CODEWITHSUNDEEP
rust
Quirinux
Quirinux

Reputation: 326

is there a trait to read from stdin or from file in rust?

As a newbie on rust i wonder to know if there is way to use a single function/macro/anything-else to read a line from a passed file or from stdin, passing as argument a kind of buffer reader maybe?

I haven't found anything that help yet, the following code works fine, once I was able to wrap some validations on a macro I know that code can be improved. I'm open for suggestion about how to improve that macro indeed

...

macro_rules! validate {
    ($line:expr, $blank:expr, $squeeze:expr, $line_count:expr, $show_number:expr) => {
        if $line.len() <= 0 {
            $blank +=1;
        } else{
            $blank = 0;
        }
        if $squeeze & ($blank > 1) {
            continue;
        }
        if $show_number {
            $line_count += 1;
        }

    }
} 


...

for file in opt.files {
        blank_line_count = 0;
        line_count = 0;
        if file.to_str() != Some("-") {
            let f = File::open(file)?;
            for line in BufReader::new(f).lines() {
                let l = line.unwrap();
                validate!(l, blank_line_count, opt.squeeze_blank, line_count, opt.number); // will continue the loop if not valid
                println!("{}", format_line(l, opt.show_ends, opt.show_tabs, opt.show_nonprinting, line_count)); // will be skipped if not valid
            }
        } else {
            let stdin = io::stdin();
            let mut bytes_read: usize;
            loop {
                let mut line = String::new();
                bytes_read = stdin.lock().read_line(&mut line).expect("Could not read line");
                if bytes_read == 0 { break; }
                line.pop();
                validate!(line, blank_line_count, opt.squeeze_blank, line_count, opt.number);// will continue the loop if not valid
                println!("{}", format_line(line, opt.show_ends, opt.show_tabs, opt.show_nonprinting, line_count)); // will be skipped if not valid
            }
        }
    }
....

As shown File and stdin have different treatments, but they both basically do the same thing, run through a loop looking for a valid entry

Upvotes: 2

Views: 2074

Answers (1)

Quirinux
Quirinux

Reputation: 326

thanks @PeterHall, that Read trait thing lighted bulb on, I didn't realized that I could pass stdin to BufReader, so that does the trick:

 let stdin = io::stdin();
 for line in BufReader::new(stdin).lines() {
...

the same way that one does:

let f = File::open(file)?;
for line in BufReader::new(f).lines() {

This is what a I was looking for.

Thanks a mil

Upvotes: 5

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