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Merge rust-bitcoin/rust-bitcoin#673: Use iterator in `blockdata::script::Instructions` 

2c28d3b448 Fix handling of empty slice in Instructions (Martin Habovštiak)
e6ff754b73 Fix doc of take_slice_or_kill (Martin Habovštiak)
0ec6d96a7b Cleanup after `Instructions` refactoring (Martin Habovstiak)
bc763259fe Move repeated code to functions in script (Martin Habovstiak)
1f55edf718 Use iterator in `blockdata::script::Instructions` (Martin Habovstiak)

Pull request description:

  This refactors `blockdata::script::Instructions` to use
  `::core::slice::Iter<'a, u8>` instead of `&'a [u8]` to better express
  the intention and to avoid some slicing mistakes. Similarly to a
  previous change this uses a macro to deduplicate the common logic and
  the new `read_uint_iter` internal function to automatically advance the
  iterator.

  Addresses:
  https://github.com/rust-bitcoin/rust-bitcoin/pull/662#pullrequestreview-768320603

ACKs for top commit:
  tcharding:
    ACK 2c28d3b448
  sanket1729:
    ACK 2c28d3b448. I don't want to hold ACKs on minor things as they can be in a fixup later.

Tree-SHA512: 9dc770b9f7958efbd0df2cc2d3546e23deca5df2f94ea2c42b089df628f4b99f08032ca4aa8822caf6643a8892903e1bda41228b78c8519b90bcaa1255d9acc6
This commit is contained in:
sanket1729 2022-04-30 15:25:09 -07:00
parent 9f817982a3 2c28d3b448
commit d5a28fc48f
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GPG Key ID: 648FFB183E0870A2
1 changed files with 70 additions and 87 deletions
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157
src/blockdata/script.rs
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@ -601,7 +601,7 @@ impl Script {
/// To force minimal pushes, use [`Self::instructions_minimal`].
pub fn instructions(&self) -> Instructions {
Instructions {
data: &self.0[..],
data: self.0.iter(),
enforce_minimal: false,
}
}
@ -609,7 +609,7 @@ impl Script {
/// Iterates over the script in the form of `Instruction`s while enforcing minimal pushes.
pub fn instructions_minimal(&self) -> Instructions {
Instructions {
data: &self.0[..],
data: self.0.iter(),
enforce_minimal: true,
}
}
@ -748,114 +748,97 @@ pub enum Instruction<'a> {
/// Iterator over a script returning parsed opcodes.
pub struct Instructions<'a> {
data: &'a [u8],
data: ::core::slice::Iter<'a, u8>,
enforce_minimal: bool,
}
impl<'a> Instructions<'a> {
/// Set the iterator to end so that it won't iterate any longer
fn kill(&mut self) {
let len = self.data.len();
self.data.nth(len.max(1) - 1);
}
/// takes `len` bytes long slice from iterator and returns it advancing iterator
/// if the iterator is not long enough [`Error::EarlyEndOfScript`] is returned and the iterator is killed
/// to avoid returning an infinite stream of errors.
fn take_slice_or_kill(&mut self, len: usize) -> Result<&'a [u8], Error> {
if self.data.len() >= len {
let slice = &self.data.as_slice()[..len];
if len > 0 {
self.data.nth(len - 1);
}
Ok(slice)
} else {
self.kill();
Err(Error::EarlyEndOfScript)
}
}
fn next_push_data_len(&mut self, len: usize, min_push_len: usize) -> Option<Result<Instruction<'a>, Error>> {
let n = match read_uint_iter(&mut self.data, len) {
Ok(n) => n,
// We do exhaustive matching to not forget to handle new variants if we extend
// `UintError` type.
// Overflow actually means early end of script (script is definitely shorter
// than `usize::max_value()`)
Err(UintError::EarlyEndOfScript) | Err(UintError::NumericOverflow) => {
self.kill();
return Some(Err(Error::EarlyEndOfScript));
},
};
if self.enforce_minimal && n < min_push_len {
self.kill();
return Some(Err(Error::NonMinimalPush));
