Mirror/CyberChef
1
0
Fork 0
mirror of https://github.com/gchq/CyberChef.git synced 2024-11-16 08:58:30 +01:00
Code Issues Projects Releases Packages Wiki Activity

Bombe: further optimisation

Browse source
This commit is contained in:
s2224834 2019-01-12 01:10:47 +00:00
parent d94e8c8187
commit 49f5c94a75
1 changed files with 32 additions and 31 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

63
src/core/lib/Bombe.mjs
View file

@ -158,27 +158,6 @@ class SharedScrambler {
}
}
/**
* Get the fully cached result, if present.
* @param {number} pos - Position of the fast rotor
* @param {number} i - Letter
* @returns {number|undefined} - undefined if not cached
*/
fullTransform(pos, i) {
return this.higherCache[pos][i];
}
/**
* Add a value to the full result cache.
* @param {number} pos - Position of the fast rotor
* @param {number} i - Letter
* @param {number} val - Transformed letter
*/
addCache(pos, i, val) {
this.higherCache[pos][i] = val;
this.higherCache[pos][val] = i;
}
/**
* Map a letter through this (partial) scrambler.
* @param {number} i - The letter
@ -209,6 +188,9 @@ class Scrambler {
this.changeRotor(rotor);
this.end1 = end1;
this.end2 = end2;
// For efficiency reasons, we pull the relevant shared cache from the baseScrambler into
// this object - this saves us a few pointer dereferences
this.cache = this.baseScrambler.higherCache[pos];
}
/**
@ -233,6 +215,7 @@ class Scrambler {
// simplifies caching the state of the majority of the scramblers. The results are the
// same, just in a slightly different order.
this.rotor.step();
this.cache = this.baseScrambler.higherCache[this.rotor.pos];
}
@ -243,14 +226,15 @@ class Scrambler {
*/
transform(i) {
let letter = i;
const cached = this.baseScrambler.fullTransform(this.rotor.pos, i);
const cached = this.cache[i];
if (cached !== undefined) {
return cached;
}
letter = this.rotor.transform(letter);
letter = this.baseScrambler.transform(letter);
letter = this.rotor.revTransform(letter);
this.baseScrambler.addCache(this.rotor.pos, i, letter);
this.cache[i] = letter;
this.cache[letter] = i;
return letter;
}
@ -513,12 +497,26 @@ export class BombeMachine {
// both.
const idxPair = 26*j + i;
this.wires[idxPair] = true;
if (i === this.testRegister || j === this.testRegister) {
this.energiseCount++;
if (this.energiseCount === 26) {
// no point continuing, bail out
return;
}
}
for (let k=0; k<this.scramblers[i].length; k++) {
const scrambler = this.scramblers[i][k];
const out = scrambler.transform(j);
const other = scrambler.getOtherEnd(i);
this.energise(other, out);
// Lift the pre-check before the call, to save some function call overhead
const otherIdx = 26*other + out;
if (!this.wires[otherIdx]) {
this.energise(other, out);
if (this.energiseCount === 26) {
return;
}
}
}
if (i === j) {
return;
@ -527,7 +525,13 @@ export class BombeMachine {
const scrambler = this.scramblers[j][k];
const out = scrambler.transform(i);
const other = scrambler.getOtherEnd(j);
this.energise(other, out);
const otherIdx = 26*other + out;
if (!this.wires[otherIdx]) {
this.energise(other, out);
if (this.energiseCount === 26) {
return;
}
}
}
}
@ -610,6 +614,7 @@ export class BombeMachine {
for (let i=0; i<this.wires.length; i++) {
this.wires[i] = false;
}
this.energiseCount = 0;
// Re-energise with the corrected hypothesis
this.energise(this.testRegister, pair);
}
@ -643,12 +648,7 @@ export class BombeMachine {
*/
checkStop() {
// Count the energised outputs
let count = 0;
for (let j=26*this.testRegister; j<26*(1+this.testRegister); j++) {
if (this.wires[j]) {
count++;
}
}
const count = this.energiseCount;
if (count === 26) {
return undefined;
}
@ -705,6 +705,7 @@ export class BombeMachine {
for (let i=0; i<this.wires.length; i++) {
this.wires[i] = false;
}
this.energiseCount = 0;
// Energise the test input, follow the current through each scrambler
// (and the diagonal board)
this.energise(...this.testInput);