1 files changed, 46 insertions, 0 deletions
diff --git a/dom/midi/MIDILog.cpp b/dom/midi/MIDILog.cpp
new file mode 100644
index 0000000000..cc9945ed58
--- /dev/null
+++ b/dom/midi/MIDILog.cpp
@@ -0,0 +1,46 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MIDILog.h"
+
+#include "mozilla/dom/MIDITypes.h"
+#include "mozilla/dom/MIDIPortBinding.h"
+
+mozilla::LazyLogModule gWebMIDILog("WebMIDI");
+
+void LogMIDIMessage(const mozilla::dom::MIDIMessage& aMessage,
+                    const nsAString& aPortId,
+                    mozilla::dom::MIDIPortType aDirection) {
+  if (MOZ_LOG_TEST(gWebMIDILog, mozilla::LogLevel::Debug)) {
+    if (MOZ_LOG_TEST(gWebMIDILog, mozilla::LogLevel::Verbose)) {
+      uint32_t byteCount = aMessage.data().Length();
+      nsAutoCString logMessage;
+      // Log long messages inline with the timestamp and the length, log
+      // longer messages a bit like xxd
+      logMessage.AppendPrintf(
+          "%s %s length=%u", NS_ConvertUTF16toUTF8(aPortId).get(),
+          aDirection == mozilla::dom::MIDIPortType::Input ? "->" : "<-",
+          byteCount);
+
+      if (byteCount <= 3) {
+        logMessage.AppendPrintf(" [");
+        // Regular messages
+        for (uint32_t i = 0; i < byteCount - 1; i++) {
+          logMessage.AppendPrintf("%x ", aMessage.data()[i]);
+        }
+        logMessage.AppendPrintf("%x]", aMessage.data()[byteCount - 1]);
+      } else {
+        // Longer messages
+        for (uint32_t i = 0; i < byteCount; i++) {
+          if (!(i % 8)) {
+            logMessage.AppendPrintf("\n%08u:\t", i);
+          }
+          logMessage.AppendPrintf("%x ", aMessage.data()[i]);
+        }
+      }
+      MOZ_LOG(gWebMIDILog, mozilla::LogLevel::Verbose,
+              ("%s", logMessage.get()));
+    }
+  }
+}