1 files changed, 39 insertions, 0 deletions
diff --git a/zap/source/amd64/mem/strcp.S b/zap/source/amd64/mem/strcp.S
new file mode 100644
index 0000000..eb5c276
--- /dev/null
+++ b/zap/source/amd64/mem/strcp.S
@@ -0,0 +1,39 @@
+# 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_strcp
+
+zap_strcp:
+ # rax: Address of the current input character.
+ # rdi: Address of the first input character.
+ # rsi: Address of the current output character.
+ # rdx: Current character.
+
+ movq %rdi,%rax
+
+ # Iterate over the strings:
+.loop:
+
+ # Copy character:
+ movb (%rax),%dl # Move it into a register...
+ movb %dl,(%rsi) # ... and then back into memory.
+
+ # Check if we have reached the null-terminator:
+ testb %dl,%dl
+ jz .done
+
+ # Continue to the next character:
+
+ incq %rax
+ incq %rsi
+ jmp .loop
+
+ # Finish:
+.done:
+
+ # Get the length of the (input) string:
+ subq %rdi,%rax
+ decq %rax # We do not count the null-terminator in the string length.
+
+ ret