PROSAGA码农传奇-ECN-如何在Haskell中高效地编写大文件

如何在Haskell中高效地编写大文件

作者: 青阳
发布时间: 2024-03-13 07:48:28 (2月前)
转自：

<div class =“post-text”itemprop =“text”>
  <P>
    我建议使用Builder，这是一种填充缓冲区的有效方法，可以直接写入句柄。
  </p>
   <pre>
    <code>
      #!/usr/bin/env stack
-- stack --resolver ghc-8.6.4 script
{-# LANGUAGE OverloadedStrings #-}
import Data.ByteString.Builder (Builder, hPutBuilder)
import Data.Foldable (fold)
import System.IO (IOMode (WriteMode), withBinaryFile)

pt :: FilePath
pt = "data2.csv"

cnt :: Int
cnt = 400000000

main :: IO ()
main = writeWithHandle pt dat

dat :: Builder
dat = "0744442339"

writeWithHandle :: FilePath -> Builder -> IO ()
writeWithHandle path tx =
  withBinaryFile path WriteMode $ \h ->
  hPutBuilder h $ makeBuilder cnt tx

makeBuilder :: Int -> Builder -> Builder
makeBuilder cnt payload = fold $ replicate cnt $ payload <> "\n"

</code>
  </pre>
  <P>
    你可以保留
     <code>
      payload
    </code>
     作为一个
     <code>
      Text
    </code>
     如果您愿意，请转换为
     <code>
      Builder
    </code>
     运用
    <a href="https://www.stackage.org/haddock/lts-13.12/text-1.2.3.1/Data-Text-Encoding.html#v:encodeUtf8Builder" rel="nofollow noreferrer">
       <code>
        encodeUtf8Builder
      </code>
    </A>
    。
  </p>
</DIV>