patch os: File.Write
This commit is contained in:
xushiwei
@@ -18,5 +18,710 @@ package io
|
||||
|
||||
// llgo:skipall
|
||||
import (
|
||||
_ "unsafe"
|
||||
"errors"
|
||||
)
|
||||
|
||||
// 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 a 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.
|
||||
//
|
||||
// If len(p) == 0, Read should always return n == 0. It may return a
|
||||
// non-nil error if some error condition is known, such as EOF.
|
||||
//
|
||||
// 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
|
||||
// (for example, offset = -2 specifies the penultimate byte of the file).
|
||||
// Seek returns the new offset relative to the start of the
|
||||
// file or an error, if any.
|
||||
//
|
||||
// Seeking to an offset before the start of the file is an error.
|
||||
// Seeking to any positive offset may be allowed, but if the new offset exceeds
|
||||
// the size of the underlying object the behavior of subsequent I/O operations
|
||||
// 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 last byte read.
|
||||
// If the last operation was not a successful call to ReadByte, UnreadByte may
|
||||
// return an error, unread the last byte read (or the byte prior to the
|
||||
// last-unread byte), or (in implementations that support the Seeker interface)
|
||||
// seek to one byte before the current offset.
|
||||
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 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 last rune read.
|
||||
// If the last operation was not a successful call to ReadRune, UnreadRune may
|
||||
// return an error, unread the last rune read (or the rune prior to the
|
||||
// last-unread rune), or (in implementations that support the Seeker interface)
|
||||
// seek to the start of the rune before the current offset.
|
||||
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 {
|
||||
var remaining int64
|
||||
const maxint64 = 1<<63 - 1
|
||||
if off <= maxint64-n {
|
||||
remaining = n + off
|
||||
} else {
|
||||
// Overflow, with no way to return error.
|
||||
// Assume we can read up to an offset of 1<<63 - 1.
|
||||
remaining = maxint64
|
||||
}
|
||||
return &SectionReader{r, off, off, remaining}
|
||||
}
|
||||
|
||||
// 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 }
|
||||
|
||||
// An OffsetWriter maps writes at offset base to offset base+off in the underlying writer.
|
||||
type OffsetWriter struct {
|
||||
w WriterAt
|
||||
base int64 // the original offset
|
||||
off int64 // the current offset
|
||||
}
|
||||
|
||||
// NewOffsetWriter returns an OffsetWriter that writes to w
|
||||
// starting at offset off.
|
||||
func NewOffsetWriter(w WriterAt, off int64) *OffsetWriter {
|
||||
return &OffsetWriter{w, off, off}
|
||||
}
|
||||
|
||||
func (o *OffsetWriter) Write(p []byte) (n int, err error) {
|
||||
n, err = o.w.WriteAt(p, o.off)
|
||||
o.off += int64(n)
|
||||
return
|
||||
}
|
||||
|
||||
func (o *OffsetWriter) WriteAt(p []byte, off int64) (n int, err error) {
|
||||
if off < 0 {
|
||||
return 0, errOffset
|
||||
}
|
||||
|
||||
off += o.base
|
||||
return o.w.WriteAt(p, off)
|
||||
}
|
||||
|
||||
func (o *OffsetWriter) Seek(offset int64, whence int) (int64, error) {
|
||||
switch whence {
|
||||
default:
|
||||
return 0, errWhence
|
||||
case SeekStart:
|
||||
offset += o.base
|
||||
case SeekCurrent:
|
||||
offset += o.off
|
||||
}
|
||||
if offset < o.base {
|
||||
return 0, errOffset
|
||||
}
|
||||
o.off = offset
|
||||
return offset - o.base, nil
|
||||
}
|
||||
|
||||
// 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
|
||||
}
|
||||
|
||||
/* TODO(xsw):
|
||||
var blackHolePool = sync.Pool{
|
||||
New: func() any {
|
||||
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
|
||||
}
|
||||
}
|
||||
*/
|
||||
panic("todo")
|
||||
}
|
||||
|
||||
// NopCloser returns a ReadCloser with a no-op Close method wrapping
|
||||
// the provided Reader r.
|
||||
// If r implements WriterTo, the returned ReadCloser will implement WriterTo
|
||||
// by forwarding calls to r.
|
||||
func NopCloser(r Reader) ReadCloser {
|
||||
if _, ok := r.(WriterTo); ok {
|
||||
return nopCloserWriterTo{r}
|
||||
}
|
||||
return nopCloser{r}
|
||||
}
|
||||
|
||||
type nopCloser struct {
|
||||
Reader
|
||||
}
|
||||
|
||||
func (nopCloser) Close() error { return nil }
|
||||
|
||||
type nopCloserWriterTo struct {
|
||||
Reader
|
||||
}
|
||||
|
||||
func (nopCloserWriterTo) Close() error { return nil }
|
||||
|
||||
func (c nopCloserWriterTo) WriteTo(w Writer) (n int64, err error) {
|
||||
return c.Reader.(WriterTo).WriteTo(w)
|
||||
}
|
||||
|
||||
// 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 {
|
||||
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
|
||||
}
|
||||
|
||||
if len(b) == cap(b) {
|
||||
// Add more capacity (let append pick how much).
|
||||
b = append(b, 0)[:len(b)]
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
Reference in New Issue
Block a user