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);

src/input/plugins/RewindInputPlugin.cxx

@@ -93,7 +93,7 @@ private:
 	 * buffer contain more data for the next read operation?
 	 */
 	bool ReadingFromBuffer() const {
-		return tail > 0 && offset < input->offset;
+		return tail > 0 && offset < input->GetOffset();
 	}
 
 	/**
@@ -116,7 +116,7 @@ private:
 			SetReady();
 		}
 
-		offset = src->offset;
+		offset = src->GetOffset();
 	}
 };
 
@@ -127,7 +127,7 @@ RewindInputStream::Read(void *ptr, size_t read_size, Error &error)
 		/* buffered read */
 
 		assert(head == (size_t)offset);
-		assert(tail == (size_t)input->offset);
+		assert(tail == (size_t)input->GetOffset());
 
 		if (read_size > tail - head)
 			read_size = tail - head;
@@ -142,7 +142,7 @@ RewindInputStream::Read(void *ptr, size_t read_size, Error &error)
 
 		size_t nbytes = input->Read(ptr, read_size, error);
 
-		if (input->offset > (InputPlugin::offset_type)sizeof(buffer))
+		if (input->GetOffset() > (offset_type)sizeof(buffer))
 			/* disable buffering */
 			tail = 0;
 		else if (tail == (size_t)offset) {
@@ -151,7 +151,7 @@ RewindInputStream::Read(void *ptr, size_t read_size, Error &error)
 			memcpy(buffer + tail, ptr, nbytes);
 			tail += nbytes;
 
-			assert(tail == (size_t)input->offset);
+			assert(tail == (size_t)input->GetOffset());
 		}
 
 		CopyAttributes();
@@ -172,7 +172,7 @@ RewindInputStream::Seek(InputPlugin::offset_type new_offset, int whence,
 
 		assert(!ReadingFromBuffer() ||
 		       head == (size_t)offset);
-		assert(tail == (size_t)input->offset);
+		assert(tail == (size_t)input->GetOffset());
 
 		head = (size_t)new_offset;
 		offset = new_offset;
@@ -194,7 +194,7 @@ InputStream *
 input_rewind_open(InputStream *is)
 {
 	assert(is != nullptr);
-	assert(is->offset == 0);
+	assert(is->GetOffset() == 0);
 
 	if (is->IsReady() && is->IsSeekable())
 		/* seekable resources don't need this plugin */