InputStream: "protect" attributes

src/input/InputStream.hxx

@@ -64,6 +64,7 @@ public:
 	 */
 	Cond &cond;
 
+protected:
 	/**
 	 * indicates whether the stream is ready for reading and
 	 * whether the other attributes in this struct are valid
@@ -80,7 +81,6 @@ public:
 	 */
 	offset_type size;
 
-public:
 	/**
 	 * the current offset within the stream
 	 */
@@ -217,6 +217,13 @@ public:
 		mime = _mime;
 	}
 
+	gcc_pure
+	bool KnownSize() const {
+		assert(ready);
+
+		return size >= 0;
+	}
+
 	gcc_pure
 	offset_type GetSize() const {
 		assert(ready);
@@ -239,6 +246,15 @@ public:
 		return offset;
 	}
 
+	gcc_pure
+	offset_type GetRest() const {
+		assert(ready);
+		assert(size >= 0);
+		assert(offset >= 0);
+
+		return size - offset;
+	}
+
 	gcc_pure
 	bool IsSeekable() const {
 		assert(ready);