/// <summary>
/// Retrieves the dictionary information in a format that can be persisted for
/// later use in creating a new dictionary.
/// </summary>
public static byte[] GetHeaderByteArray(CharacterFrequencyDictionary dict)
{
var dictKeys = dict.GetKeysAsByteArray();
var dictValues = dict.GetValuesAsByteArray();
var keyLength = BitConverter.GetBytes(dictKeys.Length);
var dictLength = BitConverter.GetBytes(dictValues.Length);
var headerLength = dictKeys.Length + dictValues.Length + keyLength.Length + dictLength.Length;
var fileHeader = new byte[headerLength];
int len = 0;
keyLength.CopyTo(fileHeader, len);
len += keyLength.Length;
dictLength.CopyTo(fileHeader, len);
len += dictLength.Length;
dictKeys.CopyTo(fileHeader, len);
len += dictKeys.Length;
dictValues.CopyTo(fileHeader, len);
return(fileHeader);
}
/// <summary>
/// Create a character frequency dictionary given a string
/// </summary>
/// <param name="input"></param>
/// <returns>A dictionary with the key being characters in the input string and the values
/// being the number of times the character appears in the input string</returns>
public static CharacterFrequencyDictionary CreateDictionary(string input)
{
var dict = new CharacterFrequencyDictionary();
foreach (var c in input.ToCharArray())
{
if (!dict.ContainsKey(c))
{
dict.Add(c, 0);
}
dict[c]++;
}
return(dict);
}
/// <summary>
/// create a character frequency dictionary given byte arrays representing the keys
/// and the values. Intended to be used with the output of <see cref="GetKeysAsByteArray"/> and
/// <see cref="GetValuesAsByteArray"/>.
/// </summary>
/// <param name="keyArray">The dictionary keys as a byte array from <see cref="GetKeysAsByteArray"/></param>
/// <param name="valueArray">The dictonary values as a byte array from <see cref="GetKeysAsByteArray"/></param>
/// <returns></returns>
public static CharacterFrequencyDictionary CreateDictionary(byte[] keyArray, byte[] valueArray)
{
var keys = Encoding.ASCII.GetString(keyArray).ToCharArray();
var values = Encoding.ASCII.GetString(valueArray).Split(',').Select(Int32.Parse).ToArray();
if (keys.Length != values.Length)
{
throw new ArgumentException(
String.Format("Key array length ({0}) does not match value array length ({1}) ", keys.Length, values.Length));
}
var dict = new CharacterFrequencyDictionary();
for (var i = 0; i < keys.Length; i++)
{
dict.Add(keys[i], values[i]);
}
return(dict);
}
