1 files changed, 78 insertions, 0 deletions
diff --git a/src/tools/unicode-table-generator/src/cascading_map.rs b/src/tools/unicode-table-generator/src/cascading_map.rs
new file mode 100644
index 000000000..02c754230
--- /dev/null
+++ b/src/tools/unicode-table-generator/src/cascading_map.rs
@@ -0,0 +1,78 @@
+use crate::fmt_list;
+use crate::raw_emitter::RawEmitter;
+use std::collections::HashMap;
+use std::fmt::Write as _;
+use std::ops::Range;
+
+impl RawEmitter {
+    pub fn emit_cascading_map(&mut self, ranges: &[Range<u32>]) -> bool {
+        let mut map: [u8; 256] = [
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        ];
+
+        let points = ranges
+            .iter()
+            .flat_map(|r| (r.start..r.end).into_iter().collect::<Vec<u32>>())
+            .collect::<Vec<u32>>();
+
+        println!("there are {} points", points.len());
+
+        // how many distinct ranges need to be counted?
+        let mut codepoints_by_high_bytes = HashMap::<usize, Vec<u32>>::new();
+        for point in points {
+            // assert that there is no whitespace over the 0x3000 range.
+            assert!(point <= 0x3000, "the highest unicode whitespace value has changed");
+            let high_bytes = point as usize >> 8;
+            let codepoints = codepoints_by_high_bytes.entry(high_bytes).or_insert_with(Vec::new);
+            codepoints.push(point);
+        }
+
+        let mut bit_for_high_byte = 1u8;
+        let mut arms = Vec::<String>::new();
+
+        let mut high_bytes: Vec<usize> =
+            codepoints_by_high_bytes.keys().map(|k| k.clone()).collect();
+        high_bytes.sort();
+        for high_byte in high_bytes {
+            let codepoints = codepoints_by_high_bytes.get_mut(&high_byte).unwrap();
+            if codepoints.len() == 1 {
+                let ch = codepoints.pop().unwrap();
+                arms.push(format!("{} => c as u32 == {:#04x}", high_byte, ch));
+                continue;
+            }
+            // more than 1 codepoint in this arm
+            for codepoint in codepoints {
+                map[(*codepoint & 0xff) as usize] |= bit_for_high_byte;
+            }
+            arms.push(format!(
+                "{} => WHITESPACE_MAP[c as usize & 0xff] & {} != 0",
+                high_byte, bit_for_high_byte
+            ));
+            bit_for_high_byte <<= 1;
+        }
+
+        writeln!(&mut self.file, "static WHITESPACE_MAP: [u8; 256] = [{}];", fmt_list(map.iter()))
+            .unwrap();
+        self.bytes_used += 256;
+
+        writeln!(&mut self.file, "#[inline]").unwrap();
+        writeln!(&mut self.file, "pub fn lookup(c: char) -> bool {{").unwrap();
+        writeln!(&mut self.file, "    match c as u32 >> 8 {{").unwrap();
+        for arm in arms {
+            writeln!(&mut self.file, "        {},", arm).unwrap();
+        }
+        writeln!(&mut self.file, "        _ => false,").unwrap();
+        writeln!(&mut self.file, "    }}").unwrap();
+        writeln!(&mut self.file, "}}").unwrap();
+
+        true
+    }
+}