added threads.h header file for example program

programs/.gitignore

@@ -3,3 +3,4 @@
 !*.c
 !Makefile
 !.gitignore
+!*.h

programs/threads.h

@@ -0,0 +1,55 @@
+#pragma once
+#define TEXT_IO_ADDR 0xff0000
+#define TEXT_IO_BUFLEN 64
+
+// these parts are taken from the ktypes.h file
+enum error_code {
+    ENOCODE = 1,    // invalid syscall code
+    EINVAL  = 2,    // invalid argument value
+    ENOMEM  = 3,    // not enough memory
+    ENOBUFS = 4,    // no space left in buffer
+    ESRCH   = 5,    // no such process
+    ETIMEOUT= 6     // timeout while waiting
+};
+
+struct optional_int {
+    enum error_code error;
+    int value;
+};
+// has_value and has_error are not dependent on the value type
+// therefore we can define them as macros
+#define has_value(optional) (optional.error == 0)
+#define has_error(optional) (!has_value(optional))
+
+void dbgln(char*, int);
+char* itoa(int value, char* str, int base);
+
+int thread(void* args);
+
+__attribute__((naked)) struct optional_int spawn(int (*target)(void*), void* args) {
+    __asm__ (
+         "li a7, 1\n"
+         "ecall\n"
+         "ret"
+    );
+    __builtin_unreachable();
+}
+
+__attribute__((naked)) struct optional_int join(int pid, int timeout) {
+    __asm__ (
+         "li a7, 3\n"
+         "ecall\n"
+         "ret"
+    );
+    __builtin_unreachable();
+}
+
+
+__attribute__((naked)) struct optional_int sleep(int timeout) {
+    __asm__ (
+         "li a7, 2\n"
+         "ecall\n"
+         "ret"
+    );
+    __builtin_unreachable();
+}