cmd: replace bio.Buf with bio.Reader and bio.Writer

Replace the bidirectional bio.Buf type with a pair of unidirectional
buffered seekable Reader and Writers.

Change-Id: I86664a06f93c94595dc67c2cbd21356feb6680ef
Reviewed-on: https://go-review.googlesource.com/21720Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/bexport.go

@@ -124,7 +124,7 @@ const exportVersion = "v0"
 const exportInlined = true // default: true
 
 type exporter struct {
-	out      *bio.Buf
+	out      *bio.Writer
 	pkgIndex map[*Pkg]int
 	typIndex map[*Type]int
 	inlined  []*Func
@@ -136,7 +136,7 @@ type exporter struct {
 }
 
 // export writes the exportlist for localpkg to out and returns the number of bytes written.
-func export(out *bio.Buf, trace bool) int {
+func export(out *bio.Writer, trace bool) int {
 	p := exporter{
 		out:      out,
 		pkgIndex: make(map[*Pkg]int),

src/cmd/compile/internal/gc/go.go

@@ -133,7 +133,7 @@ var infile string
 
 var outfile string
 
-var bout *bio.Buf
+var bout *bio.Writer
 
 var nerrors int
 
@@ -288,7 +288,7 @@ var Ctxt *obj.Link
 
 var writearchive int
 
-var bstdout *bio.Buf
+var bstdout *bio.Writer
 
 var Nacl bool
 

src/cmd/compile/internal/gc/obj.go

@@ -37,7 +37,7 @@ func dumpobj() {
 		bout.WriteString("!<arch>\n")
 		arhdr = [ArhdrSize]byte{}
 		bout.Write(arhdr[:])
-		startobj = bio.Boffset(bout)
+		startobj = bout.Offset()
 	}
 
 	fmt.Fprintf(bout, "go object %s %s %s %s\n", obj.Getgoos(), obj.Getgoarch(), obj.Getgoversion(), obj.Expstring())
@@ -45,19 +45,19 @@ func dumpobj() {
 
 	if writearchive != 0 {
 		bout.Flush()
-		size := bio.Boffset(bout) - startobj
+		size := bout.Offset() - startobj
 		if size&1 != 0 {
 			bout.WriteByte(0)
 		}
-		bio.Bseek(bout, startobj-ArhdrSize, 0)
+		bout.Seek(startobj-ArhdrSize, 0)
 		formathdr(arhdr[:], "__.PKGDEF", size)
 		bout.Write(arhdr[:])
 		bout.Flush()
 
-		bio.Bseek(bout, startobj+size+(size&1), 0)
+		bout.Seek(startobj+size+(size&1), 0)
 		arhdr = [ArhdrSize]byte{}
 		bout.Write(arhdr[:])
-		startobj = bio.Boffset(bout)
+		startobj = bout.Offset()
 		fmt.Fprintf(bout, "go object %s %s %s %s\n", obj.Getgoos(), obj.Getgoarch(), obj.Getgoversion(), obj.Expstring())
 	}
 
@@ -92,11 +92,11 @@ func dumpobj() {
 
 	if writearchive != 0 {
 		bout.Flush()
-		size := bio.Boffset(bout) - startobj
+		size := bout.Offset() - startobj
 		if size&1 != 0 {
 			bout.WriteByte(0)
 		}
-		bio.Bseek(bout, startobj-ArhdrSize, 0)
+		bout.Seek(startobj-ArhdrSize, 0)
 		formathdr(arhdr[:], "_go_.o", size)
 		bout.Write(arhdr[:])
 	}
@@ -133,7 +133,7 @@ func dumpglobls() {
 	funcsyms = nil
 }
 
