优化代码，使用writerIndex标记代替Slice

src/main/java/io/github/yezhihao/protostar/schema/CollectionSchema.java

@@ -37,7 +37,11 @@ public class CollectionSchema<T> implements Schema<List<T>> {
 
     @Override
     public List<T> readFrom(ByteBuf input, int length) {
-        return this.readFrom(input.readSlice(length));
+        int writerIndex = input.writerIndex();
+        input.writerIndex(input.readerIndex() + length);
+        List<T> result = this.readFrom(input);
+        input.writerIndex(writerIndex);
+        return result;
     }
 
     @Override

src/main/java/io/github/yezhihao/protostar/schema/ConvertSchema.java

@@ -35,8 +35,13 @@ public class ConvertSchema<T> implements Schema<T> {
 
     @Override
     public T readFrom(ByteBuf input, int length) {
-        if (length > 0)
+        if (length > 0) {
-            input = input.readSlice(length);
+            int writerIndex = input.writerIndex();
+            input.writerIndex(input.readerIndex() + length);
+            T result = converter.convert(input);
+            input.writerIndex(writerIndex);
+            return result;
+        }
         return converter.convert(input);
     }
 

src/main/java/io/github/yezhihao/protostar/schema/ObjectSchema.java

@@ -25,8 +25,13 @@ public class ObjectSchema<T> implements Schema<T> {
 
     @Override
     public T readFrom(ByteBuf input, int length) {
-        if (length > 0)
+        if (length > 0) {
-            input = input.readSlice(length);
+            int writerIndex = input.writerIndex();
+            input.writerIndex(input.readerIndex() + length);
+            T result = schema.readFrom(input);
+            input.writerIndex(writerIndex);
+            return result;
+        }
         return schema.readFrom(input);
     }