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Introduce parse_with_limits to cap the number of entities. #1

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Merged
jjbayer merged 1 commit into from
Oct 23, 2026
Merged

Introduce parse_with_limits to cap the number of entities. #1

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199 changes: 187 additions & 12 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -634,7 +634,11 @@ enum Version {
Three(Option<NonZeroUsize>),
}

fn event_parser(version: Version, clock: Clock) -> impl Fn(&[u8]) -> IResult<&[u8], Event> {
fn event_parser(
version: Version,
clock: Clock,
limits: &mut Limits,
) -> impl FnMut(&[u8]) -> IResult<&[u8], Event> + '_ {
let clock = match (version, clock) {
(Version::One, _) => Clock::Global,
(Version::Two, Clock::Dual) => Clock::Cpu, // Should be an error but I'm too lazy
Expand Down Expand Up @@ -695,6 +699,8 @@ fn event_parser(version: Version, clock: Clock) -> impl Fn(&[u8]) -> IResult<&[u
}
}

limits.spend_event(input)?;

Ok((
input,
Event {
Expand Down Expand Up @@ -728,7 +734,7 @@ fn parse_section(input: &[u8]) -> IResult<&[u8], Section> {
)(input)
}

fn parse_android_trace(input: &[u8]) -> IResult<&[u8], AndroidTraceLog> {
fn parse_android_trace(input: &[u8], mut limits: Limits) -> IResult<&[u8], AndroidTraceLog> {
use chrono::TimeZone;
let mut ret = AndroidTraceLog {
data_file_overflow: false,
Expand Down Expand Up @@ -807,7 +813,10 @@ fn parse_android_trace(input: &[u8]) -> IResult<&[u8], AndroidTraceLog> {
input = inp;
match line {
Line::NewSection(sect) => section = sect,
Line::Thread(thread) => ret.threads.push(thread),
Line::Thread(thread) => {
limits.spend_thread(input)?;
ret.threads.push(thread);
}
}
}
Section::Methods => {
Expand All @@ -822,7 +831,10 @@ fn parse_android_trace(input: &[u8]) -> IResult<&[u8], AndroidTraceLog> {
input = inp;
match line {
Line::NewSection(sect) => section = sect,
Line::Method(method) => ret.methods.push(method),
Line::Method(method) => {
limits.spend_method(input)?;
ret.methods.push(method);
}
}
}
Section::End => break,
Expand Down Expand Up @@ -880,12 +892,64 @@ fn parse_android_trace(input: &[u8]) -> IResult<&[u8], AndroidTraceLog> {
input
};

let parser = event_parser(bin_version, ret.clock);
let parser = event_parser(bin_version, ret.clock, &mut limits);
let (input, events) = many0(parser)(input)?;
ret.events = events;
Ok((input, ret))
}

struct LimitError<'a>(&'a [u8]);

impl<'a> From<LimitError<'a>> for nom::Err<nom::error::Error<&'a [u8]>> {
fn from(error: LimitError<'a>) -> Self {
Self::Failure(nom::error::Error::new(
error.0,
nom::error::ErrorKind::TooLarge,
))
}
}

/// Defines how many entities a trace log may contain.
pub struct Limits {
pub threads: usize,
pub methods: usize,
pub events: usize,
}

impl Limits {
fn spend_thread<'a>(&mut self, input: &'a [u8]) -> Result<(), LimitError<'a>> {
match self.threads.checked_sub(1) {
None => return Err(LimitError(input)),
Some(new_limit) => self.threads = new_limit,
}
Ok(())
}
fn spend_method<'a>(&mut self, input: &'a [u8]) -> Result<(), LimitError<'a>> {
match self.methods.checked_sub(1) {
None => return Err(LimitError(input)),
Some(new_limit) => self.methods = new_limit,
}
Ok(())
}
fn spend_event<'a>(&mut self, input: &'a [u8]) -> Result<(), LimitError<'a>> {
match self.events.checked_sub(1) {
None => return Err(LimitError(input)),
Some(new_limit) => self.events = new_limit,
}
Ok(())
}
}

impl Default for Limits {
fn default() -> Self {
Self {
threads: usize::MAX,
methods: usize::MAX,
events: usize::MAX,
}
}
}

/// Parse a byte array into an android trace
/// # Example
/// ```
Expand All @@ -910,7 +974,15 @@ fn parse_android_trace(input: &[u8]) -> IResult<&[u8], AndroidTraceLog> {
/// # }
/// ```
pub fn parse(bytes: &[u8]) -> Result<AndroidTraceLog, Box<dyn error::Error + '_>> {
Ok(parse_android_trace(bytes)?.1)
Ok(parse_android_trace(bytes, Limits::default())?.1)
}

