Feat(libunicode): cleaned up decode/encode

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

1 files changed, 20 insertions, 17 deletions

diff --git a/sys/libunicode/internal.h b/sys/libunicode/internal.h
index 31ed2ae..6b0657b 100644
--- a/sys/libunicode/internal.h
+++ b/sys/libunicode/internal.h
@@ -4,7 +4,9 @@
 #include <base.h>
 #include <libunicode.h>
 
-/* UTF-8 code
+/*
+ * NOTE: we use the preprocessor to ensure we have unsigned constants.
+ * UTF-8 code:
  * 1 byte:
  * 0xxxxxxx
  * 2 byte:
@@ -14,22 +16,23 @@
  * 4 byte:
  * 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
  */
-#define Bit(i) (7-(i))
-/* 0's preceded by i 1's e.g. T(Bit(2)) is 1100 0000 */
-#define Tbyte(i) (((1 << (Bit(i)+1))-1) ^ 0xFF)
-/* 0000 0000 0000 0111 1111 1111 */
-#define	RuneX(i) ((1 << (Bit(i) + ((i)-1)*Bitx))-1)
 
-enum
-{
-    Bitx  = Bit(1),
-    Tx    = Tbyte(1),
-    Rune1 = (1 << (Bit(0)+0*Bitx)) - 1,
+#define Tx     0x80u // 0b10000000 transfer header
+#define TMask  0x3Fu // 0b00111111 transfer mask
 
-    Maskx = (1 << Bitx) - 1, /* 0011 1111 */
-    Testx = Maskx ^ 0xff,    /* 1100 0000 */
+#define TByte1 0xC0u // 0b11000000
+#define TByte2 0xE0u // 0b11100000
+#define TByte3 0xF0u // 0b11110000
+#define TByte4 0xF8u // 0b11111000
 
-    SurrogateMin = 0xD800,
-    SurrogateMax = 0xDFFF,
-    Bad = RuneErr,
-};
+#define Rune1Byte 0x000080u  // 1 << 8   (1 byte)
+#define Rune2Byte 0x001000u  // 1 << 12  (2 bytes)
+#define Rune3Byte 0x020000u  // 1 << 17  (3 bytes)
+#define Rune4Byte 0x400000u  // 1 << 22  (4 bytes)
+
+#define RuneMax   0x10FFFFu
+#define RuneMask  0x1FFFFFu
+
+/* UTF-16 nonsense */
+#define RuneSurrogateMin 0x0D8000
+#define RuneSurrogateMax 0x0D8FFF