/// <summary>
/// Creates a new Bloom Filter given capacity, error rate, bit array size and number of hash functions
/// </summary>
/// <param name="capacity">Number of expected elements to be inserted</param>
/// <param name="secondaryHashFunction">Secondary hash Functions to be used to generate combination of hashes. Dont pass GetHashCode</param>
/// <param name="hashBitsSize">Size of bit array to be stored</param>
/// <param name="errorRate">Expected error rate for the bloom filter</param>
/// <param name="numberOfHashFunctions">Number of hash functions to be used while storing and retrieving value in bloom filter</param>
public BloomFilter(int capacity, HashFunction secondaryHashFunction, int hashBitsSize, float errorRate, int numberOfHashFunctions)
{
if (capacity < 1)
{
throw new ArgumentOutOfRangeException(nameof(capacity), capacity, "Number of elements to be inserted in bloom filter must be > 0");
}
if (hashBitsSize < 1)
{
throw new ArgumentOutOfRangeException(nameof(hashBitsSize), hashBitsSize, "Size of HashBits in bloom filter is expected to be >0");
}
if (errorRate <= 0 || errorRate >= 1)
{
throw new ArgumentOutOfRangeException(nameof(errorRate), errorRate, "Error rate is expected to be between (0.0,1.0)");
}
if (numberOfHashFunctions < 1)
{
throw new ArgumentOutOfRangeException(nameof(numberOfHashFunctions), numberOfHashFunctions, "Number of Hash Functions in bloom filter is expected to be >0");
}
this.HashBits = new BitArray(hashBitsSize);
this.NumberOfHashFunctions = numberOfHashFunctions;
if (secondaryHashFunction != null)
{
this.SecondaryHashFunction = secondaryHashFunction;
}
else
{
if (typeof(T) == typeof(string))
{
this.SecondaryHashFunction = HashString;
}
else
{
throw new ArgumentNullException("HashFunction", "Non null values are expected for each hash function in bloom filter");
}
}
}
/// <summary>
/// Creates a BloomFilter for the specified expected element
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="expectedElements">The expected elements.</param>
/// <param name="hashFunction">The hash function.</param>
/// <returns></returns>
public static Filter <T> Build <T>(int expectedElements, HashFunction hashFunction)
{
return(Build <T>(expectedElements, 0.01, hashFunction));
}
/// <summary>
/// Creates a BloomFilter for the specified expected element
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="expectedElements">The expected elements.</param>
/// <param name="errorRate">The error rate.</param>
/// <param name="hashFunction">The hash function.</param>
/// <returns></returns>
public static Filter <T> Build <T>(int expectedElements, double errorRate, HashFunction hashFunction)
{
return(new FilterMemory <T>(expectedElements, errorRate, hashFunction));
}
/// <summary>
/// Initializes a new instance of the <see cref="Filter{T}"/> class.
/// </summary>
/// <param name="name"></param>
/// <param name="capacity">The capacity.</param>
/// <param name="hashes">The hashes.</param>
/// <param name="hashFunction">The hash function.</param>
/// <exception cref="ArgumentOutOfRangeException">
/// capacity - capacity must be > 0
/// or
/// hashes - hashes must be > 0
/// </exception>
/// <exception cref="ArgumentNullException">hashFunction</exception>
public Filter(string name, int capacity, int hashes, HashFunction hashFunction) : base(name, capacity, hashes, hashFunction)
{
CheckElementType();
}
/// <summary>
/// Initializes a new instance of the <see cref="Filter{T}"/> class.
/// </summary>
/// <param name="name"></param>
/// <param name="expectedElements">The expected elements.</param>
/// <param name="errorRate">The error rate.</param>
/// <param name="hashFunction">The hash function.</param>
/// <exception cref="ArgumentOutOfRangeException">
/// expectedElements - expectedElements must be > 0
/// or
/// errorRate
/// </exception>
/// <exception cref="ArgumentNullException">hashFunction</exception>
public Filter(string name, int expectedElements, double errorRate, HashFunction hashFunction)
: base(name, expectedElements, errorRate, hashFunction)
{
CheckElementType();
}
/// <summary>
/// Creates a new Bloom filter, using the optimal size for the underlying data structure based on the desired capacity and error rate, as well as the optimal number of hash functions.
