1 files changed, 151 insertions, 0 deletions
diff --git a/modules/mahonia/reader.go b/modules/mahonia/reader.go
new file mode 100644
index 00000000..3514b95b
--- /dev/null
+++ b/modules/mahonia/reader.go
@@ -0,0 +1,151 @@
+package mahonia
+
+// This file is based on bufio.Reader in the Go standard library,
+// which has the following copyright notice:
+
+// 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.
+
+import (
+	"io"
+	"unicode/utf8"
+)
+
+const (
+	defaultBufSize = 4096
+)
+
+// Reader implements character-set decoding for an io.Reader object.
+type Reader struct {
+	buf    []byte
+	rd     io.Reader
+	decode Decoder
+	r, w   int
+	err    error
+}
+
+// NewReader creates a new Reader that uses the receiver to decode text.
+func (d Decoder) NewReader(rd io.Reader) *Reader {
+	b := new(Reader)
+	b.buf = make([]byte, defaultBufSize)
+	b.rd = rd
+	b.decode = d
+	return b
+}
+
+// fill reads a new chunk into the buffer.
+func (b *Reader) fill() {
+	// Slide existing data to beginning.
+	if b.r > 0 {
+		copy(b.buf, b.buf[b.r:b.w])
+		b.w -= b.r
+		b.r = 0
+	}
+
+	// Read new data.
+	n, e := b.rd.Read(b.buf[b.w:])
+	b.w += n
+	if e != nil {
+		b.err = e
+	}
+}
+
+// Read reads data into p.
+// It returns the number of bytes read into p.
+// It calls Read at most once on the underlying Reader,
+// hence n may be less than len(p).
+// At EOF, the count will be zero and err will be os.EOF.
+func (b *Reader) Read(p []byte) (n int, err error) {
+	n = len(p)
+	filled := false
+	if n == 0 {
+		return 0, b.err
+	}
+	if b.w == b.r {
+		if b.err != nil {
+			return 0, b.err
+		}
+		if n > len(b.buf) {
+			// Large read, empty buffer.
+			// Allocate a larger buffer for efficiency.
+			b.buf = make([]byte, n)
+		}
+		b.fill()
+		filled = true
+		if b.w == b.r {
+			return 0, b.err
+		}
+	}
+
+	i := 0
+	for i < n {
+		rune, size, status := b.decode(b.buf[b.r:b.w])
+
+		if status == STATE_ONLY {
+			b.r += size
+			continue
+		}
+
+		if status == NO_ROOM {
+			if b.err != nil {
+				rune = 0xfffd
+				size = b.w - b.r
+				if size == 0 {
+					break
+				}
+				status = INVALID_CHAR
+			} else if filled {
+				break
+			} else {
+				b.fill()
+				filled = true
+				continue
+			}
+		}
+
+		if i+utf8.RuneLen(rune) > n {
+			break
+		}
+
+		b.r += size
+		if rune < 128 {
+			p[i] = byte(rune)
+			i++
+		} else {
+			i += utf8.EncodeRune(p[i:], rune)
+		}
+	}
+
+	return i, nil
+}
+
+// ReadRune reads a single Unicode character and returns the
+// rune and its size in bytes.
+func (b *Reader) ReadRune() (c rune, size int, err error) {
+read:
+	c, size, status := b.decode(b.buf[b.r:b.w])
+
+	if status == NO_ROOM && b.err == nil {
+		b.fill()
+		goto read
+	}
+
+	if status == STATE_ONLY {
+		b.r += size
+		goto read
+	}
+
+	if b.r == b.w {
+		return 0, 0, b.err
+	}
+
+	if status == NO_ROOM {
+		c = 0xfffd
+		size = b.w - b.r
+		status = INVALID_CHAR
+	}
+
+	b.r += size
+	return c, size, nil
+}