constexpr + noexcept in Hash

Author: mrotteveel

src/common/CRC32C.cpp

@@ -33,7 +33,7 @@
 
 #include <nmmintrin.h>
 
-unsigned int CRC32C(unsigned int length, const unsigned char* value)
+unsigned int CRC32C(unsigned int length, const unsigned char* value) noexcept
 {
 	unsigned int hash_value = 0;
 

src/common/classes/Hash.cpp

@@ -34,13 +34,13 @@
 
 using namespace Firebird;
 
-unsigned int CRC32C(unsigned int length, const unsigned char* value);
+unsigned int CRC32C(unsigned int length, const unsigned char* value) noexcept;
 
 namespace
 {
 	typedef unsigned int (*hash_func_t)(unsigned int length, const UCHAR* value);
 
-	unsigned int basicHash(unsigned int length, const UCHAR* value)
+	unsigned int basicHash(unsigned int length, const UCHAR* value) noexcept
 	{
 		unsigned int hash_value = 0;
 
@@ -75,17 +75,17 @@ namespace
 
 #if defined(_M_IX86) || defined(_M_X64) || defined(__x86_64__) || defined(__i386__)
 
-	bool SSE4_2Supported()
+	bool SSE4_2Supported() noexcept
 	{
 #ifdef _MSC_VER
-		const int bit_SSE4_2 = 1 << 20;
+		constexpr int bit_SSE4_2 = 1 << 20;
 		// MS VC has its own definition of __cpuid
 		int flags[4];
 		__cpuid(flags, 1);
 		return (flags[2] & bit_SSE4_2) != 0;
 #else
 #if defined(__clang__) && !defined(bit_SSE4_2)
-		const int bit_SSE4_2 = bit_SSE42;
+		constexpr int bit_SSE4_2 = bit_SSE42;
 #endif
 
 		// GCC - its own
@@ -105,7 +105,7 @@ namespace
 
 }
 
-unsigned int InternalHash::hash(unsigned int length, const UCHAR* value)
+unsigned int InternalHash::hash(unsigned int length, const UCHAR* value) noexcept
 {
 	return internalHash(length, value);
 }

src/common/classes/Hash.h

@@ -76,7 +76,7 @@ namespace Firebird
 		}
 	};
 
-	const FB_SIZE_T DEFAULT_HASH_SIZE = 97;			// largest prime number < 100
+	inline constexpr FB_SIZE_T DEFAULT_HASH_SIZE = 97;	// largest prime number < 100
 
 	template <typename C,
 			  FB_SIZE_T HASHSIZE = DEFAULT_HASH_SIZE,
@@ -94,14 +94,14 @@ namespace Firebird
 			Entry* nextElement;
 
 		public:
-			Entry() : previousElement(NULL) { }
+			Entry() noexcept : previousElement(NULL), nextElement(NULL) { }
 
 			virtual ~Entry()
 			{
 				unLink();
 			}
 
-			void link(Entry** where)
+			void link(Entry** where) noexcept
 			{
 				unLink();
 
@@ -119,7 +119,7 @@ namespace Firebird
 				*previousElement = this;
 			}
 
-			void unLink()
+			void unLink() noexcept
 			{
 				// if we are linked
 				if (previousElement)
@@ -136,12 +136,12 @@ namespace Firebird
 				}
 			}
 
-			Entry** nextPtr()
+			Entry** nextPtr() noexcept
 			{
 				return &nextElement;
 			}
 
-			Entry* next() const
+			Entry* next() const noexcept
 			{
 				return nextElement;
 			}
@@ -156,20 +156,13 @@ namespace Firebird
 			virtual C* get() = 0;
 		}; // class Entry
 
-	private:
-		HashTable(const HashTable&);	// not implemented
-
 	public:
-		explicit HashTable(MemoryPool&)
-			: duplicates(false)
+		explicit HashTable(MemoryPool&) noexcept
 		{
-			clean();
 		}
 
-		HashTable()
-			: duplicates(false)
+		HashTable() noexcept
 		{
-			clean();
 		}
 
 		~HashTable()
@@ -178,6 +171,9 @@ namespace Firebird
 			cleanup(NULL);
 		}
 
+		HashTable(const HashTable&) = delete;
+		HashTable& operator= (const HashTable&) = delete;
+
 		typedef void CleanupRoutine(C* toClean);
 		void cleanup(CleanupRoutine* cleanupRoutine)
 		{
@@ -193,14 +189,14 @@ namespace Firebird
 			}
 		}
 
-		void enableDuplicates()
+		void enableDuplicates() noexcept
 		{
 			duplicates = true;
 		}
 
 	private:
-		Entry* data[HASHSIZE];
-		bool duplicates;
+		Entry* data[HASHSIZE]{};
+		bool duplicates = false;
 
 		Entry** locate(const K& key, FB_SIZE_T h)
 		{
@@ -219,7 +215,7 @@ namespace Firebird
 
 		Entry** locate(const K& key)
 		{
-			FB_SIZE_T hashValue = F::hash(key, HASHSIZE);
+			const FB_SIZE_T hashValue = F::hash(key, HASHSIZE);
 			fb_assert(hashValue < HASHSIZE);
 			return locate(key, hashValue % HASHSIZE);
 		}
@@ -254,15 +250,6 @@ namespace Firebird
 			return NULL;
 		}
 
-	private:
-		// disable use of default operator=
-		HashTable& operator= (const HashTable&);
-
-		void clean()
-		{
-			memset(data, 0, sizeof data);
-		}
-
 	public:
 		class iterator
 		{
@@ -335,9 +322,9 @@ namespace Firebird
 	class InternalHash
 	{
 	public:
-		static unsigned int hash(unsigned int length, const UCHAR* value);
+		static unsigned int hash(unsigned int length, const UCHAR* value) noexcept;
 
-		static unsigned int hash(unsigned int length, const UCHAR* value, unsigned int hashSize)
+		static unsigned int hash(unsigned int length, const UCHAR* value, unsigned int hashSize) noexcept
 		{
 			return hash(length, value) % hashSize;
 		}
@@ -358,8 +345,8 @@ namespace Firebird
 	class WeakHashContext final : public HashContext
 	{
 	public:
-		virtual void update(const void* data, FB_SIZE_T length);
-		virtual void finish(dsc& result);
+		void update(const void* data, FB_SIZE_T length) override;
+		void finish(dsc& result) override;
 
 	private:
 		SINT64 hashNumber = 0;