-func Bputname(b *bio.Buf, s *obj.LSym) {
+func Bputname(b *bio.Writer, s *obj.LSym) {
 	b.WriteString(s.Name)
 	b.WriteByte(0)
 }

src/cmd/internal/bio/buf.go

@@ -14,94 +14,116 @@ import (
 
 const EOF = -1
 
-// Buf implements a seekable buffered I/O abstraction.
-type Buf struct {
+// Reader implements a seekable buffered io.Reader.
+type Reader struct {
 	f *os.File
 	r *bufio.Reader
+}
+
+// Writer implements a seekable buffered io.Writer.
+type Writer struct {
+	f *os.File
 	w *bufio.Writer
 }
 
-func (b *Buf) Reader() *bufio.Reader { return b.r }
-func (b *Buf) Writer() *bufio.Writer { return b.w }
+// Reader returns this Reader's underlying bufio.Reader.
+func (r *Reader) Reader() *bufio.Reader { return r.r }
 
-func Create(name string) (*Buf, error) {
+// Writer returns this Writer's underlying bufio.Writer.
+func (w *Writer) Writer() *bufio.Writer { return w.w }
+
+// Create creates the file named name and returns a Writer
+// for that file.
+func Create(name string) (*Writer, error) {
 	f, err := os.Create(name)
 	if err != nil {
 		return nil, err
 	}
-	return &Buf{f: f, w: bufio.NewWriter(f)}, nil
+	return &Writer{f: f, w: bufio.NewWriter(f)}, nil
 }
 
-func Open(name string) (*Buf, error) {
+// Open returns a Reader for the file named name.
+func Open(name string) (*Reader, error) {
 	f, err := os.Open(name)
 	if err != nil {
 		return nil, err
 	}
-	return &Buf{f: f, r: bufio.NewReader(f)}, nil
+	return &Reader{f: f, r: bufio.NewReader(f)}, nil
 }
 
-func BufWriter(w io.Writer) *Buf {
-	return &Buf{w: bufio.NewWriter(w)}
+// BufWriter returns a Writer on top of w.
+// TODO(dfc) remove this method and replace caller with bufio.Writer.
+func BufWriter(w io.Writer) *Writer {
+	return &Writer{w: bufio.NewWriter(w)}
 }
 
-func BufReader(r io.Reader) *Buf {
-	return &Buf{r: bufio.NewReader(r)}
+// BufWriter returns a Reader on top of r.
+// TODO(dfc) remove this method and replace caller with bufio.Reader.
+func BufReader(r io.Reader) *Reader {
+	return &Reader{r: bufio.NewReader(r)}
 }
 
-func (b *Buf) Write(p []byte) (int, error) {
-	return b.w.Write(p)
+func (w *Writer) Write(p []byte) (int, error) {
+	return w.w.Write(p)
 }
 
-func (b *Buf) WriteString(p string) (int, error) {
-	return b.w.WriteString(p)
+func (w *Writer) WriteString(p string) (int, error) {
+	return w.w.WriteString(p)
 }
 
-func Bseek(b *Buf, offset int64, whence int) int64 {
-	if b.w != nil {
-		if err := b.w.Flush(); err != nil {
-			log.Fatalf("writing output: %v", err)
-		}
-	} else if b.r != nil {
+func (r *Reader) Seek(offset int64, whence int) int64 {
 	if whence == 1 {
-			offset -= int64(b.r.Buffered())
+		offset -= int64(r.r.Buffered())
 	}
-	}
-	off, err := b.f.Seek(offset, whence)
+	off, err := r.f.Seek(offset, whence)
 	if err != nil {
 		log.Fatalf("seeking in output: %v", err)
 	}
-	if b.r != nil {
-		b.r.Reset(b.f)
-	}
+	r.r.Reset(r.f)
 	return off
 }
 
