make Combining column human-readable

This patch introduces a `CombiningClass` type to represent the canonical
combining class of a codepoint. The `fmt::Display` implementation of
this type writes the human-readable name of the combining class, if
there is one. This replaces the previous behaviour, which was to just
print the raw byte value of the combining class.

utfdump_core/src/chardata.rs

@@ -4,7 +4,7 @@ use std::fmt;
 pub struct CharData<'a> {
     name: &'a str,
     category: Category,
-    ccc: u8,
+    ccc: CombiningClass,
 }
 
 impl<'a> CharData<'a> {
@@ -17,12 +17,12 @@ impl<'a> CharData<'a> {
         let codepoint = u32::from_str_radix(fields[0], 16).ok()?;
         let name = fields[1];
         let category = Category::from_abbr(fields[2])?;
-        let ccc = u8::from_str_radix(fields[3], 10).ok()?;
+        let ccc = CombiningClass(u8::from_str_radix(fields[3], 10).ok()?);
 
         Some((codepoint, Self::from_parts(name, category, ccc)))
     }
 
-    pub fn from_parts(name: &'a str, category: Category, ccc: u8) -> Self {
+    pub fn from_parts(name: &'a str, category: Category, ccc: CombiningClass) -> Self {
         Self { name, category, ccc }
     }
 
@@ -41,7 +41,7 @@ impl<'a> CharData<'a> {
         self.category
     }
 
-    pub fn ccc(&self) -> u8 {
+    pub fn ccc(&self) -> CombiningClass {
         self.ccc
     }
 }
@@ -235,3 +235,48 @@ impl fmt::Display for Category {
     }
 }
 
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub struct CombiningClass(pub u8);
+
+impl CombiningClass {
+    pub fn name(self) -> Option<&'static str> {
+        match self.0 {
+            0 => Some("Not_Reordered"),
+            1 => Some("Overlay"),
+            6 => Some("Han_Reading"),
+            7 => Some("Nukta"),
+            8 => Some("Kana_Voicing"),
+            9 => Some("Virama"),
+            200 => Some("Attached_Below_Left"),
+            202 => Some("Attached_Below"),
+            214 => Some("Attached_Above"),
+            216 => Some("Attached_Above_Right"),
+            218 => Some("Below_Left"),
+            220 => Some("Below"),
+            222 => Some("Below_Right"),
+            224 => Some("Left"),
+            226 => Some("Right"),
+            228 => Some("Above_Left"),
+            230 => Some("Above"),
+            232 => Some("Above_Right"),
+            233 => Some("Double_Below"),
+            234 => Some("Double_Above"),
+            240 => Some("Iota_Subscript"),
+            _ => None,
+        }
+    }
+
+    pub fn is_combining(self) -> bool {
+        self.0 != 0
+    }
+}
+
+impl fmt::Display for CombiningClass {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.name() {
+            Some(name) => write!(f, "{}", name),
+            None => write!(f, "Ccc{}", self.0),
+        }
+    }
+}
+

utfdump_core/src/encoded.rs

@@ -1,13 +1,13 @@
 use std::{collections::{HashMap, hash_map}, error, fmt, str, ops::Range};
 
-use crate::chardata::{CharData, Category};
+use crate::chardata::{CharData, Category, CombiningClass};
 
 const DATA_ENTRY_SIZE: usize = 8;
 
 const DATA_INIT_FLAG: u8 = 1;
 const DATA_REPEATED_FLAG: u8 = 2;
 
-fn encode_char_data(name_index: u32, category: Category, ccc: u8, repeated: bool) -> [u8; DATA_ENTRY_SIZE] {
+fn encode_char_data(name_index: u32, category: Category, ccc: CombiningClass, repeated: bool) -> [u8; DATA_ENTRY_SIZE] {
     let mut buf = [0u8; DATA_ENTRY_SIZE];
 
     buf[0] |= DATA_INIT_FLAG;
@@ -18,12 +18,12 @@ fn encode_char_data(name_index: u32, category: Category, ccc: u8, repeated: bool
 
     buf[1..5].copy_from_slice(&name_index.to_le_bytes());
     buf[5] = category.byte_repr();
-    buf[6] = ccc;
+    buf[6] = ccc.0;
 
     buf
 }
 
-fn decode_char_data(bytes: [u8; DATA_ENTRY_SIZE]) -> Option<(u32, Category, u8, bool)> {
+fn decode_char_data(bytes: [u8; DATA_ENTRY_SIZE]) -> Option<(u32, Category, CombiningClass, bool)> {
     let flags = bytes[0];
     
     if flags & DATA_INIT_FLAG == 0 {
@@ -32,7 +32,7 @@ fn decode_char_data(bytes: [u8; DATA_ENTRY_SIZE]) -> Option<(u32, Category, u8,
 
     let name_index = u32::from_le_bytes(bytes[1..5].try_into().unwrap());
     let category = Category::from_byte(bytes[5])?;
-    let ccc = bytes[6];
+    let ccc = CombiningClass(bytes[6]);
     let repeated = flags & DATA_REPEATED_FLAG != 0;
 
     Some((name_index, category, ccc, repeated))