1// Copyright 2018 Brian Smith.
2//
3// Permission to use, copy, modify, and/or distribute this software for any
4// purpose with or without fee is hereby granted, provided that the above
5// copyright notice and this permission notice appear in all copies.
6//
7// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
8// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
10// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
14
15use alloc::{boxed::Box, vec::Vec};
16
17pub trait Accumulator {
18 fn write_byte(&mut self, value: u8) -> Result<(), TooLongError>;
19 fn write_bytes(&mut self, value: &[u8]) -> Result<(), TooLongError>;
20}
21
22pub(super) struct LengthMeasurement {
23 len: usize,
24}
25
26impl From<LengthMeasurement> for usize {
27 fn from(len: LengthMeasurement) -> usize {
28 len.len
29 }
30}
31
32impl LengthMeasurement {
33 pub fn zero() -> Self {
34 Self { len: 0 }
35 }
36}
37
38impl Accumulator for LengthMeasurement {
39 fn write_byte(&mut self, _value: u8) -> Result<(), TooLongError> {
40 self.len = self.len.checked_add(1).ok_or_else(err:TooLongError::new)?;
41 Ok(())
42 }
43 fn write_bytes(&mut self, value: &[u8]) -> Result<(), TooLongError> {
44 self.len = self
45 .len
46 .checked_add(value.len())
47 .ok_or_else(err:TooLongError::new)?;
48 Ok(())
49 }
50}
51
52pub(super) struct Writer {
53 bytes: Vec<u8>,
54 requested_capacity: usize,
55}
56
57impl Writer {
58 pub(super) fn with_capacity(capacity: LengthMeasurement) -> Self {
59 Self {
60 bytes: Vec::with_capacity(capacity.len),
61 requested_capacity: capacity.len,
62 }
63 }
64}
65
66impl From<Writer> for Box<[u8]> {
67 fn from(writer: Writer) -> Self {
68 assert_eq!(writer.requested_capacity, writer.bytes.len());
69 writer.bytes.into_boxed_slice()
70 }
71}
72
73impl Accumulator for Writer {
74 fn write_byte(&mut self, value: u8) -> Result<(), TooLongError> {
75 self.bytes.push(value);
76 Ok(())
77 }
78 fn write_bytes(&mut self, value: &[u8]) -> Result<(), TooLongError> {
79 self.bytes.extend(iter:value);
80 Ok(())
81 }
82}
83
84pub fn write_copy(
85 accumulator: &mut dyn Accumulator,
86 to_copy: untrusted::Input,
87) -> Result<(), TooLongError> {
88 accumulator.write_bytes(to_copy.as_slice_less_safe())
89}
90
91pub struct TooLongError(());
92
93impl TooLongError {
94 pub fn new() -> Self {
95 Self(())
96 }
97}
98