Added class UniqueIdBase

src/UniqueIdBase.cpp

@@ -0,0 +1,140 @@
+/*
+ * UniqueIdBase.cpp
+ *
+ *  Created on: 4 Oct 2021
+ *      Author: David
+ */
+
+#include "UniqueIdBase.h"
+#include <Cache.h>
+
+#if SAM4E || SAM4S || SAME70
+# include <Flash.h>
+#endif
+
+// Constructor initialises it to all zeros
+void UniqueIdBase::Clear() noexcept
+{
+	for (auto& v : data)
+	{
+		v = 0;
+	}
+}
+
+// Test if we have a valid ID. We assume a valid ID cannot be all zeros.
+bool UniqueIdBase::IsValid() const noexcept
+{
+	return (data[0] | data[1] | data[2] | data[3]) != 0;
+}
+
+// Get a 32-bit hash of the ID. Used for pseudo random number generation.
+uint32_t UniqueIdBase::GetHash() const noexcept
+{
+	return data[0] ^ data[1] ^ data[2] ^ data[3];
+}
+
+// Set the ID to the ID of the board that this code is running on
+void UniqueIdBase::SetFromCurrentBoard() noexcept
+{
+#if SAME5x || SAMC21
+	for (size_t i = 0; i < 4; ++i)
+	{
+		data[i] = *reinterpret_cast<const uint32_t*>(SerialNumberAddresses[i]);
+	}
+	SetChecksumWord();
+#elif SAM4E || SAM4S || SAME70
+	const bool cacheWasEnabled = Cache::Disable();
+	const bool success = Flash::ReadUniqueId(data);
+	if (cacheWasEnabled)
+	{
+		Cache::Enable();
+	}
+
+	if (success)
+	{
+		SetChecksumWord();
+	}
+#else
+# error Unsupported processor
+#endif
+}
+
+// Set the ID from 4 dwords received from a remote board
+void UniqueIdBase::SetFromRemote(const uint8_t srcData[16]) noexcept
+{
+	memcpy(data, srcData, 16);
+	SetChecksumWord();
+}
+
+// Append the unique ID in character form to something
+void UniqueIdBase::AppendCharsTo(function_ref<void(char) /*noexcept*/> fn) const noexcept
+{
+	size_t i = 0;
+	for (;;)
+	{
+		const size_t index = (i * 5) / 32;
+		const size_t shift = (i * 5) % 32;
+		uint32_t val = data[index] >> shift;
+		if (shift > 32 - 5)
+		{
+			// We need some bits from the next dword too
+			val |= data[index + 1] << (32 - shift);
+		}
+		val &= 31;
+		char c;
+		if (val < 10)
+		{
+			c = val + '0';
+		}
+		else
+		{
+			c = val + ('A' - 10);
+			// We have 26 letters in the usual A-Z alphabet and we only need 22 of them plus 0-9.
+			// So avoid using letters C, E, I and O which are easily mistaken for G, F, 1 and 0.
+			if (c >= 'C')
+			{
+				++c;
+			}
+			if (c >= 'E')
+			{
+				++c;
+			}
+			if (c >= 'I')
+			{
+				++c;
+			}
+			if (c >= 'O')
+			{
+				++c;
+			}
+		}
+		fn(c);
+
+		++i;
+		if (i == 30)
+		{
+			break;
+		}
+
+		if ((i % 5) == 0)
+		{
+			fn('-');
+		}
+	}
+}
+
+// Append the unique ID in character form to a string
+void UniqueIdBase::AppendCharsToString(const StringRef &str) const noexcept
+{
+	AppendCharsTo([&str](char c)-> void { str.cat(c);});
+}
+
+// Set the checksum word of the unique ID
+void UniqueIdBase::SetChecksumWord() noexcept
+{
+	// We only print 30 5-bit characters = 128 data bits + 22 checksum bits. So compress the 32 checksum bits into 22.
+	data[4] = data[0] ^ data[1] ^ data[2] ^ data[3];
+	data[4] ^= (data[4] >> 10);
+}
+
+// End

src/UniqueIdBase.h

@@ -0,0 +1,43 @@
+/*
+ * UniqueIdBase.h
+ *
+ *  Created on: 4 Oct 2021
+ *      Author: David
+ *
+ *  This class represents a 128-bit processor unique ID as implemented on ATSAM processors.
+ *  We display the unique ID as a string in the form xxxxx-xxxxx-xxxxx-xxxxx-xxxxx-xxxxx
+ *  where each x is a digit or an uppercase letter that is not C, E, I or O.
+ *  This encodes the original 128 bits plus 22 checksum bits.
+ */
+
+#ifndef SRC_UNIQUEIDBASE_H_
+#define SRC_UNIQUEIDBASE_H_
+
+#include <Core.h>
+#include <General/StringRef.h>
+#include <General/function_ref.h>
+
+class UniqueIdBase
+{
+public:
+	UniqueIdBase() { Clear(); }
+
+	bool IsValid() const noexcept;
+	uint32_t GetHash() const noexcept;
+
+	void Clear() noexcept;
+	void SetFromCurrentBoard() noexcept;
+	void SetFromRemote(const uint8_t srcData[16]) noexcept;
+
+	void AppendCharsTo(function_ref<void(char) /*noexcept*/> fn) const noexcept;
+	void AppendCharsToString(const StringRef& str) const noexcept;
+
+	const uint8_t *GetRaw() const { return (const uint8_t*)data; }
+
+protected:
+	void SetChecksumWord() noexcept;
+
+	uint32_t data[5];
+};
+
+#endif /* SRC_UNIQUEIDBASE_H_ */