sparsefile
The sparsefile is a feature in the Linux operating system that allows for the creation of files that appear to be of a certain size, but actually take up less disk space. It is commonly used for testing purposes or when creating large files that do not need to be fully allocated on disk.
To create a sparsefile in assembly language, you would typically use system calls provided by the operating system. Here is an example of how you can create a sparsefile using the Linux system calls:
section .data
filename db 'sparsefile', 0
filemode db 0666
section .text
global _start
_start:
; Open the file
mov eax, 5 ; sys_open system call number
mov ebx, filename
mov ecx, 2 ; O_RDWR|O_CREAT
mov edx, filemode
int 0x80
; Check for errors
test eax, eax
js error
; Seek to the desired file size
mov eax, 19 ; sys_lseek system call number
mov ebx, eax ; File descriptor
mov ecx, 0 ; Offset
mov edx, 1024 ; Desired file size
mov esi, 0x40000000 ; SEEK_HOLE
int 0x80
; Check for errors
test eax, eax
js error
; Close the file
mov eax, 6 ; sys_close system call number
mov ebx, eax ; File descriptor
int 0x80
; Exit the program
mov eax, 1 ; sys_exit system call number
xor ebx, ebx ; Exit status
int 0x80
error:
; Handle error
; ...
This example uses the sys_open
, sys_lseek
, and sys_close
system calls to open the file, seek to the desired file size (using the SEEK_HOLE
flag), and close the file, respectively. The file is opened with read-write permissions and created if it does not exist. The desired file size is set to 1024 bytes in this example, but you can modify it as needed.
Please note that this is a simplified example and does not include error handling or other necessary code. Additionally, the specific system call numbers and register usage may vary depending on the assembly language and operating system you are using.