From ed2f31c5978911d8afe9276e55b3be22bdd0547b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gustav=20S=C3=B6rn=C3=A4s?= <gustav@sornas.net>
Date: Fri, 5 Feb 2021 17:00:09 +0100
Subject: implement read() and refactor out get_file and get_fd

---
 src/userprog/syscall.c | 77 ++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 65 insertions(+), 12 deletions(-)

(limited to 'src/userprog')

diff --git a/src/userprog/syscall.c b/src/userprog/syscall.c
index 0dd48b0..3a780c6 100644
--- a/src/userprog/syscall.c
+++ b/src/userprog/syscall.c
@@ -4,6 +4,8 @@
 #include "threads/interrupt.h"
 #include "threads/thread.h"
 
+#include "devices/input.h"
+#include "filesys/file.h"
 #include "filesys/filesys.h"
 #include "filesys/off_t.h"
 #include "threads/init.h"
@@ -58,29 +60,79 @@ open (const char *filename)
   return -1;
 }
 
-static void
-write (const char *buf)
+static struct fd *
+get_fd (struct thread *thread, int fd_i)
 {
-  printf ("printf: %s", buf);
+  if (!thread->fds) {
+    return NULL;
+  }
+
+  return thread->fds + fd_i - 2;  // -2 since 0 and 1 are reserved and not present in the array
+}
+
+static struct file *
+get_file (struct thread *thread, int fd_i)
+{
+  struct fd *fd = get_fd(thread, fd_i);
+
+  if (!fd || !fd->active) {
+    printf("[%s] get_file: invalid file descriptor\n", thread->name);
+    return NULL;
+  }
+
+  return fd->file;
+}
+
+static int
+read (int fd_i, void *buf, unsigned size)
+{
+  struct thread *thread = thread_current ();
+
+  if (fd_i == 0) {
+    // stdin
+    int i;
+    for (i = 0; i < size; i++) {
+      ((char *)buf)[i] = input_getc ();
+    }
+    return i;
+  } else if (fd_i == 1) {
+    // can't read from stdout
+    printf("[%s] read: tried to read from stdout\n", thread->name);
+    return -1;
+  }
+
+  struct file *file = get_file(thread, fd_i);
+  if (!file) {
+    return -1;
+  }
+
+  int n = file_read (file, buf, size);
+  printf("%d/%d: %s\n", n, size, (char *)buf);
+  return n;
+}
+
+static int
+write (int fd_i, const void *buf, unsigned size)
+{
+  printf ("write: %s", (char *)buf);
+  return 0;
 }
 
 static void
-close (int i)
+close (int fd_i)
 {
-  struct thread *t = thread_current ();
+  struct thread *thread = thread_current ();
 
-  if (!t->fds) {
-    printf("[%s] close: no files have been opened\n", t->name);
+  struct fd *fd = get_fd(thread, fd_i);
+  if (!fd) {
     return;
   }
-
-  struct fd *fd = t->fds + i - 2; // -2 since 0 and 1 are reserved and not present in the array
   if (!fd->active) {
-    printf("[%s] close: tried to close inactive file descriptor %d\n", t->name, i);
+    printf("[%s] close: tried to close inactive file descriptor %d\n", thread->name, fd_i);
     return;
   }
 
-  free(fd->file);
+  file_close (fd->file);
   fd->active = false;
 }
 
@@ -109,10 +161,11 @@ syscall_handler (struct intr_frame *f UNUSED)
       break;
     case 8:
       // read
+      f->eax = read (INTR_ESP (1, int), INTR_ESP (2, void *), INTR_ESP (3, unsigned));
       break;
     case 9:
       // write
-      write (INTR_ESP(2, char *));
+      f->eax = write (INTR_ESP (1, int), INTR_ESP (2, const void *), INTR_ESP (3, unsigned));
       break;
     case 12:
       // close
-- 
cgit v1.2.1