Function copy_with_buffer 

pub fn copy_with_buffer<R: Read, W: Write>(
    reader: &mut R,
    writer: &mut W,
    buffer: &mut CopyBuffer,
) -> Result<u64, ExtractionError>

Copies data from reader to writer using the provided reusable buffer.

This is an optimized version of std::io::copy that:

• Uses a caller-provided buffer (avoiding heap allocation)
• Uses checked arithmetic to detect quota overflows
• Returns the total number of bytes copied

Errors

Returns an error if:

• Reading from the source fails
• Writing to the destination fails
• Total bytes written would overflow u64 (quota protection)

Security

Quota overflow is explicitly checked using checked_add, ensuring that malicious archives cannot bypass size limits via integer overflow.

Examples

let mut buffer = CopyBuffer::new();
let mut input = std::fs::File::open("large_file.bin")?;
let mut output = std::fs::File::create("output.bin")?;

let total = copy_with_buffer(&mut input, &mut output, &mut buffer)?;
println!("Copied {} bytes without heap allocation", total);