Method read_generic

crates/vm/src/stdlib/_io.rs:1210–1278

(&mut self, n: usize, vm: &VirtualMachine)

        }

        fn read_generic(&mut self, n: usize, vm: &VirtualMachine) -> PyResult<Option<Vec<u8>>> {
            if let Some(fast) = self.read_fast(n) {
                return Ok(Some(fast));
            }

            let current_size = self.readahead() as usize;

            let mut out = vec![0u8; n];
            let mut remaining = n;
            let mut written = 0;
            if current_size > 0 {
                let slice = self.active_read_slice();
                out[..slice.len()].copy_from_slice(slice);
                remaining -= current_size;
                written += current_size;
                self.pos += current_size as Offset;
            }
            if self.writable() {
                self.flush_rewind(vm)?;
            }
            self.reset_read();
            macro_rules! handle_opt_read {
                ($x:expr) => {
                    match ($x, written > 0) {
                        (Some(0), _) | (None, true) => {
                            out.truncate(written);
                            return Ok(Some(out));
                        }
                        (Some(r), _) => r,
                        (None, _) => return Ok(None),
                    }
                };
            }
            while remaining > 0 && !self.buffer.is_empty() {
                // MINUS_LAST_BLOCK() in CPython
                let r = self.buffer.len() * (remaining / self.buffer.len());
                if r == 0 {
                    break;
                }
                let r = self.raw_read(Either::A(Some(&mut out)), written..written + r, vm)?;
                let r = handle_opt_read!(r);
                remaining -= r;
                written += r;
            }
            self.pos = 0;
            self.raw_pos = 0;
            self.read_end = 0;

            while remaining > 0 && (self.read_end as usize) < self.buffer.len() {
                let r = handle_opt_read!(self.fill_buffer(vm)?);
                if remaining > r {
                    out[written..][..r].copy_from_slice(&self.buffer[self.pos as usize..][..r]);
                    written += r;
                    self.pos += r as Offset;
                    remaining -= r;
                } else if remaining > 0 {
                    out[written..][..remaining]
                        .copy_from_slice(&self.buffer[self.pos as usize..][..remaining]);