rustLogic errorMedium

Cursor position at EOF returns zero bytes

Time: 0:00

BugFind the bug and fix the code

What it should do

Write bytes to cursor and read back into vector. Example: read_cursor_data([1, 2, 3]) -> [1, 2, 3]

What happens instead

Read returns 0 bytes because cursor stream position is at EOF after write

use std::io::{Cursor, Read, Write};

fn read_cursor_data(data: Vec<u8>) -> Vec<u8> {
    let mut cursor = Cursor::new(Vec::new());
    cursor.write_all(&data).unwrap();
    // Cursor position is at EOF after write; reading returns 0 bytes
    let mut buf = Vec::new();
    cursor.read_to_end(&mut buf).unwrap();
    buf
}

fn main() {
    println!("{:?}", read_cursor_data(vec![1, 2, 3]));
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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Hint 3

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This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

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use std::io::{Cursor, Read, Write}; fn read_cursor_data(data: Vec<u8>) -> Vec<u8> { let mut cursor = Cursor::new(Vec::new()); cursor.write_all(&data).unwrap(); // Cursor position is at EOF after write; reading returns 0 bytes let mut buf = Vec::new(); cursor.read_to_end(&mut buf).unwrap(); buf } fn main() { println!("{:?}", read_cursor_data(vec![1, 2, 3])); }

Cursor position at EOF returns zero bytes

What it should do

What happens instead

More logic errors to practise

Cursor position at EOF returns zero bytes

What it should do

What happens instead

More logic errors to practise