Struct crevice::std140::Writer

pub struct Writer<W> { /* private fields */ }

Type that enables writing correctly aligned std140 values to a buffer.

Writer is useful when many values need to be laid out in a row that cannot be represented by a struct alone, like dynamically sized arrays or dynamically laid-out values.

Example

In this example, we’ll write a length-prefixed list of lights to a buffer. std140::Writer helps align correctly, even across multiple structs, which can be tricky and error-prone otherwise.

struct PointLight {
    vec3 position;
    vec3 color;
    float brightness;
};

buffer POINT_LIGHTS {
    uint len;
    PointLight[] lights;
} point_lights;

use crevice::std140::{self, AsStd140};

#[derive(AsStd140)]
struct PointLight {
    position: mint::Point3<f32>,
    color: mint::Vector3<f32>,
    brightness: f32,
}

let lights = vec![
    PointLight {
        position: [0.0, 1.0, 0.0].into(),
        color: [1.0, 0.0, 0.0].into(),
        brightness: 0.6,
    },
    PointLight {
        position: [0.0, 4.0, 3.0].into(),
        color: [1.0, 1.0, 1.0].into(),
        brightness: 1.0,
    },
];

let target_buffer = map_gpu_buffer_for_write();
let mut writer = std140::Writer::new(target_buffer);

let light_count = lights.len() as u32;
writer.write(&light_count)?;

// Crevice will automatically insert the required padding to align the
// PointLight structure correctly. In this case, there will be 12 bytes of
// padding between the length field and the light list.

writer.write(lights.as_slice())?;

unmap_gpu_buffer();

Implementations

impl<W: Write> Writer<W>

pub fn new(writer: W) -> Self

Create a new Writer, wrapping a buffer, file, or other type that implements std::io::Write.

pub fn write<T>(&mut self, value: &T) -> Result<usize>

where T: WriteStd140 + ?Sized,

Write a new value to the underlying buffer, writing zeroed padding where necessary.

Returns the offset into the buffer that the value was written to.

pub fn write_iter<I, T>(&mut self, iter: I) -> Result<usize>

where I: IntoIterator<Item = T>, T: WriteStd140,

Write an iterator of values to the underlying buffer.

Returns the offset into the buffer that the first value was written to. If no values were written, returns the len().

pub fn write_std140<T>(&mut self, value: &T) -> Result<usize>

where T: Std140,

Write an Std140 type to the underlying buffer.

pub fn write_slice<T>(&mut self, slice: &[T]) -> Result<usize>

where T: AsStd140,

👎Deprecated since 0.6.0: Use write instead – it now works on slices.

Write a slice of values to the underlying buffer.

pub fn len(&self) -> usize

Returns the amount of data written by this Writer.