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Diffstat (limited to 'zap/src/mem/strcp.S')
-rw-r--r-- | zap/src/mem/strcp.S | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/zap/src/mem/strcp.S b/zap/src/mem/strcp.S new file mode 100644 index 0000000..04c3198 --- /dev/null +++ b/zap/src/mem/strcp.S @@ -0,0 +1,53 @@ +/* + 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_strcp + +zap_strcp: + + /* + char const * in + char const * out + */ + +#if defined(__amd64__) + + # 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 + +#endif |