Add a usage parameter to Buffer

[libs/gl.git] / source / core / buffer.h

diff --git a/source/core/buffer.h b/source/core/buffer.h
index 2366ec5ce0dd3269ee13db7d80bd53eade0fd565..a12b3373e601664bddf75d60bb930d56bbe26833 100644 (file)
--- a/source/core/buffer.h
+++ b/source/core/buffer.h
@@ -15,35 +15,52 @@ public:
        virtual ~buffer_too_small() throw() { }
 };
 
+enum BufferUsage
+{
+       STATIC,
+       STREAMING
+};
+
 /**
-A buffer for storing data in GL memory.  Putting vertex and index data in
-buffers can improve rendering performance.  The VertexArray, Mesh and
-UniformBlock classes contain built-in support for buffers.
+Stores data in GPU memory.
+
+Memory must be allocated for the buffer by calling storage().  Contents can
+then be modified either synchronously with the data() and sub_data() functions,
+or asynchronously by memory-mapping the buffer.
+
+Buffers can have a static or streaming usage pattern.  Streaming buffers can be
+memory mapped for less update overhead, but memory space is more limited.  If
+the buffer is updated only rarely, static is recommended.
+
+Applications normally don't need to deal with Buffers directly.  They're
+managed by other classes such as Mesh and ProgramData.
 */
 class Buffer: public BufferBackend
 {
        friend BufferBackend;
 
 private:
-       unsigned size = 0;
+       std::size_t size = 0;
+       BufferUsage usage = STATIC;
+       bool mapped = false;
 
 public:
-       /** Defines the storage size of the buffer.  Must be called before data can
-       be uploaded.  Storage cannot be changed once set. */
-       void storage(unsigned);
+       /** Sets storage size and usage pattern and allocates memory for the buffer.
+       Size and usage cannot be changed once set. */
+       void storage(std::size_t, BufferUsage);
 
-       /** Uploads data into the buffer, completely replacing any previous
-       contents.  Storage must be defined beforehand.  The data must have size
-       matching the defined storage. */
+       /** Replaces contents of the entire buffer.  Allocated storage must exist.
+       The data must have size matching the defined storage. */
        void data(const void *);
 
-       /** Overwrites part of the buffer data with new data.  Storage must be
-       defined beforehand. */
-       void sub_data(unsigned, unsigned, const void *);
+       /** Replaces a range of bytes in the buffer.  Allocated storage must exist.
+       The range must be fully inside the buffer. */
+       void sub_data(std::size_t, std::size_t, const void *);
 
-       unsigned get_size() const { return size; }
+       std::size_t get_size() const { return size; }
+       BufferUsage get_usage() const { return usage; }
 
-       void require_size(unsigned) const;
+       void require_size(std::size_t) const;
 
        using BufferBackend::map;
        using BufferBackend::unmap;