feat: Added parseWithError.

README.md

@@ -78,6 +78,8 @@ milo.setActiveCallbacks(parser, milo.CALLBACK_ACTIVE_ON_DATA)
 buffer.set(message, 0)
 milo.parse(parser, ptr, message.length)
 
+// Use milo.parseWithError to get the consumed characters plus an error flag in a single call.
+
 // Cleanup used resources.
 milo.destroy(parser)
 milo.dealloc(ptr, message.length)

docs/js.md

@@ -135,6 +135,23 @@ Parses `data` up to `limit` characters.
 
 It returns the number of consumed characters.
 
+#### `parseWithError(parser, data, limit)`
+
+Parses `data` up to `limit` characters.
+
+It returns an object containing the number of consumed characters and whether the parser errored:
+
+```javascript
+{
+  consumed: 0,
+  errored: false
+}
+```
+
+Internally this wraps the `parse_with_error` WebAssembly export, which returns a signed 32-bit integer: `consumed` on success, and `-(consumed + 1)` on error. The extra `+ 1` allows representing errors that happen after consuming zero bytes.
+
+Since the raw return value is a signed 32-bit integer, `parseWithError` supports up to `2_147_483_646` consumed bytes per call when an error is reported.
+
 #### `reset(parser)`
 
 Resets a parser. The second parameters specifies if to also reset the

parser/src/wasm.rs

@@ -70,6 +70,20 @@ pub fn parse(parser: *mut c_void, data: *const c_uchar, limit: usize) -> usize {
   unsafe { (*(parser as *mut Parser)).parse(data, limit) }
 }
 
+/// Parses a slice of characters. It returns consumed bytes, or -(consumed + 1)
+/// if the parser errored.
+#[unsafe(no_mangle)]
+pub fn parse_with_error(parser: *mut c_void, data: *const c_uchar, limit: usize) -> i32 {
+  let parser = unsafe { &mut *(parser as *mut Parser) };
+  let consumed = parser.parse(data, limit) as i32;
+
+  if parser.error_code == crate::ERROR_NONE {
+    consumed
+  } else {
+    -(consumed + 1)
+  }
+}
+
 /// Pauses the parser. It will have to be resumed via `resume`.
 #[unsafe(no_mangle)]
 pub fn pause(parser: *mut c_void) { unsafe { (*(parser as *mut Parser)).pause() } }

parser/src/wasm/template.js

@@ -30,6 +30,16 @@ function parse (parser, data, limit) {
   return this.parse(parser, data, limit) >>> 0
 }
 
+function parseWithError (parser, data, limit) {
+  const result = this.parse_with_error(parser, data, limit) | 0
+  const errored = result < 0
+
+  return {
+    consumed: errored ? -result - 1 : result,
+    errored
+  }
+}
+
 function fail (parser, code, description) {
   const len = description.length
   const ptr = this.alloc(len)
@@ -102,6 +112,7 @@ export function setup (env = {}) {
     create: create.bind(wasm),
     destroy: destroy.bind(wasm),
     parse: parse.bind(wasm),
+    parseWithError: parseWithError.bind(wasm),
     fail: fail.bind(wasm),
     hasDebug: hasDebug.bind(wasm),
     clear: wasm.clear,