1 files changed, 642 insertions, 0 deletions
diff --git a/src/io/io.go b/src/io/io.go
new file mode 100644
index 0000000..2724321
--- /dev/null
+++ b/src/io/io.go
@@ -0,0 +1,642 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package io provides basic interfaces to I/O primitives.
+// Its primary job is to wrap existing implementations of such primitives,
+// such as those in package os, into shared public interfaces that
+// abstract the functionality, plus some other related primitives.
+//
+// Because these interfaces and primitives wrap lower-level operations with
+// various implementations, unless otherwise informed clients should not
+// assume they are safe for parallel execution.
+package io
+
+import (
+	"errors"
+	"sync"
+)
+
+// Seek whence values.
+const (
+	SeekStart   = 0 // seek relative to the origin of the file
+	SeekCurrent = 1 // seek relative to the current offset
+	SeekEnd     = 2 // seek relative to the end
+)
+
+// ErrShortWrite means that a write accepted fewer bytes than requested
+// but failed to return an explicit error.
+var ErrShortWrite = errors.New("short write")
+
+// errInvalidWrite means that a write returned an impossible count.
+var errInvalidWrite = errors.New("invalid write result")
+
+// ErrShortBuffer means that a read required a longer buffer than was provided.
+var ErrShortBuffer = errors.New("short buffer")
+
+// EOF is the error returned by Read when no more input is available.
+// (Read must return EOF itself, not an error wrapping EOF,
+// because callers will test for EOF using ==.)
+// 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 = errors.New("EOF")
+
+// ErrUnexpectedEOF means that EOF was encountered in the
+// middle of reading a fixed-size block or data structure.
+var ErrUnexpectedEOF = errors.New("unexpected EOF")
+
+// ErrNoProgress is returned by some clients of an Reader when
+// many calls to Read have failed to return any data or error,
+// usually the sign of a broken Reader implementation.
+var ErrNoProgress = errors.New("multiple Read calls return no data or error")
+
+// Reader is the interface that wraps the basic Read method.
+//
+// Read reads up to len(p) bytes into p. It returns the number of bytes
+// read (0 <= n <= len(p)) and any error encountered. Even if Read
+// returns n < len(p), it may use all of p as scratch space during the call.
+// If some data is available but not len(p) bytes, Read conventionally
+// returns what is available instead of waiting for more.
+//
+// When Read encounters an error or end-of-file condition after
+// successfully reading n > 0 bytes, it returns the number of
+// bytes read. It may return the (non-nil) error from the same call
+// or return the error (and n == 0) from a subsequent call.
+// An instance of this general case is that a Reader returning
+// a non-zero number of bytes at the end of the input stream may
+// return either err == EOF or err == nil. The next Read should
+// return 0, EOF.
+//
+// Callers should always process the n > 0 bytes returned before
+// considering the error err. Doing so correctly handles I/O errors
+// that happen after reading some bytes and also both of the
+// allowed EOF behaviors.
+//
+// Implementations of Read are discouraged from returning a
+// zero byte count with a nil error, except when len(p) == 0.
+// Callers should treat a return of 0 and nil as indicating that
+// nothing happened; in particular it does not indicate EOF.
+//
+// Implementations must not retain p.
+type Reader interface {
+	Read(p []byte) (n int, err error)
+}
+
+// Writer is the interface that wraps the basic Write method.
+//
+// Write writes len(p) bytes from p to the underlying data stream.
+// It returns the number of bytes written from p (0 <= n <= len(p))
+// and any error encountered that caused the write to stop early.
+// Write must return a non-nil error if it returns n < len(p).
+// Write must not modify the slice data, even temporarily.
+//
+// Implementations must not retain p.
+type Writer interface {
+	Write(p []byte) (n int, err error)
+}
+
+// Closer is the interface that wraps the basic Close method.
+//
+// The behavior of Close after the first call is undefined.
+// Specific implementations may document their own behavior.
+type Closer interface {
+	Close() error
+}
+
+// Seeker is the interface that wraps the basic Seek method.
+//
+// Seek sets the offset for the next Read or Write to offset,
+// interpreted according to whence:
+// SeekStart means relative to the start of the file,
+// SeekCurrent means relative to the current offset, and
+// SeekEnd means relative to the end.
