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head: fix subtraction underflow with --bytes=-N #7036

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Merged
sylvestre merged 1 commit into from
Dec 31, 2024
Merged

head: fix subtraction underflow with --bytes=-N #7036

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3 changes: 2 additions & 1 deletion src/uu/head/src/head.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -256,6 +256,7 @@ fn catch_too_large_numbers_in_backwards_bytes_or_lines(n: u64) -> Option<usize>
}
}

/// Print to stdout all but the last `n` bytes from the given reader.
fn read_but_last_n_bytes(input: &mut impl std::io::BufRead, n: u64) -> std::io::Result<()> {
if n == 0 {
//prints everything
Expand Down Expand Up @@ -285,7 +286,7 @@ fn read_but_last_n_bytes(input: &mut impl std::io::BufRead, n: u64) -> std::io::

if total_read <= n {
// Fill the ring buffer without exceeding n bytes
let overflow = total_read - n;
let overflow = n - total_read;
ring_buffer.extend_from_slice(&buffer[..read - overflow]);
} else {
// Write the ring buffer and the part of the buffer that exceeds n
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17 changes: 17 additions & 0 deletions tests/by-util/test_head.rs
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Expand Up @@ -157,6 +157,23 @@ fn test_negative_byte_syntax() {
.stdout_is("");
}

#[test]
fn test_negative_bytes_greater_than_input_size_stdin() {
new_ucmd!()
.args(&["-c", "-2"])
.pipe_in("a")
.succeeds()
.no_output();
}

#[test]
fn test_negative_bytes_greater_than_input_size_file() {
let ts = TestScenario::new(util_name!());
let at = &ts.fixtures;
at.write_bytes("f", b"a");
ts.ucmd().args(&["-c", "-2", "f"]).succeeds().no_output();
}

#[test]
fn test_negative_zero_lines() {
new_ucmd!()
Expand Down
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