dkanus/Avarice
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Refactor numeric constants for MessageReader

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This commit is contained in:
Anton Tarasenko 2021-07-22 18:03:48 +07:00
parent 0a86852197
commit ba3ac088dd
1 changed files with 43 additions and 31 deletions
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74
src/link/mod.rs
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@ -4,11 +4,21 @@ use std::str;
extern crate custom_error;
use custom_error::custom_error;
const RECEIVED_FIELD_SIZE: usize = 4;
const LENGTH_FIELD_SIZE: usize = 4;
const HEAD_RECEIVED: u8 = 85;
const HEAD_MESSAGE: u8 = 42;
const MAX_MESSAGE_LENGTH: usize = 0xA00000;
// Defines how many bytes is used to encode "AMOUNT" field in the response from ue-server about
// amount of bytes it received since the last update
const UE_RECEIVED_FIELD_SIZE: usize = 4;
// Defines how many bytes is used to encode "LENGTH" field, describing length of
// next JSON message from ue-server
const UE_LENGTH_FIELD_SIZE: usize = 4;
// Value indicating that next byte sequence from ue-server reports amount of bytes received by
// that server so far. Value itself is arbitrary.
const HEAD_UE_RECEIVED: u8 = 85;
// Value indicating that next byte sequence from ue-server contains JSON message.
// Value itself is arbitrary.
const HEAD_UE_MESSAGE: u8 = 42;
// Maximum allowed size of JSON message sent from ue-server.
const MAX_UE_MESSAGE_LENGTH: usize = 25 * 1024 * 1024;
custom_error! { pub ReadingStreamError
InvalidHead{input: u8} = "Invalid byte used as a HEAD: {input}",
@ -37,8 +47,8 @@ pub struct MessageReader {
/// For converting byte stream expected to be generated by Acedia mod from the game server into
/// actual messages. Expected format is a sequence of either:
/// [HEAD_RECEIVED: 1 byte] [amount of bytes received by game server since last update: 4 bytes]
/// [HEAD_MESSAGE: 1 byte] [length of the message: 4 bytes] [utf8-encoded string: ??? bytes]
/// [HEAD_UE_RECEIVED: 1 byte] [amount of bytes received by game server since last update: 4 bytes]
/// [HEAD_UE_MESSAGE: 1 byte] [length of the message: 4 bytes] [utf8-encoded string: ??? bytes]
/// On any invalid input enters a failure state (can be checked by `is_broken()`) and
/// never recovers from it.
/// Use either `push_byte()` or `push()` to input byte stream from game server and `pop()` to
@ -63,9 +73,9 @@ impl MessageReader {
}
match &self.reading_state {
ReadingState::Head => {
if input == HEAD_RECEIVED {
if input == HEAD_UE_RECEIVED {
self.reading_state = ReadingState::ReceivedBytes;
} else if input == HEAD_MESSAGE {
} else if input == HEAD_UE_MESSAGE {
self.reading_state = ReadingState::Length;
} else {
self.is_broken = true;
@ -76,7 +86,7 @@ impl MessageReader {
self.next_received_bytes = self.next_received_bytes << 8;
self.next_received_bytes += input as u32;
self.read_bytes += 1;
if self.read_bytes >= RECEIVED_FIELD_SIZE {
if self.read_bytes >= UE_RECEIVED_FIELD_SIZE {
self.received_bytes += self.next_received_bytes as u64;
self.next_received_bytes = 0;
self.read_bytes = 0;
@ -87,10 +97,10 @@ impl MessageReader {
self.current_message_length = self.current_message_length << 8;
self.current_message_length += input as usize;
self.read_bytes += 1;
if self.read_bytes >= LENGTH_FIELD_SIZE {
if self.read_bytes >= UE_LENGTH_FIELD_SIZE {
self.read_bytes = 0;
self.reading_state = ReadingState::Payload;
if self.current_message_length > MAX_MESSAGE_LENGTH {
if self.current_message_length > MAX_UE_MESSAGE_LENGTH {
self.is_broken = true;
return Err(ReadingStreamError::MessageTooLong {
length: self.current_message_length,
@ -143,7 +153,7 @@ impl MessageReader {