-func Boffset(b *Buf) int64 {
-	if b.w != nil {
-		if err := b.w.Flush(); err != nil {
+func (w *Writer) Seek(offset int64, whence int) int64 {
+	if err := w.w.Flush(); err != nil {
 		log.Fatalf("writing output: %v", err)
 	}
+	off, err := w.f.Seek(offset, whence)
+	if err != nil {
+		log.Fatalf("seeking in output: %v", err)
 	}
-	off, err := b.f.Seek(0, 1)
+	return off
+}
+
+func (r *Reader) Offset() int64 {
+	off, err := r.f.Seek(0, 1)
 	if err != nil {
 		log.Fatalf("seeking in output [0, 1]: %v", err)
 	}
-	if b.r != nil {
-		off -= int64(b.r.Buffered())
+	off -= int64(r.r.Buffered())
+	return off
+}
+
+func (w *Writer) Offset() int64 {
+	if err := w.w.Flush(); err != nil {
+		log.Fatalf("writing output: %v", err)
+	}
+	off, err := w.f.Seek(0, 1)
+	if err != nil {
+		log.Fatalf("seeking in output [0, 1]: %v", err)
 	}
 	return off
 }
 
-func (b *Buf) Flush() error {
-	return b.w.Flush()
+func (w *Writer) Flush() error {
+	return w.w.Flush()
 }
 
-func (b *Buf) WriteByte(c byte) error {
-	return b.w.WriteByte(c)
+func (w *Writer) WriteByte(c byte) error {
+	return w.w.WriteByte(c)
 }
 
-func Bread(b *Buf, p []byte) int {
-	n, err := io.ReadFull(b.r, p)
+func Bread(r *Reader, p []byte) int {
+	n, err := io.ReadFull(r.r, p)
 	if n == 0 {
 		if err != nil && err != io.EOF {
 			n = -1
@@ -110,8 +132,8 @@ func Bread(b *Buf, p []byte) int {
 	return n
 }
 
-func Bgetc(b *Buf) int {
-	c, err := b.r.ReadByte()
+func Bgetc(r *Reader) int {
+	c, err := r.r.ReadByte()
 	if err != nil {
 		if err != io.EOF {
 			log.Fatalf("reading input: %v", err)
@@ -121,28 +143,29 @@ func Bgetc(b *Buf) int {
 	return int(c)
 }
 
-func (b *Buf) Read(p []byte) (int, error) {
-	return b.r.Read(p)
+func (r *Reader) Read(p []byte) (int, error) {
+	return r.r.Read(p)
 }
 
-func (b *Buf) Peek(n int) ([]byte, error) {
-	return b.r.Peek(n)
+func (r *Reader) Peek(n int) ([]byte, error) {
+	return r.r.Peek(n)
 }
 
-func Brdline(b *Buf, delim int) string {
-	s, err := b.r.ReadBytes(byte(delim))
+func Brdline(r *Reader, delim int) string {
+	s, err := r.r.ReadBytes(byte(delim))
 	if err != nil {
 		log.Fatalf("reading input: %v", err)
 	}
 	return string(s)
 }
 
-func (b *Buf) Close() error {
-	var err error
-	if b.w != nil {
-		err = b.w.Flush()
-	}
-	err1 := b.f.Close()
+func (r *Reader) Close() error {
+	return r.f.Close()
+}
+
+func (w *Writer) Close() error {
+	err := w.w.Flush()
+	err1 := w.f.Close()
 	if err == nil {
 		err = err1
 	}

src/cmd/internal/obj/link.go

@@ -629,7 +629,7 @@ type Link struct {
 	Flag_shared   int32
 	Flag_dynlink  bool
 	Flag_optimize bool
-	Bso           *bio.Buf
+	Bso           *bio.Writer
 	Pathname      string
 	Goroot        string
 	Goroot_final  string

src/cmd/internal/obj/objfile.go

@@ -121,7 +121,7 @@ import (
 // The Go and C compilers, and the assembler, call writeobj to write
 // out a Go object file. The linker does not call this; the linker
 // does not write out object files.
-func Writeobjdirect(ctxt *Link, b *bio.Buf) {
+func Writeobjdirect(ctxt *Link, b *bio.Writer) {
 	Flushplist(ctxt)
 	WriteObjFile(ctxt, b)
 }
@@ -374,7 +374,7 @@ func (w *objWriter) writeLengths() {
 	w.writeInt(int64(w.nFile))
 }
 