+// Seek returns the new offset relative to the start of the
+// file and an error, if any.
+//
+// Seeking to an offset before the start of the file is an error.
+// Seeking to any positive offset is legal, but the behavior of subsequent
+// I/O operations on the underlying object is implementation-dependent.
+type Seeker interface {
+	Seek(offset int64, whence int) (int64, error)
+}
+
+// ReadWriter is the interface that groups the basic Read and Write methods.
+type ReadWriter interface {
+	Reader
+	Writer
+}
+
+// ReadCloser is the interface that groups the basic Read and Close methods.
+type ReadCloser interface {
+	Reader
+	Closer
+}
+
+// WriteCloser is the interface that groups the basic Write and Close methods.
+type WriteCloser interface {
+	Writer
+	Closer
+}
+
+// ReadWriteCloser is the interface that groups the basic Read, Write and Close methods.
+type ReadWriteCloser interface {
+	Reader
+	Writer
+	Closer
+}
+
+// ReadSeeker is the interface that groups the basic Read and Seek methods.
+type ReadSeeker interface {
+	Reader
+	Seeker
+}
+
+// ReadSeekCloser is the interface that groups the basic Read, Seek and Close
+// methods.
+type ReadSeekCloser interface {
+	Reader
+	Seeker
+	Closer
+}
+
+// WriteSeeker is the interface that groups the basic Write and Seek methods.
+type WriteSeeker interface {
+	Writer
+	Seeker
+}
+
+// ReadWriteSeeker is the interface that groups the basic Read, Write and Seek methods.
+type ReadWriteSeeker interface {
+	Reader
+	Writer
+	Seeker
+}
+
+// ReaderFrom is the interface that wraps the ReadFrom method.
+//
+// ReadFrom reads data from r until EOF or error.
+// The return value n is the number of bytes read.
+// Any error except EOF encountered during the read is also returned.
+//
+// The Copy function uses ReaderFrom if available.
+type ReaderFrom interface {
+	ReadFrom(r Reader) (n int64, err error)
+}
+
+// WriterTo is the interface that wraps the WriteTo method.
+//
+// WriteTo writes data to w until there's no more data to write or
+// when an error occurs. The return value n is the number of bytes
+// written. Any error encountered during the write is also returned.
+//
+// The Copy function uses WriterTo if available.
+type WriterTo interface {
+	WriteTo(w Writer) (n int64, err error)
+}
+
+// ReaderAt is the interface that wraps the basic ReadAt method.
+//
+// ReadAt reads len(p) bytes into p starting at offset off in the
+// underlying input source. It returns the number of bytes
+// read (0 <= n <= len(p)) and any error encountered.
+//
+// When ReadAt returns n < len(p), it returns a non-nil error
+// explaining why more bytes were not returned. In this respect,
+// ReadAt is stricter than Read.
+//
+// Even if ReadAt returns n < len(p), it may use all of p as scratch
+// space during the call. If some data is available but not len(p) bytes,
+// ReadAt blocks until either all the data is available or an error occurs.
+// In this respect ReadAt is different from Read.
+//
+// If the n = len(p) bytes returned by ReadAt are at the end of the
+// input source, ReadAt may return either err == EOF or err == nil.
+//
+// If ReadAt is reading from an input source with a seek offset,
+// ReadAt should not affect nor be affected by the underlying
+// seek offset.
+//
+// Clients of ReadAt can execute parallel ReadAt calls on the
+// same input source.
+//
+// Implementations must not retain p.
+type ReaderAt interface {
+	ReadAt(p []byte, off int64) (n int, err error)
+}
+
+// WriterAt is the interface that wraps the basic WriteAt method.
+//
+// WriteAt writes len(p) bytes from p to the underlying data stream
+// at offset off. It returns the number of bytes written from p (0 <= n <= len(p))
+// and any error encountered that caused the write to stop early.
+// WriteAt must return a non-nil error if it returns n < len(p).
+//
+// If WriteAt is writing to a destination with a seek offset,
+// WriteAt should not affect nor be affected by the underlying
+// seek offset.
+//
+// Clients of WriteAt can execute parallel WriteAt calls on the same
+// destination if the ranges do not overlap.
+//
+// Implementations must not retain p.
