From dd9eb4b049edf3111486875c20cc55e9c0ad2229 Mon Sep 17 00:00:00 2001
From: Volker Berlin <volker.berlin@googlemail.com>
Date: Mon, 1 Apr 2019 16:17:41 +0200
Subject: [PATCH] write sourceMappingURL custom section

---
 .../binary/BinaryModuleWriter.java            | 21 +++++++++++++++++++
 .../jwebassembly/module/WasmTarget.java       | 13 ++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java b/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
index a079405..60e3a1c 100644
--- a/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
+++ b/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
@@ -125,6 +125,7 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
         writeExportSection();
         writeCodeSection();
         writeDebugNames();
+        writeSourceMappingUrl();
         writeProducersSection();
 
         wasm.close();
@@ -272,6 +273,26 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
         wasm.writeSection( SectionType.Custom, stream );
     }
 
+    /**
+     * Write the source mapping url
+     * 
+     * @throws IOException
+     *             if any I/O error occur
+     */
+    private void writeSourceMappingUrl() throws IOException {
+        if( !createSourceMap ) {
+            return;
+        }
+        String url = target.getSourceMappingURL();
+        if( url == null ) {
+            return;
+        }
+        WasmOutputStream stream = new WasmOutputStream();
+        stream.writeString( "sourceMappingURL" ); // Custom Section name "sourceMappingURL", content is part of the section length
+        stream.writeString( url );
+        wasm.writeSection( SectionType.Custom, stream );
+    }
+
     /**
      * Write producer information to wasm
      * 
diff --git a/src/de/inetsoftware/jwebassembly/module/WasmTarget.java b/src/de/inetsoftware/jwebassembly/module/WasmTarget.java
index ae8cffc..1e2a092 100644
--- a/src/de/inetsoftware/jwebassembly/module/WasmTarget.java
+++ b/src/de/inetsoftware/jwebassembly/module/WasmTarget.java
@@ -73,6 +73,19 @@ public class WasmTarget implements Closeable {
         return output;
     }
 
+    /**
+     * Get the URL for the source mapping that should be write into the assembly.
+     * 
+     * @return the URL string or null.
+     */
+    @Nonnull
+    public String getSourceMappingURL() {
+        if( file != null ) {
+            return file.getName() + ".map";
+        }
+        return null;
+    }
+
     /**
      * Get the source map OutputStream
      *