From: Matt Joiner <anacrolix@gmail.com>
Date: Thu, 26 Sep 2013 03:42:24 +0000 (+1000)
Subject: Add torrent.Mmap and MmapSpan, types that abstract memory-mapped torrent data
X-Git-Tag: v1.0.0~1824
X-Git-Url: http://www.git.stargrave.org/?a=commitdiff_plain;h=3d1fb69e368bb5191ca64b56601b0e24889f4c2c;p=btrtrc.git

Add torrent.Mmap and MmapSpan, types that abstract memory-mapped torrent data
---

diff --git a/mmap_span.go b/mmap_span.go
new file mode 100644
index 00000000..e8514168
--- /dev/null
+++ b/mmap_span.go
@@ -0,0 +1,56 @@
+package torrent
+
+import (
+	"io"
+	"launchpad.net/gommap"
+)
+
+type Mmap struct {
+	gommap.MMap
+}
+
+func (me Mmap) Size() int64 {
+	return int64(len(me.MMap))
+}
+
+type MmapSpan []Mmap
+
+func (me MmapSpan) span() (s span) {
+	for _, mmap := range me {
+		s = append(s, mmap)
+	}
+	return
+}
+
+func (me MmapSpan) Size() (ret int64) {
+	for _, mmap := range me {
+		ret += mmap.Size()
+	}
+	return
+}
+
+func (me MmapSpan) ReadAt(p []byte, off int64) (n int, err error) {
+	me.span().ApplyTo(off, func(intervalOffset int64, interval sizer) (stop bool) {
+		_n := copy(p, interval.(Mmap).MMap[intervalOffset:])
+		p = p[_n:]
+		n += _n
+		return len(p) == 0
+	})
+	if len(p) != 0 {
+		err = io.EOF
+	}
+	return
+}
+
+func (me MmapSpan) WriteAt(p []byte, off int64) (n int, err error) {
+	me.span().ApplyTo(off, func(iOff int64, i sizer) (stop bool) {
+		_n := copy(i.(Mmap).MMap[iOff:], p)
+		p = p[_n:]
+		n += _n
+		return len(p) == 0
+	})
+	if len(p) != 0 {
+		err = io.EOF
+	}
+	return
+}
diff --git a/span.go b/span.go
new file mode 100644
index 00000000..b744926b
--- /dev/null
+++ b/span.go
@@ -0,0 +1,23 @@
+package torrent
+
+type sizer interface {
+	Size() int64
+}
+
+type (
+	span []sizer
+)
+
+func (me span) ApplyTo(off int64, f func(int64, sizer) (stop bool)) {
+	for _, interval := range me {
+		iSize := interval.Size()
+		if off >= iSize {
+			off -= iSize
+		} else {
+			if f(off, interval) {
+				return
+			}
+			off = 0
+		}
+	}
+}