// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package token
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import (
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"fmt"
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"sort"
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"sync"
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)
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// -----------------------------------------------------------------------------
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// Positions
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// Position describes an arbitrary source position
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// including the file, line, and column location.
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// A Position is valid if the line number is > 0.
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//
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type Position struct {
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Filename string // filename, if any
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Offset int // offset, starting at 0
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Line int // line number, starting at 1
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Column int // column number, starting at 1 (byte count)
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}
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// IsValid reports whether the position is valid.
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func (pos *Position) IsValid() bool { return pos.Line > 0 }
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// String returns a string in one of several forms:
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//
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// file:line:column valid position with file name
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// file:line valid position with file name but no column (column == 0)
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// line:column valid position without file name
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// line valid position without file name and no column (column == 0)
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// file invalid position with file name
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// - invalid position without file name
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//
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func (pos Position) String() string {
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s := pos.Filename
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if pos.IsValid() {
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if s != "" {
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s += ":"
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}
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s += fmt.Sprintf("%d", pos.Line)
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if pos.Column != 0 {
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s += fmt.Sprintf(":%d", pos.Column)
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}
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}
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if s == "" {
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s = "-"
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}
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return s
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}
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// Pos is a compact encoding of a source position within a file set.
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// It can be converted into a Position for a more convenient, but much
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// larger, representation.
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//
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// The Pos value for a given file is a number in the range [base, base+size],
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// where base and size are specified when adding the file to the file set via
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// AddFile.
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//
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// To create the Pos value for a specific source offset (measured in bytes),
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// first add the respective file to the current file set using FileSet.AddFile
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// and then call File.Pos(offset) for that file. Given a Pos value p
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// for a specific file set fset, the corresponding Position value is
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// obtained by calling fset.Position(p).
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//
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// Pos values can be compared directly with the usual comparison operators:
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// If two Pos values p and q are in the same file, comparing p and q is
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// equivalent to comparing the respective source file offsets. If p and q
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// are in different files, p < q is true if the file implied by p was added
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// to the respective file set before the file implied by q.
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//
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type Pos int
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// The zero value for Pos is NoPos; there is no file and line information
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// associated with it, and NoPos.IsValid() is false. NoPos is always
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// smaller than any other Pos value. The corresponding Position value
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// for NoPos is the zero value for Position.
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//
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const NoPos Pos = 0
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// IsValid reports whether the position is valid.
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func (p Pos) IsValid() bool {
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return p != NoPos
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}
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// -----------------------------------------------------------------------------
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// File
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// A File is a handle for a file belonging to a FileSet.
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// A File has a name, size, and line offset table.
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//
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type File struct {
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set *FileSet
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name string // file name as provided to AddFile
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base int // Pos value range for this file is [base...base+size]
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size int // file size as provided to AddFile
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// lines and infos are protected by mutex
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mutex sync.Mutex
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lines []int // lines contains the offset of the first character for each line (the first entry is always 0)
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infos []lineInfo
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}
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// Name returns the file name of file f as registered with AddFile.
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func (f *File) Name() string {
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return f.name
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}
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// Base returns the base offset of file f as registered with AddFile.
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func (f *File) Base() int {
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return f.base
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}
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// Size returns the size of file f as registered with AddFile.
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func (f *File) Size() int {
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return f.size
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}
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// LineCount returns the number of lines in file f.
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func (f *File) LineCount() int {
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f.mutex.Lock()
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n := len(f.lines)
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f.mutex.Unlock()
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return n
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}
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// AddLine adds the line offset for a new line.
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// The line offset must be larger than the offset for the previous line
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// and smaller than the file size; otherwise the line offset is ignored.
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//
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func (f *File) AddLine(offset int) {
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f.mutex.Lock()
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if i := len(f.lines); (i == 0 || f.lines[i-1] < offset) && offset < f.size {
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f.lines = append(f.lines, offset)
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}
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f.mutex.Unlock()
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}
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// MergeLine merges a line with the following line. It is akin to replacing
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// the newline character at the end of the line with a space (to not change the
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// remaining offsets). To obtain the line number, consult e.g. Position.Line.