-func newObjWriter(ctxt *Link, b *bio.Buf) *objWriter {
+func newObjWriter(ctxt *Link, b *bio.Writer) *objWriter {
 	return &objWriter{
 		ctxt:    ctxt,
 		wr:      b.Writer(),
@@ -383,7 +383,7 @@ func newObjWriter(ctxt *Link, b *bio.Buf) *objWriter {
 	}
 }
 
-func WriteObjFile(ctxt *Link, b *bio.Buf) {
+func WriteObjFile(ctxt *Link, b *bio.Writer) {
 	w := newObjWriter(ctxt, b)
 
 	// Magic header

src/cmd/link/internal/ld/ar.go

@@ -82,7 +82,7 @@ func hostArchive(name string) {
 	}
 
 	var arhdr ArHdr
-	l := nextar(f, bio.Boffset(f), &arhdr)
+	l := nextar(f, f.Offset(), &arhdr)
 	if l <= 0 {
 		Exitf("%s missing armap", name)
 	}
@@ -118,7 +118,7 @@ func hostArchive(name string) {
 			l = atolwhex(arhdr.size)
 
 			h := ldobj(f, "libgcc", l, pname, name, ArchiveObj)
-			bio.Bseek(f, h.off, 0)
+			f.Seek(h.off, 0)
 			h.ld(f, h.pkg, h.length, h.pn)
 		}
 
@@ -131,7 +131,7 @@ func hostArchive(name string) {
 type archiveMap map[string]uint64
 
 // readArmap reads the archive symbol map.
-func readArmap(filename string, f *bio.Buf, arhdr ArHdr) archiveMap {
+func readArmap(filename string, f *bio.Reader, arhdr ArHdr) archiveMap {
 	is64 := arhdr.name == "/SYM64/"
 	wordSize := 4
 	if is64 {

src/cmd/link/internal/ld/go.go

@@ -27,7 +27,7 @@ func expandpkg(t0 string, pkg string) string {
 //	once the dust settles, try to move some code to
 //		libmach, so that other linkers and ar can share.
 
-func ldpkg(f *bio.Buf, pkg string, length int64, filename string, whence int) {
+func ldpkg(f *bio.Reader, pkg string, length int64, filename string, whence int) {
 	var p0, p1 int
 
 	if Debug['g'] != 0 {

src/cmd/link/internal/ld/ldelf.go

@@ -268,7 +268,7 @@ type ElfSect struct {
 }
 
 type ElfObj struct {
-	f         *bio.Buf
+	f         *bio.Reader
 	base      int64 // offset in f where ELF begins
 	length    int64 // length of ELF
 	is64      int
@@ -447,13 +447,13 @@ func parseArmAttributes(e binary.ByteOrder, data []byte) {
 	}
 }
 
-func ldelf(f *bio.Buf, pkg string, length int64, pn string) {
+func ldelf(f *bio.Reader, pkg string, length int64, pn string) {
 	if Debug['v'] != 0 {
 		fmt.Fprintf(&Bso, "%5.2f ldelf %s\n", obj.Cputime(), pn)
 	}
 
 	Ctxt.IncVersion()
-	base := int32(bio.Boffset(f))
+	base := f.Offset()
 
 	var add uint64
 	var e binary.ByteOrder
@@ -601,7 +601,7 @@ func ldelf(f *bio.Buf, pkg string, length int64, pn string) {
 
 	elfobj.nsect = uint(elfobj.shnum)
 	for i := 0; uint(i) < elfobj.nsect; i++ {
-		if bio.Bseek(f, int64(uint64(base)+elfobj.shoff+uint64(int64(i)*int64(elfobj.shentsize))), 0) < 0 {
+		if f.Seek(int64(uint64(base)+elfobj.shoff+uint64(int64(i)*int64(elfobj.shentsize))), 0) < 0 {
 			goto bad
 		}
 		sect = &elfobj.sect[i]
@@ -987,7 +987,7 @@ func elfmap(elfobj *ElfObj, sect *ElfSect) (err error) {
 
