make scrammaps work (in rust)

rewriter/Cargo.lock

@@ -233,6 +233,12 @@ version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"
 
+[[package]]
+name = "bytes"
+version = "1.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d71b6127be86fdcfddb610f7182ac57211d4b18a3e9c82eb2d17662f2227ad6a"
+
 [[package]]
 name = "cast"
 version = "0.3.0"
@@ -768,6 +774,7 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "boa_engine",
+ "bytes",
  "criterion",
  "oxc",
  "rewriter",

rewriter/native/Cargo.toml

@@ -8,6 +8,7 @@ workspace = true
 
 [dependencies]
 anyhow = "1.0.97"
+bytes = "1.10.1"
 oxc = { workspace = true }
 rewriter = { version = "0.1.0", path = "../rewriter" }
 url = "2.5.4"

rewriter/native/src/main.rs

@@ -1,6 +1,7 @@
 use std::{env, fs, str::FromStr, sync::Arc};
 
 use anyhow::{Context, Result};
+use bytes::{Buf, Bytes, BytesMut};
 use oxc::diagnostics::NamedSource;
 use rewriter::{cfg::Config, rewrite, RewriteResult};
 use url::Url;
@@ -38,6 +39,64 @@ fn dorewrite(data: &str) -> Result<RewriteResult> {
 	.context("failed to rewrite file")
 }
 
+#[derive(Debug)]
+enum RewriteType {
+	Insert { pos: u32, size: u32 },
+	Replace { start: u32, end: u32, str: Bytes },
+}
+
+fn dounrewrite(res: RewriteResult) -> Vec<u8> {
+	let js = res.js.as_slice();
+	let mut map = Bytes::from(res.sourcemap);
+	let rewrite_cnt = map.get_u32_le();
+	let mut rewrites = Vec::with_capacity(rewrite_cnt as usize);
+
+	for x in 0..rewrite_cnt {
+		let ty = map.get_u8();
+		if ty == 0 {
+			rewrites.push(RewriteType::Insert {
+				pos: map.get_u32_le(),
+				size: map.get_u32_le(),
+			});
+		} else if ty == 1 {
+			let len = map.get_u32_le();
+			rewrites.push(RewriteType::Replace {
+				start: map.get_u32_le(),
+				end: map.get_u32_le(),
+				str: map.split_to(len as usize),
+			});
+		} else {
+			panic!(
+				"{x} {ty} {:X?} {:#?}",
+				map.slice(0..10).as_ref(),
+				&rewrites.last_chunk::<3>()
+			)
+		}
+	}
+
+	let mut out = BytesMut::with_capacity(res.js.len());
+
+	let mut lastpos: u32 = 0;
+
+	for rewrite in rewrites {
+		match rewrite {
+			RewriteType::Insert { pos, size } => {
+				out.extend_from_slice(&js[lastpos as usize..pos as usize]);
+				lastpos = pos + size;
+			}
+			RewriteType::Replace { start, end, str } => {
+				out.extend_from_slice(&js[lastpos as usize..start as usize]);
+				out.extend_from_slice(&str);
+				lastpos = end;
+			}
+		}
+	}
+
+	out.extend_from_slice(&js[lastpos as usize..]);
+
+	out.to_vec()
+}
+
 fn main() -> Result<()> {
 	let file = env::args().nth(1).unwrap_or_else(|| "test.js".to_string());
 	let data = fs::read_to_string(file).context("failed to read file")?;
@@ -49,23 +108,33 @@ fn main() -> Result<()> {
 			let _ = dorewrite(&data);
 			i += 1;
 			if i % 100 == 0 {
-				println!("{}...", i);
+				println!("{i}...");
 			}
 		}
 	} else {
+		println!("orig:\n{data}");
+
 		let res = dorewrite(&data)?;
 
