public FieldHasher(PropertyInfo[] props, FieldHasherOptions options)
{
this.Props = props;
this.expr = CreateExpression(props, options);
}
private Func <T1, int> CreateExpression(PropertyInfo[] fields, FieldHasherOptions options)
{
/*
* $hash = 17;
* $hash += $hash * 23 + .Call ($obj.a).GetHashCode();
* $hash += $hash * 23 + .Call ($obj.b).GetHashCode();
* .If ($obj.s != null) {
* $hash += $hash * 23 + .Call (.Call ($obj.s).Trim()).GetHashCode()
* } .Else {
* $hash *= 23
* };
* $hash += $hash * 23 + .Call ($obj.date).GetHashCode();
* $hash += $hash * 23 + .Call ($obj.mynullable).GetHashCode();
* $hash
*/
const int prim = 17;
const int prim2 = 23;
var t1param = EE.Param <T1>("obj");
var resultHash = EE.Param <int>("hash");
var ass = Expression.Assign(resultHash, Expression.Constant(prim));
var block = new List <Expression>();
block.Add(ass);
var returnLabel = Expression.Label(typeof(int));
var whenNull = options.ZeroIfNulls ? Expression.Return(returnLabel, Expression.Constant(0))
: resultHash.MulAssign(prim2);
block.AddRange(fields.Select(pi =>
{
var dotted = t1param.Dot(pi.Name);
var propType = pi.PropertyType;
var addAssignHashCode = Expression.AddAssign(resultHash,
resultHash.Mul(prim2).Add(dotted.Call("GetHashCode")));
// nullable
if (options.ZeroIfNulls && Nullable.GetUnderlyingType(propType) != null)
{
return(Expression.IfThenElse(
dotted.NotNull(),
addAssignHashCode,
whenNull));
}
// value type but not nullabl
if (propType.IsValueType)
{
return((Expression)addAssignHashCode);
}
// normalized string
var normalized = propType == typeof(string) && options.StringNormalizer != null
? options.StringNormalizer(dotted)
: dotted;
var iffed = Expression.IfThenElse(dotted.NotNull(),
Expression.AddAssign(resultHash,
resultHash.Mul(prim2).Add(normalized.Call("GetHashCode"))),
whenNull);
return(iffed);
}));
block.Add(Expression.Label(returnLabel, resultHash));
var eblock = Expression.Block(new [] { resultHash }, block);
var l = Expression.Lambda <Func <T1, int> >(eblock, t1param);
return(l.Compile());
}