 	sect.base = make([]byte, sect.size)
 	err = fmt.Errorf("short read")
-	if bio.Bseek(elfobj.f, int64(uint64(elfobj.base)+sect.off), 0) < 0 || bio.Bread(elfobj.f, sect.base) != len(sect.base) {
+	if elfobj.f.Seek(int64(uint64(elfobj.base)+sect.off), 0) < 0 || bio.Bread(elfobj.f, sect.base) != len(sect.base) {
 		return err
 	}
 

src/cmd/link/internal/ld/ldmacho.go

@@ -43,7 +43,7 @@ const (
 )
 
 type LdMachoObj struct {
-	f          *bio.Buf
+	f          *bio.Reader
 	base       int64 // off in f where Mach-O begins
 	length     int64 // length of Mach-O
 	is64       bool
@@ -299,7 +299,7 @@ func macholoadrel(m *LdMachoObj, sect *LdMachoSect) int {
 	rel := make([]LdMachoRel, sect.nreloc)
 	n := int(sect.nreloc * 8)
 	buf := make([]byte, n)
-	if bio.Bseek(m.f, m.base+int64(sect.reloff), 0) < 0 || bio.Bread(m.f, buf) != n {
+	if m.f.Seek(m.base+int64(sect.reloff), 0) < 0 || bio.Bread(m.f, buf) != n {
 		return -1
 	}
 	var p []byte
@@ -345,7 +345,7 @@ func macholoaddsym(m *LdMachoObj, d *LdMachoDysymtab) int {
 	n := int(d.nindirectsyms)
 
 	p := make([]byte, n*4)
-	if bio.Bseek(m.f, m.base+int64(d.indirectsymoff), 0) < 0 || bio.Bread(m.f, p) != len(p) {
+	if m.f.Seek(m.base+int64(d.indirectsymoff), 0) < 0 || bio.Bread(m.f, p) != len(p) {
 		return -1
 	}
 
@@ -362,7 +362,7 @@ func macholoadsym(m *LdMachoObj, symtab *LdMachoSymtab) int {
 	}
 
 	strbuf := make([]byte, symtab.strsize)
-	if bio.Bseek(m.f, m.base+int64(symtab.stroff), 0) < 0 || bio.Bread(m.f, strbuf) != len(strbuf) {
+	if m.f.Seek(m.base+int64(symtab.stroff), 0) < 0 || bio.Bread(m.f, strbuf) != len(strbuf) {
 		return -1
 	}
 
@@ -372,7 +372,7 @@ func macholoadsym(m *LdMachoObj, symtab *LdMachoSymtab) int {
 	}
 	n := int(symtab.nsym * uint32(symsize))
 	symbuf := make([]byte, n)
-	if bio.Bseek(m.f, m.base+int64(symtab.symoff), 0) < 0 || bio.Bread(m.f, symbuf) != len(symbuf) {
+	if m.f.Seek(m.base+int64(symtab.symoff), 0) < 0 || bio.Bread(m.f, symbuf) != len(symbuf) {
 		return -1
 	}
 	sym := make([]LdMachoSym, symtab.nsym)
@@ -402,7 +402,7 @@ func macholoadsym(m *LdMachoObj, symtab *LdMachoSymtab) int {
 	return 0
 }
 
-func ldmacho(f *bio.Buf, pkg string, length int64, pn string) {
+func ldmacho(f *bio.Reader, pkg string, length int64, pn string) {
 	var err error
 	var j int
 	var is64 bool
@@ -432,7 +432,7 @@ func ldmacho(f *bio.Buf, pkg string, length int64, pn string) {
 	var name string
 
