1/*
  2    Copyright 2018 0KIMS association.
  3
  4    This file is part of circom (Zero Knowledge Circuit Compiler).
  5
  6    circom is a free software: you can redistribute it and/or modify it
  7    under the terms of the GNU General Public License as published by
  8    the Free Software Foundation, either version 3 of the License, or
  9    (at your option) any later version.
 10
 11    circom is distributed in the hope that it will be useful, but WITHOUT
 12    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 13    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
 14    License for more details.
 15
 16    You should have received a copy of the GNU General Public License
 17    along with circom. If not, see <https://www.gnu.org/licenses/>.
 18*/
 19
 20/*
 21    Copyright 2018 0KIMS association.
 22
 23    This file is part of circom (Zero Knowledge Circuit Compiler).
 24
 25    circom is a free software: you can redistribute it and/or modify it
 26    under the terms of the GNU General Public License as published by
 27    the Free Software Foundation, either version 3 of the License, or
 28    (at your option) any later version.
 29
 30    circom is distributed in the hope that it will be useful, but WITHOUT
 31    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 32    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
 33    License for more details.
 34
 35    You should have received a copy of the GNU General Public License
 36    along with circom. If not, see <https://www.gnu.org/licenses/>.
 37*/
 38
 39// --> Assignation without constraint
 40// <-- Assignation without constraint
 41// === Constraint
 42// <== Assignation with constraint
 43// ==> Assignation with constraint
 44// All variables are members of the field F[p]
 45// https://github.com/zcash-hackworks/sapling-crypto
 46// https://github.com/ebfull/bellman
 47
 48/*
 49function log2(a) {
 50    if (a==0) {
 51        return 0;
 52    }
 53    let n = 1;
 54    let r = 1;
 55    while (n<a) {
 56        r++;
 57        n *= 2;
 58    }
 59    return r;
 60}
 61*/
 62
 63template EscalarProduct(w) {
 64    signal input in1[w];
 65    signal input in2[w];
 66    signal output out;
 67    signal aux[w];
 68    var lc = 0;
 69    for (var i=0; i<w; i++) {
 70        aux[i] <== in1[i]*in2[i];
 71        lc = lc + aux[i];
 72    }
 73    out <== lc;
 74}
 75
 76template Decoder(w) {
 77    signal input inp;
 78    signal output out[w];
 79    signal output success;
 80    var lc=0;
 81
 82    for (var i=0; i<w; i++) {
 83        out[i] <-- (inp == i) ? 1 : 0;
 84        out[i] * (inp-i) === 0;
 85        lc = lc + out[i];
 86    }
 87
 88    lc ==> success;
 89    success * (success -1) === 0;
 90}
 91
 92
 93template Multiplexer(wIn, nIn) {
 94    signal input inp[nIn][wIn];
 95    signal input sel;
 96    signal output out[wIn];
 97    component dec = Decoder(nIn);
 98    component ep[wIn];
 99
100    for (var k=0; k<wIn; k++) {
101        ep[k] = EscalarProduct(nIn);
102    }
103
104    sel ==> dec.inp;
105    for (var j=0; j<wIn; j++) {
106        for (var k=0; k<nIn; k++) {
107            inp[k][j] ==> ep[j].in1[k];
108            dec.out[k] ==> ep[j].in2[k];
109        }
110        ep[j].out ==> out[j];
111    }
112    dec.success === 1;
113}