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// MergeLine will panic if given an invalid line number.
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//
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func (f *File) MergeLine(line int) {
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if line < 1 {
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panic("illegal line number (line numbering starts at 1)")
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}
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f.mutex.Lock()
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defer f.mutex.Unlock()
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if line >= len(f.lines) {
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panic("illegal line number")
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}
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// To merge the line numbered <line> with the line numbered <line+1>,
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// we need to remove the entry in lines corresponding to the line
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// numbered <line+1>. The entry in lines corresponding to the line
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// numbered <line+1> is located at index <line>, since indices in lines
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// are 0-based and line numbers are 1-based.
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copy(f.lines[line:], f.lines[line+1:])
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f.lines = f.lines[:len(f.lines)-1]
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}
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// SetLines sets the line offsets for a file and reports whether it succeeded.
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// The line offsets are the offsets of the first character of each line;
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// for instance for the content "ab\nc\n" the line offsets are {0, 3}.
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// An empty file has an empty line offset table.
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// Each line offset must be larger than the offset for the previous line
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// and smaller than the file size; otherwise SetLines fails and returns
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// false.
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// Callers must not mutate the provided slice after SetLines returns.
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//
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func (f *File) SetLines(lines []int) bool {
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// verify validity of lines table
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size := f.size
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for i, offset := range lines {
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if i > 0 && offset <= lines[i-1] || size <= offset {
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return false
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}
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}
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// set lines table
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f.mutex.Lock()
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f.lines = lines
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f.mutex.Unlock()
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return true
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}
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// SetLinesForContent sets the line offsets for the given file content.
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// It ignores position-altering //line comments.
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func (f *File) SetLinesForContent(content []byte) {
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var lines []int
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line := 0
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for offset, b := range content {
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if line >= 0 {
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lines = append(lines, line)
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}
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line = -1
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if b == '\n' {
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line = offset + 1
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}
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}
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// set lines table
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f.mutex.Lock()
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f.lines = lines
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f.mutex.Unlock()
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}
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// LineStart returns the Pos value of the start of the specified line.
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// It ignores any alternative positions set using AddLineColumnInfo.
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// LineStart panics if the 1-based line number is invalid.
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func (f *File) LineStart(line int) Pos {
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if line < 1 {
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panic("illegal line number (line numbering starts at 1)")
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}
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f.mutex.Lock()
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defer f.mutex.Unlock()
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if line > len(f.lines) {
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panic("illegal line number")
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}
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return Pos(f.base + f.lines[line-1])
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}
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// A lineInfo object describes alternative file, line, and column
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// number information (such as provided via a //line directive)
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// for a given file offset.
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type lineInfo struct {
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// fields are exported to make them accessible to gob
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Offset int
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Filename string
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Line, Column int
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}
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// AddLineInfo is like AddLineColumnInfo with a column = 1 argument.
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// It is here for backward-compatibility for code prior to Go 1.11.
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//
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func (f *File) AddLineInfo(offset int, filename string, line int) {
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f.AddLineColumnInfo(offset, filename, line, 1)
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}
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// AddLineColumnInfo adds alternative file, line, and column number
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// information for a given file offset. The offset must be larger
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// than the offset for the previously added alternative line info
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// and smaller than the file size; otherwise the information is
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// ignored.
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//
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// AddLineColumnInfo is typically used to register alternative position
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// information for line directives such as //line filename:line:column.
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//
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func (f *File) AddLineColumnInfo(offset int, filename string, line, column int) {
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f.mutex.Lock()
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if i := len(f.infos); i == 0 || f.infos[i-1].Offset < offset && offset < f.size {
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f.infos = append(f.infos, lineInfo{offset, filename, line, column})
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}
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f.mutex.Unlock()
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}
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// Pos returns the Pos value for the given file offset;
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// the offset must be <= f.Size().
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// f.Pos(f.Offset(p)) == p.
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//
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func (f *File) Pos(offset int) Pos {
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if offset > f.size {
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panic("illegal file offset")
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}
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return Pos(f.base + offset)
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}
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// Offset returns the offset for the given file position p;
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// p must be a valid Pos value in that file.
