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use std::mem::size_of;
use unsigned_varint::decode;
#[derive(Debug, Clone)]
pub enum TSDBError {
Default,
SymbolTableLookup,
}
pub type Result<T> = std::result::Result<T, TSDBError>;
pub fn slice_bytes(buf: &[u8], size: usize, pos: usize) -> &[u8] {
&buf[pos..pos + size]
}
pub fn get_checksum(buf: &[u8], pos: usize) -> Result<u32> {
read_u32(buf, pos)
}
macro_rules! read_varint {
($func:ident, $typ:ty, $ti:ident) => {
pub fn $func(buf: &[u8], pos: usize) -> Result<($typ, usize)> {
if buf.len() <= pos {
return Ok((0, 0));
}
let varint_vec = &buf[pos..];
match decode::$ti(varint_vec) {
Ok((int, rest)) => return Ok((int, varint_vec.len() - rest.len())),
Err(_) => {
return Err(TSDBError::Default);
}
}
}
};
}
read_varint!(read_varint_u32, u32, u32);
read_varint!(read_varint_u64, u64, u64);
macro_rules! read {
($func:ident, $typ:ty) => {
pub fn $func(buf: &[u8], pos: usize) -> Result<$typ> {
let b = slice_bytes(buf, size_of::<$typ>(), pos);
match TryInto::<[u8; size_of::<$typ>()]>::try_into(b) {
Ok(bytes) => Ok(<$typ>::from_be_bytes(bytes)),
Err(_) => Err(TSDBError::Default),
}
}
};
}
read!(read_u32, u32);
read!(read_u64, u64);
pub fn read_varint_i64(buf: &[u8], pos: usize) -> Result<(i64, usize)> {
let (u, size) = read_varint_u64(buf, pos)?;
Ok((zigzag_dec(u), size))
}
fn zigzag_dec(u: u64) -> i64 {
(u >> 1) as i64 ^ -((u & 1) as i64)
}