Feat(libunicode): cleaned up decode/encode

Additionally, decode can now apply backwards on a byte string.

1 files changed, 68 insertions, 10 deletions

diff --git a/sys/libunicode/decode.c b/sys/libunicode/decode.c
index 79271f2..01797f1 100644
--- a/sys/libunicode/decode.c
+++ b/sys/libunicode/decode.c
@@ -1,32 +1,90 @@
 #include "internal.h"
 
+#define ACCEPT 0
+#define REJECT 12
+
+static uint8 decode[] = {
+    /*
+     * the first part of the table maps bytes to character classes that
+     * to reduce the size of the transition table and create bitmasks
+     */
+     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,
+     1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,  9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
+     7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,  7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+     8,8,2,2,2,2,2,2,2,2,2,2,2,2,2,2,  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
+    10,3,3,3,3,3,3,3,3,3,3,3,3,4,3,3, 11,6,6,6,5,8,8,8,8,8,8,8,8,8,8,8,
+
+    /*
+     * the second part is a transition table that maps a combination
+     * of a state of the automaton and a character class to a state
+     */
+     0,12,24,36,60,96,84,12,12,12,48,72, 12,12,12,12,12,12,12,12,12,12,12,12,
+    12, 0,12,12,12,12,12, 0,12, 0,12,12, 12,24,12,12,12,12,12,24,12,24,12,12,
+    12,12,12,12,12,12,12,24,12,12,12,12, 12,24,12,12,12,12,12,12,12,24,12,12,
+    12,12,12,12,12,12,12,36,12,36,12,12, 12,36,12,12,12,12,12,36,12,36,12,12,
+    12,36,12,12,12,12,12,12,12,12,12,12,
+};
+
+int
+utf8·decode(char *s, rune *r)
+{
+    int   n;
+    rune  v;
+    uint8 b, t, x=ACCEPT;
+
+    b = ((uint8 *)s)[0];
+    t = decode[b];
+    v = (0xFF >> t) & b;
+    x = decode[256+x+t];
+
+    for(n=1; x > REJECT && n < UTFmax; n++){
+        b = ((uint8 *)s)[n];
+        t = decode[b];
+        v = (v << 6) | (b & TMask);
+        x = decode[256+x+t];
+    }
+
+    if(x != ACCEPT){
+        *r = RuneErr;
+        return 1;
+    }
+
+    *r = v;
+    return n;
+}
+
+#if 0
 int
-utf8·decode(byte *s, rune* r)
+utf8·decode(byte *s, rune *r)
 {
     int c[UTFmax], i;
     rune l;
 
     c[0] = *(ubyte*)(s);
-    if(c[0] < Tx) {
+    if(c[0] < Tx){
         *r = c[0];
         return 1;
     }
 
     l = c[0];
-    for(i = 1; i < UTFmax; i++) {
+    for(i = 1; i < UTFmax; i++){
         c[i]  = *(ubyte*)(s+i);
         c[i] ^= Tx;
-        if (c[i] & Testx) goto bad;
+        if(c[i] & Testx) goto bad;
 
         l = (l << Bitx) | c[i];
-        if(c[0] < Tbyte(i + 2)) {
+        if(c[0] < Tbyte(i + 2)){
             l &= RuneX(i + 1);
-            if (i == 1) {
-                if (c[0] < Tbyte(2) || l <= Rune1)
+            if(i == 1){
+                if(c[0] < Tbyte(2) || l <= Rune1)
                     goto bad;
-            } else if (l <= RuneX(i) || l > RuneMax)
+            }else if(l <= RuneX(i) || l > RuneMax)
                 goto bad;
-            if (i == 2 && SurrogateMin <= l && l <= SurrogateMax)
+
+            if(i == 2 && SurrogateMin <= l && l <= SurrogateMax)
                 goto bad;
 
             *r = l;
@@ -37,4 +95,4 @@ bad:
     *r = RuneErr;
     return 1;
 }
-
+#endif