Update to last common bleve (#3986)

vendor/github.com/philhofer/fwd/writer.go

@@ -0,0 +1,224 @@
+package fwd
+
+import "io"
+
+const (
+	// DefaultWriterSize is the
+	// default write buffer size.
+	DefaultWriterSize = 2048
+
+	minWriterSize = minReaderSize
+)
+
+// Writer is a buffered writer
+type Writer struct {
+	w   io.Writer // writer
+	buf []byte    // 0:len(buf) is bufered data
+}
+
+// NewWriter returns a new writer
+// that writes to 'w' and has a buffer
+// that is `DefaultWriterSize` bytes.
+func NewWriter(w io.Writer) *Writer {
+	if wr, ok := w.(*Writer); ok {
+		return wr
+	}
+	return &Writer{
+		w:   w,
+		buf: make([]byte, 0, DefaultWriterSize),
+	}
+}
+
+// NewWriterSize returns a new writer
+// that writes to 'w' and has a buffer
+// that is 'size' bytes.
+func NewWriterSize(w io.Writer, size int) *Writer {
+	if wr, ok := w.(*Writer); ok && cap(wr.buf) >= size {
+		return wr
+	}
+	return &Writer{
+		w:   w,
+		buf: make([]byte, 0, max(size, minWriterSize)),
+	}
+}
+
+// Buffered returns the number of buffered bytes
+// in the reader.
+func (w *Writer) Buffered() int { return len(w.buf) }
+
+// BufferSize returns the maximum size of the buffer.
+func (w *Writer) BufferSize() int { return cap(w.buf) }
+
+// Flush flushes any buffered bytes
+// to the underlying writer.
+func (w *Writer) Flush() error {
+	l := len(w.buf)
+	if l > 0 {
+		n, err := w.w.Write(w.buf)
+
+		// if we didn't write the whole
+		// thing, copy the unwritten
+		// bytes to the beginnning of the
+		// buffer.
+		if n < l && n > 0 {
+			w.pushback(n)
+			if err == nil {
+				err = io.ErrShortWrite
+			}
+		}
+		if err != nil {
+			return err
+		}
+		w.buf = w.buf[:0]
+		return nil
+	}
+	return nil
+}
+
+// Write implements `io.Writer`
+func (w *Writer) Write(p []byte) (int, error) {
+	c, l, ln := cap(w.buf), len(w.buf), len(p)
+	avail := c - l
+
+	// requires flush
+	if avail < ln {
+		if err := w.Flush(); err != nil {
+			return 0, err
+		}
+		l = len(w.buf)
+	}
+	// too big to fit in buffer;
+	// write directly to w.w
+	if c < ln {
+		return w.w.Write(p)
+	}
+
+	// grow buf slice; copy; return
+	w.buf = w.buf[:l+ln]
+	return copy(w.buf[l:], p), nil
+}
+
+// WriteString is analogous to Write, but it takes a string.
+func (w *Writer) WriteString(s string) (int, error) {
+	c, l, ln := cap(w.buf), len(w.buf), len(s)
+	avail := c - l
+
+	// requires flush
+	if avail < ln {
+		if err := w.Flush(); err != nil {
+			return 0, err
+		}
+		l = len(w.buf)
+	}
+	// too big to fit in buffer;
+	// write directly to w.w
+	//
+	// yes, this is unsafe. *but*
+	// io.Writer is not allowed
+	// to mutate its input or
+	// maintain a reference to it,
+	// per the spec in package io.
+	//
+	// plus, if the string is really
+	// too big to fit in the buffer, then
+	// creating a copy to write it is
+	// expensive (and, strictly speaking,
+	// unnecessary)
+	if c < ln {
+		return w.w.Write(unsafestr(s))
+	}
+
+	// grow buf slice; copy; return
+	w.buf = w.buf[:l+ln]
+	return copy(w.buf[l:], s), nil
+}
+
+// WriteByte implements `io.ByteWriter`
+func (w *Writer) WriteByte(b byte) error {
+	if len(w.buf) == cap(w.buf) {
+		if err := w.Flush(); err != nil {
+			return err
+		}
+	}
+	w.buf = append(w.buf, b)
+	return nil
+}
+
+// Next returns the next 'n' free bytes
+// in the write buffer, flushing the writer
+// as necessary. Next will return `io.ErrShortBuffer`
+// if 'n' is greater than the size of the write buffer.
+// Calls to 'next' increment the write position by
+// the size of the returned buffer.
+func (w *Writer) Next(n int) ([]byte, error) {
+	c, l := cap(w.buf), len(w.buf)
+	if n > c {
+		return nil, io.ErrShortBuffer
+	}
+	avail := c - l
+	if avail < n {
+		if err := w.Flush(); err != nil {
+			return nil, err
+		}
+		l = len(w.buf)
+	}
+	w.buf = w.buf[:l+n]
+	return w.buf[l:], nil
+}
+
+// take the bytes from w.buf[n:len(w.buf)]
+// and put them at the beginning of w.buf,
+// and resize to the length of the copied segment.
+func (w *Writer) pushback(n int) {
+	w.buf = w.buf[:copy(w.buf, w.buf[n:])]
+}
+
+// ReadFrom implements `io.ReaderFrom`
+func (w *Writer) ReadFrom(r io.Reader) (int64, error) {
+	// anticipatory flush
+	if err := w.Flush(); err != nil {
+		return 0, err
+	}
+
+	w.buf = w.buf[0:cap(w.buf)] // expand buffer
+
+	var nn int64  // written
+	var err error // error
+	var x int     // read
+
+	// 1:1 reads and writes
+	for err == nil {
+		x, err = r.Read(w.buf)
+		if x > 0 {
+			n, werr := w.w.Write(w.buf[:x])
+			nn += int64(n)
+
+			if err != nil {
+				if n < x && n > 0 {
+					w.pushback(n - x)
+				}
+				return nn, werr
+			}
+			if n < x {
+				w.pushback(n - x)
+				return nn, io.ErrShortWrite
+			}
+		} else if err == nil {
+			err = io.ErrNoProgress
+			break
+		}
+	}
+	if err != io.EOF {
+		return nn, err
+	}
+
+	// we only clear here
+	// because we are sure
+	// the writes have
+	// succeeded. otherwise,
+	// we retain the data in case
+	// future writes succeed.
+	w.buf = w.buf[0:0]
+
+	return nn, nil
+}