From ce05175372a9ddca1a225db0765ace1127a39293 Mon Sep 17 00:00:00 2001
From: Nicholas <nbnoll@eml.cc>
Date: Fri, 12 Nov 2021 09:22:01 -0800
Subject: chore: simplified organizational structure

---
 src/libutf/decode.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 src/libutf/decode.c

(limited to 'src/libutf/decode.c')

diff --git a/src/libutf/decode.c b/src/libutf/decode.c
new file mode 100644
index 0000000..01797f1
--- /dev/null
+++ b/src/libutf/decode.c
@@ -0,0 +1,98 @@
+#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)
+{
+    int c[UTFmax], i;
+    rune l;
+
+    c[0] = *(ubyte*)(s);
+    if(c[0] < Tx){
+        *r = c[0];
+        return 1;
+    }
+
+    l = c[0];
+    for(i = 1; i < UTFmax; i++){
+        c[i]  = *(ubyte*)(s+i);
+        c[i] ^= Tx;
+        if(c[i] & Testx) goto bad;
+
+        l = (l << Bitx) | c[i];
+        if(c[0] < Tbyte(i + 2)){
+            l &= RuneX(i + 1);
+            if(i == 1){
+                if(c[0] < Tbyte(2) || l <= Rune1)
+                    goto bad;
+            }else if(l <= RuneX(i) || l > RuneMax)
+                goto bad;
+
+            if(i == 2 && SurrogateMin <= l && l <= SurrogateMax)
+                goto bad;
+
+            *r = l;
+            return i + 1;
+        }
+    }
+bad:
+    *r = RuneErr;
+    return 1;
+}
+#endif
-- 
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