io: allocate I/O descriptors for process

src/io.c

@@ -0,0 +1,36 @@
+/*
+ * lux - a lightweight unix-like operating system
+ * Omar Elghoul, 2024
+ * 
+ * Core Microkernel
+ */
+
+/* Abstractions for file systems and sockets */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <kernel/sched.h>
+#include <kernel/io.h>
+
+/* openIO(): opens an I/O descriptor in the current process
+ * params: p - process to open descriptor in
+ * params: iod - destination to store pointer to I/O descriptor structure
+ * returns: I/O descriptor, negative error code on fail
+ */
+
+int openIO(void *pv, void **iodv) {
+    Process *p = (Process *)pv;
+    IODescriptor *iod = (IODescriptor *)iodv;
+
+    if(p->iodCount >= MAX_IO_DESCRIPTORS) return -ESRCH;
+
+    /* randomly allocate descriptors instead of sequential numbering */
+    int desc;
+    do {
+        desc = rand() % MAX_IO_DESCRIPTORS;
+    } while(p->io[desc].valid);
+
+    p->io[desc].valid = true;
+    p->io[desc].type = IO_WAITING;
+    return desc;
+}