Skip to content

Commit

Permalink
perf(sourcemap): avoid copying sources
Browse files Browse the repository at this point in the history
  • Loading branch information
@overlookmotel
overlookmotel committed Jul 29, 2024
1 parent 94c2cc6 commit 0ae5a70
Showing 1 changed file with 163 additions and 24 deletions.
187 changes: 163 additions & 24 deletions crates/oxc_sourcemap/src/encode.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -48,10 +48,10 @@ pub fn encode_to_string(sourcemap: &SourceMap) -> String {
}

contents.push("\"names\":[".into());
contents.push_list(sourcemap.names.iter().map(escape_json_string));
contents.push_list(sourcemap.names.iter(), escape_json_string);

contents.push("],\"sources\":[".into());
contents.push_list(sourcemap.sources.iter().map(escape_json_string));
contents.push_list(sourcemap.sources.iter(), escape_json_string);

// Quote `source_content` in parallel
if let Some(source_contents) = &sourcemap.source_contents {
Expand All @@ -60,27 +60,32 @@ pub fn encode_to_string(sourcemap: &SourceMap) -> String {
if #[cfg(feature = "concurrent")] {
let quoted_source_contents: Vec<_> = source_contents
.par_iter()
.map(escape_json_string)
.map(|source| {
let mut thread_contents = PreAllocatedString::new(source.len());
escape_json_string(source, &mut thread_contents);
thread_contents
})
.collect();
contents.push_list(quoted_source_contents.into_iter());
contents.push_list(quoted_source_contents.into_iter(), |thread_contents, contents| {
contents.extend_from(thread_contents);
});
} else {
contents.push_list(source_contents.iter().map(escape_json_string));
contents.push_list(source_contents.iter(), escape_json_string);
}
};
}

if let Some(x_google_ignore_list) = &sourcemap.x_google_ignore_list {
contents.push("],\"x_google_ignoreList\":[".into());
contents.push_list(x_google_ignore_list.iter().map(ToString::to_string));
contents.push_list(x_google_ignore_list.iter(), |n, contents| {
contents.push(Cow::Owned(n.to_string()));
});
}

contents.push("],\"mappings\":\"".into());
contents.push(serialize_sourcemap_mappings(sourcemap).into());
contents.push("\"}".into());

// Check we calculated number of segments required correctly
debug_assert!(contents.num_segments() <= max_segments);

contents.consume()
}

Expand Down Expand Up @@ -208,41 +213,171 @@ impl<'a> PreAllocatedString<'a> {
}

#[inline]
fn push_list<I>(&mut self, mut iter: I)
fn push_list<S, I, P>(&mut self, mut iter: I, pusher: P)
where
I: Iterator<Item = String>,
I: Iterator<Item = S>,
P: Fn(S, &mut Self) -> (),
{
let Some(first) = iter.next() else {
return;
};
self.push(Cow::Owned(first));
pusher(first, self);

for other in iter {
self.push(Cow::Borrowed(","));
self.push(Cow::Owned(other));
pusher(other, self);
}
}

#[allow(dead_code)] // Only used when `concurrent` mode enabled
fn extend_from(&mut self, mut other: Self) {
self.buf.extend(other.buf.drain(..));
}

#[inline]
fn consume(self) -> String {
let mut buf = String::with_capacity(self.len);
buf.extend(self.buf);
buf
}
}

fn num_segments(&self) -> usize {
self.buf.len()
}
#[derive(Clone, Copy, PartialEq)]
#[repr(u8)]
enum EscapeCode {
None = 0,
Z0 = 1,
Z1 = 2,
Z2 = 3,
Z3 = 4,
Z4 = 5,
Z5 = 6,
Z6 = 7,
Z7 = 8,
BB = 9,
TT = 10,
NN = 11,
ZB = 12,
FF = 13,
RR = 14,
ZE = 15,
ZF = 16,
S0 = 17,
S1 = 18,
S2 = 19,
S3 = 20,
S4 = 21,
S5 = 22,
S6 = 23,
S7 = 24,
S8 = 25,
S9 = 26,
SA = 27,
SB = 28,
SC = 29,
SD = 30,
SE = 31,
SF = 32,
QU = 33,
BS = 34,
}

