MB-47318: [BP] Add a make_wire_encoded_string factory method in xattr utils

Add code that can generate a xattr encoding value into xattr utils
so it is easily accessible to all modules.

Change-Id: I5743d0afd0308b57edb0f78cc7789e18a28710e3
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/165018
Tested-by: Build Bot <[email protected]>
Reviewed-by: Dave Rigby <[email protected]>
Well-Formed: Restriction Checker

Author: jimwwalker

include/xattr/utils.h

@@ -20,6 +20,7 @@
 #include <xattr/visibility.h>
 
 #include <string>
+#include <unordered_map>
 
 namespace cb {
 /**
@@ -119,5 +120,18 @@ size_t get_system_xattr_size(uint8_t datatype, const cb::const_char_buffer doc);
  */
 XATTR_PUBLIC_API
 size_t get_body_size(uint8_t datatype, cb::const_char_buffer value);
+
+/**
+ * Make a wire encoded XATTR value in a std::string. This will encode the given
+ * 'body' and xattrs as per the mcbp protocol
+ *
+ * @param body the 'body' of the document
+ * @param xattMap map of XATTR key -> value pairs to encode in the output
+ *        document/string.
+ */
+XATTR_PUBLIC_API
+std::string make_wire_encoded_string(
+        const std::string& body,
+        const std::unordered_map<std::string, std::string>& xattrMap);
 }
 }

xattr/utils.cc

@@ -181,5 +181,23 @@ size_t get_body_size(uint8_t datatype, cb::const_char_buffer value) {
 
     return value.size() - get_body_offset(value);
 }
+
+std::string make_wire_encoded_string(
+        const std::string& body,
+        const std::unordered_map<std::string, std::string>& xattrSet) {
+    Blob xattrs;
+    for (auto itr = xattrSet.begin(); itr != xattrSet.end(); ++itr) {
+        xattrs.set(itr->first, itr->second);
+    }
+    auto data = xattrs.finalize();
+    std::string encoded{data.data(), data.size()};
+    if (!cb::xattr::validate(encoded)) {
+        throw std::logic_error(
+                "cb::xattr::make_wire_encoded_string Invalid xattr encoding");
+    }
+    encoded.append(body);
+    return encoded;
+}
+
 }
 }