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use std::collections::{hash_map::DefaultHasher, HashMap, HashSet};
use std::fmt;
use std::hash::{Hash, Hasher};
use super::{Backtrace, Symbol, SymbolTrace, Trace};
/// An adjacency list representation of an execution tree.
///
/// This tree provides a convenient intermediate representation for formatting
/// [`Trace`] as a tree.
pub(super) struct Tree {
/// The roots of the trees.
///
/// There should only be one root, but the code is robust to multiple roots.
roots: HashSet<Symbol>,
/// The adjacency list of symbols in the execution tree(s).
edges: HashMap<Symbol, HashSet<Symbol>>,
}
impl Tree {
/// Constructs a [`Tree`] from [`Trace`]
pub(super) fn from_trace(trace: Trace) -> Self {
let mut roots: HashSet<Symbol> = HashSet::default();
let mut edges: HashMap<Symbol, HashSet<Symbol>> = HashMap::default();
for trace in trace.backtraces {
let trace = to_symboltrace(trace);
if let Some(first) = trace.first() {
roots.insert(first.to_owned());
}
let mut trace = trace.into_iter().peekable();
while let Some(frame) = trace.next() {
let subframes = edges.entry(frame).or_default();
if let Some(subframe) = trace.peek() {
subframes.insert(subframe.clone());
}
}
}
Tree { roots, edges }
}
/// Produces the sub-symbols of a given symbol.
fn consequences(&self, frame: &Symbol) -> Option<impl ExactSizeIterator<Item = &Symbol>> {
Some(self.edges.get(frame)?.iter())
}
/// Format this [`Tree`] as a textual tree.
fn display<W: fmt::Write>(
&self,
f: &mut W,
root: &Symbol,
is_last: bool,
prefix: &str,
) -> fmt::Result {
let root_fmt = format!("{}", root);
let current;
let next;
if is_last {
current = format!("{prefix}└╼\u{a0}{root_fmt}");
next = format!("{}\u{a0}\u{a0}\u{a0}", prefix);
} else {
current = format!("{prefix}├╼\u{a0}{root_fmt}");
next = format!("{}│\u{a0}\u{a0}", prefix);
}
write!(f, "{}", {
let mut current = current.chars();
current.next().unwrap();
current.next().unwrap();
¤t.as_str()
})?;
if let Some(consequences) = self.consequences(root) {
let len = consequences.len();
for (i, consequence) in consequences.enumerate() {
let is_last = i == len - 1;
writeln!(f)?;
self.display(f, consequence, is_last, &next)?;
}
}
Ok(())
}
}
impl fmt::Display for Tree {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
for root in &self.roots {
self.display(f, root, true, " ")?;
}
Ok(())
}
}
/// Resolve a sequence of [`backtrace::BacktraceFrame`]s into a sequence of
/// [`Symbol`]s.
fn to_symboltrace(backtrace: Backtrace) -> SymbolTrace {
// Resolve the backtrace frames to symbols.
let backtrace: Backtrace = {
let mut backtrace = backtrace::Backtrace::from(backtrace);
backtrace.resolve();
backtrace.into()
};
// Accumulate the symbols in descending order into `symboltrace`.
let mut symboltrace: SymbolTrace = vec![];
let mut state = DefaultHasher::new();
for frame in backtrace.into_iter().rev() {
for symbol in frame.symbols().iter().rev() {
let symbol = Symbol {
symbol: symbol.clone(),
parent_hash: state.finish(),
};
symbol.hash(&mut state);
symboltrace.push(symbol);
}
}
symboltrace
}