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Add details about max_count to read_list docstring

This commit is contained in:
Deirdre Connolly 2019-10-09 22:12:03 -04:00 committed by Deirdre Connolly
parent 4ec7590b42
commit e1f2eaa446
1 changed files with 10 additions and 9 deletions
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19
zebra-chain/src/serialization.rs
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@ -245,7 +245,16 @@ pub trait ReadZcashExt: io::Read {
Ok(bytes)
}
/// Convenience method to read a `Vec<T>` with a leading count in a safer manner.
/// Convenience method to read a `Vec<T>` with a leading count in
/// a safer manner.
///
/// This method preallocates a buffer, performing a single
/// allocation in the honest case. It's possible for someone to
/// send a short message with a large count field, so if we
/// naively trust the count field we could be tricked into
/// preallocating a large buffer. Instead, we rely on the passed
/// maximum count for a valid message and select the min of the
/// two values.
#[inline]
fn read_list<T: ZcashDeserialize>(
&mut self,
@ -258,14 +267,6 @@ pub trait ReadZcashExt: io::Read {
let count = self2.read_compactsize()? as usize;
// Preallocate a buffer, performing a single allocation in the
// honest case. Although the size of the received data buffer
// is bounded by the codec's max_len field, it's still
// possible for someone to send a short message with a large
// count field, so if we naively trust the count field we
// could be tricked into preallocating a large
// buffer. Instead, calculate the maximum count for a valid
// message from the codec's max_len using encoded_type_size.
let mut items = Vec::with_capacity(std::cmp::min(count, max_count));
for _ in 0..count {