143 lines
3.8 KiB
Go
143 lines
3.8 KiB
Go
// Copyright 2013 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 main
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// This file defines utilities for working with file positions.
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import (
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"fmt"
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"go/build"
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"go/parser"
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"go/token"
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"os"
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"path/filepath"
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"strconv"
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"strings"
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"golang.org/x/tools/go/ast/astutil"
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"golang.org/x/tools/go/buildutil"
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)
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// parseOctothorpDecimal returns the numeric value if s matches "#%d",
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// otherwise -1.
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func parseOctothorpDecimal(s string) int {
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if s != "" && s[0] == '#' {
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if s, err := strconv.ParseInt(s[1:], 10, 32); err == nil {
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return int(s)
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}
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}
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return -1
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}
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// parsePos parses a string of the form "file:pos" or
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// file:start,end" where pos, start, end match #%d and represent byte
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// offsets, and returns its components.
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//
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// (Numbers without a '#' prefix are reserved for future use,
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// e.g. to indicate line/column positions.)
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//
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func parsePos(pos string) (filename string, startOffset, endOffset int, err error) {
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if pos == "" {
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err = fmt.Errorf("no source position specified")
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return
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}
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colon := strings.LastIndex(pos, ":")
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if colon < 0 {
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err = fmt.Errorf("bad position syntax %q", pos)
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return
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}
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filename, offset := pos[:colon], pos[colon+1:]
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startOffset = -1
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endOffset = -1
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if comma := strings.Index(offset, ","); comma < 0 {
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// e.g. "foo.go:#123"
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startOffset = parseOctothorpDecimal(offset)
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endOffset = startOffset
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} else {
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// e.g. "foo.go:#123,#456"
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startOffset = parseOctothorpDecimal(offset[:comma])
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endOffset = parseOctothorpDecimal(offset[comma+1:])
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}
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if startOffset < 0 || endOffset < 0 {
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err = fmt.Errorf("invalid offset %q in query position", offset)
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return
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}
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return
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}
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// fileOffsetToPos translates the specified file-relative byte offsets
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// into token.Pos form. It returns an error if the file was not found
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// or the offsets were out of bounds.
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//
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func fileOffsetToPos(file *token.File, startOffset, endOffset int) (start, end token.Pos, err error) {
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// Range check [start..end], inclusive of both end-points.
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if 0 <= startOffset && startOffset <= file.Size() {
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start = file.Pos(int(startOffset))
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} else {
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err = fmt.Errorf("start position is beyond end of file")
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return
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}
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if 0 <= endOffset && endOffset <= file.Size() {
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end = file.Pos(int(endOffset))
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} else {
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err = fmt.Errorf("end position is beyond end of file")
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return
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}
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return
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}
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// sameFile returns true if x and y have the same basename and denote
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// the same file.
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//
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func sameFile(x, y string) bool {
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if filepath.Base(x) == filepath.Base(y) { // (optimisation)
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if xi, err := os.Stat(x); err == nil {
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if yi, err := os.Stat(y); err == nil {
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return os.SameFile(xi, yi)
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}
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}
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}
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return false
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}
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// fastQueryPos parses the position string and returns a queryPos.
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// It parses only a single file and does not run the type checker.
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func fastQueryPos(ctxt *build.Context, pos string) (*queryPos, error) {
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filename, startOffset, endOffset, err := parsePos(pos)
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if err != nil {
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return nil, err
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}
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// Parse the file, opening it the file via the build.Context
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// so that we observe the effects of the -modified flag.
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fset := token.NewFileSet()
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cwd, _ := os.Getwd()
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f, err := buildutil.ParseFile(fset, ctxt, nil, cwd, filename, parser.Mode(0))
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// ParseFile usually returns a partial file along with an error.
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// Only fail if there is no file.
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if f == nil {
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return nil, err
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}
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if !f.Pos().IsValid() {
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return nil, fmt.Errorf("%s is not a Go source file", filename)
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}
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start, end, err := fileOffsetToPos(fset.File(f.Pos()), startOffset, endOffset)
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if err != nil {
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return nil, err
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}
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path, exact := astutil.PathEnclosingInterval(f, start, end)
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if path == nil {
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return nil, fmt.Errorf("no syntax here")
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}
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return &queryPos{fset, start, end, path, exact, nil}, nil
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}
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