#[test]
fn message_push_byte() {
let mut reader = MessageReader::new();
reader.push_byte(HEAD_MESSAGE).unwrap();
reader.push_byte(HEAD_UE_MESSAGE).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
@ -161,7 +171,7 @@ fn message_push_byte() {
reader.push_byte(0x6c).unwrap(); // l
reader.push_byte(0x64).unwrap(); // d
reader.push_byte(0x21).unwrap(); // <exclamation mark>
reader.push_byte(HEAD_MESSAGE).unwrap();
reader.push_byte(HEAD_UE_MESSAGE).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
@ -177,19 +187,19 @@ fn message_push_byte() {
#[test]
fn received_push_byte() {
let mut reader = MessageReader::new();
reader.push_byte(HEAD_RECEIVED).unwrap();
reader.push_byte(HEAD_UE_RECEIVED).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(243).unwrap();
assert_eq!(reader.received_bytes(), 243);
reader.push_byte(HEAD_RECEIVED).unwrap();
reader.push_byte(HEAD_UE_RECEIVED).unwrap();
reader.push_byte(65).unwrap();
reader.push_byte(25).unwrap();
reader.push_byte(178).unwrap();
reader.push_byte(4).unwrap();
assert_eq!(reader.received_bytes(), 1092203255);
reader.push_byte(HEAD_RECEIVED).unwrap();
reader.push_byte(HEAD_UE_RECEIVED).unwrap();
reader.push_byte(231).unwrap();
reader.push_byte(34).unwrap();
reader.push_byte(154).unwrap();
@ -199,12 +209,12 @@ fn received_push_byte() {
#[test]
fn mixed_push_byte() {
let mut reader = MessageReader::new();
reader.push_byte(HEAD_RECEIVED).unwrap();
reader.push_byte(HEAD_UE_RECEIVED).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(243).unwrap();
reader.push_byte(HEAD_MESSAGE).unwrap();
reader.push_byte(HEAD_UE_MESSAGE).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
@ -212,7 +222,7 @@ fn mixed_push_byte() {
reader.push_byte(0x59).unwrap(); // Y
reader.push_byte(0x6f).unwrap(); // o
reader.push_byte(0x21).unwrap(); // <exclamation mark>
reader.push_byte(HEAD_RECEIVED).unwrap();
reader.push_byte(HEAD_UE_RECEIVED).unwrap();
reader.push_byte(65).unwrap();
reader.push_byte(25).unwrap();
reader.push_byte(178).unwrap();
@ -227,12 +237,12 @@ fn pushing_many_bytes_at_once() {
let mut reader = MessageReader::new();
reader
.push(&[
HEAD_RECEIVED,
HEAD_UE_RECEIVED,
0,
0,
0,
243,
HEAD_MESSAGE,
HEAD_UE_MESSAGE,
0,
0,
0,
@ -240,7 +250,7 @@ fn pushing_many_bytes_at_once() {
0x59, // Y
0x6f, // o
0x21, // <exclamation mark>
HEAD_RECEIVED,
HEAD_UE_RECEIVED,
65,
25,
178,
@ -255,7 +265,7 @@ fn pushing_many_bytes_at_once() {
#[test]
fn generates_error_invalid_head() {
let mut reader = MessageReader::new();
reader.push_byte(HEAD_RECEIVED).unwrap();
reader.push_byte(HEAD_UE_RECEIVED).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
@ -270,14 +280,16 @@ fn generates_error_invalid_head() {
#[test]
fn generates_error_message_too_long() {
let mut reader = MessageReader::new();
reader.push_byte(HEAD_MESSAGE).unwrap();
// Max length right now is `0xA00000`
reader.push_byte(0).unwrap();
reader.push_byte(0xA0).unwrap();
reader.push_byte(0).unwrap();
let huge_length = MAX_UE_MESSAGE_LENGTH + 1;
let bytes = (huge_length as u32).to_be_bytes();
reader.push_byte(HEAD_UE_MESSAGE).unwrap();
reader.push_byte(bytes[0]).unwrap();
reader.push_byte(bytes[1]).unwrap();
reader.push_byte(bytes[2]).unwrap();
assert!(!reader.is_broken());
reader
.push_byte(1)
.push_byte(bytes[3])
.expect_err("Testing failing on exceeding allowed message length");
assert!(reader.is_broken());
}
@ -285,7 +297,7 @@ fn generates_error_message_too_long() {
#[test]
fn generates_error_invalid_unicode() {
let mut reader = MessageReader::new();
reader.push_byte(HEAD_MESSAGE).unwrap();
reader.push_byte(HEAD_UE_MESSAGE).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();
reader.push_byte(0).unwrap();