1 files changed, 59 insertions, 0 deletions
diff --git a/zap/src/mem/fndbyte.S b/zap/src/mem/fndbyte.S
new file mode 100644
index 0000000..4413b42
--- /dev/null
+++ b/zap/src/mem/fndbyte.S
@@ -0,0 +1,59 @@
+/*
+	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 <zap/priv.h>
+
+.globl zap_fndbyte
+
+zap_fndbyte:
+
+	/*
+		void const *  ptr
+		zap_sz        num
+		unsigned char byte
+	*/
+
+#if defined(__amd64__)
+
+	# rax: Address of the current element.
+	# rdi: Address of the first element.
+	# rsi: Address of the element after the last element.
+	# rdx: Byte value.
+	# rcx: Current byte.
+
+	movq %rdi,%rax
+
+	addq %rdi,%rsi
+
+	# Iterate over the array:
+.loop:
+
+	# Check if we have reached the end of the array:
+	cmpq %rax,%rsi
+	je .nfnd
+	
+	# Check if we have found the byte value:
+	movb (%rax),%cl
+	cmpb %cl,%dl
+	je .fnd
+
+	# Continue to the next byte:
+	incq %rax
+	jmp .loop
+
+	# Found:
+.fnd:
+
+	subq %rdi,%rax
+	ret
+
+	# Not found:
+.nfnd:
+
+	movq $0xFFFFFFFFFFFFFFFF,%rax
+	ret
+
+#endif