rust-mqtt/src/utils/buffer_reader.rs

use core::mem;
use core::str;

use crate::encoding::variable_byte_integer::VariableByteIntegerDecoder;

#[derive(Debug)]
#[derive(Clone)]
pub struct EncodedString<'a> {
    pub string: &'a str,
    pub len: u16,
}

impl EncodedString<'_> {
    pub fn new() -> Self {
        Self { string: "", len: 0 }
    }

    pub fn len(&self) -> u16 {
        return self.len + 2;
    }
}

#[derive(Debug)]
#[derive(Clone)]
pub struct BinaryData<'a> {
    pub bin: &'a [u8],
    pub len: u16,
}

impl BinaryData<'_> {
    pub fn new() -> Self {
        Self { bin: &[0], len: 0 }
    }

    pub fn len(&self) -> u16 {
        return self.len + 2;
    }
}

#[derive(Debug)]
pub struct StringPair<'a> {
    pub name: EncodedString<'a>,
    pub value: EncodedString<'a>,
}

impl StringPair<'_> {
    pub fn len(&self) -> u16 {
        let ln = self.name.len() + self.value.len();
        return ln;
    }
}

#[derive(Debug)]
pub struct TopicFilter<'a> {
    pub filter: EncodedString<'a>,
    pub sub_options: u8,
}

impl TopicFilter<'_> {
    pub fn new() -> Self {
        Self {
            filter: EncodedString::new(),
            sub_options: 0,
        }
    }

    pub fn len(&self) -> u16 {
        return self.filter.len + 3;
    }
}

#[derive(core::fmt::Debug, Clone)]
pub enum ParseError {
    Utf8Error,
    IndexOutOfBounce,
    VariableByteIntegerError,
    IdNotFound,
    EncodingError,
    DecodingError,
}

pub struct BuffReader<'a> {
    buffer: &'a [u8],
    pub position: usize,
}

impl<'a> BuffReader<'a> {
    pub fn increment_position(&mut self, increment: usize) {
        self.position = self.position + increment;
    }

    pub fn new(buffer: &'a [u8]) -> Self {
        return BuffReader {
            buffer: buffer,
            position: 0,
        };
    }

    pub fn read_variable_byte_int(&mut self) -> Result<u32, ParseError> {
        let variable_byte_integer: [u8; 4] = [
            self.buffer[self.position],
            self.buffer[self.position + 1],
            self.buffer[self.position + 2],
            self.buffer[self.position + 3],
        ];
        let mut len: usize = 1;
        if variable_byte_integer[0] & 0x80 == 1 {
            len = len + 1;
            if variable_byte_integer[1] & 0x80 == 1 {
                len = len + 1;
                if variable_byte_integer[2] & 0x80 == 1 {
                    len = len + 1;
                }
            }
        }
        self.increment_position(len);
        return VariableByteIntegerDecoder::decode(variable_byte_integer);
    }

    pub fn read_u32(&mut self) -> Result<u32, ParseError> {
        let (int_bytes, rest) = self.buffer[self.position..].split_at(mem::size_of::<u32>());
        let ret: u32 = u32::from_be_bytes(int_bytes.try_into().unwrap());
        //let ret: u32 = (((self.buffer[self.position] as u32) << 24) | ((self.buffer[self.position + 1] as u32) << 16) | ((self.buffer[self.position + 2] as u32) << 8) | (self.buffer[self.position + 3] as u32)) as u32;
        self.increment_position(4);
        return Ok(ret);
    }

    pub fn read_u16(&mut self) -> Result<u16, ParseError> {
        let (int_bytes, rest) = self.buffer[self.position..].split_at(mem::size_of::<u16>());
        let ret: u16 = u16::from_be_bytes(int_bytes.try_into().unwrap());
        //(((self.buffer[self.position] as u16) << 8) | (self.buffer[self.position + 1] as u16)) as u16;
        self.increment_position(2);
        return Ok(ret);
    }

    pub fn read_u8(&mut self) -> Result<u8, ParseError> {
        let ret: u8 = self.buffer[self.position];
        self.increment_position(1);
        return Ok(ret);
    }

    pub fn read_string(&mut self) -> Result<EncodedString<'a>, ParseError> {
        let len = self.read_u16();
        match len {
            Err(err) => return Err(err),
            _ => log::debug!("[parseString] let not parsed"),
        }
        let len_res = len.unwrap();
        let res_str =
            str::from_utf8(&(self.buffer[self.position..(self.position + len_res as usize)]));
        if res_str.is_err() {
            log::error!("Could not parse utf-8 string");
            return Err(ParseError::Utf8Error);
        }
        self.increment_position(len_res as usize);
        return Ok(EncodedString {
            string: res_str.unwrap(),
            len: len_res,
        });
    }

    //TODO: Index out of bounce err !!!!!
    pub fn read_binary(&mut self) -> Result<BinaryData<'a>, ParseError> {
        let len = self.read_u16();
        match len {
            Err(err) => return Err(err),
            _ => log::debug!("[parseBinary] let not parsed"),
        }
        let len_res = len.unwrap();
        let res_bin = &(self.buffer[self.position..(self.position + len_res as usize)]);
        return Ok(BinaryData {
            bin: res_bin,
            len: len_res,
        });
    }

    pub fn read_string_pair(&mut self) -> Result<StringPair<'a>, ParseError> {
        let name = self.read_string();
        match name {
            Err(err) => return Err(err),
            _ => log::debug!("[String pair] name not parsed"),
        }
        let value = self.read_string();
        match value {
            Err(err) => return Err(err),
            _ => log::debug!("[String pair] value not parsed"),
        }
        return Ok(StringPair {
            name: name.unwrap(),
            value: value.unwrap(),
        });
    }

    pub fn read_message(&mut self, total_len: usize) -> &'a [u8] {
        return &self.buffer[self.position..total_len];
    }
}