code review 5636046: io: API tweaks

io: API tweaks
- eliminate local Error type (a historical artifact)
- fix documentation of CopyN
- fix documentation of WriteString
Fixes issue 2859.

[r, 2012-02-06 03:25:54]

Hello rsc (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg/

[bradfitz, 2012-02-06 04:06:32]

LGTM
On Feb 5, 2012 7:26 PM, <r@golang.org> wrote:

> Reviewers: rsc,
>
> Message:
> Hello rsc (cc: golang-dev@googlegroups.com),
>
> I'd like you to review this change to
> https://go.googlecode.com/hg/
>
>
> Description:
> io: API tweaks
> - eliminate local Error type (a historical artifact)
> - fix documentation of CopyN
> - fix documentation of WriteString
> Fixes issue 2859
>
> Please review this at
http://codereview.appspot.com/**5636046/<http://codereview.appspot.com/5636046/>
>
> Affected files:
>  M src/pkg/io/io.go
>  M src/pkg/io/pipe.go
>
>
> Index: src/pkg/io/io.go
> ==============================**==============================**=======
> --- a/src/pkg/io/io.go
> +++ b/src/pkg/io/io.go
> @@ -8,30 +8,27 @@
>  // abstract the functionality, plus some other related primitives.
>  package io
>
> -// Error represents an unexpected I/O behavior.
> -type Error struct {
> -       ErrorString string
> -}
> -
> -func (err *Error) Error() string { return err.ErrorString }
> +import (
> +       "errors"
> +)
>
>  // ErrShortWrite means that a write accepted fewer bytes than requested
>  // but failed to return an explicit error.
> -var ErrShortWrite error = &Error{"short write"}
> +var ErrShortWrite = errors.New("short write")
>
>  // ErrShortBuffer means that a read required a longer buffer than was
> provided.
> -var ErrShortBuffer error = &Error{"short buffer"}
> +var ErrShortBuffer = errors.New("short buffer")
>
>  // EOF is the error returned by Read when no more input is available.
>  // Functions should return EOF only to signal a graceful end of input.
>  // If the EOF occurs unexpectedly in a structured data stream,
>  // the appropriate error is either ErrUnexpectedEOF or some other error
>  // giving more detail.
> -var EOF error = &Error{"EOF"}
> +var EOF = errors.New("EOF")
>
>  // ErrUnexpectedEOF means that EOF was encountered in the
>  // middle of reading a fixed-size block or data structure.
> -var ErrUnexpectedEOF error = &Error{"unexpected EOF"}
> +var ErrUnexpectedEOF = errors.New("unexpected EOF")
>
>  // Reader is the interface that wraps the basic Read method.
>  //
> @@ -220,6 +217,7 @@
>  }
>
>  // WriteString writes the contents of the string s to w, which accepts an
> array of bytes.
> +// If w already implements a WriteString method, it is invoked directly.
>  func WriteString(w Writer, s string) (n int, err error) {
>        if sw, ok := w.(stringWriter); ok {
>                return sw.WriteString(s)
> @@ -268,7 +266,7 @@
>  // (including EOF), so can CopyN.
>  //
>  // If dst implements the ReaderFrom interface,
> -// the copy is implemented by calling dst.ReadFrom(src).
> +// the copy is implemented using it.
>  func CopyN(dst Writer, src Reader, n int64) (written int64, err error) {
>        // If the writer has a ReadFrom method, use it to do the copy.
>        // Avoids a buffer allocation and a copy.
> @@ -411,8 +409,8 @@
>        return
>  }
>
> -var errWhence = &Error{"Seek: invalid whence"}
> -var errOffset = &Error{"Seek: invalid offset"}
> +var errWhence = errors.New("Seek: invalid whence")
> +var errOffset = errors.New("Seek: invalid offset")
>
>  func (s *SectionReader) Seek(offset int64, whence int) (ret int64, err
> error) {
>        switch whence {
> Index: src/pkg/io/pipe.go
> ==============================**==============================**=======
> --- a/src/pkg/io/pipe.go
> +++ b/src/pkg/io/pipe.go
> @@ -7,10 +7,13 @@
>
>  package io
>
> -import "sync"
> +import (
> +       "errors"
> +       "sync"
> +)
>
>  // ErrClosedPipe is the error used for read or write operations on a
> closed pipe.
> -var ErrClosedPipe = &Error{"io: read/write on closed pipe"}
> +var ErrClosedPipe = errors.New("io: read/write on closed pipe")
>
>  type pipeResult struct {
>        n   int
>
>
>

[r, 2012-02-06 04:09:55]

*** Submitted as http://code.google.com/p/go/source/detail?r=afa99ad294e7 ***

io: API tweaks
- eliminate local Error type (a historical artifact)
- fix documentation of CopyN
- fix documentation of WriteString
Fixes issue 2859.

R=rsc, bradfitz
CC=golang-dev
http://codereview.appspot.com/5636046