1 files changed, 44 insertions, 0 deletions
diff --git a/zap/source/amd64/mem/fndbyte.S b/zap/source/amd64/mem/fndbyte.S
new file mode 100644
index 0000000..9298b73
--- /dev/null
+++ b/zap/source/amd64/mem/fndbyte.S
@@ -0,0 +1,44 @@
+# 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/.
+
+.globl zap_fndbyte
+
+zap_fndbyte:
+ # 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