repository cleanup

server/channelserver/compression/nullcomp/nullcomp.go

@@ -0,0 +1,98 @@
+package nullcomp
+
+import (
+	"bytes"
+	"io"
+)
+
+// Decompress decompresses null-compressesed data.
+func Decompress(compData []byte) ([]byte, error) {
+	r := bytes.NewReader(compData)
+
+	header := make([]byte, 16)
+	n, err := r.Read(header)
+	if err != nil {
+		return nil, err
+	} else if n != len(header) {
+		return nil, err
+	}
+
+	// Just return the data if it doesn't contain the cmp header.
+	if !bytes.Equal(header, []byte("cmp\x2020110113\x20\x20\x20\x00")) {
+		return compData, nil
+	}
+
+	var output []byte
+	for {
+		b, err := r.ReadByte()
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return nil, err
+		}
+
+		if b == 0 {
+			// If it's a null byte, then the next byte is how many nulls to add.
+			nullCount, err := r.ReadByte()
+			if err == io.EOF {
+				break
+			} else if err != nil {
+				return nil, err
+			}
+
+			output = append(output, make([]byte, int(nullCount))...)
+		} else {
+			output = append(output, b)
+		}
+	}
+
+	return output, nil
+}
+
+// Compress null compresses give given data.
+func Compress(rawData []byte) ([]byte, error) {
+	r := bytes.NewReader(rawData)
+	var output []byte
+	output = append(output, []byte("cmp\x2020110113\x20\x20\x20\x00")...)
+	for {
+		b, err := r.ReadByte()
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return nil, err
+		}
+		if b == 0 {
+			output = append(output, []byte{0x00}...)
+			// read to get null count
+			nullCount := 1
+			for {
+				i, err := r.ReadByte()
+				if err == io.EOF {
+					output = append(output, []byte{byte(nullCount)}...)
+					break
+				} else if i != 0 && nullCount != 0 {
+					r.UnreadByte()
+					output = append(output, []byte{byte(nullCount)}...)
+					break
+				} else if i != 0 && nullCount == 0 {
+					r.UnreadByte()
+					output = output[:len(output)-2]
+					output = append(output, []byte{byte(0xFF)}...)
+					break
+				} else if err != nil {
+					return nil, err
+				}
+				nullCount++
+
+				// Flush the null-count if it gets to 255, start on the next null count.
+				if nullCount == 255 {
+					output = append(output, []byte{0xFF, 0x00}...)
+					nullCount = 0
+				}
+			}
+		} else {
+			output = append(output, b)
+		}
+	}
+	return output, nil
+}