ASM: cpp-and-asm-a.asm

global _allCaps
_allCaps:
	mov rax, rdi		; get the pointer to the buffer from calling function / rax is the return value
	xor rcx, rcx		; counter=0
top:	mov BYTE dl, [rax]	; mov the byte at the address in rax into dl
	inc rcx			; add one to the length counter
	xor dh, dh		; Zero out the High Bit of dx
	cmp dl, 0x00		; check for end of buffer
	je go_back		; if we've reached a 0, return from this function 
	and dl, 0x5F		; make the ASCII character capitol
	mov [rax], dl		; put the modified character back into the buffer
	inc rax			; point to next character
	jmp top			; go back to the top of the loop
go_back:dec rcx			; subtract 1 from counter (becuase that last one was a 0 signifying the end of the buffer)
	mov rax, rcx		; since rax is what gets returned, put the counter value (rcx) into rax
	ret			; return from this function


CPP: cpp-and-asm-c.cpp

#include <stdio.h>
extern "C" int allCaps(char*);
int main(int argc, char **argv)
{
  char buf[]="hello";
  printf( "Buffer: [%s]\n", buf );
  allCaps(buf);
  printf( "Buffer: [%s]\n", buf );
  printf( "Size: %d\n", allCaps(buf));
  return(0);
}


MAKEFILE: Makefile

cpp-and-asm : cpp-and-asm_a.asm
	nasm -f macho64 cpp-and-asm_a.asm -o $(LIB_DIR)cpp-and-asm_a.o
	g++ -c $(OPT) $(CPP_FLAGS) cpp-and-asm-c.cpp -o $(LIB_DIR)cpp-and-asm_c.o
	g++ $(LIB_DIR)cpp-and-asm-c.o $(LIB_DIR)cpp-and-asm-a.o   -o $(BIN_DIR)cpp-and-asm