/// </summary>
/// <param name="capacity">The anticipated number of items to be added to the filter. More than this number of items can be added, but the error rate will exceed what is expected.</param>
/// <param name="errorRate">The accepable false-positive rate (e.g., 0.01F = 1%)</param>
/// <param name="hashFunction">The function to hash the input values. Do not use GetHashCode(). If it is null, and T is string or int a hash function will be provided for you.</param>
public Filter(int capacity, float errorRate, HashFunction hashFunction) : this(capacity, errorRate, hashFunction, bestM(capacity, errorRate), bestK(capacity, errorRate))
{
}
/// <summary>
/// Creates a new Bloom filter, specifying an error rate of 1/capacity, using the optimal size for the underlying data structure based on the desired capacity and error rate, as well as the optimal number of hash functions.
/// </summary>
/// <param name="capacity">The anticipated number of items to be added to the filter. More than this number of items can be added, but the error rate will exceed what is expected.</param>
/// <param name="hashFunction">The function to hash the input values. Do not use GetHashCode(). If it is null, and T is string or int a hash function will be provided for you.</param>
public Filter(int capacity, HashFunction hashFunction) : this(capacity, bestErrorRate(capacity), hashFunction)
{
}
/// <summary>
/// Initializes a new instance of the <see cref="FilterMemory{T}"/> class.
/// </summary>
/// <param name="size">The size.</param>
/// <param name="hashes">The hashes.</param>
/// <param name="hashFunction">The hash function.</param>
public FilterMemory(int size, int hashes, HashFunction hashFunction)
: base(size, hashes, hashFunction)
{
_hashBits = new BitArray(Capacity);
}
/// <summary>
/// Initializes a new instance of the <see cref="FilterMemory{T}"/> class.
/// </summary>
/// <param name="expectedElements">The expected elements.</param>
/// <param name="errorRate">The error rate.</param>
/// <param name="hashFunction">The hash function.</param>
public FilterMemory(int expectedElements, double errorRate, HashFunction hashFunction)
: base(expectedElements, errorRate, hashFunction)
{
_hashBits = new BitArray(Capacity);
}
/// <summary>
/// Creates a BloomFilter for the specified expected element
/// </summary>
/// <param name="expectedElements">The expected elements.</param>
/// <param name="errorRate">The error rate.</param>
/// <param name="hashFunction">The hash function.</param>
/// <param name="name"></param>
/// <returns></returns>
public static IBloomFilter Build(int expectedElements, double errorRate, HashFunction hashFunction, string name = BloomFilterConstValue.DefaultInMemoryName)
{
return(new FilterMemory(name, expectedElements, errorRate, hashFunction));
}
/// <summary>
/// Creates a BloomFilter for the specified expected element
/// </summary>
/// <param name="expectedElements">The expected elements.</param>
/// <param name="hashFunction">The hash function.</param>
/// <param name="name"></param>
/// <returns></returns>
public static IBloomFilter Build(int expectedElements, HashFunction hashFunction, string name = BloomFilterConstValue.DefaultInMemoryName)
{
return(Build(expectedElements, 0.01, hashFunction, name));
}
/// <summary>
/// Creates a new Bloom Filter given capacity, error rate and number of hash functions
/// BitArray size is calculated for given parameters
/// </summary>
/// <param name="capacity">Number of expected elements to be inserted</param>
/// <param name="secondaryHashFunction">Secondary hash Functions to be used to generate combination of hashes. Dont pass GetHashCode</param>
/// <param name="errorRate">Expected error rate for the bloom filter</param>
/// <param name="numberOfHashFunctions">Number of hash functions to be used while storing and retrieving value in bloom filter</param>
public BloomFilter(int capacity, HashFunction secondaryHashFunction, float errorRate, int numberOfHashFunctions)
: this(capacity, secondaryHashFunction, OptimalNumberOfHashBits(capacity, errorRate), errorRate, OptimalNumberOfHashes(capacity, errorRate))
{
}
/// <summary>
/// Creates a new Bloom Filter given capacity and size of bitarray
/// Error Rate and Number of hash functions are calculated for given parameters
/// </summary>
/// <param name="capacity">Number of expected elements to be inserted</param>
/// <param name="secondaryHashFunction">Secondary hash Functions to be used to generate combination of hashes. Dont pass GetHashCode</param>
/// <param name="hashBitsSize">Size of bit array to be stored</param>
public BloomFilter(int capacity, HashFunction secondaryHashFunction, int hashBitsSize)
: this(capacity, secondaryHashFunction, hashBitsSize, OptimalErrorRate(capacity), OptimalNumberOfHashes(capacity, OptimalErrorRate(capacity)))
{
}
