Fixed up Bitset (#36)

* Fixed up Bitset

* code review changes

* cast changed from int to uint32_t

Author: Mogball

lib/wlib/CMakeLists.txt

@@ -1,13 +1,13 @@
 project(wlib)
 
 file (GLOB header_files
-        "Wlib.h"
-        "strings/*.h"
-        "stl/*.h"
-        "memory/*.h")
+		"Wlib.h"
+		"strings/*.h"
+		"stl/*.h"
+		"memory/*.h")
 
 file (GLOB source_files
-        "memory/*.cpp")
+		"memory/*.cpp")
 
 set(HEADER_FILES ${header_files} )
 set(SOURCE_FILES ${source_files})

lib/wlib/Wlib.h

@@ -1,11 +1,10 @@
 #ifndef EMBEDDEDTESTS_WLIB_H
 #define EMBEDDEDTESTS_WLIB_H
 
-#define max(a,b) \
-   ({ __typeof__ (a) _a = (a); \
-       __typeof__ (b) _b = (b); \
-     _a > _b ? _a : _b; })
-
+#define max(x, y) (((x) > (y)) ? (x) : (y))
 #define min(x, y) (((x) < (y)) ? (x) : (y))
 
+#define BYTE_SIZE 8
+#define INT_SIZE (BYTE_SIZE * sizeof(uint32_t))
+
 #endif //EMBEDDEDTESTS_WLIB_H

lib/wlib/stl/Bitset.h

@@ -17,149 +17,215 @@
 #include <stdint.h>
 #include <math.h>
 
+#include "Wlib.h"
+
 namespace wlp {
-#define NO_OF_BITS (8 * sizeof(unsigned int))
 
-	template<uint8_t bits>
+	/**
+	 * Computes the mask corresponding to the number of bits
+	 * or the exponent in the from 2^n - 1.
+	 * @tparam exp the number of bits, 32 or less
+	 */
+	template<uint8_t exp>
+	struct pow_mask {
+		static const uint32_t value = (uint32_t) ((1 << exp) - 1);
+	};
+
+	/**
+	 * Template specialization for 32 bits to
+	 * prevent overflow.
+	 */
+	template<> struct pow_mask<32> {
+		static const uint32_t value = 0xffffffff;
+	};
+
+	/**
+	 * Compute the minimum number of integers
+	 * needed to store a certain number of bits.
+	 * @tparam nBits the bits to store
+	 */
+	template<uint8_t nBits>
+	struct ceil_bits {
+		static const uint32_t value = (nBits + INT_SIZE - 1) / INT_SIZE;
+	};
+
+	template<uint8_t nBits>
 	class Bitset {
 	public:
 		/**
-		 * Default Constructor creates an empty bitset
+		 * Default Constructor creates an empty bitset.
 		 */
 		Bitset() {
 			memset(m_array, 0, sizeof(m_array));
 		}
 
 		/**
-		 * Constructor creates a bitset from a number that can be of max
-		 * 64 bit in size
+		 * Constructor creates a bitset from a number that
+		 * can be of max 64 bit in size.
 		 *
-		 * @param number the number to create bitset from
+		 * @param n the number to create bitset from
 		 */
-		explicit Bitset(uint64_t number){
-			memset(m_array, 0, sizeof(m_array));
-
-			uint16_t size = sizeof(number) * 8;
+		explicit Bitset(uint64_t n) {
+			setFromNumber(n);
+		}
 
-			if (size > bits) size = bits;
+		/**
+		 * Copy constructor.
+		 * @param b Bitset to copy
+		 */
+		Bitset(Bitset<nBits>& b) {
+			uint32_t end = ceil_bits<nBits>::value;
+			for (uint16_t i = 0; i < end; i++) {
+				m_array[i] = (m_array[i] & 0) | b.m_array[i];
+			}
+		}
 
-			for (uint16_t index = 0; index < size; ++index) {
-				uint8_t remainder = (uint8_t) (number % 2);
-				number /= 2;
+		/**
+		 * Copy constructor for const.
+		 * @param b Bitset to copy
+		 */
+		Bitset(const Bitset<nBits>& b) {
+			uint32_t end = ceil_bits<nBits>::value;
+			for (uint16_t i = 0; i < end; i++) {
+				m_array[i] = (m_array[i] & 0) | b.m_array[i];
+			}
+		}
 
-				if (remainder) set(index);
-				else reset(index);
+		/**
+		 * Set the value of the Bitset from a number
+		 * of maximum 64 bit size.
+		 * @param n the number to set from
+		 */
+		void setFromNumber(uint64_t n) {
+			memset(m_array, 0, sizeof(m_array));
+			constexpr uint32_t end = nBits / INT_SIZE;
+			constexpr uint32_t extra = nBits - end * INT_SIZE;
+			for (uint16_t i = 0; i < end; ++i) {
+				m_array[i] = (uint32_t) n;
+				n >>= INT_SIZE;
+			}
+			if (extra) {
+				m_array[end] = ((uint32_t) n) & pow_mask<extra>::value;
 			}
 		}
 
 
 		/**
-		 * Sets the bit at @code index to be true
+		 * Sets the bit at @code index to be true.
 		 *
 		 * @param index the index of the bit
 		 */
 		void set(uint16_t index) {
-			m_array[index / NO_OF_BITS] |= (1U << (index % NO_OF_BITS));
+			m_array[index / INT_SIZE] |= (1U << (index % INT_SIZE));
 		}
 