 	Ctxt.IncVersion()
-	base := bio.Boffset(f)
+	base := f.Offset()
 	if bio.Bread(f, hdr[:]) != len(hdr) {
 		goto bad
 	}
@@ -557,7 +557,7 @@ func ldmacho(f *bio.Buf, pkg string, length int64, pn string) {
 	}
 
 	dat = make([]byte, c.seg.filesz)
-	if bio.Bseek(f, m.base+int64(c.seg.fileoff), 0) < 0 || bio.Bread(f, dat) != len(dat) {
+	if f.Seek(m.base+int64(c.seg.fileoff), 0) < 0 || bio.Bread(f, dat) != len(dat) {
 		err = fmt.Errorf("cannot load object data: %v", err)
 		goto bad
 	}

src/cmd/link/internal/ld/ldpe.go

@@ -118,7 +118,7 @@ type PeSect struct {
 }
 
 type PeObj struct {
-	f      *bio.Buf
+	f      *bio.Reader
 	name   string
 	base   uint32
 	sect   []PeSect
@@ -129,14 +129,14 @@ type PeObj struct {
 	snames []byte
 }
 
-func ldpe(f *bio.Buf, pkg string, length int64, pn string) {
+func ldpe(f *bio.Reader, pkg string, length int64, pn string) {
 	if Debug['v'] != 0 {
 		fmt.Fprintf(&Bso, "%5.2f ldpe %s\n", obj.Cputime(), pn)
 	}
 
 	var sect *PeSect
 	Ctxt.IncVersion()
-	base := int32(bio.Boffset(f))
+	base := f.Offset()
 
 	peobj := new(PeObj)
 	peobj.f = f
@@ -174,14 +174,14 @@ func ldpe(f *bio.Buf, pkg string, length int64, pn string) {
 	// TODO return error if found .cormeta
 
 	// load string table
-	bio.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(peobj.fh.NumberOfSymbols), 0)
+	f.Seek(int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(peobj.fh.NumberOfSymbols), 0)
 
 	if bio.Bread(f, symbuf[:4]) != 4 {
 		goto bad
 	}
 	l = Le32(symbuf[:])
 	peobj.snames = make([]byte, l)
-	bio.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(peobj.fh.NumberOfSymbols), 0)
+	f.Seek(int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(peobj.fh.NumberOfSymbols), 0)
 	if bio.Bread(f, peobj.snames) != len(peobj.snames) {
 		goto bad
 	}
@@ -202,9 +202,9 @@ func ldpe(f *bio.Buf, pkg string, length int64, pn string) {
 	peobj.pesym = make([]PeSym, peobj.fh.NumberOfSymbols)
 
 	peobj.npesym = uint(peobj.fh.NumberOfSymbols)
-	bio.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable), 0)
+	f.Seek(int64(base)+int64(peobj.fh.PointerToSymbolTable), 0)
 	for i := 0; uint32(i) < peobj.fh.NumberOfSymbols; i += numaux + 1 {
-		bio.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(i), 0)
+		f.Seek(int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(i), 0)
 		if bio.Bread(f, symbuf[:]) != len(symbuf) {
 			goto bad
 		}
@@ -290,7 +290,7 @@ func ldpe(f *bio.Buf, pkg string, length int64, pn string) {
 		}
 
 		r = make([]Reloc, rsect.sh.NumberOfRelocations)
-		bio.Bseek(f, int64(peobj.base)+int64(rsect.sh.PointerToRelocations), 0)
+		f.Seek(int64(peobj.base)+int64(rsect.sh.PointerToRelocations), 0)
 		for j = 0; j < int(rsect.sh.NumberOfRelocations); j++ {
 			rp = &r[j]
 			if bio.Bread(f, symbuf[:10]) != 10 {
@@ -466,7 +466,7 @@ func pemap(peobj *PeObj, sect *PeSect) int {
 	if sect.sh.PointerToRawData == 0 { // .bss doesn't have data in object file
 		return 0
 	}
-	if bio.Bseek(peobj.f, int64(peobj.base)+int64(sect.sh.PointerToRawData), 0) < 0 || bio.Bread(peobj.f, sect.base) != len(sect.base) {
+	if peobj.f.Seek(int64(peobj.base)+int64(sect.sh.PointerToRawData), 0) < 0 || bio.Bread(peobj.f, sect.base) != len(sect.base) {
 		return -1
 	}
 

