From 6318ddb69ad8380694bbca35ca5a72230c2ee694 Mon Sep 17 00:00:00 2001
From: Nicholas Noll <nbnoll@eml.cc>
Date: Thu, 28 Oct 2021 11:55:47 -0700
Subject: Feat(libunicode): cleaned up decode/encode

Additionally, decode can now apply backwards on a byte string.
---
 sys/libunicode/encode.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

(limited to 'sys/libunicode/encode.c')

diff --git a/sys/libunicode/encode.c b/sys/libunicode/encode.c
index 8f4d212..fa7c93e 100644
--- a/sys/libunicode/encode.c
+++ b/sys/libunicode/encode.c
@@ -1,5 +1,42 @@
 #include "internal.h"
 
+int
+utf8·encode(rune *r, byte *s)
+{
+    rune c;
+
+    c = *r;
+    if(c < Rune1Byte){ // 7 bits
+        s[0] = (uint8)c;
+        return 1;
+    }
+
+    if(c < Rune2Byte){ // 11 bits
+        s[0] = TByte1 | (c >> 6);
+        s[1] = Tx     | (c & TMask);
+        return 2;
+    }
+
+    if(c < Rune3Byte){ // 16 bits
+        s[0] = TByte2 | ((c >> 12));
+        s[1] = Tx     | ((c >> 6) & TMask);
+        s[2] = Tx     | ((c)      & TMask);
+        return 3;
+    }
+
+    // 22 bits
+    if(c > RuneMax || (RuneSurrogateMin <= c && c <= RuneSurrogateMax))
+        c = RuneErr;
+
+    s[0] = TByte3 | ((c >> 18));
+    s[1] = Tx     | ((c >> 12) & TMask);
+    s[2] = Tx     | ((c >> 6)  & TMask);
+    s[3] = Tx     | ((c)       & TMask);
+
+    return 4;
+}
+
+#if 0
 int
 utf8·encode(rune* r, byte* s)
 {
@@ -29,3 +66,4 @@ utf8·encode(rune* r, byte* s)
 
     return UTFmax;
 }
+#endif
-- 
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