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315 lines
6.6 KiB
Markdown
315 lines
6.6 KiB
Markdown
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# fwd
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import "github.com/philhofer/fwd"
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The `fwd` package provides a buffered reader
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and writer. Each has methods that help improve
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the encoding/decoding performance of some binary
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protocols.
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The `fwd.Writer` and `fwd.Reader` type provide similar
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functionality to their counterparts in `bufio`, plus
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a few extra utility methods that simplify read-ahead
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and write-ahead. I wrote this package to improve serialization
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performance for <a href="http://github.com/tinylib/msgp">http://github.com/tinylib/msgp</a>,
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where it provided about a 2x speedup over `bufio` for certain
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workloads. However, care must be taken to understand the semantics of the
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extra methods provided by this package, as they allow
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the user to access and manipulate the buffer memory
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directly.
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The extra methods for `fwd.Reader` are `Peek`, `Skip`
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and `Next`. `(*fwd.Reader).Peek`, unlike `(*bufio.Reader).Peek`,
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will re-allocate the read buffer in order to accommodate arbitrarily
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large read-ahead. `(*fwd.Reader).Skip` skips the next `n` bytes
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in the stream, and uses the `io.Seeker` interface if the underlying
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stream implements it. `(*fwd.Reader).Next` returns a slice pointing
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to the next `n` bytes in the read buffer (like `Peek`), but also
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increments the read position. This allows users to process streams
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in arbitrary block sizes without having to manage appropriately-sized
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slices. Additionally, obviating the need to copy the data from the
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buffer to another location in memory can improve performance dramatically
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in CPU-bound applications.
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`fwd.Writer` only has one extra method, which is `(*fwd.Writer).Next`, which
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returns a slice pointing to the next `n` bytes of the writer, and increments
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the write position by the length of the returned slice. This allows users
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to write directly to the end of the buffer.
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## Constants
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``` go
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const (
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// DefaultReaderSize is the default size of the read buffer
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DefaultReaderSize = 2048
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)
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```
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``` go
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const (
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// DefaultWriterSize is the
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// default write buffer size.
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DefaultWriterSize = 2048
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)
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```
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## type Reader
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``` go
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type Reader struct {
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// contains filtered or unexported fields
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}
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```
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Reader is a buffered look-ahead reader
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### func NewReader
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``` go
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func NewReader(r io.Reader) *Reader
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```
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NewReader returns a new *Reader that reads from 'r'
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### func NewReaderSize
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``` go
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func NewReaderSize(r io.Reader, n int) *Reader
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```
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NewReaderSize returns a new *Reader that
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reads from 'r' and has a buffer size 'n'
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### func (\*Reader) BufferSize
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``` go
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func (r *Reader) BufferSize() int
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```
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BufferSize returns the total size of the buffer
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### func (\*Reader) Buffered
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``` go
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func (r *Reader) Buffered() int
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```
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Buffered returns the number of bytes currently in the buffer
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### func (\*Reader) Next
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``` go
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func (r *Reader) Next(n int) ([]byte, error)
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```
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Next returns the next 'n' bytes in the stream.
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Unlike Peek, Next advances the reader position.
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The returned bytes point to the same
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data as the buffer, so the slice is
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only valid until the next reader method call.
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An EOF is considered an unexpected error.
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If an the returned slice is less than the
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length asked for, an error will be returned,
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and the reader position will not be incremented.
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### func (\*Reader) Peek
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``` go
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func (r *Reader) Peek(n int) ([]byte, error)
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```
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Peek returns the next 'n' buffered bytes,
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reading from the underlying reader if necessary.
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It will only return a slice shorter than 'n' bytes
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if it also returns an error. Peek does not advance
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the reader. EOF errors are *not* returned as
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io.ErrUnexpectedEOF.
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### func (\*Reader) Read
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``` go
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func (r *Reader) Read(b []byte) (int, error)
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```
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Read implements `io.Reader`
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### func (\*Reader) ReadByte
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``` go
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func (r *Reader) ReadByte() (byte, error)
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```
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ReadByte implements `io.ByteReader`
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### func (\*Reader) ReadFull
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``` go
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func (r *Reader) ReadFull(b []byte) (int, error)
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```
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ReadFull attempts to read len(b) bytes into
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'b'. It returns the number of bytes read into
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'b', and an error if it does not return len(b).
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EOF is considered an unexpected error.
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### func (\*Reader) Reset
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``` go
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func (r *Reader) Reset(rd io.Reader)
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```
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Reset resets the underlying reader
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and the read buffer.
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### func (\*Reader) Skip
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``` go
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func (r *Reader) Skip(n int) (int, error)
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```
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Skip moves the reader forward 'n' bytes.
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Returns the number of bytes skipped and any
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errors encountered. It is analogous to Seek(n, 1).
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If the underlying reader implements io.Seeker, then
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that method will be used to skip forward.
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If the reader encounters
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an EOF before skipping 'n' bytes, it
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returns io.ErrUnexpectedEOF. If the
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underlying reader implements io.Seeker, then
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those rules apply instead. (Many implementations
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will not return `io.EOF` until the next call
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to Read.)
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### func (\*Reader) WriteTo
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``` go
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func (r *Reader) WriteTo(w io.Writer) (int64, error)
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```
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WriteTo implements `io.WriterTo`
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## type Writer
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``` go
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type Writer struct {
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// contains filtered or unexported fields
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}
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```
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Writer is a buffered writer
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### func NewWriter
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``` go
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func NewWriter(w io.Writer) *Writer
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```
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NewWriter returns a new writer
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that writes to 'w' and has a buffer
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that is `DefaultWriterSize` bytes.
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### func NewWriterSize
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``` go
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func NewWriterSize(w io.Writer, size int) *Writer
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```
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NewWriterSize returns a new writer
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that writes to 'w' and has a buffer
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that is 'size' bytes.
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### func (\*Writer) BufferSize
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``` go
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func (w *Writer) BufferSize() int
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```
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BufferSize returns the maximum size of the buffer.
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### func (\*Writer) Buffered
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``` go
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func (w *Writer) Buffered() int
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```
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Buffered returns the number of buffered bytes
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in the reader.
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### func (\*Writer) Flush
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``` go
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func (w *Writer) Flush() error
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```
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Flush flushes any buffered bytes
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to the underlying writer.
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### func (\*Writer) Next
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``` go
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func (w *Writer) Next(n int) ([]byte, error)
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```
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Next returns the next 'n' free bytes
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in the write buffer, flushing the writer
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as necessary. Next will return `io.ErrShortBuffer`
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if 'n' is greater than the size of the write buffer.
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Calls to 'next' increment the write position by
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the size of the returned buffer.
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### func (\*Writer) ReadFrom
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``` go
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func (w *Writer) ReadFrom(r io.Reader) (int64, error)
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```
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ReadFrom implements `io.ReaderFrom`
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### func (\*Writer) Write
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``` go
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func (w *Writer) Write(p []byte) (int, error)
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```
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Write implements `io.Writer`
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### func (\*Writer) WriteByte
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``` go
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func (w *Writer) WriteByte(b byte) error
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```
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WriteByte implements `io.ByteWriter`
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### func (\*Writer) WriteString
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``` go
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func (w *Writer) WriteString(s string) (int, error)
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```
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WriteString is analogous to Write, but it takes a string.
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- - -
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