Merge pull request #63 from Mark-Simulacrum/direct-write
Directly write to output instead of local String buffer
diff --git a/src/lib.rs b/src/lib.rs
index 7eb1c42..cafec2f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -146,19 +146,24 @@
}
#[cfg(feature = "std")]
-fn demangle_line(line: &str, include_hash: bool) -> std::borrow::Cow<str> {
- let mut line = std::borrow::Cow::Borrowed(line);
+fn demangle_line(
+ line: &str,
+ output: &mut impl std::io::Write,
+ include_hash: bool,
+) -> std::io::Result<()> {
let mut head = 0;
- loop {
+ while head < line.len() {
// Move to the next potential match
- head = match (line[head..].find("_ZN"), line[head..].find("_R")) {
+ let next_head = match (line[head..].find("_ZN"), line[head..].find("_R")) {
(Some(idx), None) | (None, Some(idx)) => head + idx,
(Some(idx1), Some(idx2)) => head + idx1.min(idx2),
(None, None) => {
- // No more matches, we can return our line.
- return line;
+ // No more matches...
+ line.len()
}
};
+ output.write_all(line[head..next_head].as_bytes())?;
+ head = next_head;
// Find the non-matching character.
//
// If we do not find a character, then until the end of the line is the
@@ -169,29 +174,26 @@
.unwrap_or(line.len());
let mangled = &line[head..match_end];
+ head = head + mangled.len();
if let Ok(demangled) = try_demangle(mangled) {
- let demangled = if include_hash {
- format!("{}", demangled)
+ if include_hash {
+ write!(output, "{}", demangled)?;
} else {
- format!("{:#}", demangled)
- };
- line.to_mut().replace_range(head..match_end, &demangled);
- // Start again after the replacement.
- head = head + demangled.len();
+ write!(output, "{:#}", demangled)?;
+ }
} else {
- // Skip over the full symbol. We don't try to find a partial Rust symbol in the wider
- // matched text today.
- head = head + mangled.len();
+ output.write_all(mangled.as_bytes())?;
}
}
+ Ok(())
}
/// Process a stream of data from `input` into the provided `output`, demangling any symbols found
/// within.
///
-/// This currently is implemented by buffering each line of input in memory, but that may be
-/// changed in the future. Symbols never cross line boundaries so this is just an implementation
-/// detail.
+/// Note that the underlying implementation will perform many relatively small writes to the
+/// output. If the output is expensive to write to (e.g., requires syscalls), consider using
+/// `std::io::BufWriter`.
#[cfg(feature = "std")]
#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
pub fn demangle_stream<R: std::io::BufRead, W: std::io::Write>(
@@ -206,8 +208,7 @@
// trailing data during demangling. In the future we might directly stream to the output but at
// least right now that seems to be less efficient.
while input.read_line(&mut buf)? > 0 {
- let demangled_line = demangle_line(&buf, include_hash);
- output.write_all(demangled_line.as_bytes())?;
+ demangle_line(&buf, output, include_hash)?;
buf.clear();
}
Ok(())
@@ -560,11 +561,18 @@
);
}
+ #[cfg(feature = "std")]
+ fn demangle_str(input: &str) -> String {
+ let mut output = Vec::new();
+ super::demangle_line(input, &mut output, false);
+ String::from_utf8(output).unwrap()
+ }
+
#[test]
#[cfg(feature = "std")]
fn find_multiple() {
assert_eq!(
- super::demangle_line("_ZN3fooE.llvm moocow _ZN3fooE.llvm", false),
+ demangle_str("_ZN3fooE.llvm moocow _ZN3fooE.llvm"),
"foo.llvm moocow foo.llvm"
);
}
@@ -573,7 +581,7 @@
#[cfg(feature = "std")]
fn interleaved_new_legacy() {
assert_eq!(
- super::demangle_line("_ZN3fooE.llvm moocow _RNvMNtNtNtNtCs8a2262Dv4r_3mio3sys4unix8selector5epollNtB2_8Selector6select _ZN3fooE.llvm", false),
+ demangle_str("_ZN3fooE.llvm moocow _RNvMNtNtNtNtCs8a2262Dv4r_3mio3sys4unix8selector5epollNtB2_8Selector6select _ZN3fooE.llvm"),
"foo.llvm moocow <mio::sys::unix::selector::epoll::Selector>::select foo.llvm"
);
}