+type WriterAt interface {
+	WriteAt(p []byte, off int64) (n int, err error)
+}
+
+// ByteReader is the interface that wraps the ReadByte method.
+//
+// ReadByte reads and returns the next byte from the input or
+// any error encountered. If ReadByte returns an error, no input
+// byte was consumed, and the returned byte value is undefined.
+//
+// ReadByte provides an efficient interface for byte-at-time
+// processing. A Reader that does not implement  ByteReader
+// can be wrapped using bufio.NewReader to add this method.
+type ByteReader interface {
+	ReadByte() (byte, error)
+}
+
+// ByteScanner is the interface that adds the UnreadByte method to the
+// basic ReadByte method.
+//
+// UnreadByte causes the next call to ReadByte to return the same byte
+// as the previous call to ReadByte.
+// It may be an error to call UnreadByte twice without an intervening
+// call to ReadByte.
+type ByteScanner interface {
+	ByteReader
+	UnreadByte() error
+}
+
+// ByteWriter is the interface that wraps the WriteByte method.
+type ByteWriter interface {
+	WriteByte(c byte) error
+}
+
+// RuneReader is the interface that wraps the ReadRune method.
+//
+// ReadRune reads a single UTF-8 encoded Unicode character
+// and returns the rune and its size in bytes. If no character is
+// available, err will be set.
+type RuneReader interface {
+	ReadRune() (r rune, size int, err error)
+}
+
+// RuneScanner is the interface that adds the UnreadRune method to the
+// basic ReadRune method.
+//
+// UnreadRune causes the next call to ReadRune to return the same rune
+// as the previous call to ReadRune.
+// It may be an error to call UnreadRune twice without an intervening
+// call to ReadRune.
+type RuneScanner interface {
+	RuneReader
+	UnreadRune() error
+}
+
+// StringWriter is the interface that wraps the WriteString method.
+type StringWriter interface {
+	WriteString(s string) (n int, err error)
+}
+
+// WriteString writes the contents of the string s to w, which accepts a slice of bytes.
+// If w implements StringWriter, its WriteString method is invoked directly.
+// Otherwise, w.Write is called exactly once.
+func WriteString(w Writer, s string) (n int, err error) {
+	if sw, ok := w.(StringWriter); ok {
+		return sw.WriteString(s)
+	}
+	return w.Write([]byte(s))
+}
+
+// ReadAtLeast reads from r into buf until it has read at least min bytes.
+// It returns the number of bytes copied and an error if fewer bytes were read.
+// The error is EOF only if no bytes were read.
+// If an EOF happens after reading fewer than min bytes,
+// ReadAtLeast returns ErrUnexpectedEOF.
+// If min is greater than the length of buf, ReadAtLeast returns ErrShortBuffer.
+// On return, n >= min if and only if err == nil.
+// If r returns an error having read at least min bytes, the error is dropped.
+func ReadAtLeast(r Reader, buf []byte, min int) (n int, err error) {
+	if len(buf) < min {
+		return 0, ErrShortBuffer
+	}
+	for n < min && err == nil {
+		var nn int
+		nn, err = r.Read(buf[n:])
+		n += nn
+	}
+	if n >= min {
+		err = nil
+	} else if n > 0 && err == EOF {
+		err = ErrUnexpectedEOF
+	}
+	return
+}
+
+// ReadFull reads exactly len(buf) bytes from r into buf.
+// It returns the number of bytes copied and an error if fewer bytes were read.
+// The error is EOF only if no bytes were read.
+// If an EOF happens after reading some but not all the bytes,
+// ReadFull returns ErrUnexpectedEOF.
+// On return, n == len(buf) if and only if err == nil.
+// If r returns an error having read at least len(buf) bytes, the error is dropped.
+func ReadFull(r Reader, buf []byte) (n int, err error) {
+	return ReadAtLeast(r, buf, len(buf))
+}
+
+// CopyN copies n bytes (or until an error) from src to dst.
+// It returns the number of bytes copied and the earliest
+// error encountered while copying.
+// On return, written == n if and only if err == nil.
+//
+// If dst implements the ReaderFrom interface,
+// the copy is implemented using it.
+func CopyN(dst Writer, src Reader, n int64) (written int64, err error) {
+	written, err = Copy(dst, LimitReader(src, n))
+	if written == n {
+		return n, nil
+	}
+	if written < n && err == nil {
+		// src stopped early; must have been EOF.