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// f.Offset(f.Pos(offset)) == offset.
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//
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func (f *File) Offset(p Pos) int {
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if int(p) < f.base || int(p) > f.base+f.size {
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panic("illegal Pos value")
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}
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return int(p) - f.base
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}
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// Line returns the line number for the given file position p;
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// p must be a Pos value in that file or NoPos.
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//
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func (f *File) Line(p Pos) int {
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return f.Position(p).Line
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}
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func searchLineInfos(a []lineInfo, x int) int {
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return sort.Search(len(a), func(i int) bool { return a[i].Offset > x }) - 1
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}
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// unpack returns the filename and line and column number for a file offset.
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// If adjusted is set, unpack will return the filename and line information
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// possibly adjusted by //line comments; otherwise those comments are ignored.
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//
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func (f *File) unpack(offset int, adjusted bool) (filename string, line, column int) {
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f.mutex.Lock()
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defer f.mutex.Unlock()
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filename = f.name
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if i := searchInts(f.lines, offset); i >= 0 {
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line, column = i+1, offset-f.lines[i]+1
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}
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if adjusted && len(f.infos) > 0 {
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// few files have extra line infos
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if i := searchLineInfos(f.infos, offset); i >= 0 {
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alt := &f.infos[i]
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filename = alt.Filename
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if i := searchInts(f.lines, alt.Offset); i >= 0 {
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// i+1 is the line at which the alternative position was recorded
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d := line - (i + 1) // line distance from alternative position base
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line = alt.Line + d
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if alt.Column == 0 {
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// alternative column is unknown => relative column is unknown
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// (the current specification for line directives requires
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// this to apply until the next PosBase/line directive,
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// not just until the new newline)
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column = 0
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} else if d == 0 {
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// the alternative position base is on the current line
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// => column is relative to alternative column
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column = alt.Column + (offset - alt.Offset)
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}
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}
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}
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}
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return
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}
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func (f *File) position(p Pos, adjusted bool) (pos Position) {
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offset := int(p) - f.base
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pos.Offset = offset
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pos.Filename, pos.Line, pos.Column = f.unpack(offset, adjusted)
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return
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}
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// PositionFor returns the Position value for the given file position p.
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// If adjusted is set, the position may be adjusted by position-altering
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// //line comments; otherwise those comments are ignored.
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// p must be a Pos value in f or NoPos.
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//
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func (f *File) PositionFor(p Pos, adjusted bool) (pos Position) {
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if p != NoPos {
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if int(p) < f.base || int(p) > f.base+f.size {
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panic("illegal Pos value")
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}
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pos = f.position(p, adjusted)
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}
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return
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}
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// Position returns the Position value for the given file position p.
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// Calling f.Position(p) is equivalent to calling f.PositionFor(p, true).
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//
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func (f *File) Position(p Pos) (pos Position) {
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return f.PositionFor(p, true)
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}
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// -----------------------------------------------------------------------------
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// FileSet
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// A FileSet represents a set of source files.
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// Methods of file sets are synchronized; multiple goroutines
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// may invoke them concurrently.
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//
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type FileSet struct {
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mutex sync.RWMutex // protects the file set
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base int // base offset for the next file
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files []*File // list of files in the order added to the set
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last *File // cache of last file looked up
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}
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// NewFileSet creates a new file set.
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func NewFileSet() *FileSet {
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return &FileSet{
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base: 1, // 0 == NoPos
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}
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}
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// Base returns the minimum base offset that must be provided to
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// AddFile when adding the next file.
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//
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func (s *FileSet) Base() int {
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s.mutex.RLock()
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b := s.base
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s.mutex.RUnlock()
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return b
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}
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// AddFile adds a new file with a given filename, base offset, and file size
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// to the file set s and returns the file. Multiple files may have the same
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// name. The base offset must not be smaller than the FileSet's Base(), and
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// size must not be negative. As a special case, if a negative base is provided,
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// the current value of the FileSet's Base() is used instead.
