Core/Bitset: Add Read method and FromPointer static method

include/Nazara/Core/Bitset.hpp

@@ -24,6 +24,7 @@ namespace Nz
 
 		public:
 			class Bit;
+			using PointerSequence = std::pair<const void*, std::size_t>; //< Start pointer, bit offset
 
 			Bitset();
 			explicit Bitset(std::size_t bitCount, bool val);
@@ -49,6 +50,9 @@ namespace Nz
 			std::size_t GetCapacity() const;
 			std::size_t GetSize() const;
 
+			PointerSequence Read(const void* ptr, std::size_t bitCount);
+			PointerSequence Read(const PointerSequence& sequence, std::size_t bitCount);
+
 			void PerformsAND(const Bitset& a, const Bitset& b);
 			void PerformsNOT(const Bitset& a);
 			void PerformsOR(const Bitset& a, const Bitset& b);
@@ -107,6 +111,8 @@ namespace Nz
 			static constexpr std::size_t bitsPerBlock = std::numeric_limits<Block>::digits;
 			static constexpr std::size_t npos = std::numeric_limits<std::size_t>::max();
 
+			static Bitset FromPointer(const void* ptr, std::size_t bitCount, PointerSequence* sequence = nullptr);
+
 		private:
 			std::size_t FindFirstFrom(std::size_t blockIndex) const;
 			Block GetLastBlockMask() const;

include/Nazara/Core/Bitset.inl

@@ -323,6 +323,76 @@ namespace Nz
 		return m_bitCount;
 	}
 
+	/*!
+	* \brief Read a byte sequence into a bitset
+	*
+	* This function expand the bitset with bits read from a byte sequence
+	*
+	* \param ptr A pointer to the start of the byte sequence
+	* \param bitCount Number of bits to read from the byte sequence
+	*
+	* \returns A pointer to the next byte to read along with the next bit index (useful when reading multiple times)
+	*
+	* \remark For technical reasons, ceil(bitCount / 8) bytes from the sequence will always be read (even with non-multiple-of-8 bitCount)
+	*
+	* \see AppendBits
+	* \see Read
+	*/
+	template<typename Block, class Allocator>
+	typename Bitset<Block, Allocator>::PointerSequence Bitset<Block, Allocator>::Read(const void* ptr, std::size_t bitCount)
+	{
+		return Read(PointerSequence(ptr, 0U), bitCount);
+	}
+
+	/*!
+	* \brief Read a byte sequence into a bitset
+	*
+	* This function expand the bitset with bits read from a pointer sequence (made of a pointer and a bit index)
+	*
+	* \param sequence A pointer sequence to the start of the byte sequence
+	* \param bitCount Number of bits to read from the byte sequence
+	*
+	* \returns A pointer to the next byte to read along with the next bit index (useful when reading multiple times)
+	*
+	* \remark For technical reasons, ceil(bitCount / 8) bytes from the sequence will always be read (even with non-multiple-of-8 bitCount)
+	*
+	* \see AppendBits
+	* \see Read
+	*/
+	template<typename Block, class Allocator>
+	typename Bitset<Block, Allocator>::PointerSequence Bitset<Block, Allocator>::Read(const PointerSequence& sequence, std::size_t bitCount)
+	{
+		NazaraAssert(sequence.first, "Invalid pointer sequence");
+		NazaraAssert(sequence.second < 8, "Invalid next bit index (must be < 8)");
+
+		std::size_t totalBitCount = sequence.second + bitCount;
+
+		const UInt8* u8Ptr = static_cast<const UInt8*>(sequence.first);
+		const UInt8* endPtr = u8Ptr + ((totalBitCount != 0) ? (totalBitCount - 1) / 8 : 0);
+		const UInt8* nextPtr = endPtr + ((totalBitCount % 8 != 0) ? 0 : 1);
+
+		// Read the first block apart to apply a mask on the first byte if necessary
+		if (sequence.second != 0)
+		{
+			UInt8 mask = ~((1U << sequence.second) - 1U);
+
+			std::size_t readCount = std::min(bitCount, 8 - sequence.second);
+			AppendBits(Block(*u8Ptr++ & mask) >> sequence.second, readCount);
+			bitCount -= readCount;
+		}
+
+		// And then read the remaining bytes
+		while (u8Ptr <= endPtr)
+		{
+			std::size_t bitToRead = std::min<std::size_t>(bitCount, 8);
+			AppendBits(*u8Ptr++, bitToRead);
+			bitCount -= bitToRead;
+		}
+
+		// Returns informations to continue reading
+		return PointerSequence(nextPtr, totalBitCount % 8);
+	}
+
 	/*!
 	* \brief Performs the "AND" operator between two bitsets
 	*
@@ -1039,6 +1109,35 @@ namespace Nz
 		return *this;
 	}
 
