* Created internal function _cucul_argb32_to_argb4() that splits an argb

fg/bg value into its separate argb 4-bit fields.

cucul/colour.c

@@ -23,6 +23,12 @@
 #include "cucul.h"
 #include "cucul_internals.h"
 
+static const uint16_t ansitab[16] =
+{
+    0xf000, 0xf008, 0xf080, 0xf088, 0xf800, 0xf808, 0xf880, 0xf888,
+    0xf444, 0xf44f, 0xf4f4, 0xf4ff, 0xff44, 0xff4f, 0xfff4, 0xffff,
+};
+
 /* FIXME: could this be inlined? */
 
 uint8_t _cucul_argb32_to_ansi8(uint32_t c)
@@ -43,3 +49,25 @@ uint8_t _cucul_argb32_to_ansi4bg(uint32_t c)
     return (c & 0x000f0000) >> 16;
 }
 
+void _cucul_argb32_to_argb4(uint32_t c, uint8_t argb[8])
+{
+    uint16_t fg = c & 0xffff;
+    uint16_t bg = c >> 16;
+
+    if(fg < 0x0016)
+        fg = ansitab[fg];
+
+    if(bg < 0x0016)
+        bg = ansitab[bg];
+
+    argb[0] = bg >> 12;
+    argb[1] = (bg >> 8) & 0xf;
+    argb[2] = (bg >> 4) & 0xf;
+    argb[3] = bg & 0xf;
+
+    argb[4] = fg >> 12;
+    argb[5] = (fg >> 8) & 0xf;
+    argb[6] = (fg >> 4) & 0xf;
+    argb[7] = fg & 0xf;
+}
+

cucul/cucul_internals.h

@@ -65,6 +65,7 @@ extern uint32_t _cucul_cp437_to_utf32(uint8_t);
 uint8_t _cucul_argb32_to_ansi8(uint32_t);
 uint8_t _cucul_argb32_to_ansi4fg(uint32_t);
 uint8_t _cucul_argb32_to_ansi4bg(uint32_t);
+void _cucul_argb32_to_argb4(uint32_t, uint8_t[8]);
 
 /* Export functions */
 extern void _cucul_get_ansi(cucul_t *, struct cucul_export *);