diff options
Diffstat (limited to 'zap/source/amd64/mem/strlen.S')
| -rw-r--r-- | zap/source/amd64/mem/strlen.S | 25 |
1 files changed, 14 insertions, 11 deletions
diff --git a/zap/source/amd64/mem/strlen.S b/zap/source/amd64/mem/strlen.S index e8739e2..a3f68b1 100644 --- a/zap/source/amd64/mem/strlen.S +++ b/zap/source/amd64/mem/strlen.S @@ -5,30 +5,33 @@ .globl zap_strlen zap_strlen: - # rax: Address of the current character. - # rdi: Address of the first character. - # rdx: Current character. +# Address of the current character: +#define addr %rax +# Address of the first character: +#define start %rdi +# Current character: +#define chr %dl - movq %rdi,%rax + movq start,addr # Iterate over the string: .loop: # Move the character into a register: - movb (%rax),%dl + movb (addr),chr # chr = *addr # Check if we have reached the null-terminator: - testb %dl,%dl - jz .done # If so, we are done. + testb chr,chr # if (chr == 0x0) + jz .done # goto done # Continue to the next character: - incq %rax - jmp .loop + incq addr # ++addr + jmp .loop # goto loop # Done: .done: # Get the length: - subq %rdi,%rax + subq start,addr # addr -= start - ret + ret # return addr |