1 files changed, 85 insertions, 0 deletions
diff --git a/src/hexcolour.c b/src/hexcolour.c
new file mode 100644
index 0000000..7d0ad43
--- /dev/null
+++ b/src/hexcolour.c
@@ -0,0 +1,85 @@
+/*
+ * Copyright © 2024 Michael Smith <mikesmiffy128@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <string.h>
+
+#include "intdefs.h"
+
+void hexcolour_rgb(uchar out[static 4], const char *s) {
+	const char *p = s;
+	for (uchar *q = out; q - out < 3; ++q) {
+		if (*p >= '0' && *p <= '9') {
+			*q = *p++ - '0' << 4;
+		}
+		else if ((*p | 32) >= 'a' && (*p | 32) <= 'f') {
+			*q = 10 + (*p++ | 32) - 'a' << 4;
+		}
+		else {
+			// screw it, just fall back on white, I guess.
+			// note: this also handles *p == '\0' so we don't overrun the string
+			memset(out, 255, 4); // should be a single mov
+			return;
+		}
+		// repetitive unrolled nonsense
+		if (*p >= '0' && *p <= '9') {
+			*q |= *p++ - '0';
+		}
+		else if ((*p | 32) >= 'a' && (*p | 32) <= 'f') {
+			*q |= 10 + (*p++ | 32) - 'a';
+		}
+		else {
+			memset(out, 255, 4); // should be a single mov
+			return;
+		}
+	}
+	//out[3] = 255; // never changes!
+}
+
+void hexcolour_rgba(uchar out[static 4], const char *s) {
+	const char *p = s;
+	// same again but with 4 pairs of digits instead of 3!
+	for (uchar *q = out; q - out < 4; ++q) {
+		if (*p >= '0' && *p <= '9') {
+			*q = *p++ - '0' << 4;
+		}
+		else if ((*p | 32) >= 'a' && (*p | 32) <= 'f') {
+			*q = 10 + (*p++ | 32) - 'a' << 4;
+		}
+		else {
+			if (q - out == 3 && !*p) {
+				// ONLY if both the last alpha digits are missing: use provided
+				// RGB at full opacity. otherwise same white fallback as before.
+				out[3] = 255;
+				return;
+			}
+			memset(out, 255, 4);
+			return;
+		}
+		// even more repetitive unrolled nonsense
+		if (*p >= '0' && *p <= '9') {
+			*q |= *p++ - '0';
+		}
+		else if ((*p | 32) >= 'a' && (*p | 32) <= 'f') {
+			*q |= 10 + (*p++ | 32) - 'a';
+		}
+		else {
+			memset(out, 255, 4);
+			return;
+		}
+	}
+}
+
+// vi: sw=4 ts=4 noet tw=80 cc=80