96 lines
3.7 KiB
Rust
96 lines
3.7 KiB
Rust
use std::fs::File;
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use std::io::Write;
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use std::path::Path;
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use std::env;
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use std::string::String;
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/// Generate the name of the swizzle function and what it returns.
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/// NOTE: This function assumes that variables are in ASCII format
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#[cfg(feature = "swizzle")]
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fn gen_swizzle_nth<'a>(variables: &'a str, mut i: usize, upto: usize) -> Option<(String, String)> {
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debug_assert!(i > 0); // zeroth permutation is empty
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let mut swizzle_impl = String::new();
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let mut swizzle = String::new();
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let n = variables.len()+1;
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for _ in 0..upto {
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if i == 0 { break; }
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if i % n == 0 { return None; }
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let c = variables.as_bytes()[i%n - 1] as char;
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swizzle.push(c);
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swizzle_impl.push_str(&format!("self.{}, ", c));
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i = i/n;
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}
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Some((swizzle, swizzle_impl))
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}
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/// A function that generates swizzle functions as a string.
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/// `variables`: swizzle variables (e.g. "xyz")
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/// `upto`: largest output vector size (e.g. for `variables = "xy"` and `upto = 4`, `xyxy()` is a
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/// valid swizzle operator.
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/// NOTE: This function assumes that variables are in ASCII format
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#[cfg(feature = "swizzle")]
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fn gen_swizzle_functions(variables: &'static str, upto: usize) -> String {
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let mut result = String::new();
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let nn = (variables.len()+1).pow(upto as u32);
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for i in 1..nn {
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if let Some((swizzle_name, swizzle_impl)) = gen_swizzle_nth(variables, i, upto) {
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let dim = format!("{}", swizzle_name.len());
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result.push_str(
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&format!("
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/// Swizzle operator that creates a new type with dimension {2} from variables `{0}`.
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#[inline] pub fn {0}(&self) -> $vector_type{2}<$S> {{ $vector_type{2}::new({1}) }}\n",
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swizzle_name, swizzle_impl, dim));
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}
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}
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result
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}
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#[cfg(not(feature = "swizzle"))]
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fn gen_swizzle_functions(_: &'static str, _: usize) -> String {
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String::new()
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}
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/// This script generates the macro for building swizzle operators for multidimensional
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/// vectors and points. This macro is included in macros.rs
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fn main() {
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// save the file to output directory
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let out_dir = env::var("OUT_DIR").unwrap();
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let swizzle_file_path = Path::new(&out_dir).join("swizzle_operator_macro.rs");
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// This is the string representing the generated macro
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let data = format!(
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"/// Generate glm/glsl style swizzle operators
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macro_rules! impl_swizzle_functions {{
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($vector_type1:ident, $vector_type2:ident, $vector_type3:ident, $S:ident, x) => {{
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{x3}
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}};
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($vector_type1:ident, $vector_type2:ident, $vector_type3:ident, $S:ident, xy) => {{
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{xy3}
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}};
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($vector_type1:ident, $vector_type2:ident, $vector_type3:ident, $S:ident, xyz) => {{
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{xyz3}
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}};
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($vector_type1:ident, $vector_type2:ident, $vector_type3:ident, $vector_type4:ident, $S:ident, x) => {{
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{x4}
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}};
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($vector_type1:ident, $vector_type2:ident, $vector_type3:ident, $vector_type4:ident, $S:ident, xy) => {{
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{xy4}
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}};
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($vector_type1:ident, $vector_type2:ident, $vector_type3:ident, $vector_type4:ident, $S:ident, xyz) => {{
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{xyz4}
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}};
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($vector_type1:ident, $vector_type2:ident, $vector_type3:ident, $vector_type4:ident, $S:ident, xyzw) => {{
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{xyzw4}
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}};
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}}", x3 = gen_swizzle_functions("x", 3),
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xy3 = gen_swizzle_functions("xy", 3),
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xyz3 = gen_swizzle_functions("xyz", 3),
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x4 = gen_swizzle_functions("x", 4),
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xy4 = gen_swizzle_functions("xy", 4),
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xyz4 = gen_swizzle_functions("xyz", 4),
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xyzw4 = gen_swizzle_functions("xyzw", 4));
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let mut f = File::create(swizzle_file_path)
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.expect("Unable to create file that defines the swizzle operator macro.");
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f.write_all(data.as_bytes()).expect("Unable to write swizzle operator macro.");
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}
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