src/cmd/link/internal/ld/lib.go

@@ -241,9 +241,10 @@ const (
 var (
 	headstring string
 	// buffered output
-	Bso bio.Buf
+	Bso bio.Writer
 )
 
+// TODO(dfc) outBuf duplicates bio.Writer
 type outBuf struct {
 	w   *bufio.Writer
 	f   *os.File
@@ -739,11 +740,11 @@ func loadlib() {
  * look for the next file in an archive.
  * adapted from libmach.
  */
-func nextar(bp *bio.Buf, off int64, a *ArHdr) int64 {
+func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
 	if off&1 != 0 {
 		off++
 	}
-	bio.Bseek(bp, off, 0)
+	bp.Seek(off, 0)
 	buf := make([]byte, SAR_HDR)
 	if n := bio.Bread(bp, buf); n < len(buf) {
 		if n >= 0 {
@@ -782,9 +783,9 @@ func objfile(lib *Library) {
 	magbuf := make([]byte, len(ARMAG))
 	if bio.Bread(f, magbuf) != len(magbuf) || !strings.HasPrefix(string(magbuf), ARMAG) {
 		/* load it as a regular file */
-		l := bio.Bseek(f, 0, 2)
+		l := f.Seek(0, 2)
 
-		bio.Bseek(f, 0, 0)
+		f.Seek(0, 0)
 		ldobj(f, pkg, l, lib.File, lib.File, FileObj)
 		f.Close()
 
@@ -792,7 +793,7 @@ func objfile(lib *Library) {
 	}
 
 	/* process __.PKGDEF */
-	off := bio.Boffset(f)
+	off := f.Offset()
 
 	var arhdr ArHdr
 	l := nextar(f, off, &arhdr)
@@ -808,12 +809,12 @@ func objfile(lib *Library) {
 	}
 
 	if Buildmode == BuildmodeShared {
-		before := bio.Boffset(f)
+		before := f.Offset()
 		pkgdefBytes := make([]byte, atolwhex(arhdr.size))
 		bio.Bread(f, pkgdefBytes)
 		hash := sha1.Sum(pkgdefBytes)
 		lib.hash = hash[:]
-		bio.Bseek(f, before, 0)
+		f.Seek(before, 0)
 	}
 
 	off += l
@@ -853,7 +854,7 @@ out:
 }
 
 type Hostobj struct {
-	ld     func(*bio.Buf, string, int64, string)
+	ld     func(*bio.Reader, string, int64, string)
 	pkg    string
 	pn     string
 	file   string
@@ -874,7 +875,7 @@ var internalpkg = []string{
 	"runtime/msan",
 }
 
-func ldhostobj(ld func(*bio.Buf, string, int64, string), f *bio.Buf, pkg string, length int64, pn string, file string) *Hostobj {
+func ldhostobj(ld func(*bio.Reader, string, int64, string), f *bio.Reader, pkg string, length int64, pn string, file string) *Hostobj {
 	isinternal := false
 	for i := 0; i < len(internalpkg); i++ {
 		if pkg == internalpkg[i] {
@@ -905,24 +906,22 @@ func ldhostobj(ld func(*bio.Buf, string, int64, string), f *bio.Buf, pkg string,
 	h.pkg = pkg
 	h.pn = pn
 	h.file = file
-	h.off = bio.Boffset(f)
+	h.off = f.Offset()
 	h.length = length
 	return h
 }
 
 func hostobjs() {
-	var f *bio.Buf
 	var h *Hostobj
 
 	for i := 0; i < len(hostobj); i++ {
 		h = &hostobj[i]
-		var err error
-		f, err = bio.Open(h.file)
-		if f == nil {
+		f, err := bio.Open(h.file)
+		if err != nil {
 			Exitf("cannot reopen %s: %v", h.pn, err)
 		}
 
