From 021ea9b271f2144f7b16ae41a9236292dea7897d Mon Sep 17 00:00:00 2001
From: Benji Dial <benji3.141@gmail.com>
Date: Sun, 24 May 2020 21:55:12 -0400
Subject: basic fs type stuff, fat16, removing stack segment and using data
 segment

---
 src/kernel/fat.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 74 insertions(+), 8 deletions(-)

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

diff --git a/src/kernel/fat.c b/src/kernel/fat.c
index 00fa61f..e574da5 100644
--- a/src/kernel/fat.c
+++ b/src/kernel/fat.c
@@ -1,21 +1,87 @@
 #include "fat.h"
 #include "ata.h"
 #include "panic.h"
+#include "fs.h"
 
 void load_fat() {
   read_sectors(FAT_INFO->reserved_sectors, FAT_INFO->sectors_per_fat, FAT);
 }
 
-uint16_t get_cluster(uint16_t n) {
-  uint32_t t = *(uint32_t *)(FAT + (n / 2) * 3);
-  return (n % 2 ? (t >> 12) : t) & 0xfff;
+bool check_fat_name(uint8_t *fname, uint8_t *sname) {
+  panic("Not implemented (check_fat_name)");
 }
 
-void set_cluster(uint16_t n, uint16_t v) {
-  uint32_t *t = (uint32_t *)(FAT + (n / 2) * 3);
-  *t = (*t & (n % 2 ? 0xff000fff : 0xfffff000)) | (n % 2 ? v << 12 : v);
+bool check_fat_names(uint8_t *lname, uint8_t *rname) {
+  return (* (uint32_t *)lname       ==  *(uint32_t *)rname) &&
+         (*((uint32_t *)lname +  1) == *((uint32_t *)rname +  1)) &&
+         (*((uint16_t *)lname +  4) == *((uint16_t *)rname +  4)) &&
+         (*(            lname + 10) == *(            rname + 10));
 }
 
-uint16_t get_start_cluster(uint8_t *path) {
-  panic("Not implemented (get_start_cluster).");
+struct directory_entry buffer[16];
+uint16_t dir_start, buffer_from;
+
+
+void load_root() {
+  dir_start = FAT_INFO->reserved_sectors + FAT_INFO->sectors_per_fat;
+}
+
+struct directory_entry *load_subentry(uint8_t *name) {
+  struct directory_entry *ptr = buffer;
+  uint16_t dir_current = dir_start;
+  do
+    if (((ptr == buffer + 16) && !read_sectors(buffer_from = dir_current++, 1, ptr = buffer)) || !ptr->name[0])
+      return 0;
+  while (!check_fat_name(ptr->name, name));
+  return ptr;
+}
+
+bool load_subdir(uint8_t *name) {
+  struct directory_entry *e = load_subentry(name);
+  if (!e)
+    return true;
+  dir_start = e->first_cluster;
+  return false;
+}
+
+struct directory_entry *load_entry(uint8_t *path) {
+  load_root();
+  for (uint8_t *ptr = path; ptr; ++ptr)
+    if (*ptr = '/') {
+      *ptr = 0;
+      if (load_subdir(path))
+        return 0;
+      path = ptr + 1;
+    }
+  return load_subentry(path);
+}
+
+bool get_entry(uint8_t *path, struct directory_entry *at) {
+  struct directory_entry *e = load_entry(path);
+  if (!e)
+    return true;
+  *at = *e;
+  return false;
+}
+
+bool update_entry(uint8_t *path, struct directory_entry *value) {
+  struct directory_entry *e = load_entry(path);
+  if (!e)
+    return true;
+  *e = *value;
+  write_sectors(buffer_from, 1, buffer);
+  return false;
+}
+
+bool create_entry(uint8_t *dir_path, struct directory_entry *value) {
+  fs_handle h = fs_open(dir_path);
+  struct directory_entry *check;
+  while (fs_read(h, 32, check))
+    if (check_fat_names(check->name, value->name)) {
+      fs_close(h);
+      return true;
+    }
+  fs_write(h, 32, value);
+  fs_close(h);
+  return false;
 }
\ No newline at end of file
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