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use std::cmp::max;
use proc_macro2::TokenStream;
use quote::quote;
use fnv::FnvHashMap as Map;
use crate::graph::{NodeId, Fork, Range};
use crate::generator::{Generator, Context};
use crate::util::ToIdent;
type Targets = Map<NodeId, Vec<Range>>;
impl<'a> Generator<'a> {
pub fn generate_fork(&mut self, this: NodeId, fork: &Fork, mut ctx: Context) -> TokenStream {
let mut targets: Targets = Map::default();
for (range, then) in fork.branches() {
targets.entry(then).or_default().push(range);
}
let loops_to_self = self.meta[this].loop_entry_from.contains(&this);
match targets.len() {
1 if loops_to_self => return self.generate_fast_loop(fork, ctx),
0..=2 => (),
_ => return self.generate_fork_jump_table(this, fork, targets, ctx),
}
let miss = ctx.miss(fork.miss, self);
let end = self.fork_end(this, &miss);
let (byte, read) = self.fork_read(this, end, &mut ctx);
let branches = targets.into_iter().map(|(id, ranges)| {
let next = self.goto(id, ctx.advance(1));
match *ranges {
[range] => {
quote!(#range => #next,)
},
[a, b] if a.is_byte() && b.is_byte() => {
quote!(#a | #b => #next,)
},
_ => {
let test = self.generate_test(ranges).clone();
let next = self.goto(id, ctx.advance(1));
quote!(byte if #test(byte) => #next,)
},
}
});
quote! {
#read
match #byte {
#(#branches)*
_ => #miss,
}
}
}
fn generate_fork_jump_table(&mut self, this: NodeId, fork: &Fork, targets: Targets, mut ctx: Context) -> TokenStream {
let miss = ctx.miss(fork.miss, self);
let end = self.fork_end(this, &miss);
let (byte, read) = self.fork_read(this, end, &mut ctx);
let mut table: [u8; 256] = [0; 256];
let mut jumps = vec!["__".to_ident()];
let branches = targets.into_iter().enumerate().map(|(idx, (id, ranges))| {
let idx = (idx as u8) + 1;
let next = self.goto(id, ctx.advance(1));
jumps.push(format!("J{}", id).to_ident());
for byte in ranges.into_iter().flatten() {
table[byte as usize] = idx;
}
let jump = jumps.last().unwrap();
quote!(Jump::#jump => #next,)
}).collect::<TokenStream>();
let jumps = &jumps;
let table = table.iter().copied().map(|idx| &jumps[idx as usize]);
quote! {
enum Jump {
#(#jumps,)*
}
const LUT: [Jump; 256] = {
use Jump::*;
[#(#table),*]
};
#read
match LUT[#byte as usize] {
#branches
Jump::__ => #miss,
}
}
}
fn fork_end(&self, this: NodeId, miss: &TokenStream) -> TokenStream {
if this == self.root {
quote!(_end(lex))
} else {
miss.clone()
}
}
fn fork_read(&self, this: NodeId, end: TokenStream, ctx: &mut Context) -> (TokenStream, TokenStream) {
let min_read = self.meta[this].min_read;
if ctx.remainder() >= max(min_read, 1) {
let read = ctx.read_unchecked(0);
return (
quote!(byte),
quote!(let byte = unsafe { #read };),
);
}
match min_read {
0 | 1 => {
let read = ctx.read(0);
(
quote!(byte),
quote! {
let byte = match #read {
Some(byte) => byte,
None => return #end,
};
},
)
},
len => {
let read = ctx.read(len);
(
quote!(arr[0]),
quote! {
let arr = match #read {
Some(arr) => arr,
None => return #end,
};
},
)
},
}
}
fn generate_fast_loop(&mut self, fork: &Fork, ctx: Context) -> TokenStream {
let miss = ctx.miss(fork.miss, self);
let ranges = fork.branches().map(|(range, _)| range).collect::<Vec<_>>();
let test = self.generate_test(ranges);
quote! {
_fast_loop!(lex, #test, #miss);
}
}
pub fn fast_loop_macro() -> TokenStream {
quote! {
macro_rules! _fast_loop {
($lex:ident, $test:ident, $miss:expr) => {
while let Some(arr) = $lex.read::<&[u8; 16]>() {
if $test(arr[0]) { if $test(arr[1]) { if $test(arr[2]) { if $test(arr[3]) {
if $test(arr[4]) { if $test(arr[5]) { if $test(arr[6]) { if $test(arr[7]) {
if $test(arr[8]) { if $test(arr[9]) { if $test(arr[10]) { if $test(arr[11]) {
if $test(arr[12]) { if $test(arr[13]) { if $test(arr[14]) { if $test(arr[15]) {
$lex.bump_unchecked(16); continue; } $lex.bump_unchecked(15); return $miss; }
$lex.bump_unchecked(14); return $miss; } $lex.bump_unchecked(13); return $miss; }
$lex.bump_unchecked(12); return $miss; } $lex.bump_unchecked(11); return $miss; }
$lex.bump_unchecked(10); return $miss; } $lex.bump_unchecked(9); return $miss; }
$lex.bump_unchecked(8); return $miss; } $lex.bump_unchecked(7); return $miss; }
$lex.bump_unchecked(6); return $miss; } $lex.bump_unchecked(5); return $miss; }
$lex.bump_unchecked(4); return $miss; } $lex.bump_unchecked(3); return $miss; }
$lex.bump_unchecked(2); return $miss; } $lex.bump_unchecked(1); return $miss; }
return $miss;
}
while $lex.test($test) {
$lex.bump_unchecked(1);
}
$miss
};
}
}
}
}