multihash.R

openssl_multihash <- function(con, algos = c('md5', 'sha1', 'sha256', 'sha384', 'sha512')){
  if(!isOpen(con)){
    open(con, "rb")
    on.exit(close(con))
  }
  states <- lapply(algos, function(algo){
    structure(openssl:::md_init(algo), algo = algo) 
  })
  while(length(data <- readBin(con, raw(), 512*1024))){
    lapply(states, openssl:::md_feed, data = data)
  }
  hashes <- lapply(states, function(x){
    hash <- openssl:::md_final(x)
    structure(hash, class = c("hash", attr(x, 'algo')))
  })
    
  structure(hashes, names = algos)
}

openssl_multihash(curl::curl("https://zenodo.org/record/3678928/files/vostok.icecore.co2"))