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//
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// Adding the file will set the file set's Base() value to base + size + 1
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// as the minimum base value for the next file. The following relationship
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// exists between a Pos value p for a given file offset offs:
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//
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// int(p) = base + offs
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//
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// with offs in the range [0, size] and thus p in the range [base, base+size].
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// For convenience, File.Pos may be used to create file-specific position
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// values from a file offset.
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//
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func (s *FileSet) AddFile(filename string, base, size int) *File {
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s.mutex.Lock()
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defer s.mutex.Unlock()
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if base < 0 {
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base = s.base
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}
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if base < s.base || size < 0 {
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panic("illegal base or size")
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}
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// base >= s.base && size >= 0
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f := &File{set: s, name: filename, base: base, size: size, lines: []int{0}}
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base += size + 1 // +1 because EOF also has a position
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if base < 0 {
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panic("token.Pos offset overflow (> 2G of source code in file set)")
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}
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// add the file to the file set
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s.base = base
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s.files = append(s.files, f)
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s.last = f
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return f
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}
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// Iterate calls f for the files in the file set in the order they were added
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// until f returns false.
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//
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func (s *FileSet) Iterate(f func(*File) bool) {
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for i := 0; ; i++ {
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var file *File
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s.mutex.RLock()
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if i < len(s.files) {
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file = s.files[i]
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}
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s.mutex.RUnlock()
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if file == nil || !f(file) {
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break
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}
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}
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}
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func searchFiles(a []*File, x int) int {
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return sort.Search(len(a), func(i int) bool { return a[i].base > x }) - 1
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}
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func (s *FileSet) file(p Pos) *File {
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s.mutex.RLock()
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// common case: p is in last file
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if f := s.last; f != nil && f.base <= int(p) && int(p) <= f.base+f.size {
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s.mutex.RUnlock()
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return f
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}
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// p is not in last file - search all files
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if i := searchFiles(s.files, int(p)); i >= 0 {
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f := s.files[i]
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// f.base <= int(p) by definition of searchFiles
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if int(p) <= f.base+f.size {
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s.mutex.RUnlock()
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s.mutex.Lock()
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s.last = f // race is ok - s.last is only a cache
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s.mutex.Unlock()
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return f
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}
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}
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s.mutex.RUnlock()
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return nil
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}
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// File returns the file that contains the position p.
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// If no such file is found (for instance for p == NoPos),
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// the result is nil.
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//
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func (s *FileSet) File(p Pos) (f *File) {
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if p != NoPos {
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f = s.file(p)
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}
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return
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}
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// PositionFor converts a Pos p in the fileset into a Position value.
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// If adjusted is set, the position may be adjusted by position-altering
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// //line comments; otherwise those comments are ignored.
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// p must be a Pos value in s or NoPos.
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//
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func (s *FileSet) PositionFor(p Pos, adjusted bool) (pos Position) {
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if p != NoPos {
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if f := s.file(p); f != nil {
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return f.position(p, adjusted)
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}
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}
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return
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}
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// Position converts a Pos p in the fileset into a Position value.
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// Calling s.Position(p) is equivalent to calling s.PositionFor(p, true).
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//
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func (s *FileSet) Position(p Pos) (pos Position) {
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return s.PositionFor(p, true)
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}
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// -----------------------------------------------------------------------------
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// Helper functions
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func searchInts(a []int, x int) int {
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// This function body is a manually inlined version of:
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//
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// return sort.Search(len(a), func(i int) bool { return a[i] > x }) - 1
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//
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// With better compiler optimizations, this may not be needed in the
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// future, but at the moment this change improves the go/printer
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// benchmark performance by ~30%. This has a direct impact on the
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// speed of gofmt and thus seems worthwhile (2011-04-29).
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// TODO(gri): Remove this when compilers have caught up.
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i, j := 0, len(a)
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for i < j {
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h := i + (j-i)/2 // avoid overflow when computing h
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// i ≤ h < j
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if a[h] <= x {
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i = h + 1
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} else {
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j = h
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}
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}
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return i - 1
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}
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