 		/**
-		 * Sets the bit at @code index to be false
+		 * Sets the bit at @code index to be false.
 		 *
 		 * @param index the index of the bit
 		 */
 		void reset(uint16_t index) {
-			m_array[index / NO_OF_BITS] &= ~(1U << (index % NO_OF_BITS));
+			m_array[index / INT_SIZE] &= ~(1U << (index % INT_SIZE));
 		}
 
 		/**
-		 * Toggles the but at @code index
+		 * Toggles the but at @code index.
 		 *
 		 * @param index the index of the bit
 		 */
 		void flip(uint16_t index) {
-			m_array[index / NO_OF_BITS] ^= (1U << (index % NO_OF_BITS));
+			m_array[index / INT_SIZE] ^= (1U << (index % INT_SIZE));
 		}
 
 		/**
-		 * Returns the value of bit at @code index
+		 * Returns the value of bit at @code index.
 		 *
 		 * @param index the index of the bit
 		 * @return the bit value
 		 */
-		bool test(uint16_t index) {
-			return (m_array[index / NO_OF_BITS] & (1U << (index % NO_OF_BITS))) != 0;
+		bool test(uint16_t index) const {
+			return (m_array[index / INT_SIZE] & (1U << (index % INT_SIZE))) != 0;
 		}
 
 		/**
 		 * Converts the bits into 64 bit unsigned integer
 		 *
 		 * @return unsigned 64 bit integer
 		 */
-		uint64_t to_uint64_t() {
-			uint64_t number = 0;
-
-			for (uint8_t i = 0; i < 64; ++i) {
-				uint64_t powerVal = (uint64_t) ceil(pow(2, i));
-				uint8_t bitVal = (uint8_t) test(i);
-				number += bitVal * powerVal;
+		uint64_t to_uint64_t() const {
+			if (nBits <= 32) {
+				return to_uint32_t();
 			}
-
-			return number;
+			return (((uint64_t) m_array[1]) << INT_SIZE) | ((uint32_t) m_array[0]);
 		}
 
 		/**
 		 * Converts the bits into 32 bit unsigned integer
 		 *
 		 * @return unsigned 32 bit integer
 		 */
-		uint32_t to_uint32_t() {
-			uint32_t number = 0;
-
-			for (uint8_t i = 0; i < 32; ++i) {
-				uint32_t powerVal = (uint32_t) ceil(pow(2, i));
-				uint8_t bitVal = (uint8_t) test(i);
-				number += bitVal * powerVal;
-			}
-
-			return number;
+		uint32_t to_uint32_t() const {
+			return (uint32_t) m_array[0];
 		}
 
 		/**
 		 * Converts the bits into 16 bit unsigned integer
 		 *
 		 * @return unsigned 16 bit integer
 		 */
-		uint16_t to_uint16_t() {
-			uint16_t number = 0;
-
-			for (uint8_t i = 0; i < 16; ++i) {
-				uint16_t powerVal = (uint16_t) ceil(pow(2, i));
-				uint8_t bitVal = (uint8_t) test(i);
-				number += bitVal * powerVal;
-			}
-
-			return number;
+		uint16_t to_uint16_t() const {
+			return (uint16_t) (m_array[0] & pow_mask<16>::value);
 		}
 
 		/**
 		 * Converts the bits into 8 bit unsigned integer
 		 *
 		 * @return unsigned 8 bit integer
 		 */
-		uint8_t to_uint8_t() {
-			uint8_t number = 0;
+		uint8_t to_uint8_t() const {
+			return (uint8_t) (m_array[0] & pow_mask<8>::value);
+		}
 
-			for (uint8_t i = 0; i < 8; ++i) {
-				uint8_t powerVal = (uint8_t) ceil(pow(2, i));
-				uint8_t bitVal = (uint8_t) test(i);
-				number += bitVal * powerVal;
+		/**
+		 * Access operator returns the bit at the given position.
+		 * @param i the position of the bit to test
+		 * @return the value of the bit
+		 */
+		bool operator[](const uint16_t i) const {
+			return test(i);
+		}
+
+		/**
+		 * Assignment operator copies the contents of the bitset.
+		 * @param b Bitset to assign
+		 */
+		Bitset<nBits>& operator=(Bitset<nBits>& b) {
+			uint32_t end = ceil_bits<nBits>::value;
+			for (uint16_t i = 0; i < end; i++) {
+				m_array[i] = (m_array[i] & 0) | b.m_array[i];
 			}
+			return *this;
+		}
 
-			return number;
+		/**
+		 * Assignment operator copies the contents of the bitset.
+		 * @param b Bitset to assign
+		 */
+		Bitset<nBits>& operator=(const Bitset<nBits>& b) {
+			uint32_t end = ceil_bits<nBits>::value;
+			for (uint16_t i = 0; i < end; i++) {
+				m_array[i] = (m_array[i] & 0) | b.m_array[i];
+			}
+			return *this;
 		}
 
 	private:
-		int m_array[bits/ NO_OF_BITS];
+		/**
+		 * Backing array of integers that contain the bites.
+		 * Integer type arrays generally have the fastest access
+		 * times in C++.
+		 */
+		uint32_t m_array[ceil_bits<nBits>::value];
 	};
 }
 

tests/CMakeLists.txt

@@ -10,6 +10,7 @@ include_directories(${WLIB_INCLUDE_DIR})
 
 file(GLOB files
         "test.cpp"
+        "stl/*.cpp"
         "strings/*.cpp")
 
 add_executable(tests ${files})