1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82
use std::fmt;
/// A LimitTracker enforces a particular limit within the parser. It keeps
/// track of utilization so that we can report how close to a limit we
/// approached over the lifetime of the tracker.
/// ```rust
/// use apollo_parser::Parser;
///
/// let query = "
/// {
/// animal
/// ...snackSelection
/// ... on Pet {
/// playmates {
/// count
/// }
/// }
/// }
/// ";
/// // Create a new instance of a parser given a query and a
/// // recursion limit
/// let parser = Parser::new(query).recursion_limit(4);
/// // Parse the query, and return a SyntaxTree.
/// let cst = parser.parse();
/// // Retrieve the limits
/// let usage = cst.recursion_limit();
/// // Print out some of the usage details to see what happened during
/// // our parse. `limit` just reports the limit we set, `high` is the
/// // high-water mark of recursion usage.
/// println!("{:?}", usage);
/// println!("{:?}", usage.limit);
/// println!("{:?}", usage.high);
/// // Check that are no errors. These are not part of the CST.
/// assert_eq!(0, cst.errors().len());
///
/// // Get the document root node
/// let doc = cst.document();
/// // ... continue
/// ```
#[derive(PartialEq, Eq, Clone, Copy)]
pub struct LimitTracker {
pub(crate) current: usize,
/// High Water mark for this limit
pub high: usize,
/// Limit.
pub limit: usize,
}
impl LimitTracker {
pub fn new(limit: usize) -> Self {
Self {
current: 0,
high: 0,
limit,
}
}
/// Return whether the limit was reached
#[must_use]
pub fn check_and_increment(&mut self) -> bool {
self.current += 1;
if self.current > self.high {
self.high = self.current;
}
let reached = self.current > self.limit;
if reached {
// Caller is gonna return early, keep increments and decrements balanced:
self.decrement()
}
reached
}
pub fn decrement(&mut self) {
self.current -= 1;
}
}
impl fmt::Debug for LimitTracker {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "recursion limit: {}, high: {}", self.limit, self.high)
}
}