Merge branch 'Alex/24-implement-seek-system-call' into 'feature/system-calls'

Implemented the system call seek

See merge request !21

Makefile.build

@@ -74,6 +74,8 @@ userprog_SRC += userprog/file_descriptors_map.c
 userprog_SRC += userprog/syscall_read.c
 userprog_SRC += userprog/syscall_filesize.c
 userprog_SRC += userprog/syscall_tell.c
+userprog_SRC += userprog/syscall_seek.c
+userprog_SRC += userprog/syscall_close.c
 
 # No virtual memory code yet.
 #vm_SRC = vm/file.c			# Some file.

userprog/syscall.c

@@ -88,6 +88,12 @@ syscall_handler (struct intr_frame *f UNUSED)
   case SYSCALL_TELL:
     syscall_tell(f);
     break;
+  case SYSCALL_SEEK:
+	  syscall_seek(f);
+	  break;
+  case SYSCALL_CLOSE:
+    syscall_close(f);
+    break;
   default:
     printf ("WARNING: Invalid Syscall (%d)\n", syscall_number);
     thread_exit ();

userprog/syscall_close.c

@@ -14,7 +14,7 @@
 
 void syscall_close(struct intr_frame *f) {
 	// pop off first int argument from interrupt frame
-	int* file_descriptor = (void*)(*(int*)f->esp + 1);
+	int file_descriptor = *((int*)f->esp + 1);
 	// Get file associated with file_descriptor
 	struct file *file = get_associated_file_pointer(file_descriptor);
 	if (file == NULL) { // Checking if file is empty or non-existent

userprog/syscall_seek.c

+/*
+* Changes the next byte to be read or written in open file fd to position, 
+* Expressed in bytes from the beginning of the file. (Thus, a position of 0
+* Is the file’s start.)
+*
+* Authored by Alex Stratford
+*/
+
+#include "system_calls.h"
+#include <stddef.h> // Dependency for NULL
+#include "threads/interrupt.h" // Dependency for intr_frame struct
+#include "filesys/file.h" // Dependency for file struct and file_seek function
+
+void syscall_seek(struct intr_frame *f) {
+	// pop off first int argument from interrupt frame
+	int file_descriptor = *((int*)f->esp + 1);
+	// pop off second int argument from interrupt frame
+	unsigned file_pos = *((unsigned*)((int*)f->esp + 2));
+	struct file *file = get_associated_file_pointer(file_descriptor);
+	// Seek through the file
+	file_seek(file, file_pos);
+}

userprog/system_calls.h

@@ -75,6 +75,19 @@ void syscall_remove(struct intr_frame *f);
  */
 void syscall_tell(struct intr_frame *f);
 
+/*
+* Changes the next byte to be read or written in open file fd to position,
+* Expressed in bytes from the beginning of the file. (Thus, a position of 0
+* Is the file’s start.)
+*/
+void syscall_seek(struct intr_frame *f);
+
+/*
+ * Closes file descriptor fd. Exiting or terminating a process implicitly closes
+ * all its open file descriptors, as if by calling this function for each one.
+ */
+void syscall_close(struct intr_frame *f);
+
 /*
  * special additional stuff for handling file descriptors because they're annoying
  */