-		bio.Bseek(f, h.off, 0)
+		f.Seek(h.off, 0)
 		h.ld(f, h.pkg, h.length, h.pn)
 		f.Close()
 	}
@@ -1266,15 +1265,15 @@ func hostlinkArchArgs() []string {
 // ldobj loads an input object. If it is a host object (an object
 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
 // it is a Go object, it returns nil.
-func ldobj(f *bio.Buf, pkg string, length int64, pn string, file string, whence int) *Hostobj {
-	eof := bio.Boffset(f) + length
+func ldobj(f *bio.Reader, pkg string, length int64, pn string, file string, whence int) *Hostobj {
+	eof := f.Offset() + length
 
-	start := bio.Boffset(f)
+	start := f.Offset()
 	c1 := bio.Bgetc(f)
 	c2 := bio.Bgetc(f)
 	c3 := bio.Bgetc(f)
 	c4 := bio.Bgetc(f)
-	bio.Bseek(f, start, 0)
+	f.Seek(start, 0)
 
 	magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
 	if magic == 0x7f454c46 { // \x7F E L F
@@ -1334,7 +1333,7 @@ func ldobj(f *bio.Buf, pkg string, length int64, pn string, file string, whence
 	}
 
 	/* skip over exports and other info -- ends with \n!\n */
-	import0 := bio.Boffset(f)
+	import0 := f.Offset()
 
 	c1 = '\n' // the last line ended in \n
 	c2 = bio.Bgetc(f)
@@ -1349,13 +1348,13 @@ func ldobj(f *bio.Buf, pkg string, length int64, pn string, file string, whence
 		}
 	}
 
-	import1 := bio.Boffset(f)
+	import1 := f.Offset()
 
-	bio.Bseek(f, import0, 0)
+	f.Seek(import0, 0)
 	ldpkg(f, pkg, import1-import0-2, pn, whence) // -2 for !\n
-	bio.Bseek(f, import1, 0)
+	f.Seek(import1, 0)
 
-	LoadObjFile(Ctxt, f, pkg, eof-bio.Boffset(f), pn)
+	LoadObjFile(Ctxt, f, pkg, eof-f.Offset(), pn)
 	return nil
 }
 

src/cmd/link/internal/ld/link.go

@@ -165,7 +165,8 @@ type Link struct {
 	Headtype  int
 	Arch      *sys.Arch
 	Debugvlog int32
-	Bso       *bio.Buf
+
+	Bso     *bio.Writer
 	Windows int32
 	Goroot  string
 

src/cmd/link/internal/ld/objfile.go

@@ -147,8 +147,8 @@ type objReader struct {
 	file        []*LSym
 }
 
-func LoadObjFile(ctxt *Link, f *bio.Buf, pkg string, length int64, pn string) {
-	start := bio.Boffset(f)
+func LoadObjFile(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
+	start := f.Offset()
 	r := &objReader{
 		rd:     f.Reader(),
 		pkg:    pkg,
@@ -157,8 +157,8 @@ func LoadObjFile(ctxt *Link, f *bio.Buf, pkg string, length int64, pn string) {
 		dupSym: &LSym{Name: ".dup"},
 	}
 	r.loadObjFile()
-	if bio.Boffset(f) != start+length {
-		log.Fatalf("%s: unexpected end at %d, want %d", pn, int64(bio.Boffset(f)), int64(start+length))
+	if f.Offset() != start+length {
+		log.Fatalf("%s: unexpected end at %d, want %d", pn, f.Offset(), start+length)
 	}
 }