Ton

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int check_signatures(msg_hash, signatures, signers, bitmask_size) impure {
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  var bitmask = 0;
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  var id = -1;
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  do {
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    (id, var signature, var f) = signatures.udict_get_next?(32, id);
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    if (f){
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      var sig = signature.preload_bits(512);
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      var public_key = -1;
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      do {
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        (public_key, var cs, var _found) = signers.udict_get_next?(256, public_key);
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        if (_found){
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          if (check_signature(msg_hash, sig, public_key)){
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            var signer_index = cs~load_uint(bitmask_size);
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                    bitmask = bitmask | (1 << (signer_index - 1));  
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          } 
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        }
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      } until (~ _found);
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      ;; signature~touch(); 
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    }
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  } until (~ f);
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  return bitmask;
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}
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