72 lines
2.3 KiB
D
72 lines
2.3 KiB
D
import std.stdio, std.array, std.algorithm, std.range, std.ascii,
|
|
std.conv, std.string, std.regex, std.typecons;
|
|
|
|
string unique(in string s) pure nothrow @safe {
|
|
string result;
|
|
foreach (immutable char c; s)
|
|
if (!result.representation.canFind(c)) // Assumes ASCII string.
|
|
result ~= c;
|
|
return result;
|
|
}
|
|
|
|
struct Playfair {
|
|
string from, to;
|
|
string[string] enc, dec;
|
|
|
|
this(in string key, in string from_ = "J", in string to_ = null)
|
|
pure /*nothrow @safe*/ {
|
|
this.from = from_;
|
|
if (to_.empty)
|
|
this.to = (from_ == "J") ? "I" : "";
|
|
|
|
immutable m = _canonicalize(key ~ uppercase)
|
|
.unique
|
|
.chunks(5)
|
|
.map!text
|
|
.array;
|
|
auto I5 = 5.iota;
|
|
|
|
foreach (immutable R; m)
|
|
foreach (immutable i, immutable j; cartesianProduct(I5, I5))
|
|
if (i != j)
|
|
enc[[R[i], R[j]]] = [R[(i + 1) % 5], R[(j+1) % 5]];
|
|
|
|
foreach (immutable r; I5) {
|
|
immutable c = m.transversal(r).array;
|
|
foreach (immutable i, immutable j; cartesianProduct(I5, I5))
|
|
if (i != j)
|
|
enc[[c[i], c[j]]] = [c[(i + 1) % 5], c[(j+1) % 5]];
|
|
}
|
|
|
|
foreach (i1, j1, i2, j2; cartesianProduct(I5, I5, I5, I5))
|
|
if (i1 != i2 && j1 != j2)
|
|
enc[[m[i1][j1], m[i2][j2]]] = [m[i1][j2], m[i2][j1]];
|
|
|
|
dec = enc.byKeyValue.map!(t => tuple(t.value, t.key)).assocArray;
|
|
}
|
|
|
|
private string _canonicalize(in string s) const pure @safe {
|
|
return s.toUpper.removechars("^A-Z").replace(from, to);
|
|
}
|
|
|
|
string encode(in string s) const /*pure @safe*/ {
|
|
return _canonicalize(s)
|
|
.matchAll(r"(.)(?:(?!\1)(.))?")
|
|
.map!(m => enc[m[0].leftJustify(2, 'X')])
|
|
.join(' ');
|
|
}
|
|
|
|
string decode(in string s) const pure @safe {
|
|
return _canonicalize(s).chunks(2).map!(p => dec[p.text]).join(' ');
|
|
}
|
|
}
|
|
|
|
void main() /*@safe*/ {
|
|
/*immutable*/ const pf = Playfair("Playfair example");
|
|
immutable orig = "Hide the gold in...the TREESTUMP!!!";
|
|
writeln("Original: ", orig);
|
|
immutable enc = pf.encode(orig);
|
|
writeln(" Encoded: ", enc);
|
|
writeln(" Decoded: ", pf.decode(enc));
|
|
}
|