From db2091dd94d04a2309371a8d80ba9e2584a2370e Mon Sep 17 00:00:00 2001
From: Thad House <ThadHouse@users.noreply.github.com>
Date: Sat, 10 Dec 2016 22:40:44 -0800
Subject: [PATCH] Adds safe serial port write methods (#396)

The old method had a fairly large risk of undefined behavior, and the way the docs
were written could cause users to get confused.
Deprecate the old method and add StringRef method as preferred approach.
---
 wpilibc/athena/include/SerialPort.h |  7 +++++++
 wpilibc/athena/src/SerialPort.cpp   | 29 +++++++++++++++++++++++++++--
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/wpilibc/athena/include/SerialPort.h b/wpilibc/athena/include/SerialPort.h
index f2e140d455..0de241f4b0 100644
--- a/wpilibc/athena/include/SerialPort.h
+++ b/wpilibc/athena/include/SerialPort.h
@@ -10,6 +10,8 @@
 #include <string>
 
 #include "ErrorBase.h"
+#include "llvm/StringRef.h"
+#include "support/deprecated.h"
 
 namespace frc {
 
@@ -60,7 +62,12 @@ class SerialPort : public ErrorBase {
   void DisableTermination();
   int GetBytesReceived();
   int Read(char* buffer, int count);
+  WPI_DEPRECATED(
+      "Potential for unexpected behavior. Please use StringRef overload for "
+      "custom length buffers using std::string")
   int Write(const std::string& buffer, int count);
+  int Write(const char* buffer, int count);
+  int Write(llvm::StringRef buffer);
   void SetTimeout(double timeout);
   void SetReadBufferSize(int size);
   void SetWriteBufferSize(int size);
diff --git a/wpilibc/athena/src/SerialPort.cpp b/wpilibc/athena/src/SerialPort.cpp
index 2b2937eb8a..466e4583c9 100644
--- a/wpilibc/athena/src/SerialPort.cpp
+++ b/wpilibc/athena/src/SerialPort.cpp
@@ -134,6 +134,21 @@ int SerialPort::Read(char* buffer, int count) {
   return retVal;
 }
 
+/**
+ * Write raw bytes to the buffer. Deprecated, please use StringRef overload. Use
+ * Write({data, len}) to get a buffer that is shorter then the length of the
+ * std::string.
+ *
+ * @param buffer Pointer to the buffer to read the bytes from. If string.size()
+ * is less then count, only the length of string.size() will be sent.
+ * @param count  The maximum number of bytes to write.
+ * @return The number of bytes actually written into the port.
+ */
+int SerialPort::Write(const std::string& buffer, int count) {
+  return Write(llvm::StringRef(
+      buffer.data(), std::min(static_cast<int>(buffer.size()), count)));
+}
+
 /**
  * Write raw bytes to the buffer.
  *
@@ -141,10 +156,20 @@ int SerialPort::Read(char* buffer, int count) {
  * @param count  The maximum number of bytes to write.
  * @return The number of bytes actually written into the port.
  */
-int SerialPort::Write(const std::string& buffer, int count) {
+int SerialPort::Write(const char* buffer, int count) {
+  return Write(llvm::StringRef(buffer, static_cast<size_t>(count)));
+}
+
+/**
+ * Write raw bytes to the buffer.
+ *
+ * @param buffer StringRef to the buffer to read the bytes from.
+ * @return The number of bytes actually written into the port.
+ */
+int SerialPort::Write(llvm::StringRef buffer) {
   int32_t status = 0;
   int retVal = HAL_WriteSerial(static_cast<HAL_SerialPort>(m_port),
-                               buffer.c_str(), count, &status);
+                               buffer.data(), buffer.size(), &status);
   wpi_setErrorWithContext(status, HAL_GetErrorMessage(status));
   return retVal;
 }