/// Like [`parse`], but with [`Limits`] on the number of entities.
pub fn parse_with_limits(
bytes: &[u8],
limits: Limits,
) -> Result<AndroidTraceLog, Box<dyn error::Error + '_>> {
Ok(parse_android_trace(bytes, limits)?.1)
}

#[cfg(test)]
Expand Down Expand Up @@ -1064,7 +1136,8 @@ mod tests {
}
#[test]
fn events() {
let parser1 = event_parser(Version::One, Clock::Global);
let mut limits1 = Limits::default();
let mut parser1 = event_parser(Version::One, Clock::Global, &mut limits1);
assert_eq!(
parser1(b"\x45\x04\x00\x00\x00\x01\x00\x00\x00"),
Ok((
Expand All @@ -1078,7 +1151,8 @@ mod tests {
))
);
assert!(parser1(b"\x45\x03\x00\x00\x00\x01\x00\x00\x00").is_err());
let parser2 = event_parser(Version::Two, Clock::Wall);
let mut limits2 = Limits::default();
let mut parser2 = event_parser(Version::Two, Clock::Wall, &mut limits2);
assert_eq!(
parser2(b"\x39\x05\x09\x00\x00\x00\x01\x00\x00\x00"),
Ok((
Expand All @@ -1094,7 +1168,12 @@ mod tests {
}
))
);
let parser3 = event_parser(Version::Three(NonZeroUsize::new(20)), Clock::Dual);
let mut limits3 = Limits::default();
let mut parser3 = event_parser(
Version::Three(NonZeroUsize::new(20)),
Clock::Dual,
&mut limits3,
);
assert_eq!(
parser3(
b"\xFF\xFF\x02\x00\x00\x00\x10\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00"
Expand All @@ -1116,9 +1195,26 @@ mod tests {
}

#[test]
fn trace_and_event_view() {
fn event_limit_failure_preserves_remaining_input() {
let bytes = b"\x45\x04\x00\x00\x00\x01\x00\x00\x00tail";
let mut limits = Limits {
events: 0,
..Limits::default()
};
let parser = event_parser(Version::One, Clock::Global, &mut limits);

assert_eq!(
many0(parser)(bytes),
Err(nom::Err::Failure(nom::error::Error::new(
&bytes[9..],
nom::error::ErrorKind::TooLarge,
)))
);
}

fn example_trace() -> AndroidTraceLog {
let now = chrono::Utc::now();
let trace = AndroidTraceLog {
AndroidTraceLog {
data_file_overflow: true,
clock: Clock::Dual,
elapsed_time: Duration::from_secs(10),
Expand Down Expand Up @@ -1200,8 +1296,12 @@ mod tests {
action: Action::Unwind,
},
],
};
}
}

#[test]
fn trace_and_event_view() {
let trace = example_trace();
let mut iter = trace.iter();
let view = iter.next().unwrap();
assert_eq!(
Expand Down Expand Up @@ -1246,6 +1346,81 @@ mod tests {
assert_eq!(trace, trace2);
}

#[test]
fn exceeded_trace_limits_are_failures() {
let trace = example_trace();
let bytes = trace.serialize().unwrap();
for (entity, limits) in [
(
"threads",
Limits {
threads: trace.threads.len() - 1,
..Limits::default()
},
),
(
"methods",
Limits {
methods: trace.methods.len() - 1,
..Limits::default()
},
),
(
"events",
Limits {
events: trace.events.len() - 1,
..Limits::default()
},
),
] {
let result = parse_android_trace(&bytes, limits);
assert!(
matches!(
result,
Err(nom::Err::Failure(nom::error::Error {
code: nom::error::ErrorKind::TooLarge,
..
}))
),
"expected a limit failure for {entity}, got {result:?}"
);
}
}

#[test]
fn exact_trace_limits_succeed() {
let trace = example_trace();
let bytes = trace.serialize().unwrap();
let limits = Limits {
threads: trace.threads.len(),
methods: trace.methods.len(),
events: trace.events.len(),
};

let (remaining, parsed) = parse_android_trace(&bytes, limits).unwrap();
assert!(remaining.is_empty());
assert_eq!(parsed, trace);
}

#[test]
fn zero_limits_allow_an_empty_trace() {
let mut trace = example_trace();
trace.threads.clear();
trace.methods.clear();
trace.events.clear();
trace.total_method_calls = 0;
let bytes = trace.serialize().unwrap();
let limits = Limits {
threads: 0,
methods: 0,
events: 0,
};

let (remaining, parsed) = parse_android_trace(&bytes, limits).unwrap();
assert!(remaining.is_empty());
assert_eq!(parsed, trace);
}

#[test]
fn invalid_start_time_does_not_panic() {
let trace = AndroidTraceLog {
Expand Down
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