Add support for (un)marshalling variable-sized integers

The current serialization code only supports 8/16/32-bit fixed size
integers.

However, a variable sized representation is often more space efficient,
and allows to seamlessly expand the integer size without breaking
compatibility.

This patch uses the common scheme of using 7 bits for data, plus 1 bit
to indicate termination of the integer, all encoded in little endian order.

Signed integers are first transformed to unsigned ones where bit 0 is
the sign bit.

1 files changed, 17 insertions, 0 deletions

diff --git a/crawl-ref/source/tags.h b/crawl-ref/source/tags.h
index 88f71096f6..acd36801da 100644
--- a/crawl-ref/source/tags.h
+++ b/crawl-ref/source/tags.h
@@ -145,6 +145,9 @@ inline void marshallEnum(writer& wr, enm value)
     marshallEnumVal(wr, &enum_details<enm>::desc, static_cast<int>(value));
 }
 
+void marshallUnsigned(writer& th, uint64_t v);
+void marshallSigned(writer& th, int64_t v);
+
 /* ***********************************************************************
  * reader API
  * *********************************************************************** */
@@ -199,6 +202,20 @@ inline enm unmarshallEnum(writer& wr)
     return static_cast<enm>(unmarshallEnumVal(wr, &enum_details<enm>::desc));
 }
 
+uint64_t unmarshallUnsigned(reader& th);
+template<typename T>
+static inline void unmarshallUnsigned(reader& th, T& v)
+{
+    v = (T)unmarshallUnsigned(th);
+}
+
+int64_t unmarshallSigned(reader& th);
+template<typename T>
+static inline void unmarshallSigned(reader& th, T& v)
+{
+    v = (T)unmarshallSigned(th);
+}
+
 /* ***********************************************************************
  * Tag interface
  * *********************************************************************** */