1 files changed, 88 insertions, 0 deletions
diff --git a/src/main.S b/src/main.S
new file mode 100644
index 0000000..0a21f83
--- /dev/null
+++ b/src/main.S
@@ -0,0 +1,88 @@
+#include "SDL_interface.S"
+
+#define SCREEN_WIDTH 800
+#define SCREEN_HEIGHT 600
+
+// integer-params:  RDI, RSI, RDX, RCX, R8, R9
+// caller-saved:    RAX, RCX, RDX, RSI, RDI, R8-R11
+// callee-saved:    RBX, RSP, RBP, R12-R15
+
+.section .rodata
+  failed_to_create_window:  .string "Window could not be created\nSDL_error: %s\n"
+  failed_to_initialize_sdl: .string "SDL could not be initialized\nSDL_error: %s\n"
+  greeting:                 .string "Hello, SDL!\n"
+  window_title:             .string "snake.s"
+
+.section .text
+  .global main
+
+  // void _print_sdl_error(char const * format)
+  .type _print_sdl_error, @function
+  _print_sdl_error:
+    push %rbp
+    mov %rsp, %rbp
+
+    push %rdi
+    sub $8, %rsp
+ 
+    call SDL_GetError@PLT
+    mov %rax, %rsi
+ 
+    add $8, %rsp
+    pop %rdi
+
+    call printf@PLT
+    jmp .Lexit
+
+    leave
+    ret
+
+  .type main, @function
+  main: 
+    push %rbp
+    mov %rsp, %rbp
+
+    // initialize SDL
+    mov $SDL_INIT_VIDEO, %rdi
+    call SDL_Init@PLT
+
+    // check if initialization was successful
+    cmp $0, %rax
+    jae 1f
+      lea failed_to_initialize_sdl(%rip), %rdi
+      call _print_sdl_error@PLT
+      mov $1, %rax
+      jmp .Lexit
+  1:
+
+    // create a window
+    lea window_title(%rip), %rdi
+    mov $SDL_WINDOWPOS_UNDEFINED, %rsi
+    mov $SDL_WINDOWPOS_UNDEFINED, %rdx
+    mov $SCREEN_WIDTH, %rcx
+    mov $SCREEN_HEIGHT, %r8
+    mov $SDL_WINDOW_SHOWN, %r9
+    call SDL_CreateWindow@PLT
+
+    cmp $0, %rax
+    jne 1f
+      lea failed_to_create_window(%rip), %rdi
+      call _print_sdl_error@PLT
+      mov $1, %rax
+      jmp .Lexit
+  1:
+
+  mov %rax, %rdi
+  call SDL_DestroyWindow@PLT
+  call SDL_Quit@PLT
+
+  .Lsuccess:
+    lea greeting(%rip), %rdi
+    xor %rax, %rax
+    call printf@PLT
+
+    xor %rax, %rax
+
+  .Lexit:
+    leave
+    ret