fn escape_json_string<S: AsRef<str>>(s: S) -> String {
// Lookup table of escape sequences. A value of b'x' at index i means that byte
// i is escaped as "\x" in JSON. A value of 0 means that byte i is not escaped.
static ESCAPE_TABLE: [EscapeCode; 256] = {
use EscapeCode::*;
let __ = EscapeCode::None;
[
// 1 2 3 4 5 6 7 8 9 A B C D E F
Z0, Z1, Z2, Z3, Z4, Z5, Z6, Z7, BB, TT, NN, ZB, FF, RR, ZE, ZF, // 0
S0, S1, S2, S3, S4, S5, S6, S7, S8, S9, SA, SB, SC, SD, SE, SF, // 1
__, __, QU, __, __, __, __, __, __, __, __, __, __, __, __, __, // 2
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 3
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 4
__, __, __, __, __, __, __, __, __, __, __, __, BS, __, __, __, // 5
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 6
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 7
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 8
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 9
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // A
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // B
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // C
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // D
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // E
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // F
]
};

static ESCAPES: [&'static str; 35] = [
"", // Not used
"\\u0000", // \x00
"\\u0001", // \x01
"\\u0002", // \x02
"\\u0003", // \x03
"\\u0004", // \x04
"\\u0005", // \x05
"\\u0006", // \x06
"\\u0007", // \x07
"\\b", // \x08
"\\t", // \x09
"\\n", // \x0A
"\\u000b", // \x0B
"\\f", // \x0C
"\\r", // \x0D
"\\u000e", // \x0E
"\\u000f", // \x0F
"\\u0010", // \x10
"\\u0011", // \x11
"\\u0012", // \x12
"\\u0013", // \x13
"\\u0014", // \x14
"\\u0015", // \x15
"\\u0016", // \x16
"\\u0017", // \x17
"\\u0018", // \x18
"\\u0019", // \x19
"\\u001a", // \x1A
"\\u001b", // \x1B
"\\u001c", // \x1C
"\\u001d", // \x1D
"\\u001e", // \x1E
"\\u001f", // \x1F
"\\\"", // \x22
"\\\\", // \x5C
];

fn escape_json_string<'a, S: AsRef<str>>(s: S, contents: &mut PreAllocatedString<'a>) {
contents.push(Cow::Borrowed("\""));

let s = s.as_ref();
let mut escaped_buf = Vec::with_capacity(s.len() * 2 + 2);
// This call is infallible as only error it can return is if the writer errors.
// Writing to a `Vec<u8>` is infallible, so that's not possible here.
serde::Serialize::serialize(s, &mut serde_json::Serializer::new(&mut escaped_buf)).unwrap();
// Safety: `escaped_buf` is valid utf8.
unsafe { String::from_utf8_unchecked(escaped_buf) }
// Extend lifetime of `s`.
// SAFETY: This is safe, because all strings are owned by `SourceMap` and live until after
// `PreAllocatedString` is dropped.
// TODO: Sort out lifetimes to make this work properly without `unsafe`.
let s: &'a str = unsafe { std::mem::transmute(s) };

let bytes = s.as_bytes();
let mut start = 0;
for (i, &byte) in bytes.iter().enumerate() {
let escape = ESCAPE_TABLE[byte as usize];
if escape == EscapeCode::None {
continue;
}

if start < i {
contents.push(Cow::Borrowed(&s[start..i]));
}

contents.push(Cow::Borrowed(ESCAPES[escape as usize]));

start = i + 1;
}

if start < bytes.len() {
contents.push(Cow::Borrowed(&s[start..]));
}

contents.push(Cow::Borrowed("\""));
}

#[test]
Expand All @@ -265,7 +400,11 @@ fn test_escape_json_string() {
for (c, expected) in FIXTURES {
let mut input = String::new();
input.push(*c);
assert_eq!(escape_json_string(input), *expected);
let mut contents = PreAllocatedString::new(0);
escape_json_string(&input, &mut contents);
let encoded = contents.consume();
let _ = input; // Keep `input` alive until after `contents` consumed
assert_eq!(encoded, *expected);
}
}

Expand Down

0 comments on commit 0ae5a70

Please sign in to comment.