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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::{cmp::min, mem};
use crate::codec::Decoder;
#[derive(Clone, Debug, Default)]
pub struct IncrementalDecoderUint {
v: u64,
remaining: Option<usize>,
}
impl IncrementalDecoderUint {
#[must_use]
pub fn min_remaining(&self) -> usize {
self.remaining.unwrap_or(1)
}
/// Consume some data.
///
/// # Panics
///
/// Never, but this is not something the compiler can tell.
pub fn consume(&mut self, dv: &mut Decoder) -> Option<u64> {
if let Some(r) = &mut self.remaining {
let amount = min(*r, dv.remaining());
if amount < 8 {
self.v <<= amount * 8;
}
self.v |= dv.decode_uint(amount).unwrap();
*r -= amount;
if *r == 0 {
Some(self.v)
} else {
None
}
} else {
let (v, remaining) = dv.decode_byte().map_or_else(
|| unreachable!(),
|b| {
(
u64::from(b & 0x3f),
match b >> 6 {
0 => 0,
1 => 1,
2 => 3,
3 => 7,
_ => unreachable!(),
},
)
},
);
self.remaining = Some(remaining);
self.v = v;
if remaining == 0 {
Some(v)
} else {
None
}
}
}
#[must_use]
pub const fn decoding_in_progress(&self) -> bool {
self.remaining.is_some()
}
}
#[derive(Clone, Debug)]
pub struct IncrementalDecoderBuffer {
v: Vec<u8>,
remaining: usize,
}
impl IncrementalDecoderBuffer {
#[must_use]
pub const fn new(n: usize) -> Self {
Self {
v: Vec::new(),
remaining: n,
}
}
#[must_use]
pub const fn min_remaining(&self) -> usize {
self.remaining
}
/// Consume some bytes from the decoder.
///
/// # Panics
///
/// Never; but rust doesn't know that.
pub fn consume(&mut self, dv: &mut Decoder) -> Option<Vec<u8>> {
let amount = min(self.remaining, dv.remaining());
let b = dv.decode(amount).unwrap();
self.v.extend_from_slice(b);
self.remaining -= amount;
if self.remaining == 0 {
Some(mem::take(&mut self.v))
} else {
None
}
}
}
#[derive(Clone, Debug)]
pub struct IncrementalDecoderIgnore {
remaining: usize,
}
impl IncrementalDecoderIgnore {
/// Make a new ignoring decoder.
///
/// # Panics
///
/// If the amount to ignore is zero.
#[must_use]
pub fn new(n: usize) -> Self {
assert_ne!(n, 0);
Self { remaining: n }
}
#[must_use]
pub const fn min_remaining(&self) -> usize {
self.remaining
}
pub fn consume(&mut self, dv: &mut Decoder) -> bool {
let amount = min(self.remaining, dv.remaining());
_ = dv.decode(amount);
self.remaining -= amount;
self.remaining == 0
}
}
#[cfg(test)]
mod tests {
use super::{
Decoder, IncrementalDecoderBuffer, IncrementalDecoderIgnore, IncrementalDecoderUint,
};
use crate::codec::Encoder;
#[test]
fn buffer_incremental() {
let b = &[1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
let mut dec = IncrementalDecoderBuffer::new(b.len());
let mut i = 0;
while i < b.len() {
// Feed in b in increasing-sized chunks.
let incr = if i < b.len() / 2 { i + 1 } else { b.len() - i };
let mut dv = Decoder::from(&b[i..i + incr]);
i += incr;
match dec.consume(&mut dv) {
None => {
assert!(i < b.len());
}
Some(res) => {
assert_eq!(i, b.len());
assert_eq!(res, b);
}
}
}
}
struct UintTestCase {
b: String,
v: u64,
}
impl UintTestCase {
pub fn run(&self) {
eprintln!(
"IncrementalDecoderUint decoder with {:?} ; expect {:?}",
self.b, self.v
);
let decoder = IncrementalDecoderUint::default();
let mut db = Encoder::from_hex(&self.b);
// Add padding so that we can verify that the reader doesn't over-consume.
db.encode_byte(0xff);
for tail in 1..db.len() {
let split = db.len() - tail;
let mut dv = Decoder::from(&db.as_ref()[0..split]);
eprintln!(" split at {split}: {dv:?}");
// Clone the basic decoder for each iteration of the loop.
let mut dec = decoder.clone();
let mut res = None;
while dv.remaining() > 0 {
res = dec.consume(&mut dv);
}
assert!(dec.min_remaining() < tail);
if tail > 1 {
assert_eq!(res, None);
assert!(dec.min_remaining() > 0);
let mut dv = Decoder::from(&db.as_ref()[split..]);
eprintln!(" split remainder {split}: {dv:?}");
res = dec.consume(&mut dv);
assert_eq!(dv.remaining(), 1);
}
assert_eq!(dec.min_remaining(), 0);
assert_eq!(res.unwrap(), self.v);
}
}
}
macro_rules! uint_tc {
[$( $b:expr => $v:expr ),+ $(,)?] => {
vec![ $( UintTestCase { b: String::from($b), v: $v, } ),+]
};
}
#[test]
fn varint() {
for c in uint_tc![
"00" => 0,
"01" => 1,
"3f" => 63,
"4040" => 64,
"7fff" => 16383,
"80004000" => 16384,
"bfffffff" => (1 << 30) - 1,
"c000000040000000" => 1 << 30,
"ffffffffffffffff" => (1 << 62) - 1,
] {
c.run();
}
}
#[test]
fn zero_len() {
let enc = Encoder::from_hex("ff");
let mut dec = Decoder::new(enc.as_ref());
let mut incr = IncrementalDecoderBuffer::new(0);
assert_eq!(incr.consume(&mut dec), Some(Vec::new()));
assert_eq!(dec.remaining(), enc.len());
}
#[test]
fn ignore() {
let db = Encoder::from_hex("12345678ff");
let decoder = IncrementalDecoderIgnore::new(4);
for tail in 1..db.len() {
let split = db.len() - tail;
let mut dv = Decoder::from(&db.as_ref()[0..split]);
eprintln!(" split at {split}: {dv:?}");
// Clone the basic decoder for each iteration of the loop.
let mut dec = decoder.clone();
let mut res = dec.consume(&mut dv);
assert_eq!(dv.remaining(), 0);
assert!(dec.min_remaining() < tail);
if tail > 1 {
assert!(!res);
assert!(dec.min_remaining() > 0);
let mut dv = Decoder::from(&db.as_ref()[split..]);
eprintln!(" split remainder {split}: {dv:?}");
res = dec.consume(&mut dv);
assert_eq!(dv.remaining(), 1);
}
assert_eq!(dec.min_remaining(), 0);
assert!(res);
}
}
}