 		let source = Arc::new(
-			NamedSource::new(data, "https://google.com/glorngle/si.js").with_language("javascript"),
+			NamedSource::new(data.clone(), "https://google.com/glorngle/si.js")
+				.with_language("javascript"),
 		);
 		eprintln!("errors:");
-		for err in res.errors {
+		for err in res.errors.clone() {
 			eprintln!("{}", err.with_source_code(source.clone()));
 		}
 
 		println!(
 			"rewritten:\n{}",
-			String::from_utf8(res.js).context("failed to parse rewritten js")?
+			str::from_utf8(&res.js).context("failed to parse rewritten js")?
+		);
+
+		let unrewritten = dounrewrite(res);
+
+		println!(
+			"unrewritten matches orig: {}",
+			data.as_bytes() == unrewritten.as_slice()
 		);
 	}
 

rewriter/rewriter/src/changes.rs

@@ -416,6 +416,7 @@ impl JsChanges {
 		E: Clone,
 	{
 		let mut offset = 0;
+		let mut added = 0i64;
 		let mut buffer = Vec::with_capacity(js.len() * 2);
 
 		macro_rules! tryget {
@@ -427,10 +428,14 @@ impl JsChanges {
 		macro_rules! eval {
 			($change:expr) => {
 				match $change {
-					Change::Str(x) => buffer.extend_from_slice(x.as_bytes()),
+					Change::Str(x) => {
+						buffer.extend_from_slice(x.as_bytes());
+						x.len()
+					}
 					Change::Number(x) => {
 						let x = format_compact_str!("{}", x);
 						buffer.extend_from_slice(x.as_bytes());
+						x.len()
 					}
 				}
 			};
@@ -439,7 +444,7 @@ impl JsChanges {
 		let mut map = Vec::with_capacity(js.len() * 2);
 		map.extend_from_slice(&(self.inner.len() as u32).to_le_bytes());
 
-		self.inner.sort_unstable();
+		self.inner.sort();
 
 		for change in &self.inner {
 			let span = change.get_span();
@@ -450,37 +455,47 @@ impl JsChanges {
 
 			match change.to_inner(cfg, offset) {
 				JsChangeInner::Insert { loc, str } => {
-					// INSERT op
-					map.push(0);
-					// offset
-					map.extend_from_slice(&(offset as u32).to_le_bytes());
-					// start
-					map.extend_from_slice(&loc.to_le_bytes());
-					// size
-					map.extend_from_slice(&(str.len() as u32).to_le_bytes());
-
+					let mut len = 0u32;
 					let loc = loc as usize;
 					buffer.extend_from_slice(tryget!(start..loc).as_bytes());
-					for str in str {
-						eval!(str);
+					for str in &str {
+						len += eval!(str) as u32;
 					}
 					buffer.extend_from_slice(tryget!(loc..end).as_bytes());
+
+					// INSERT op
+					map.push(0);
+					// pos
+					map.extend_from_slice(
+						&((loc as u32).wrapping_add_signed(added as i32)).to_le_bytes(),
+					);
+					// size
+					map.extend_from_slice(&len.to_le_bytes());
+
+					added += len as i64;
 				}
 				JsChangeInner::Replace { str } => {
+					let mut len = 0u32;
+					for str in &str {
+						len += eval!(str) as u32;
+					}
+
 					// REPLACE op
 					map.push(1);
-					// offset
-					map.extend_from_slice(&(offset as u32).to_le_bytes());
+					// len
+					map.extend_from_slice(&(span.end - span.start).to_le_bytes());
 					// start
-					map.extend_from_slice(&span.start.to_le_bytes());
+					map.extend_from_slice(
+						&(span.start.wrapping_add_signed(added as i32)).to_le_bytes(),
+					);
 					// end
-					map.extend_from_slice(&span.end.to_le_bytes());
+					map.extend_from_slice(
+						&((span.start + len).wrapping_add_signed(added as i32)).to_le_bytes(),
+					);
 					// oldstr
 					map.extend_from_slice(tryget!(start..end).as_bytes());
 
-					for str in str {
-						eval!(str);
-					}
+					added += len as i64 - (span.end - span.start) as i64;
 				}
 			}