1 files changed, 57 insertions, 0 deletions
diff --git a/src/pkg/image/tiff/buffer.go b/src/pkg/image/tiff/buffer.go
new file mode 100644
index 000000000..7c0714225
--- /dev/null
+++ b/src/pkg/image/tiff/buffer.go
@@ -0,0 +1,57 @@
+// Copyright 2011 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 tiff
+
+import (
+	"io"
+	"os"
+)
+
+// buffer buffers an io.Reader to satisfy io.ReaderAt.
+type buffer struct {
+	r   io.Reader
+	buf []byte
+}
+
+func (b *buffer) ReadAt(p []byte, off int64) (int, os.Error) {
+	o := int(off)
+	end := o + len(p)
+	if int64(end) != off+int64(len(p)) {
+		return 0, os.EINVAL
+	}
+
+	m := len(b.buf)
+	if end > m {
+		if end > cap(b.buf) {
+			newcap := 1024
+			for newcap < end {
+				newcap *= 2
+			}
+			newbuf := make([]byte, end, newcap)
+			copy(newbuf, b.buf)
+			b.buf = newbuf
+		} else {
+			b.buf = b.buf[:end]
+		}
+		if n, err := io.ReadFull(b.r, b.buf[m:end]); err != nil {
+			end = m + n
+			b.buf = b.buf[:end]
+			return copy(p, b.buf[o:end]), err
+		}
+	}
+
+	return copy(p, b.buf[o:end]), nil
+}
+
+// newReaderAt converts an io.Reader into an io.ReaderAt.
+func newReaderAt(r io.Reader) io.ReaderAt {
+	if ra, ok := r.(io.ReaderAt); ok {
+		return ra
+	}
+	return &buffer{
+		r:   r,
+		buf: make([]byte, 0, 1024),
+	}
+}