From c3388c58f9559e49cde943697b31d9ab8378c0be Mon Sep 17 00:00:00 2001
From: Gary Talent <gtalent2@gmail.com>
Date: Sun, 30 Apr 2017 20:25:37 -0500
Subject: [PATCH] Fix issue with writing setting field presence mask for empty
 arrays

---
 src/ox/mc/presencemask.cpp | 10 ++++++++--
 src/ox/mc/write.hpp        | 41 ++++++++++++++++++++------------------
 2 files changed, 30 insertions(+), 21 deletions(-)

diff --git a/src/ox/mc/presencemask.cpp b/src/ox/mc/presencemask.cpp
index c6e28d144..0860efdb7 100644
--- a/src/ox/mc/presencemask.cpp
+++ b/src/ox/mc/presencemask.cpp
@@ -10,6 +10,9 @@
 #include "err.hpp"
 #include "presencemask.hpp"
 
+#include <iostream>
+using namespace std;
+
 namespace ox {
 
 FieldPresenseMask::FieldPresenseMask(uint8_t *mask, size_t maxLen) {
@@ -26,9 +29,12 @@ bool FieldPresenseMask::get(int i) {
 }
 
 int FieldPresenseMask::set(int i, bool on) {
-	uint8_t val = on ? 1 : 0; // normalize to 0 or 1
 	if (i / 8 < m_maxLen) {
-		m_mask[i / 8] |= val << (i % 8);
+		if (on) {
+			m_mask[i / 8] |= 1 << (i % 8);
+		} else {
+			m_mask[i / 8] &= ~(1 << (i % 8));
+		}
 		return 0;
 	} else {
 		return MC_PRESENCEMASKOUTBOUNDS;
diff --git a/src/ox/mc/write.hpp b/src/ox/mc/write.hpp
index 577a148e8..c3b5b9f42 100644
--- a/src/ox/mc/write.hpp
+++ b/src/ox/mc/write.hpp
@@ -70,7 +70,7 @@ int MetalClawWriter::op(const char*, ox::bstring<L> *val) {
 			m_buffIt += val->size();
 			fieldSet = true;
 		} else {
-			err = 1;
+			err = MC_BUFFENDED;
 		}
 	}
 	err |= m_fieldPresence.set(m_field, fieldSet);
@@ -84,6 +84,7 @@ int MetalClawWriter::op(const char*, T *val) {
 	MetalClawWriter writer(m_buff + m_buffIt, m_buffLen - m_buffIt);
 	err |= ioOp(&writer, val);
 	m_buffIt += writer.m_buffIt;
+	m_field++;
 	return err;
 };
 
@@ -110,26 +111,28 @@ int MetalClawWriter::op(const char*, T *val, size_t len) {
 	int err = 0;
 	bool fieldSet = false;
 
-	// write the length
-	typedef uint32_t ArrayLength;
-	if (m_buffIt + sizeof(ArrayLength) < m_buffLen) {
-		*((T*) &m_buff[m_buffIt]) = ox::std::bigEndianAdapt((ArrayLength) len);
-		m_buffIt += sizeof(ArrayLength);
-	} else {
-		err = MC_BUFFENDED;
+	if (len) {
+		// write the length
+		typedef uint32_t ArrayLength;
+		if (m_buffIt + sizeof(ArrayLength) < m_buffLen) {
+			*((T*) &m_buff[m_buffIt]) = ox::std::bigEndianAdapt((ArrayLength) len);
+			m_buffIt += sizeof(ArrayLength);
+		} else {
+			err = MC_BUFFENDED;
+		}
+
+		MetalClawWriter writer(m_buff + m_buffIt, m_buffLen - m_buffIt);
+		writer.setFields(len);
+
+		// write the array
+		for (size_t i = 0; i < len; i++) {
+			err |= writer.op("", &val[i]);
+		}
+
+		m_buffIt += writer.m_buffIt;
+		fieldSet = true;
 	}
 
-	MetalClawWriter writer(m_buff + m_buffIt, m_buffLen - m_buffIt);
-	writer.setFields(len);
-
-	// write the string
-	for (size_t i = 0; i < len; i++) {
-		err |= writer.op("", &val[i]);
-	}
-
-	m_buffIt += writer.m_buffIt;
-	fieldSet = true;
-
 	err |= m_fieldPresence.set(m_field, fieldSet);
 	m_field++;
 	return err;