From b0604362e0ed3309c3199ce6652e502affd0e9e8 Mon Sep 17 00:00:00 2001
From: Rick Altherr <kc8apf@kc8apf.net>
Date: Thu, 18 Jan 2018 20:00:28 -0800
Subject: [PATCH] lib: xc7series: const all the Span<>s

Span<T> can be converted to a Span<const T> but the reverse is not true.
Since most of the uses of spans do not allow modification of the data,
taking a Span<const T> is more versatile and importantly allows them to
be used in const methods.

Signed-off-by: Rick Altherr <kc8apf@kc8apf.net>
---
 lib/include/prjxray/xilinx/xc7series/bitstream_writer.h     | 4 ++--
 lib/include/prjxray/xilinx/xc7series/configuration.h        | 4 ++--
 lib/include/prjxray/xilinx/xc7series/configuration_packet.h | 6 +++---
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/lib/include/prjxray/xilinx/xc7series/bitstream_writer.h b/lib/include/prjxray/xilinx/xc7series/bitstream_writer.h
index 73d6c134..ae0634d7 100644
--- a/lib/include/prjxray/xilinx/xc7series/bitstream_writer.h
+++ b/lib/include/prjxray/xilinx/xc7series/bitstream_writer.h
@@ -25,8 +25,8 @@ class BitstreamWriter {
 	typedef std::array<uint32_t, 6> header_t;
 	typedef std::vector<ConfigurationPacket> packets_t;
 	// Only defined if a packet exists
-	typedef absl::optional<absl::Span<uint32_t>> op_data_t;
-	typedef absl::Span<uint32_t>::iterator data_iterator_t;
+	typedef absl::optional<absl::Span<const uint32_t>> op_data_t;
+	typedef absl::Span<const uint32_t>::iterator data_iterator_t;
 	using itr_value_type = uint32_t;
 
 	class packet_iterator
diff --git a/lib/include/prjxray/xilinx/xc7series/configuration.h b/lib/include/prjxray/xilinx/xc7series/configuration.h
index fa10a19d..20dea9c3 100644
--- a/lib/include/prjxray/xilinx/xc7series/configuration.h
+++ b/lib/include/prjxray/xilinx/xc7series/configuration.h
@@ -16,7 +16,7 @@ namespace xc7series {
 
 class Configuration {
        public:
-	using FrameMap = std::map<FrameAddress, absl::Span<uint32_t>>;
+	using FrameMap = std::map<FrameAddress, absl::Span<const uint32_t>>;
 
 	template <typename Collection>
 	static absl::optional<Configuration> InitWithPackets(
@@ -28,7 +28,7 @@ class Configuration {
 	    : part_(part) {
 		for (auto& frame : *frames) {
 			frames_[frame.first] =
-			    absl::Span<uint32_t>(frame.second);
+			    absl::Span<const uint32_t>(frame.second);
 		}
 	}
 
diff --git a/lib/include/prjxray/xilinx/xc7series/configuration_packet.h b/lib/include/prjxray/xilinx/xc7series/configuration_packet.h
index 80cfe9bb..f60d370b 100644
--- a/lib/include/prjxray/xilinx/xc7series/configuration_packet.h
+++ b/lib/include/prjxray/xilinx/xc7series/configuration_packet.h
@@ -27,7 +27,7 @@ class ConfigurationPacket {
 	ConfigurationPacket(unsigned int header_type,
 	                    Opcode opcode,
 	                    ConfigurationRegister address,
-	                    const absl::Span<uint32_t>& data)
+	                    const absl::Span<const uint32_t>& data)
 	    : header_type_(header_type),
 	      opcode_(opcode),
 	      address_(address),
@@ -47,13 +47,13 @@ class ConfigurationPacket {
 	unsigned int header_type() const { return header_type_; }
 	const Opcode opcode() const { return opcode_; }
 	const ConfigurationRegister address() const { return address_; }
-	const absl::Span<uint32_t>& data() const { return data_; }
+	const absl::Span<const uint32_t>& data() const { return data_; }
 
        private:
 	unsigned int header_type_;
 	Opcode opcode_;
 	ConfigurationRegister address_;
-	absl::Span<uint32_t> data_;
+	absl::Span<const uint32_t> data_;
 };
 
 std::ostream& operator<<(std::ostream& o, const ConfigurationPacket& packet);