Title here
Summary here
String Formatting in Assembly Language
section .data
struct_fmt db "struct1: {%d %d}", 10, 0
struct_fmt2 db "struct2: {x:%d y:%d}", 10, 0
type_fmt db "type: point", 10, 0
bool_fmt db "bool: %s", 10, 0
int_fmt db "int: %d", 10, 0
bin_fmt db "bin: %b", 10, 0
char_fmt db "char: %c", 10, 0
hex_fmt db "hex: %x", 10, 0
float_fmt db "float1: %f", 10, 0
float_fmt2 db "float2: %e", 10, 0
float_fmt3 db "float3: %E", 10, 0
str_fmt db "str1: %s", 10, 0
str_fmt2 db 'str2: "%s"', 10, 0
str_fmt3 db "str3: ", 0
pointer_fmt db "pointer: %p", 10, 0
width_fmt db "width1: |%6d|%6d|", 10, 0
width_fmt2 db "width2: |%6.2f|%6.2f|", 10, 0
width_fmt3 db "width3: |%-6.2f|%-6.2f|", 10, 0
width_fmt4 db "width4: |%6s|%6s|", 10, 0
width_fmt5 db "width5: |%-6s|%-6s|", 10, 0
sprintf_fmt db "sprintf: a %s", 10, 0
io_fmt db "io: an %s", 10, 0
true_str db "true", 0
string_val db '"string"', 0
hex_str db "hex this", 0
foo_str db "foo", 0
b_str db "b", 0
error_str db "error", 0
section .bss
buffer resb 100
section .text
global _start
_start:
; struct1: {1 2}
push 2
push 1
push struct_fmt
call printf
add esp, 12
; struct2: {x:1 y:2}
push 2
push 1
push struct_fmt2
call printf
add esp, 12
; type: point
push type_fmt
call printf
add esp, 4
; bool: true
push true_str
push bool_fmt
call printf
add esp, 8
; int: 123
push 123
push int_fmt
call printf
add esp, 8
; bin: 1110
push 14
push bin_fmt
call printf
add esp, 8
; char: !
push 33
push char_fmt
call printf
add esp, 8
; hex: 1c8
push 456
push hex_fmt
call printf
add esp, 8
; float1: 78.900000
push dword 0x429dc000 ; 78.9 in IEEE 754 format
push float_fmt
call printf
add esp, 8
; float2: 1.234000e+08
push dword 0x4ceb79a3 ; 123400000.0 in IEEE 754 format
push float_fmt2
call printf
add esp, 8
; float3: 1.234000E+08
push dword 0x4ceb79a3 ; 123400000.0 in IEEE 754 format
push float_fmt3
call printf
add esp, 8
; str1: "string"
push string_val
push str_fmt
call printf
add esp, 8
; str2: "\"string\""
push string_val
push str_fmt2
call printf
add esp, 8
; str3: 6865782074686973
push str_fmt3
call printf
add esp, 4
mov esi, hex_str
mov ecx, 8
print_hex:
xor eax, eax
lodsb
push ecx
push eax
push hex_fmt
call printf
add esp, 8
pop ecx
loop print_hex
push 10
call putchar
add esp, 4
; pointer: (memory address)
push esp
push pointer_fmt
call printf
add esp, 8
; width1: | 12| 345|
push 345
push 12
push width_fmt
call printf
add esp, 12
; width2: | 1.20| 3.45|
push dword 0x40599999 ; 3.45 in IEEE 754 format
push dword 0x3f99999a ; 1.2 in IEEE 754 format
push width_fmt2
call printf
add esp, 12
; width3: |1.20 |3.45 |
push dword 0x40599999 ; 3.45 in IEEE 754 format
push dword 0x3f99999a ; 1.2 in IEEE 754 format
push width_fmt3
call printf
add esp, 12
; width4: | foo| b|
push b_str
push foo_str
push width_fmt4
call printf
add esp, 12
; width5: |foo |b |
push b_str
push foo_str
push width_fmt5
call printf
add esp, 12
; sprintf: a string
push string_val
push sprintf_fmt
push buffer
call sprintf
add esp, 12
push buffer
call printf
add esp, 4
; io: an error
push error_str
push io_fmt
call printf
add esp, 8
; Exit the program
mov eax, 1
xor ebx, ebx
int 0x80This Assembly Language code demonstrates various string formatting techniques. It uses the C standard library functions like printf and sprintf for formatting and printing. Here’s a breakdown of the key points:
- We define various format strings and data in the
.datasection. - The
.bsssection is used for uninitialized data, like our buffer forsprintf. - In the
.textsection, we implement the main logic:- We use
pushto pass arguments to functions in reverse order. - We call
printffor most formatting operations. - For floating-point numbers, we use their IEEE 754 representations.
- We demonstrate width and precision formatting for integers, floats, and strings.
- We show left-justification using the
-flag in the format specifier. - We use
sprintfto format a string into a buffer.
- We use
Note that Assembly Language doesn’t have built-in high-level formatting functions like Go’s fmt package. We rely on C library functions for most formatting operations. The hex string printing is done manually as an example of low-level string manipulation in Assembly.
To run this program, you would need to assemble it with NASM, link it with the C standard library, and then execute the resulting binary. The exact commands may vary depending on your system and assembler.