From bc54f34a4d115572beb9a96a64bf7e5841a28e98 Mon Sep 17 00:00:00 2001
From: Timerix <timerix11@gmail.com>
Date: Sat, 16 Nov 2024 23:08:38 +0500
Subject: [PATCH] SYS

---
 src/instructions/impl/SYS.c | 51 +++++++++++++++++++++++++++----------
 1 file changed, 38 insertions(+), 13 deletions(-)

diff --git a/src/instructions/impl/SYS.c b/src/instructions/impl/SYS.c
index 3394ad9..08fce28 100644
--- a/src/instructions/impl/SYS.c
+++ b/src/instructions/impl/SYS.c
@@ -14,25 +14,50 @@ FILE* NULLABLE(fileFromN)(VM* vm, u32 file_n){
     return f;
 }
 
+// sys_read
+// bx - file n
+// cx - buffer ptr
+// dx - buffer size
+i32 SYS_read(VM* vm){
+    const u32 file_n = vm->bx.u32v;
+    u8* const buf = vm->data + vm->cx.u32v;
+    const u32 size = vm->dx.u32v;
+
+    if(buf + size > vm->data + vm->data_size)
+        return 40;
+    
+    FILE* f = fileFromN(vm, file_n);
+    return fread(buf, 1, size, f);
+}
+
+// sys_write
+// bx - file n
+// cx - buffer ptr
+// dx - buffer size
+i32 SYS_write(VM* vm){
+    const u32 file_n = vm->bx.u32v;
+    u8* const buf = vm->data + vm->cx.u32v;
+    const u32 size = vm->dx.u32v;
+
+    if(buf + size > vm->data + vm->data_size)
+        return 41;
+    
+    FILE* f = fileFromN(vm, file_n);
+    return fwrite(buf, 1, size, f);
+}
+
 /// SYS
-/// ax - func code
+/// before call: ax - func code
+/// after  call: ax - result code
 i32 SYS_impl(VM* vm){
     u8 func_code = vm->ax.u8v0;
-    size_t result_code = 0;
+    u32 result_code = 0;
     switch(func_code){
-        // sys_read
-        // bx - file n
-        // cx - buffer ptr
-        // dx - buffer size
-        case 0:;
-            result_code = fread(vm->data + vm->cx.u32v, 1, vm->dx.u32v, fileFromN(vm, vm->bx.u32v));
+        case 0:
+            result_code = SYS_read(vm);
             break;
-        // sys_write
-        // bx - file n
-        // cx - buffer ptr
-        // dx - buffer size
         case 1:;
-            result_code = fwrite(vm->data + vm->cx.u32v, 1, vm->dx.u32v, fileFromN(vm, vm->bx.u32v));
+            result_code = SYS_write(vm);
             break;
         default:
             VM_setError(vm, "invalid system call (%x) ", func_code);