From 4fa8614db068e92c2628456df7a7d5483e4afe5b Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@swtch.com>
Date: Tue, 11 Jan 2011 13:54:23 -0500
Subject: [PATCH] missing file memide.c

---
 memide.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 memide.c

diff --git a/memide.c b/memide.c
new file mode 100644
index 0000000..d2c5bb7
--- /dev/null
+++ b/memide.c
@@ -0,0 +1,58 @@
+// Fake IDE disk; stores blocks in memory.
+// Useful for running kernel without scratch disk.
+
+#include "types.h"
+#include "defs.h"
+#include "param.h"
+#include "mmu.h"
+#include "proc.h"
+#include "x86.h"
+#include "traps.h"
+#include "spinlock.h"
+#include "buf.h"
+
+extern uchar _binary_fs_img_start[], _binary_fs_img_size[];
+
+static int disksize;
+static uchar *memdisk;
+
+void
+ideinit(void)
+{
+  memdisk = _binary_fs_img_start;
+  disksize = (uint)_binary_fs_img_size/512;
+}
+
+// Interrupt handler.
+void
+ideintr(void)
+{
+  // no-op
+}
+
+// Sync buf with disk. 
+// If B_DIRTY is set, write buf to disk, clear B_DIRTY, set B_VALID.
+// Else if B_VALID is not set, read buf from disk, set B_VALID.
+void
+iderw(struct buf *b)
+{
+  uchar *p;
+
+  if(!(b->flags & B_BUSY))
+    panic("iderw: buf not busy");
+  if((b->flags & (B_VALID|B_DIRTY)) == B_VALID)
+    panic("iderw: nothing to do");
+  if(b->dev != 1)
+    panic("iderw: request not for disk 1");
+  if(b->sector >= disksize)
+    panic("iderw: sector out of range");
+
+  p = memdisk + b->sector*512;
+  
+  if(b->flags & B_DIRTY){
+    b->flags &= ~B_DIRTY;
+    memmove(p, b->data, 512);
+  } else
+    memmove(b->data, p, 512);
+  b->flags |= B_VALID;
+}