Feat(libunicode): Added an explicit unicode library

Refactored code to pull out utf8 functions from base into a standalone
library. Also left the required function inside arg.c so that code that
calls ARG_BEGIN doesn't have to link to libunicode.

1 files changed, 31 insertions, 0 deletions

diff --git a/sys/libunicode/runetobyte.c b/sys/libunicode/runetobyte.c
new file mode 100644
index 0000000..27f252b
--- /dev/null
+++ b/sys/libunicode/runetobyte.c
@@ -0,0 +1,31 @@
+#include "internal.h"
+
+int
+utf8·runetobyte(byte* s, rune* r)
+{
+    int i, j;
+    rune c;
+
+    c = *r;
+    if(c <= Rune1) {
+        s[0] = c;
+        return 1;
+    }
+
+    for(i = 2; i < UTFmax + 1; i++){
+        if(i == 3){
+            if(c > RuneMax)
+                c = RuneErr;
+            if(SurrogateMin <= c && c <= SurrogateMax)
+                c = RuneErr;
+        }
+        if(c <= RuneX(i) || i == UTFmax) {
+            s[0] = Tbyte(i) |  (c >> (i - 1)*Bitx);
+            for(j = 1; j < i; j++)
+                s[j] = Tx | ((c >> (i - j - 1)*Bitx) & Maskx);
+            return i;
+        }
+    }
+
+    return UTFmax;
+}