From 02f14113cbf14c6f842fb43ecbc68d0c851ef3b0 Mon Sep 17 00:00:00 2001
From: Benji Dial <benji3.141@gmail.com>
Date: Sun, 24 May 2020 11:02:43 -0400
Subject: very basic vga, ata, serial drivers. start of fat and fs drivers

---
 src/kernel/fs.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 src/kernel/fs.c

(limited to 'src/kernel/fs.c')

diff --git a/src/kernel/fs.c b/src/kernel/fs.c
new file mode 100644
index 0000000..129e631
--- /dev/null
+++ b/src/kernel/fs.c
@@ -0,0 +1,82 @@
+#include <stdint.h>
+#include "fs.h"
+#include "ata.h"
+#include "fat.h"
+#include <stdbool.h>
+#include "panic.h"
+
+#define MAX_HANDLES 32
+#define FILE_BUFFER(h) ((void *)(0x0002be00 + (h << 9)))
+#define HANDLE(h) ((handles - 1)[h])
+#define HEAD(h) (FILE_BUFFER(h) + HANDLE(h).seek % 512)
+
+struct handle_info {
+  uint16_t start_cluster;
+  uint16_t seek;
+  uint16_t loaded_cluster;
+  bool dirty;
+};
+
+struct handle_info handles[MAX_HANDLES];
+
+void clear_fs_handles() {
+  struct handle_info *f = handles;
+  while (f < handles + MAX_HANDLES)
+    (f++)->start_cluster = 0;
+}
+
+fs_handle next_handle() {
+  fs_handle r = 0;
+  while (HANDLE(++r).start_cluster)
+    if (r == MAX_HANDLES)
+      return 0;
+  return r;
+}
+
+void write_buffer(fs_handle handle) {
+  HANDLE(handle).dirty = false;
+  panic("Not implemented (write_buffer).");
+}
+
+void read_buffer(fs_handle handle) {
+  if (HANDLE(handle).dirty)
+    write_buffer(handle);
+  HANDLE(handle).loaded_cluster = HANDLE(handle).seek >> 9;
+  panic("Not implemented (read_buffer).");
+}
+
+fs_handle fs_open(uint8_t *path) {
+  fs_handle next = next_handle();
+  if (!next)
+    return 0;
+  uint16_t s = get_start_cluster(path);
+  if (!s)
+    return 0;
+  HANDLE(next).start_cluster = s;
+  HANDLE(next).seek = 0;
+  HANDLE(next).dirty = false;
+  read_buffer(next);
+  return next;
+}
+
+int16_t fs_seek(fs_handle handle, int16_t by) {
+  uint16_t old = HANDLE(handle).seek;
+  uint16_t to = -by > old ? 0 : old + by;
+  HANDLE(handle).seek = to;
+  if ((to ^ old) & 0xfe00)
+    read_buffer(handle);
+}
+
+uint16_t fs_read(fs_handle handle, uint16_t max, void *buffer) {
+  panic("Not implemented (fs_read).");
+}
+
+uint16_t fs_write(fs_handle handle, uint16_t max, void *buffer) {
+  panic("Not implemented (fs_write).");
+}
+
+void fs_close(fs_handle handle) {
+  if (HANDLE(handle).dirty)
+    write_buffer(handle);
+  HANDLE(handle).start_cluster = 0;
+}
\ No newline at end of file
-- 
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