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我想從輸入文件中的隨機位置獲取數據,並將它們順序輸出到輸出文件。優選地,沒有不必要的分配。如何地理/有效地從讀取+尋求寫入數據?
This is one kind of solution I have figured out:
use std::io::{ self, SeekFrom, Cursor, Read, Write, Seek };
#[test]
fn read_write() {
// let's say this is input file
let mut input_file = Cursor::new(b"worldhello");
// and this is output file
let mut output_file = Vec::<u8>::new();
assemble(&mut input_file, &mut output_file).unwrap();
assert_eq!(b"helloworld", &output_file[..]);
}
// I want to take data from random locations in input file
// and output them sequentially to output file
pub fn assemble<I, O>(input: &mut I, output: &mut O) -> Result<(), io::Error>
where I: Read + Seek, O: Write
{
// first seek and output "hello"
try!(input.seek(SeekFrom::Start(5)));
let mut hello_buf = [0u8; 5];
try!(input.take(5).read(&mut hello_buf));
try!(output.write(&hello_buf));
// then output "world"
try!(input.seek(SeekFrom::Start(0)));
let mut world_buf = [0u8; 5];
try!(input.take(5).read(&mut world_buf));
try!(output.write(&world_buf));
Ok(())
}
讓我們不要擔心I/O延遲在這裏。
問題:
- 是否穩定的鏽有一些幫手採取x字節從一個流並將它們推到另一個流?或者我必須推出自己的?
- 如果我必須自己推出,也許有更好的方法?
無關:更改彙編以使用''而且它更通用(允許特質對象)。 – bluss