glGetNamedBufferSubData

glGetBufferSubData: man4/glGetBufferSubData.xml

glGetBufferSubData and glGetNamedBufferSubData return some or all of the data contents of the data store of the specified buffer object. Data starting at byte offset offset and extending for size bytes is copied from the buffer object's data store to the memory pointed to by data. An error is thrown if the buffer object is currently mapped, or if offset and size together define a range beyond the bounds of the buffer object's data store.

If an error is generated, no change is made to the contents of data. The GL_ATOMIC_COUNTER_BUFFER target is available only if the GL version is 4.2 or greater. The GL_DISPATCH_INDIRECT_BUFFER and GL_SHADER_STORAGE_BUFFER targets are available only if the GL version is 4.3 or greater. The GL_QUERY_BUFFER target is available only if the GL version is 4.4 or greater.