+		err = EOF
+	}
+	return
+}
+
+// Copy copies from src to dst until either EOF is reached
+// on src or an error occurs. It returns the number of bytes
+// copied and the first error encountered while copying, if any.
+//
+// A successful Copy returns err == nil, not err == EOF.
+// Because Copy is defined to read from src until EOF, it does
+// not treat an EOF from Read as an error to be reported.
+//
+// If src implements the WriterTo interface,
+// the copy is implemented by calling src.WriteTo(dst).
+// Otherwise, if dst implements the ReaderFrom interface,
+// the copy is implemented by calling dst.ReadFrom(src).
+func Copy(dst Writer, src Reader) (written int64, err error) {
+	return copyBuffer(dst, src, nil)
+}
+
+// CopyBuffer is identical to Copy except that it stages through the
+// provided buffer (if one is required) rather than allocating a
+// temporary one. If buf is nil, one is allocated; otherwise if it has
+// zero length, CopyBuffer panics.
+//
+// If either src implements WriterTo or dst implements ReaderFrom,
+// buf will not be used to perform the copy.
+func CopyBuffer(dst Writer, src Reader, buf []byte) (written int64, err error) {
+	if buf != nil && len(buf) == 0 {
+		panic("empty buffer in CopyBuffer")
+	}
+	return copyBuffer(dst, src, buf)
+}
+
+// copyBuffer is the actual implementation of Copy and CopyBuffer.
+// if buf is nil, one is allocated.
+func copyBuffer(dst Writer, src Reader, buf []byte) (written int64, err error) {
+	// If the reader has a WriteTo method, use it to do the copy.
+	// Avoids an allocation and a copy.
+	if wt, ok := src.(WriterTo); ok {
+		return wt.WriteTo(dst)
+	}
+	// Similarly, if the writer has a ReadFrom method, use it to do the copy.
+	if rt, ok := dst.(ReaderFrom); ok {
+		return rt.ReadFrom(src)
+	}
+	if buf == nil {
+		size := 32 * 1024
+		if l, ok := src.(*LimitedReader); ok && int64(size) > l.N {
+			if l.N < 1 {
+				size = 1
+			} else {
+				size = int(l.N)
+			}
+		}
+		buf = make([]byte, size)
+	}
+	for {
+		nr, er := src.Read(buf)
+		if nr > 0 {
+			nw, ew := dst.Write(buf[0:nr])
+			if nw < 0 || nr < nw {
+				nw = 0
+				if ew == nil {
+					ew = errInvalidWrite
+				}
+			}
+			written += int64(nw)
+			if ew != nil {
+				err = ew
+				break
+			}
+			if nr != nw {
+				err = ErrShortWrite
+				break
+			}
+		}
+		if er != nil {
+			if er != EOF {
+				err = er
+			}
+			break
+		}
+	}
+	return written, err
+}
+
+// LimitReader returns a Reader that reads from r
+// but stops with EOF after n bytes.
+// The underlying implementation is a *LimitedReader.
+func LimitReader(r Reader, n int64) Reader { return &LimitedReader{r, n} }
+
+// A LimitedReader reads from R but limits the amount of
+// data returned to just N bytes. Each call to Read
+// updates N to reflect the new amount remaining.
+// Read returns EOF when N <= 0 or when the underlying R returns EOF.
+type LimitedReader struct {
+	R Reader // underlying reader
+	N int64  // max bytes remaining
+}
+
+func (l *LimitedReader) Read(p []byte) (n int, err error) {
+	if l.N <= 0 {
+		return 0, EOF
+	}
+	if int64(len(p)) > l.N {
+		p = p[0:l.N]
+	}
+	n, err = l.R.Read(p)
+	l.N -= int64(n)
+	return
+}
+
+// NewSectionReader returns a SectionReader that reads from r
+// starting at offset off and stops with EOF after n bytes.
+func NewSectionReader(r ReaderAt, off int64, n int64) *SectionReader {
+	return &SectionReader{r, off, off, off + n}
+}
+
+// SectionReader implements Read, Seek, and ReadAt on a section
+// of an underlying ReaderAt.
