1 files changed, 119 insertions, 0 deletions
diff --git a/lib/internal/child_process/serialization.js b/lib/internal/child_process/serialization.js
new file mode 100644
index 0000000000..1381f29926
--- /dev/null
+++ b/lib/internal/child_process/serialization.js
@@ -0,0 +1,119 @@
+'use strict';
+
+const { JSON } = primordials;
+const { Buffer } = require('buffer');
+const { StringDecoder } = require('string_decoder');
+const v8 = require('v8');
+const { isArrayBufferView } = require('internal/util/types');
+const assert = require('internal/assert');
+
+const kMessageBuffer = Symbol('kMessageBuffer');
+const kJSONBuffer = Symbol('kJSONBuffer');
+const kStringDecoder = Symbol('kStringDecoder');
+
+// Extend V8's serializer APIs to give more JSON-like behaviour in
+// some cases; in particular, for native objects this serializes them the same
+// way that JSON does rather than throwing an exception.
+const kArrayBufferViewTag = 0;
+const kNotArrayBufferViewTag = 1;
+class ChildProcessSerializer extends v8.DefaultSerializer {
+  _writeHostObject(object) {
+    if (isArrayBufferView(object)) {
+      this.writeUint32(kArrayBufferViewTag);
+      return super._writeHostObject(object);
+    } else {
+      this.writeUint32(kNotArrayBufferViewTag);
+      this.writeValue({ ...object });
+    }
+  }
+}
+
+class ChildProcessDeserializer extends v8.DefaultDeserializer {
+  _readHostObject() {
+    const tag = this.readUint32();
+    if (tag === kArrayBufferViewTag)
+      return super._readHostObject();
+
+    assert(tag === kNotArrayBufferViewTag);
+    return this.readValue();
+  }
+}
+
+// Messages are parsed in either of the following formats:
+// - Newline-delimited JSON, or
+// - V8-serialized buffers, prefixed with their length as a big endian uint32
+//   (aka 'advanced')
+const advanced = {
+  initMessageChannel(channel) {
+    channel[kMessageBuffer] = Buffer.alloc(0);
+    channel.buffering = false;
+  },
+
+  *parseChannelMessages(channel, readData) {
+    if (readData.length === 0) return;
+
+    let messageBuffer = Buffer.concat([channel[kMessageBuffer], readData]);
+    while (messageBuffer.length > 4) {
+      const size = messageBuffer.readUInt32BE();
+      if (messageBuffer.length < 4 + size) {
+        break;
+      }
+
+      const deserializer = new ChildProcessDeserializer(
+        messageBuffer.subarray(4, 4 + size));
+      messageBuffer = messageBuffer.subarray(4 + size);
+
+      deserializer.readHeader();
+      yield deserializer.readValue();
+    }
+    channel[kMessageBuffer] = messageBuffer;
+    channel.buffering = messageBuffer.length > 0;
+  },
+
+  writeChannelMessage(channel, req, message, handle) {
+    const ser = new ChildProcessSerializer();
+    ser.writeHeader();
+    ser.writeValue(message);
+    const serializedMessage = ser.releaseBuffer();
+    const sizeBuffer = Buffer.allocUnsafe(4);
+    sizeBuffer.writeUInt32BE(serializedMessage.length);
+    return channel.writeBuffer(req, Buffer.concat([
+      sizeBuffer,
+      serializedMessage
+    ]), handle);
+  },
+};
+
+const json = {
+  initMessageChannel(channel) {
+    channel[kJSONBuffer] = '';
+    channel[kStringDecoder] = undefined;
+  },
+
+  *parseChannelMessages(channel, readData) {
+    if (readData.length === 0) return;
+
+    if (channel[kStringDecoder] === undefined)
+      channel[kStringDecoder] = new StringDecoder('utf8');
+    const chunks = channel[kStringDecoder].write(readData).split('\n');
+    const numCompleteChunks = chunks.length - 1;
+    // Last line does not have trailing linebreak
+    const incompleteChunk = chunks[numCompleteChunks];
+    if (numCompleteChunks === 0) {
+      channel[kJSONBuffer] += incompleteChunk;
+    } else {
+      chunks[0] = channel[kJSONBuffer] + chunks[0];
+      for (let i = 0; i < numCompleteChunks; i++)
+        yield JSON.parse(chunks[i]);
+      channel[kJSONBuffer] = incompleteChunk;
+    }
+    channel.buffering = channel[kJSONBuffer].length !== 0;
+  },
+
+  writeChannelMessage(channel, req, message, handle) {
+    const string = JSON.stringify(message) + '\n';
+    return channel.writeUtf8String(req, string, handle);
+  },
+};
+
+module.exports = { advanced, json };