perf(ext/web): Add fast path for non-streaming TextDecoder (#14217)

Co-authored-by: Divy Srivastava <dj.srivastava23@gmail.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/ext/web/lib.rs b/ext/web/lib.rs
index 0d57bf10e..ae5cf2d80 100644
--- a/ext/web/lib.rs
+++ b/ext/web/lib.rs
@@ -90,6 +90,7 @@ pub fn init<P: TimersPermission + 'static>(
       op_base64_atob::decl(),
       op_base64_btoa::decl(),
       op_encoding_normalize_label::decl(),
+      op_encoding_decode_single::decl(),
       op_encoding_new_decoder::decl(),
       op_encoding_decode::decl(),
       op_encoding_encode_into::decl(),
@@ -216,6 +217,64 @@ fn op_encoding_normalize_label(label: String) -> Result<String, AnyError> {
 }
 
 #[op]
+fn op_encoding_decode_single(
+  data: ZeroCopyBuf,
+  options: DecoderOptions,
+) -> Result<U16String, AnyError> {
+  let DecoderOptions {
+    label,
+    ignore_bom,
+    fatal,
+  } = options;
+
+  let encoding = Encoding::for_label(label.as_bytes()).ok_or_else(|| {
+    range_error(format!(
+      "The encoding label provided ('{}') is invalid.",
+      label
+    ))
+  })?;
+
+  let mut decoder = if ignore_bom {
+    encoding.new_decoder_without_bom_handling()
+  } else {
+    encoding.new_decoder_with_bom_removal()
+  };
+
+  let max_buffer_length = decoder
+    .max_utf16_buffer_length(data.len())
+    .ok_or_else(|| range_error("Value too large to decode."))?;
+
+  let mut output = vec![0; max_buffer_length];
+
+  if fatal {
+    let (result, _, written) =
+      decoder.decode_to_utf16_without_replacement(&data, &mut output, true);
+    match result {
+      DecoderResult::InputEmpty => {
+        output.truncate(written);
+        Ok(output.into())
+      }
+      DecoderResult::OutputFull => {
+        Err(range_error("Provided buffer too small."))
+      }
+      DecoderResult::Malformed(_, _) => {
+        Err(type_error("The encoded data is not valid."))
+      }
+    }
+  } else {
+    let (result, _, written, _) =
+      decoder.decode_to_utf16(&data, &mut output, true);
+    match result {
+      CoderResult::InputEmpty => {
+        output.truncate(written);
+        Ok(output.into())
+      }
+      CoderResult::OutputFull => Err(range_error("Provided buffer too small.")),
+    }
+  }
+}
+
+#[op]
 fn op_encoding_new_decoder(
   state: &mut OpState,
   options: DecoderOptions,