+type SectionReader struct {
+	r     ReaderAt
+	base  int64
+	off   int64
+	limit int64
+}
+
+func (s *SectionReader) Read(p []byte) (n int, err error) {
+	if s.off >= s.limit {
+		return 0, EOF
+	}
+	if max := s.limit - s.off; int64(len(p)) > max {
+		p = p[0:max]
+	}
+	n, err = s.r.ReadAt(p, s.off)
+	s.off += int64(n)
+	return
+}
+
+var errWhence = errors.New("Seek: invalid whence")
+var errOffset = errors.New("Seek: invalid offset")
+
+func (s *SectionReader) Seek(offset int64, whence int) (int64, error) {
+	switch whence {
+	default:
+		return 0, errWhence
+	case SeekStart:
+		offset += s.base
+	case SeekCurrent:
+		offset += s.off
+	case SeekEnd:
+		offset += s.limit
+	}
+	if offset < s.base {
+		return 0, errOffset
+	}
+	s.off = offset
+	return offset - s.base, nil
+}
+
+func (s *SectionReader) ReadAt(p []byte, off int64) (n int, err error) {
+	if off < 0 || off >= s.limit-s.base {
+		return 0, EOF
+	}
+	off += s.base
+	if max := s.limit - off; int64(len(p)) > max {
+		p = p[0:max]
+		n, err = s.r.ReadAt(p, off)
+		if err == nil {
+			err = EOF
+		}
+		return n, err
+	}
+	return s.r.ReadAt(p, off)
+}
+
+// Size returns the size of the section in bytes.
+func (s *SectionReader) Size() int64 { return s.limit - s.base }
+
+// TeeReader returns a Reader that writes to w what it reads from r.
+// All reads from r performed through it are matched with
+// corresponding writes to w. There is no internal buffering -
+// the write must complete before the read completes.
+// Any error encountered while writing is reported as a read error.
+func TeeReader(r Reader, w Writer) Reader {
+	return &teeReader{r, w}
+}
+
+type teeReader struct {
+	r Reader
+	w Writer
+}
+
+func (t *teeReader) Read(p []byte) (n int, err error) {
+	n, err = t.r.Read(p)
+	if n > 0 {
+		if n, err := t.w.Write(p[:n]); err != nil {
+			return n, err
+		}
+	}
+	return
+}
+
+// Discard is a Writer on which all Write calls succeed
+// without doing anything.
+var Discard Writer = discard{}
+
+type discard struct{}
+
+// discard implements ReaderFrom as an optimization so Copy to
+// io.Discard can avoid doing unnecessary work.
+var _ ReaderFrom = discard{}
+
+func (discard) Write(p []byte) (int, error) {
+	return len(p), nil
+}
+
+func (discard) WriteString(s string) (int, error) {
+	return len(s), nil
+}
+
+var blackHolePool = sync.Pool{
+	New: func() interface{} {
+		b := make([]byte, 8192)
+		return &b
+	},
+}
+
+func (discard) ReadFrom(r Reader) (n int64, err error) {
+	bufp := blackHolePool.Get().(*[]byte)
+	readSize := 0
+	for {
+		readSize, err = r.Read(*bufp)
+		n += int64(readSize)
+		if err != nil {
+			blackHolePool.Put(bufp)
+			if err == EOF {
+				return n, nil
+			}
+			return
+		}
+	}
+}
+
+// NopCloser returns a ReadCloser with a no-op Close method wrapping
+// the provided Reader r.
+func NopCloser(r Reader) ReadCloser {
+	return nopCloser{r}
+}
+
+type nopCloser struct {
+	Reader
+}
+
+func (nopCloser) Close() error { return nil }
+
+// ReadAll reads from r until an error or EOF and returns the data it read.
+// A successful call returns err == nil, not err == EOF. Because ReadAll is
+// defined to read from src until EOF, it does not treat an EOF from Read
+// as an error to be reported.
+func ReadAll(r Reader) ([]byte, error) {
+	b := make([]byte, 0, 512)
+	for {
+		if len(b) == cap(b) {
+			// Add more capacity (let append pick how much).
+			b = append(b, 0)[:len(b)]
+		}
+		n, err := r.Read(b[len(b):cap(b)])
+		b = b[:len(b)+n]
+		if err != nil {
+			if err == EOF {
+				err = nil
+			}
+			return b, err
+		}
+	}
+}