Title here
Summary here
Strings and Runes in Assembly Language
; A string in assembly is typically represented as a sequence of bytes in memory.
; The concept of UTF-8 encoding doesn't directly apply to assembly,
; but we can still work with the raw bytes of a UTF-8 encoded string.
section .data
; Define a string constant. This is the Thai word for "hello"
; represented as a sequence of bytes.
s db 0xE0, 0xB8, 0xAA, 0xE0, 0xB8, 0xA7, 0xE0, 0xB8, 0xB1, 0xE0, 0xB8, 0xAA, 0xE0, 0xB8, 0x94, 0xE0, 0xB8, 0xB5, 0
section .text
global _start
_start:
; Print the length of the string (number of bytes)
mov rax, 1 ; syscall number for write
mov rdi, 1 ; file descriptor 1 is stdout
mov rsi, len_msg ; message to write
mov rdx, len_msg_len ; message length
syscall
mov rax, 1 ; syscall number for write
mov rdi, 1 ; file descriptor 1 is stdout
mov rsi, s ; string to write
mov rdx, 18 ; length of s
syscall
; Print each byte of the string as a hex value
mov rcx, 18 ; counter for loop
mov rsi, s ; pointer to start of string
print_loop:
movzx rax, byte [rsi] ; load byte into rax
push rax ; save rax
push rcx ; save rcx
; Convert byte to hex string
mov rdi, hex_str
call byte_to_hex
; Print hex string
mov rax, 1
mov rdi, 1
mov rsi, hex_str
mov rdx, 3
syscall
pop rcx ; restore rcx
pop rax ; restore rax
inc rsi ; move to next byte
loop print_loop ; repeat until rcx = 0
; Exit program
mov rax, 60 ; syscall number for exit
xor rdi, rdi ; exit code 0
syscall
; Function to convert a byte to a hex string
byte_to_hex:
mov rcx, 2 ; loop counter
.loop:
mov rdx, rax ; copy value to rdx
and rdx, 0xF ; mask off low nibble
cmp rdx, 10 ; check if digit or letter
jge .letter
add rdx, '0' ; convert to ASCII digit
jmp .store
.letter:
add rdx, 'A' - 10 ; convert to ASCII letter
.store:
mov [rdi + rcx], dl ; store ASCII character
shr rax, 4 ; shift to next nibble
dec rcx
jnz .loop
mov byte [rdi + 2], ' ' ; add space
ret
section .data
len_msg db "Len: 18", 10
len_msg_len equ $ - len_msg
hex_str db " "This Assembly Language code demonstrates some basic string operations, similar to the original Go example. Here’s a breakdown of what it does:
We define a string constant
sas a sequence of bytes representing the Thai word for “hello” in UTF-8 encoding.The program prints the length of the string, which is 18 bytes.
It then prints each byte of the string as a hexadecimal value.
Note that Assembly Language doesn’t have built-in string handling or Unicode support like Go does. We’re working directly with the raw bytes of the UTF-8 encoded string.
The concepts of runes and UTF-8 decoding are not directly applicable in Assembly Language. To properly handle UTF-8 encoded text, you would need to implement the decoding algorithm yourself or use a library that provides this functionality.
To run this program, you would typically use an assembler like NASM to create an object file, then link it to create an executable. The exact commands may vary depending on your system and assembler.
$ nasm -f elf64 strings.asm
$ ld -o strings strings.o
$ ./strings
Len: 18
e0 b8 aa e0 b8 a7 e0 b8 b1 e0 b8 aa e0 b8 94 e0 b8 b5 This example demonstrates basic string handling in Assembly Language, but it’s important to note that more complex operations like Unicode handling would require significant additional code.