glBufferStorage

glBufferStorage is an OpenGL function that creates immutable storage for a buffer object bound to a specified target. Introduced with the ARB_buffer_storage extension and core in OpenGL 4.4, it allocates a data store of the given size for the bound buffer object. The storage cannot be resized via glBufferData, making it immutable; however, the contents can be updated with glBufferSubData or by mapping, provided the appropriate access is permitted by the specified flags. If data is non-null, the initial contents are copied into the buffer; otherwise the storage is uninitialized or zero-initialized depending on implementation.

The function signature is void glBufferStorage(GLenum target, GLsizeiptr size, const void * data, GLbitfield flags). The target is a buffer binding point such as GL_ARRAY_BUFFER or GL_ELEMENT_ARRAY_BUFFER. The data pointer may be NULL to allocate uninitialized storage, or point to an initial data store copied into the buffer. The last parameter, flags, is a bitfield that controls access and behavior of the storage.

Common flags include:

- GL_MAP_READ_BIT and GL_MAP_WRITE_BIT to allow mapped access by the client.

- GL_DYNAMIC_STORAGE_BIT to indicate the storage will be updated frequently.

- GL_MAP_PERSISTENT_BIT and GL_MAP_COHERENT_BIT to enable persistent and coherent mapping, enabling the client to keep maps across frames with reduced synchronization overhead.

- GL_CLIENT_STORAGE_BIT (where supported) to request client-provided storage.

Usage typically involves binding the buffer, calling glBufferStorage with the desired size and flags, and optionally mapping the buffer (especially with persistent mapping) to write data directly. If persistent mapping is used, care is required to synchronize access between CPU and GPU operations. glBufferStorage requires OpenGL 4.4 or ARB_buffer_storage support.