[Haskell-cafe] How to deal with C buf in Haskell?

Hi, I am warping some C libs. In one function, I do this: 183 allocaBytes bufLen $ \buf -> do 184 ret <- {# call buf_read #} 185 bluh 186 bala 187 buf 188 bufLen 189 if ret < 0 190 then userError "bufRead error" 191 else -- what should I do here? I am thinking about bytestring, to pass the content of the buf to the outside of the function. But I am not sure. What should I do? -- 竹密岂妨流水过 山高哪阻野云飞