| //+------------------------------------------------------------------+
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| //| HashFunction.mqh |
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| //| Copyright 2000-2025, MetaQuotes Ltd. |
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| //| https://www.mql5.com |
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| //+------------------------------------------------------------------+
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| //+------------------------------------------------------------------+
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| //| Unioun BitInterpreter. |
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| //| Usage: Provides the ability to interpret the same bit sequence in|
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| //| different types. |
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| //+------------------------------------------------------------------+
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| union BitInterpreter
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| {
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| bool bool_value;
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| char char_value;
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| uchar uchar_value;
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| short short_value;
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| ushort ushort_value;
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| color color_value;
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| int int_value;
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| uint uint_value;
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| datetime datetime_value;
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| long long_value;
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| ulong ulong_value;
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| float float_value;
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| double double_value;
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| };
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for boolean. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const bool value)
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| {
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| return((value)?true:false);
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for character. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const char value)
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| {
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| return((int)value | ((int)value << 16));
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for unsigned character. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const uchar value)
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| {
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| return((int)value | ((int)value << 16));
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for short. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const short value)
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| {
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| return(((int)((ushort)value) | (((int)value) << 16)));
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for unsigned short. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const ushort value)
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| {
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| return((int)value);
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for color. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const color value)
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| {
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| return((int)value);
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for integer. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const int value)
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| {
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| return(value);
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for unsigned integer. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const uint value)
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| {
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| return((int)value);
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for datetime. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const datetime value)
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| {
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| long ticks=(long)value;
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| return(((int)ticks) ^ (int)(ticks >> 32));
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for long. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const long value)
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| {
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| return(((int)((long)value)) ^ (int)(value >> 32));
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for unsigned long. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const ulong value)
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| {
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| return(((int)value) ^ (int)(value >> 32));
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for float. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const float value)
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| {
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| if(value==0)
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| {
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| //--- ensure that 0 and -0 have the same hash code
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| return(0);
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| }
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| BitInterpreter convert;
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| convert.float_value=value;
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| return(convert.int_value);
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for string. |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const double value)
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| {
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| if(value==0)
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| {
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| //--- ensure that 0 and -0 have the same hash code
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| return(0);
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| }
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| BitInterpreter convert;
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| convert.double_value=value;
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| long lvalue=convert.long_value;
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| return(((int)lvalue) ^ ((int)(lvalue >> 32)));
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for string. |
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| //| The hashcode for a string is computed as: |
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| //| |
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| //| s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1] |
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| //| |
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| //| using int arithmetic, where s[i] is the ith character of the |
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| //| string, n is the length of the string, and ^ indicates |
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| //| exponentiation. (The hash value of the empty string is zero.) |
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| //+------------------------------------------------------------------+
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| int GetHashCode(const string value)
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| {
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| int len=StringLen(value);
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| int hash=0;
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| //--- check length of string
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| if(len>0)
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| {
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| //--- calculate a hash as a fucntion of each char
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| for(int i=0; i<len; i++)
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| hash=31*hash+value[i];
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| }
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| return(hash);
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| }
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| //+------------------------------------------------------------------+
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| //| Returns a hashcode for custom object. |
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| //+------------------------------------------------------------------+
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| template<typename T>
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| int GetHashCode(T value)
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| {
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| //--- try to convert to equality comparable object
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| IEqualityComparable<T>*equtable=dynamic_cast<IEqualityComparable<T>*>(value);
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| if(equtable)
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| {
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| //--- calculate hash by specied method
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| return equtable.HashCode();
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| }
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| else
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| {
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| //--- calculate hash from name of object
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| return GetHashCode(typename(value));
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| }
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| }
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| //+------------------------------------------------------------------+
|
