mirror of
https://github.com/logos-storage/logos-storage-proofs-circuits.git
synced 2026-01-09 08:53:09 +00:00
39 lines
724 B
Plaintext
39 lines
724 B
Plaintext
pragma circom 2.0.0;
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//
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// given an input `inp`, this template checks that inp == 2^out
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// with 0 < out <= n
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//
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// we also output a mask vector which is 1 for i=0..out-1, and 0 elsewhere
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//
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template Log2(n) {
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signal input inp;
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signal output out;
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signal output mask[n+1];
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// mask will be a vector [1,1,1,...1,0,...,0,0]
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// which can change only where inp == 2^out
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var log2 = -1;
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for(var i=0; i<=n; i++) {
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mask[i] <-- ((2**i) < inp) ? 1 : 0;
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if (2**i == inp) { log2 = i; }
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}
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out <-- log2;
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mask[0] === 1;
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mask[n] === 0;
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var sum = 0;
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for(var i=0; i<n; i++) {
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sum += (2**(i+1)) * (mask[i] - mask[i+1]);
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0 === (mask[i] - mask[i+1]) * (i + 1 - out);
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}
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inp === sum;
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}
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