go/token position: code improvements per rsc's suggestion

R=rsc
CC=golang-dev
https://golang.org/cl/3183041

diff --git a/src/pkg/go/token/position.go b/src/pkg/go/token/position.go
index 00e9bbf80126a3851bddbc569a0ecf9cd24a22fe..03c353d136b657cf97a182a517a1f4669ca0cd11 100644 (file)
--- a/src/pkg/go/token/position.go
+++ b/src/pkg/go/token/position.go
@@ -94,19 +94,12 @@ func (p Pos) IsValid() bool {
 
 
 func searchFiles(a []*File, x int) int {
-       i := sort.Search(len(a), func(i int) bool { return a[i].base < x })
-       // TODO(gri) The code below is really unfortunate. With the old
-       //           semantics of sort.Search, it was possible to simply
-       //           return i! Need to rethink the Search API.
-       if i == 0 || i < len(a) && a[i].base == x {
-               return i
-       }
-       return i - 1
+       return sort.Search(len(a), func(i int) bool { return a[i].base <= x }) - 1
 }
 
 
 func (s *FileSet) file(p Pos) *File {
-       if i := searchFiles(s.files, int(p)); i < len(s.files) {
+       if i := searchFiles(s.files, int(p)); i >= 0 {
                return s.files[i]
        }
        return nil
@@ -259,39 +252,25 @@ func (f *File) Position(offset int) Position {
 
 
 func searchUints(a []int, x int) int {
-       i := sort.Search(len(a), func(i int) bool { return a[i] < x })
-       // TODO(gri) The code below is really unfortunate. With the old
-       //           semantics of sort.Search, it was possible to simply
-       //           return i! Need to rethink the Search API.
-       if i == 0 || i < len(a) && a[i] == x {
-               return i
-       }
-       return i - 1
+       return sort.Search(len(a), func(i int) bool { return a[i] <= x }) - 1
 }
 
 
 func searchLineInfos(a []lineInfo, x int) int {
-       i := sort.Search(len(a), func(i int) bool { return a[i].offset < x })
-       // TODO(gri) The code below is really unfortunate. With the old
-       //           semantics of sort.Search, it was possible to simply
-       //           return i! Need to rethink the Search API.
-       if i == 0 || i < len(a) && a[i].offset == x {
-               return i
-       }
-       return i - 1
+       return sort.Search(len(a), func(i int) bool { return a[i].offset <= x }) - 1
 }
 
 
 // info returns the file name, line, and column number for a file offset.
 func (f *File) info(offset int) (filename string, line, column int) {
        filename = f.name
-       if i := searchUints(f.lines, offset); i < len(f.lines) {
+       if i := searchUints(f.lines, offset); i >= 0 {
                line, column = i+1, offset-f.lines[i]+1
        }
-       if i := searchLineInfos(f.infos, offset); i < len(f.infos) {
+       if i := searchLineInfos(f.infos, offset); i >= 0 {
                alt := &f.infos[i]
                filename = alt.filename
-               if i := searchUints(f.lines, alt.offset); i < len(f.lines) {
+               if i := searchUints(f.lines, alt.offset); i >= 0 {
                        line += alt.line - i - 1
                }
        }