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tutorial: Use chunks_exact/chunks_exact_mut instead of the normal chunks iterator

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We always want as many items as given, no less. And this also enables
the compiler to optimize the code further.
This commit is contained in:
Sebastian Dröge 2019-01-25 16:42:27 +02:00
parent b8d19920a8
commit 4c618394b7
2 changed files with 12 additions and 12 deletions
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22
gst-plugin-tutorial/src/rgb2gray.rs
View file

@ -489,22 +489,22 @@ impl BaseTransformImpl for Rgb2Gray {
// Iterate over each line of the input and output frame, mutable for the output frame.
// Each input line has in_stride bytes, each output line out_stride. We use the
// chunks/chunks_mut iterators here for getting a chunks of that many bytes per
// chunks_exact/chunks_exact_mut iterators here for getting a chunks of that many bytes per
// iteration and zip them together to have access to both at the same time.
for (in_line, out_line) in in_data
.chunks(in_stride)
.zip(out_data.chunks_mut(out_stride))
.chunks_exact(in_stride)
.zip(out_data.chunks_exact_mut(out_stride))
{
// Next iterate the same way over each actual pixel in each line. Every pixel is 4
// bytes in the input and output, so we again use the chunks/chunks_mut iterators
// bytes in the input and output, so we again use the chunks_exact/chunks_exact_mut iterators
// to give us each pixel individually and zip them together.
//
// Note that we take a sub-slice of the whole lines: each line can contain an
// arbitrary amount of padding at the end (e.g. for alignment purposes) and we
// don't want to process that padding.
for (in_p, out_p) in in_line[..in_line_bytes]
.chunks(4)
.zip(out_line[..out_line_bytes].chunks_mut(4))
.chunks_exact(4)
.zip(out_line[..out_line_bytes].chunks_exact_mut(4))
{
assert_eq!(out_p.len(), 4);
@ -529,22 +529,22 @@ impl BaseTransformImpl for Rgb2Gray {
// Iterate over each line of the input and output frame, mutable for the output frame.
// Each input line has in_stride bytes, each output line out_stride. We use the
// chunks/chunks_mut iterators here for getting a chunks of that many bytes per
// chunks_exact/chunks_exact_mut iterators here for getting a chunks of that many bytes per
// iteration and zip them together to have access to both at the same time.
for (in_line, out_line) in in_data
.chunks(in_stride)
.zip(out_data.chunks_mut(out_stride))
.chunks_exact(in_stride)
.zip(out_data.chunks_exact_mut(out_stride))
{
// Next iterate the same way over each actual pixel in each line. Every pixel is 4
// bytes in the input and 1 byte in the output, so we again use the
// chunks/chunks_mut iterators to give us each pixel individually and zip them
// chunks_exact/chunks_exact_mut iterators to give us each pixel individually and zip them
// together.
//
// Note that we take a sub-slice of the whole lines: each line can contain an
// arbitrary amount of padding at the end (e.g. for alignment purposes) and we
// don't want to process that padding.
for (in_p, out_p) in in_line[..in_line_bytes]
.chunks(4)
.chunks_exact(4)
.zip(out_line[..out_line_bytes].iter_mut())
{
// Use our above-defined function to convert a BGRx pixel with the settings to

2
gst-plugin-tutorial/src/sinesrc.rs
View file

@ -172,7 +172,7 @@ impl SineSrc {
let mut accumulator = *accumulator_ref;
let step = two_pi * freq / rate;
for chunk in data.chunks_mut(channels as usize) {
for chunk in data.chunks_exact_mut(channels as usize) {
let value = vol * F::sin(NumCast::from(accumulator).unwrap());
for sample in chunk {
*sample = value;