Big refactor

pkg/chunk/chunk.go

@@ -0,0 +1,51 @@
+package chunk
+
+import (
+	"container/list"
+	"hash/crc32"
+)
+
+// Chunk of memory
+type Chunk struct {
+	clean bool
+	*chunkHeader
+	bytes []byte
+	item  *list.Element
+}
+
+type chunkHeader struct {
+	id       RequestID
+	size     uint32
+	checksum uint32
+}
+
+func (c *Chunk) valid(id RequestID) bool {
+	if c.id != id {
+		return false
+	}
+	if !c.clean {
+		c.clean = c.checksum == c.calculateChecksum()
+	}
+	return c.clean
+}
+
+func (c *Chunk) update(id RequestID, bytes []byte) {
+	c.id = id
+	c.size = uint32(copy(c.bytes, bytes))
+	c.checksum = c.calculateChecksum()
+	c.clean = true
+}
+
+func (c *Chunk) calculateChecksum() uint32 {
+	size := c.size
+	if nil == c.bytes || size == 0 {
+		return 0
+	}
+	maxSize := uint32(len(c.bytes))
+	if size > maxSize {
+		// corrupt size or truncated chunk, fix size
+		c.size = maxSize
+		return crc32.Checksum(c.bytes, crc32Table)
+	}
+	return crc32.Checksum(c.bytes[:size], crc32Table)
+}