 +1,485 @@ +// 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" +) + +// ----------------------------------------------------------------------------- +// 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 (character count) +} + +// IsValid returns true if 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 +// line:column valid position without file name +// 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:%d", pos.Line, 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 adding the file to the file set via +// AddFile. +// +// To create the Pos value for a specific source offset, first add +// the respective file to the current file set (via 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 returns true if 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 { + set *FileSet + 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 set.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.set.mutex.RLock() + n := len(f.lines) + f.set.mutex.RUnlock() + 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.set.mutex.Lock() + if i := len(f.lines); (i == 0 || f.lines[i-1] < offset) && offset < f.size { + f.lines = append(f.lines, offset) + } + f.set.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 <= 0 { + panic("illegal line number (line numbering starts at 1)") + } + f.set.mutex.Lock() + defer f.set.mutex.Unlock() + if line >= len(f.lines) { + panic("illegal line number") + } + // 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 returns true if successful. +// 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. +// +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.set.mutex.Lock() + f.lines = lines + f.set.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.set.mutex.Lock() + f.lines = lines + f.set.mutex.Unlock() +} + +// A lineInfo object describes alternative file and line number +// information (such as provided via a //line comment in a .go +// file) for a given file offset. +type lineInfo struct { + // fields are exported to make them accessible to gob + Offset int + Filename string + Line int +} + +// AddLineInfo adds alternative file and line 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. +// +// AddLineInfo is typically used to register alternative position +// information for //line filename:line comments in source files. +// +func (f *File) AddLineInfo(offset int, filename string, line int) { + f.set.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}) + } + f.set.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("illegal file offset") + } + 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("illegal Pos value") + } + 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) { + 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 { + // almost no 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 { + line += alt.Line - i - 1 + } + } + } + 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("illegal Pos value") + } + 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. +// +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 *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 { + s.mutex.Lock() + defer s.mutex.Unlock() + if base < 0 { + base = s.base + } + if base < s.base || size < 0 { + panic("illegal base or size") + } + // base >= s.base && size >= 0 + f := &File{s, filename, base, size, []int{0}, nil} + 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 = 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 { + s.mutex.RLock() + // common case: p is in last file + if f := s.last; f != nil && f.base <= int(p) && int(p) <= f.base+f.size { + s.mutex.RUnlock() + return f + } + // 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 { + s.mutex.RUnlock() + s.mutex.Lock() + s.last = f // race is ok - s.last is only a cache + s.mutex.Unlock() + return f + } + } + s.mutex.RUnlock() + 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 { + pos = 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 := i + (j-i)/2 // avoid overflow when computing h + // i ≤ h < j + if a[h] <= x { + i = h + 1 + } else { + j = h + } + } + return i - 1 +} |