+	/*!
+	* \brief Builds a bitset from a byte sequence
+	*
+	* This function builds a bitset using a byte sequence by reading bitCount bits from it
+	*
+	* \param ptr A pointer to the start of the byte sequence
+	* \param bitCount Number of bits to read from the byte sequence
+	* \param sequence Optional data to pass to a next call to Read
+	*
+	* \return The constructed bitset
+	*
+	* \remark For technical reasons, ceil(bitCount / 8) bytes from the sequence will always be read (even with non-multiple-of-8 bitCount)
+	*
+	* \see AppendBits
+	* \see Read
+	*/
+	template<typename Block, class Allocator>
+	Bitset<Block, Allocator> Bitset<Block, Allocator>::FromPointer(const void* ptr, std::size_t bitCount, PointerSequence* sequence)
+	{
+		Bitset bitset;
+
+		if (sequence)
+			*sequence = bitset.Read(ptr, bitCount);
+		else
+			bitset.Read(ptr, bitCount);
+
+		return bitset;
+	}
+
 	/*!
 	* \brief Finds the position of the first bit set to true after the blockIndex
 	* \return The position of the bit

tests/Engine/Core/Bitset.cpp

@@ -10,6 +10,7 @@ template<typename Block> void CheckAppend(const char* title);
 template<typename Block> void CheckBitOps(const char* title);
 template<typename Block> void CheckConstructor(const char* title);
 template<typename Block> void CheckCopyMoveSwap(const char* title);
+template<typename Block> void CheckRead(const char* title);
 
 SCENARIO("Bitset", "[CORE][BITSET]")
 {
@@ -28,6 +29,7 @@ void Check(const char* title)
 	CheckBitOps<Block>(title);
 
 	CheckAppend<Block>(title);
+	CheckRead<Block>(title);
 }
 
 template<typename Block>
@@ -217,3 +219,55 @@ void CheckCopyMoveSwap(const char* title)
 	}
 }
 
+template<typename Block>
+void CheckRead(const char* title)
+{
+	SECTION(title)
+	{
+		GIVEN("An empty bitset filled by reading")
+		{
+			#define BitVal1 10010101
+			#define BitVal2 11010010
+			#define BitVal3 01101010
+			std::array<Nz::UInt8, 3> data = {NazaraPrefixMacro(BitVal1, 0b), NazaraPrefixMacro(BitVal2, 0b), NazaraPrefixMacro(BitVal3, 0b)};
+			const char result[] = NazaraStringifyMacro(BitVal3) NazaraStringifyMacro(BitVal2) NazaraStringifyMacro(BitVal1);
+			std::size_t resultLength = Nz::CountOf(result) - 1;
+			std::size_t bitCount = data.size() * 8;
+			#undef BitVal1
+			#undef BitVal2
+			#undef BitVal3
+
+			std::array<std::pair<const char*, std::size_t>, 8> tests = {
+				{
+					{"We read bits one by one", 1},
+					{"We read bits two by two", 2},
+					{"We read bits three by three", 3},
+					{"We read bits four by four", 4},
+					{"We read bits six by six", 6},
+					{"We read bits byte by byte", 8},
+					{"We read bits twelve by twelve", 12},
+					{"We read bits all at once", 24}
+				}
+			};
+
+			for (auto& pair : tests)
+			{
+				WHEN(pair.first)
+				{
+					Nz::Bitset<Block> bitset;
+
+					auto seq = bitset.Read(data.data(), pair.second);
+					for (std::size_t i = pair.second; i < bitCount; i += pair.second)
+						seq = bitset.Read(seq, pair.second);
+
+					REQUIRE(bitset.GetSize() == bitCount);
+
+					Nz::Bitset<Block> expectedBitset(result);
+
+					CHECK(bitset == expectedBitset);
+					CHECK(bitset.GetBlockCount() == (bitCount / bitset.bitsPerBlock + std::min<std::size_t>(1, bitCount % bitset.bitsPerBlock)));
+				}
+			}
+		}
+	}
+}