From 8ae6cb2e9617a93d8de5f1409e8c268ec4921144 Mon Sep 17 00:00:00 2001
From: Andrew Gutekanst <andrew.gutekanst@gmail.com>
Date: Wed, 4 Mar 2020 10:52:34 -0500
Subject: [PATCH] Use bytes.Reader for deltacomp

---
 .../compression/deltacomp/deltacomp.go        | 94 ++++++++++++++++++-
 1 file changed, 91 insertions(+), 3 deletions(-)

diff --git a/server/channelserver/compression/deltacomp/deltacomp.go b/server/channelserver/compression/deltacomp/deltacomp.go
index 4c4cc07a7..66414a357 100644
--- a/server/channelserver/compression/deltacomp/deltacomp.go
+++ b/server/channelserver/compression/deltacomp/deltacomp.go
@@ -1,11 +1,98 @@
 package deltacomp
 
 import (
-	"errors"
-
-	"github.com/Andoryuuta/byteframe"
+	"io"
+	"bytes"
 )
 
+
+func checkReadUint8(r *bytes.Reader) (uint8, error) {
+	b, err := r.ReadByte()
+	if err != nil {
+		return 0, err
+	}
+	return b, nil
+}
+
+func checkReadUint16(r *bytes.Reader) (uint16, error) {
+	data := make([]byte, 2)
+	n, err := r.Read(data)
+	if err != nil {
+		return 0, err
+	} else if n != len(data) {
+		return 0, io.EOF
+	}
+
+	return uint16(data[0])<<8 | uint16(data[1]), nil
+}
+
+func readCount(r *bytes.Reader) (int, error) {
+	var count int
+
+	count8, err := checkReadUint8(r)
+	if err != nil {
+		return 0, err
+	}
+	count = int(count8)
+
+	if count == 0 {
+		count16, err := checkReadUint16(r)
+		if err != nil {
+			return 0, err
+		}
+		count = int(count16)
+	}
+
+	return int(count), nil
+}
+
+// ApplyDataDiff applies a delta data diff patch onto given base data.
+func ApplyDataDiff(diff []byte, baseData []byte) []byte {
+	// Make a copy of the base data to return,
+	// (probably just make this modify the given slice in the future).
+	baseCopy := make([]byte, len(baseData))
+	copy(baseCopy, baseData)
+
+	patch := bytes.NewReader(diff)
+
+	// The very first matchCount is +1 more than it should be, so we start at -1.
+	dataOffset := -1
+	for {
+		// Read the amount of matching bytes.
+		matchCount, err := readCount(patch)
+		if err != nil {
+			// No more data
+			break
+		}
+
+		dataOffset += matchCount
+
+		// Read the amount of differing bytes.
+		differentCount, err := readCount(patch)
+		if err != nil {
+			// No more data
+			break
+		}
+		differentCount -= 1
+
+		// Apply the patch bytes.
+		for i := 0; i < differentCount; i++ {
+			b, err := checkReadUint8(patch)
+			if err != nil {
+				panic("Invalid or misunderstood patch format!")
+			}
+			baseCopy[dataOffset+i] = b
+		}
+
+		dataOffset += differentCount - 1
+
+	}
+
+	return baseCopy
+}
+
+
+/*
 func checkReadUint8(bf *byteframe.ByteFrame) (uint8, error) {
 	if len(bf.DataFromCurrent()) >= 1 {
 		return bf.ReadUint8(), nil
@@ -84,3 +171,4 @@ func ApplyDataDiff(diff []byte, baseData []byte) []byte {
 
 	return baseCopy
 }
+*/
\ No newline at end of file