1 files changed, 54 insertions, 0 deletions
diff --git a/rgo/src/strlen.c b/rgo/src/strlen.c
new file mode 100644
index 0000000..6ddbf8b
--- /dev/null
+++ b/rgo/src/strlen.c
@@ -0,0 +1,54 @@
+/*
+	Copyright 2022 Gabriel Jensen.
+	This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
+	If a copy of the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
+*/
+
+#include <rgo-priv.h>
+
+#if defined(rgo_priv_fastimpl)
+__asm__ (
+	".global rgo_strlen\n"
+
+	"rgo_strlen:\n"
+		/*
+			char const * str
+		*/
+#if defined(sus_arch_amd64)
+		/* rax: Address of the current character. */
+		"movq %rdi,%rax\n"
+		/* rdx: Current character. */
+	".loop:\n"
+		"movb (%rax),%dl\n"
+		"testb %dl,%dl\n"
+		"jz .done\n" /* Exit loop if we have reached the null-terminator. */
+		"incq %rax\n" /* Continue to the next character. */
+		"jmp .loop\n"
+	".done:\n"
+		"subq %rdi,%rax\n"
+		"ret\n"
+#elif defined(sus_arch_ia32)
+		/* eax: Address of the current character. */
+		"movl 0x4(%esp),%eax\n"
+		/* ecx: Current character. */
+	".loop:\n"
+		"movb (%eax),%cl\n"
+		"testb %cl,%cl\n"
+		"jz .done\n" /* Exit loop if we have reached the null-terminator. */
+		"incl %eax\n" /* Continue to the next character. */
+		"jmp .loop\n"
+	".done:\n"
+		"subl 0x4(%esp),%eax\n"
+		"ret\n"
+#endif
+);
+#else
+sus_typ_usz rgo_strlen(char const * const sus_restr _str) {
+	char const * sus_restr pos = _str;
+	for (;;++pos) {
+		char const chr = *pos;
+		sus_unlikely (chr == '\x0') {return (sus_typ_usz)(pos - _str);}
+	}
+	sus_unreach();
+}
+#endif