/
pos.go
149 lines (132 loc) · 3.8 KB
/
pos.go
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package oracle
// This file defines utilities for working with file positions.
import (
"fmt"
"go/parser"
"go/token"
"os"
"path/filepath"
"strconv"
"strings"
"code.google.com/p/go.tools/astutil"
)
// parseOctothorpDecimal returns the numeric value if s matches "#%d",
// otherwise -1.
func parseOctothorpDecimal(s string) int {
if s != "" && s[0] == '#' {
if s, err := strconv.ParseInt(s[1:], 10, 32); err == nil {
return int(s)
}
}
return -1
}
// parsePosFlag parses a string of the form "file:pos" or
// file:start,end" where pos, start, end match #%d and represent byte
// offsets, and returns its components.
//
// (Numbers without a '#' prefix are reserved for future use,
// e.g. to indicate line/column positions.)
//
func parsePosFlag(posFlag string) (filename string, startOffset, endOffset int, err error) {
if posFlag == "" {
err = fmt.Errorf("no source position specified (-pos flag)")
return
}
colon := strings.LastIndex(posFlag, ":")
if colon < 0 {
err = fmt.Errorf("invalid source position -pos=%q", posFlag)
return
}
filename, offset := posFlag[:colon], posFlag[colon+1:]
startOffset = -1
endOffset = -1
if hyphen := strings.Index(offset, ","); hyphen < 0 {
// e.g. "foo.go:#123"
startOffset = parseOctothorpDecimal(offset)
endOffset = startOffset
} else {
// e.g. "foo.go:#123,#456"
startOffset = parseOctothorpDecimal(offset[:hyphen])
endOffset = parseOctothorpDecimal(offset[hyphen+1:])
}
if startOffset < 0 || endOffset < 0 {
err = fmt.Errorf("invalid -pos offset %q", offset)
return
}
return
}
// findQueryPos searches fset for filename and translates the
// specified file-relative byte offsets into token.Pos form. It
// returns an error if the file was not found or the offsets were out
// of bounds.
//
func findQueryPos(fset *token.FileSet, filename string, startOffset, endOffset int) (start, end token.Pos, err error) {
var file *token.File
fset.Iterate(func(f *token.File) bool {
if sameFile(filename, f.Name()) {
// (f.Name() is absolute)
file = f
return false // done
}
return true // continue
})
if file == nil {
err = fmt.Errorf("couldn't find file containing position")
return
}
// Range check [start..end], inclusive of both end-points.
if 0 <= startOffset && startOffset <= file.Size() {
start = file.Pos(int(startOffset))
} else {
err = fmt.Errorf("start position is beyond end of file")
return
}
if 0 <= endOffset && endOffset <= file.Size() {
end = file.Pos(int(endOffset))
} else {
err = fmt.Errorf("end position is beyond end of file")
return
}
return
}
// sameFile returns true if x and y have the same basename and denote
// the same file.
//
func sameFile(x, y string) bool {
if filepath.Base(x) == filepath.Base(y) { // (optimisation)
if xi, err := os.Stat(x); err == nil {
if yi, err := os.Stat(y); err == nil {
return os.SameFile(xi, yi)
}
}
}
return false
}
// fastQueryPos parses the -pos flag and returns a QueryPos.
// It parses only a single file, and does not run the type checker.
//
// Caveat: the token.{FileSet,Pos} info it contains is not comparable
// with that from the oracle's FileSet! (We don't accept oracle.fset
// as a parameter because we don't want the same filename to appear
// multiple times in one FileSet.)
//
func fastQueryPos(posFlag string) (*QueryPos, error) {
filename, startOffset, endOffset, err := parsePosFlag(posFlag)
if err != nil {
return nil, err
}
fset := token.NewFileSet()
f, err := parser.ParseFile(fset, filename, nil, 0)
if err != nil {
return nil, err
}
start, end, err := findQueryPos(fset, filename, startOffset, endOffset)
if err != nil {
return nil, err
}
path, exact := astutil.PathEnclosingInterval(f, start, end)
if path == nil {
return nil, fmt.Errorf("no syntax here")
}
return &QueryPos{fset, start, end, path, exact, nil}, nil
}