}
Some(self.take_slice_or_kill(n).map(Instruction::PushBytes))
}
}
impl<'a> Iterator for Instructions<'a> {
type Item = Result<Instruction<'a>, Error>;
fn next(&mut self) -> Option<Result<Instruction<'a>, Error>> {
if self.data.is_empty() {
return None;
}
let &byte = self.data.next()?;
// classify parameter does not really matter here since we are only using
// it for pushes and nums
match opcodes::All::from(self.data[0]).classify(opcodes::ClassifyContext::Legacy) {
match opcodes::All::from(byte).classify(opcodes::ClassifyContext::Legacy) {
opcodes::Class::PushBytes(n) => {
// make sure safety argument holds across refactorings
let n: u32 = n;
// casting is safe because we don't support 16-bit architectures
let n = n as usize;
if self.data.len() < n + 1 {
self.data = &[]; // Kill iterator so that it does not return an infinite stream of errors
return Some(Err(Error::EarlyEndOfScript));
}
if self.enforce_minimal {
if n == 1 && (self.data[1] == 0x81 || (self.data[1] > 0 && self.data[1] <= 16)) {
self.data = &[];
return Some(Err(Error::NonMinimalPush));
let op_byte = self.data.as_slice().first();
match (self.enforce_minimal, op_byte, n) {
(true, Some(&op_byte), 1) if op_byte == 0x81 || (op_byte > 0 && op_byte <= 16) => {
self.kill();
Some(Err(Error::NonMinimalPush))
},
(_, None, 0) => {
// the iterator is already empty, may as well use this information to avoid
// whole take_slice_or_kill function
Some(Ok(Instruction::PushBytes(&[])))
},
_ => {
Some(self.take_slice_or_kill(n).map(Instruction::PushBytes))
}
}
let ret = Some(Ok(Instruction::PushBytes(&self.data[1..n+1])));
self.data = &self.data[n + 1..];
ret
}
opcodes::Class::Ordinary(opcodes::Ordinary::OP_PUSHDATA1) => {
if self.data.len() < 2 {
self.data = &[];
return Some(Err(Error::EarlyEndOfScript));
}
let n = match read_uint(&self.data[1..], 1) {
Ok(n) => n,
Err(e) => {
self.data = &[];
return Some(Err(e));
}
};
if self.data.len() < n + 2 {
self.data = &[];
return Some(Err(Error::EarlyEndOfScript));
}
if self.enforce_minimal && n < 76 {
self.data = &[];
return Some(Err(Error::NonMinimalPush));
}
let ret = Some(Ok(Instruction::PushBytes(&self.data[2..n+2])));
self.data = &self.data[n + 2..];
ret
self.next_push_data_len(1, 76)
}
opcodes::Class::Ordinary(opcodes::Ordinary::OP_PUSHDATA2) => {
if self.data.len() < 3 {
self.data = &[];
return Some(Err(Error::EarlyEndOfScript));
}
let n = match read_uint(&self.data[1..], 2) {
Ok(n) => n,
Err(e) => {
self.data = &[];
return Some(Err(e));
}
};
if self.enforce_minimal && n < 0x100 {
self.data = &[];
return Some(Err(Error::NonMinimalPush));
}
if self.data.len() < n + 3 {
self.data = &[];
return Some(Err(Error::EarlyEndOfScript));
}
let ret = Some(Ok(Instruction::PushBytes(&self.data[3..n + 3])));
self.data = &self.data[n + 3..];
ret
self.next_push_data_len(2, 0x100)
}
opcodes::Class::Ordinary(opcodes::Ordinary::OP_PUSHDATA4) => {
if self.data.len() < 5 {
self.data = &[];
return Some(Err(Error::EarlyEndOfScript));
}
let n = match read_uint(&self.data[1..], 4) {
Ok(n) => n,
Err(e) => {
self.data = &[];
return Some(Err(e));
}
};
if self.enforce_minimal && n < 0x10000 {
self.data = &[];
return Some(Err(Error::NonMinimalPush));
}
if self.data.len() < n + 5 {
self.data = &[];
return Some(Err(Error::EarlyEndOfScript));
}
let ret = Some(Ok(Instruction::PushBytes(&self.data[5..n + 5])));
self.data = &self.data[n + 5..];
ret
self.next_push_data_len(4, 0x10000)
}
// Everything else we can push right through
_ => {
let ret = Some(Ok(Instruction::Op(opcodes::All::from(self.data[0]))));
self.data = &self.data[1..];
ret
Some(Ok(Instruction::Op(opcodes::All::from(byte))))
}
}
}