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|
use std::marker::PhantomData;
use std::mem::size_of_val;
use std::ptr::null;
use safer_ffi::layout::ReprC;
use crate::CurrentContextWithFns;
#[derive(Debug)]
pub struct Buffer<Item: ReprC>
{
buf: crate::sys::types::GLuint,
_pd: PhantomData<Item>,
}
impl<Item: ReprC> Buffer<Item>
{
#[must_use]
pub fn new(current_context: &CurrentContextWithFns<'_>) -> Self
{
let mut buffer = crate::sys::types::GLuint::default();
unsafe {
current_context.fns().CreateBuffers(1, &raw mut buffer);
};
Self { buf: buffer, _pd: PhantomData }
}
/// Stores items in this buffer.
///
/// # Errors
/// Returns `Err` if the total size (in bytes) is too large.
pub fn store(
&self,
current_context: &CurrentContextWithFns<'_>,
items: &[Item],
usage: Usage,
) -> Result<(), Error>
{
let total_size = size_of_val(items);
let total_size: crate::sys::types::GLsizeiptr =
total_size
.try_into()
.map_err(|_| Error::TotalItemsSizeTooLarge {
total_size,
max_total_size: crate::sys::types::GLsizeiptr::MAX as usize,
})?;
unsafe {
current_context.fns().NamedBufferData(
self.buf,
total_size,
items.as_ptr().cast(),
usage.into_gl(),
);
}
Ok(())
}
/// Maps the values in the `values` slice into `Item`s which is stored into this
/// buffer.
///
/// # Errors
/// Returns `Err` if the total size (in bytes) is too large.
pub fn store_mapped<Value>(
&self,
current_context: &CurrentContextWithFns<'_>,
values: &[Value],
usage: Usage,
mut map_func: impl FnMut(&Value) -> Item,
) -> Result<(), Error>
{
let item_size: crate::sys::types::GLsizeiptr = const {
assert!(size_of::<Item>() <= crate::sys::types::GLsizeiptr::MAX as usize);
size_of::<Item>().cast_signed()
};
let total_size = size_of::<Item>() * values.len();
let total_size: crate::sys::types::GLsizeiptr =
total_size
.try_into()
.map_err(|_| Error::TotalItemsSizeTooLarge {
total_size,
max_total_size: crate::sys::types::GLsizeiptr::MAX as usize,
})?;
unsafe {
current_context.fns().NamedBufferData(
self.buf,
total_size,
null(),
usage.into_gl(),
);
}
for (index, value) in values.iter().enumerate() {
let item = map_func(value);
let offset = index * size_of::<Item>();
let Ok(offset_casted) = crate::sys::types::GLintptr::try_from(offset) else {
unreachable!(); // Reason: The total size can be casted to a GLintptr
// (done above) so offsets should be castable as well
};
unsafe {
current_context.fns().NamedBufferSubData(
self.buf,
offset_casted,
item_size,
(&raw const item).cast(),
);
}
}
Ok(())
}
pub(crate) fn object(&self) -> crate::sys::types::GLuint
{
self.buf
}
}
/// Buffer usage.
#[derive(Debug)]
pub enum Usage
{
/// The buffer data is set only once and used by the GPU at most a few times.
Stream,
/// The buffer data is set only once and used many times.
Static,
/// The buffer data is changed a lot and used many times.
Dynamic,
}
impl Usage
{
fn into_gl(self) -> crate::sys::types::GLenum
{
match self {
Self::Stream => crate::sys::STREAM_DRAW,
Self::Static => crate::sys::STATIC_DRAW,
Self::Dynamic => crate::sys::DYNAMIC_DRAW,
}
}
}
#[derive(Debug, thiserror::Error)]
pub enum Error
{
#[error(
"Total size of items ({total_size}) is too large. Must be < {max_total_size}"
)]
TotalItemsSizeTooLarge
{
total_size: usize,
max_total_size: usize,
},
}
|
