From 15d02f51ed61dd7ef26ea0fa84ab9c47424ecc2c Mon Sep 17 00:00:00 2001
From: Rubidium <rubidium@openttd.org>
Date: Sun, 28 Jan 2024 13:28:07 +0100
Subject: [PATCH] Codechange: use span to send bytes to Packet and add span
 recv function

---
 src/network/core/packet.cpp    | 31 +++++++++++++++++++++++--------
 src/network/core/packet.h      |  3 ++-
 src/network/network_server.cpp |  9 ++++-----
 3 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/src/network/core/packet.cpp b/src/network/core/packet.cpp
index f314dc803c..5339c43677 100644
--- a/src/network/core/packet.cpp
+++ b/src/network/core/packet.cpp
@@ -176,16 +176,15 @@ void Packet::Send_buffer(const std::vector<byte> &data)
 /**
  * Send as many of the bytes as possible in the packet. This can mean
  * that it is possible that not all bytes are sent. To cope with this
- * the function returns the amount of bytes that were actually sent.
- * @param begin The begin of the buffer to send.
- * @param end   The end of the buffer to send.
- * @return The number of bytes that were added to this packet.
+ * the function returns the span of bytes that were not sent.
+ * @param span The span describing the range of bytes to send.
+ * @return The span of bytes that were not written.
  */
-size_t Packet::Send_bytes(const byte *begin, const byte *end)
+std::span<const byte> Packet::Send_bytes(const std::span<const byte> span)
 {
-	size_t amount = std::min<size_t>(end - begin, this->limit - this->Size());
-	this->buffer.insert(this->buffer.end(), begin, begin + amount);
-	return amount;
+	size_t amount = std::min<size_t>(span.size(), this->limit - this->Size());
+	this->buffer.insert(this->buffer.end(), span.data(), span.data() + amount);
+	return span.subspan(amount);
 }
 
 /*
@@ -370,6 +369,22 @@ std::vector<byte> Packet::Recv_buffer()
 	return data;
 }
 
+/**
+ * Extract at most the length of the span bytes from the packet into the span.
+ * @param span The span to write the bytes to.
+ * @return The number of bytes that were actually read.
+ */
+size_t Packet::Recv_bytes(std::span<byte> span)
+{
+	auto tranfer_to_span = [](std::span<byte> destination, const char *source, size_t amount) {
+		size_t to_copy = std::min(amount, destination.size());
+		std::copy(source, source + to_copy, destination.data());
+		return to_copy;
+	};
+
+	return this->TransferOut(tranfer_to_span, span);
+}
+
 /**
  * Reads characters (bytes) from the packet until it finds a '\0', or reaches a
  * maximum of \c length characters.
diff --git a/src/network/core/packet.h b/src/network/core/packet.h
index f403f37ae7..ccb56738ff 100644
--- a/src/network/core/packet.h
+++ b/src/network/core/packet.h
@@ -66,7 +66,7 @@ public:
 	void   Send_uint64(uint64_t data);
 	void   Send_string(const std::string_view data);
 	void   Send_buffer(const std::vector<byte> &data);
-	size_t Send_bytes (const byte *begin, const byte *end);
+	std::span<const byte> Send_bytes(const std::span<const byte> span);
 
 	/* Reading/receiving of packets */
 	bool HasPacketSizeData() const;
@@ -82,6 +82,7 @@ public:
 	uint32_t Recv_uint32();
 	uint64_t Recv_uint64();
 	std::vector<byte> Recv_buffer();
+	size_t Recv_bytes(std::span<byte> span);
 	std::string Recv_string(size_t length, StringValidationSettings settings = SVS_REPLACE_WITH_QUESTION_MARK);
 
 	size_t RemainingBytesToTransfer() const;
diff --git a/src/network/network_server.cpp b/src/network/network_server.cpp
index 65cb5388ae..2e6c51920e 100644
--- a/src/network/network_server.cpp
+++ b/src/network/network_server.cpp
@@ -145,14 +145,13 @@ struct PacketWriter : SaveFilter {
 
 		if (this->current == nullptr) this->current = std::make_unique<Packet>(this->cs, PACKET_SERVER_MAP_DATA, TCP_MTU);
 
-		byte *bufe = buf + size;
-		while (buf != bufe) {
-			size_t written = this->current->Send_bytes(buf, bufe);
-			buf += written;
+		std::span<const byte> to_write(buf, size);
+		while (!to_write.empty()) {
+			to_write = this->current->Send_bytes(to_write);
 
 			if (!this->current->CanWriteToPacket(1)) {
 				this->packets.push_back(std::move(this->current));
-				if (buf != bufe) this->current = std::make_unique<Packet>(this->cs, PACKET_SERVER_MAP_DATA, TCP_MTU);
+				if (!to_write.empty()) this->current = std::make_unique<Packet>(this->cs, PACKET_SERVER_MAP_DATA, TCP_MTU);
 			}
 		}