Generate xml

Bug: b/252835416
Test: use sample code in ag/20349112, output xmp metadata should be identical to the sample

Change-Id: I1fa8d40c3fab1a8e3ebe70db42582d632bcdb7d5
diff --git a/libs/jpegrecoverymap/recoverymap.cpp b/libs/jpegrecoverymap/recoverymap.cpp
index 5d25722..8d3cd00 100644
--- a/libs/jpegrecoverymap/recoverymap.cpp
+++ b/libs/jpegrecoverymap/recoverymap.cpp
@@ -14,10 +14,29 @@
  * limitations under the License.
  */
 
+#include "image_io/xml/xml_writer.h"
+
 #include <jpegrecoverymap/recoverymap.h>
+#include <sstream>
+#include <string>
+
+using namespace std;
 
 namespace android::recoverymap {
 
+/*
+ * Helper function used for generating XMP metadata.
+ *
+ * @param prefix The prefix part of the name.
+ * @param suffix The suffix part of the name.
+ * @return A name of the form "prefix:suffix".
+ */
+string Name(const string &prefix, const string &suffix) {
+  std::stringstream ss;
+  ss << prefix << ":" << suffix;
+  return ss.str();
+}
+
 status_t RecoveryMap::encodeJPEGR(jr_uncompressed_ptr uncompressed_p010_image,
                                   jr_uncompressed_ptr uncompressed_yuv_420_image,
                                   void* dest) {
@@ -137,4 +156,53 @@
   return NO_ERROR;
 }
 
+string RecoveryMap::generateXmp(int secondary_image_length, float hdr_ratio) {
+  const string kContainerPrefix = "GContainer";
+  const string kContainerUri    = "http://ns.google.com/photos/1.0/container/";
+  const string kItemPrefix      = "Item";
+  const string kRecoveryMap     = "RecoveryMap";
+  const string kDirectory       = "Directory";
+  const string kImageJpeg       = "image/jpeg";
+  const string kItem            = "Item";
+  const string kLength          = "Length";
+  const string kMime            = "Mime";
+  const string kPrimary         = "Primary";
+  const string kSemantic        = "Semantic";
+  const string kVersion         = "Version";
+  const int    kVersionValue    = 1;
+
+  const string kConDir          = Name(kContainerPrefix, kDirectory);
+  const string kContainerItem   = Name(kContainerPrefix, kItem);
+  const string kItemLength      = Name(kItemPrefix, kLength);
+  const string kItemMime        = Name(kItemPrefix, kMime);
+  const string kItemSemantic    = Name(kItemPrefix, kSemantic);
+
+  const vector<string> kConDirSeq({kConDir, string("rdf:Seq")});
+  const vector<string> kLiItem({string("rdf:li"), kContainerItem});
+
+  std::stringstream ss;
+  photos_editing_formats::image_io::XmlWriter writer(ss);
+  writer.StartWritingElement("x:xmpmeta");
+  writer.WriteXmlns("x", "adobe:ns:meta/");
+  writer.WriteAttributeNameAndValue("x:xmptk", "Adobe XMP Core 5.1.2");
+  writer.StartWritingElement("rdf:RDF");
+  writer.WriteXmlns("rdf", "http://www.w3.org/1999/02/22-rdf-syntax-ns#");
+  writer.StartWritingElement("rdf:Description");
+  writer.WriteXmlns(kContainerPrefix, kContainerUri);
+  writer.WriteElementAndContent(Name(kContainerPrefix, kVersion), kVersionValue);
+  writer.WriteElementAndContent(Name(kContainerPrefix, "HdrRatio"), hdr_ratio);
+  writer.StartWritingElements(kConDirSeq);
+  size_t item_depth = writer.StartWritingElements(kLiItem);
+  writer.WriteAttributeNameAndValue(kItemSemantic, kPrimary);
+  writer.WriteAttributeNameAndValue(kItemMime, kImageJpeg);
+  writer.FinishWritingElementsToDepth(item_depth);
+  writer.StartWritingElements(kLiItem);
+  writer.WriteAttributeNameAndValue(kItemSemantic, kRecoveryMap);
+  writer.WriteAttributeNameAndValue(kItemMime, kImageJpeg);
+  writer.WriteAttributeNameAndValue(kItemLength, secondary_image_length);
+  writer.FinishWriting();
+
+  return ss.str();
+}
+
 } // namespace android::recoverymap