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extract read_hdr_window fn

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This commit is contained in:
Vinzenz Schroeter 2024-05-08 13:32:13 +02:00
parent 5ffebe7b0b
commit 414981f617
1 changed files with 26 additions and 22 deletions
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48
src/main.rs
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@ -1,5 +1,5 @@
use std::mem::size_of;
use std::net::{UdpSocket};
use std::net::UdpSocket;
use clap::Parser;
use num_derive::FromPrimitive;
@ -76,29 +76,12 @@ fn main2(cli: &Cli) -> std::io::Result<()> {
let (amount, source) = socket.recv_from(&mut buf)?;
let received = &mut buf[..amount];
if amount < size_of::<HdrWindow>() {
println!("received a packet that is too small from {:?}", source);
let header = read_hdr_window(&received[..10]);
if header.is_err() {
println!("could not read header: {}", header.err().unwrap());
continue;
}
let command_u16 =
u16::from_be(unsafe { std::ptr::read(received[0..=1].as_ptr() as *const u16) });
let maybe_command = num::FromPrimitive::from_u16(command_u16);
if maybe_command.is_none() {
println!(
"command {} received from {:?} is invalid",
command_u16, source
);
continue;
}
let header: HdrWindow = HdrWindow {
command: maybe_command.unwrap(),
x: u16::from_be(unsafe { std::ptr::read(received[2..=3].as_ptr() as *const u16) }),
y: u16::from_be(unsafe { std::ptr::read(received[4..=5].as_ptr() as *const u16) }),
w: u16::from_be(unsafe { std::ptr::read(received[6..=7].as_ptr() as *const u16) }),
h: u16::from_be(unsafe { std::ptr::read(received[8..=9].as_ptr() as *const u16) }),
};
let header = header.unwrap();
let payload = &received[10..];
println!(
@ -132,6 +115,26 @@ fn main2(cli: &Cli) -> std::io::Result<()> {
}
}
fn read_hdr_window(buffer: &[u8]) -> Result<HdrWindow, String> {
if buffer.len() < size_of::<HdrWindow>() {
return Err("received a packet that is too small".into());
}
let command_u16 = u16::from_be(unsafe { std::ptr::read(buffer[0..=1].as_ptr() as *const u16) });
let maybe_command = num::FromPrimitive::from_u16(command_u16);
if maybe_command.is_none() {
return Err(format!("received invalid command {}", command_u16));
}
return Ok(HdrWindow {
command: maybe_command.unwrap(),
x: u16::from_be(unsafe { std::ptr::read(buffer[2..=3].as_ptr() as *const u16) }),
y: u16::from_be(unsafe { std::ptr::read(buffer[4..=5].as_ptr() as *const u16) }),
w: u16::from_be(unsafe { std::ptr::read(buffer[6..=7].as_ptr() as *const u16) }),
h: u16::from_be(unsafe { std::ptr::read(buffer[8..=9].as_ptr() as *const u16) }),
});
}
fn check_payload_size(buf: &[u8], expected: usize) -> bool {
let actual = buf.len();
if actual == expected {
@ -170,6 +173,7 @@ fn print_bitmap_linear_win(header: &HdrWindow, payload: &[u8]) {
}
}
// TODO: actually convert from CP437
fn print_cp437_data(header: &HdrWindow, payload: &[u8]) {
if !check_payload_size(payload, (header.w * header.h) as usize) {
return;