Started writing fat.c

1 files changed, 247 insertions, 0 deletions

diff --git a/kernel/fs/fat.c b/kernel/fs/fat.c
new file mode 100644
index 0000000..9168301
--- /dev/null
+++ b/kernel/fs/fat.c
@@ -0,0 +1,247 @@
+#include <stdint.h>
+#include <stdbool.h>
+
+#include <string.h>
+
+// various errors with fat32
+enum
+{
+    FAT_ERR_NONE  = 0,
+    FAT_ERR_NOFAT = -1,
+    FAT_ERR_BROKEN  = -2,
+    FAT_ERR_IO    = -3,
+    FAT_ERR_PARAM = -4,
+    FAT_ERR_PATH   = -5,
+    // also can tell if files don't exist.
+    FAT_ERR_EOF   = -6,
+    //
+    FAT_ERR_DENIED = -7,
+    FAT_ERR_FULL   = -8,
+};
+
+enum
+{
+  FAT_ATTR_NONE     = 0x00,
+  FAT_ATTR_RO       = 0x01,
+  FAT_ATTR_HIDDEN   = 0x02,
+  FAT_ATTR_SYS      = 0x04,
+  FAT_ATTR_LABEL    = 0x08,
+  FAT_ATTR_DIR      = 0x10,
+  FAT_ATTR_ARCHIVE  = 0x20,
+  FAT_ATTR_LFN      = 0x0f,
+};
+
+enum
+{
+  FAT_WRITE      = 0x01, // Open file for writing
+  FAT_READ       = 0x02, // Open file for reading
+  FAT_APPEND     = 0x04, // Set file offset to the end of the file
+  FAT_TRUNC      = 0x08, // Truncate the file after opening
+  FAT_CREATE     = 0x10, // Create the file if it do not exist
+
+  FAT_ACCESSED   = 0x20, // do not use (internal)
+  FAT_MODIFIED   = 0x40, // do not use (internal)
+  FAT_FILE_DIRTY = 0x80, // do not use (internal)
+};
+
+enum
+{
+  FAT_SEEK_START,
+  FAT_SEEK_CURR,
+  FAT_SEEK_END,
+};
+
+
+typedef struct
+{
+  bool (*read)(uint8_t* buf, uint32_t sect);
+  bool (*write)(const uint8_t* buf, uint32_t sect);
+} DiskOps;
+
+// time checker if I can be bothered to implement it.
+typedef struct
+{
+  uint8_t hour;
+  uint8_t min;
+  uint8_t sec;
+  uint8_t day;
+  uint8_t month;
+  uint16_t year;
+} Timestamp;
+
+typedef struct Fat
+{
+  struct Fat* next;
+  DiskOps ops;
+  uint32_t clust_msk;
+  uint32_t clust_cnt;
+  uint32_t info_sect;
+  uint32_t fat_sect[2];
+  uint32_t data_sect;  
+  uint32_t root_clust;
+  uint32_t last_used;
+  uint32_t free_cnt;
+  uint32_t sect;
+  uint8_t buf[512];
+  uint8_t flags;
+  uint8_t clust_shift;
+  uint8_t name_len;
+  char name[32];
+} Fat;
+
+typedef struct
+{
+  //Timestamp created;
+  //Timestamp modified;
+  uint32_t size;
+  uint8_t attr;
+  char name[255];
+  uint8_t name_len;
+} DirInfo;
+
+typedef struct
+{
+  Fat* fat;
+  uint32_t sclust;
+  uint32_t clust;
+  uint32_t sect;
+  uint16_t idx;
+} Dir;
+
+// file structure
+typedef struct
+{
+  Fat* fat;
+  uint32_t dir_sect;
+  uint32_t sclust;
+  uint32_t clust;
+  uint32_t sect;
+  uint32_t size;
+  uint32_t offset;
+  uint16_t dir_idx;
+  uint8_t attr;
+  uint8_t flags;
+  uint8_t buf[512];
+} File;
+
+
+typedef struct __attribute__((packed))
+{
+  uint8_t jump[3];
+  char name[8];
+  uint16_t bytes_per_sect;
+  uint8_t sect_per_clust;
+  uint16_t res_sect_cnt;
+  uint8_t fat_cnt;
+  uint16_t root_ent_cnt;
+  uint16_t sect_cnt_16;
+  uint8_t media;
+  uint16_t sect_per_fat_16;
+  uint16_t sect_per_track;
+  uint16_t head_cnt;
+  uint32_t hidden_sect_cnt;
+  uint32_t sect_cnt_32;
+  uint32_t sect_per_fat_32;
+  uint16_t ext_flags;
+  uint8_t minor;
+  uint8_t major;
+  uint32_t root_cluster;
+  uint16_t info_sect;
+  uint16_t copy_bpb_sector;
+  uint8_t reserved_0[12];
+  uint8_t drive_num;
+  uint8_t reserved_1;
+  uint8_t boot_sig;
+  uint32_t volume_id;
+  char volume_label[11];
+  char fs_type[8];
+  uint8_t reserved_2[420];
+  uint8_t sign[2];
+} Bpb;
+
+typedef struct __attribute__((packed))
+{
+  uint32_t head_sig;
+  uint8_t reserved_0[480];
+  uint32_t struct_sig;
+  uint32_t free_cnt;
+  uint32_t next_free;
+  uint8_t reserved_1[12];
+  uint32_t tail_sig;
+} FsInfo;
+
+typedef struct __attribute__((packed))
+{
+  uint8_t name[11];
+  uint8_t attr;
+  uint8_t reserved;
+  uint8_t tenth;
+  uint16_t cre_time;
+  uint16_t cre_date;
+  uint16_t acc_date;
+  uint16_t clust_hi;
+  uint16_t mod_time;
+  uint16_t mod_date;
+  uint16_t clust_lo;
+  uint32_t size;
+} Sfn;
+
+typedef union __attribute__((packed))
+{
+  uint8_t raw[32];
+  struct
+  {
+    uint8_t seq;
+    uint8_t name0[10];
+    uint8_t attr;
+    uint8_t type;
+    uint8_t crc;
+    uint8_t name1[12];
+    uint16_t clust;
+    uint8_t name2[4];
+  };
+} Lfn;
+
+typedef struct
+{
+  uint32_t sect;
+  uint16_t idx;
+} Loc;
+
+
+static Fat* g_fat_list;
+static uint8_t g_buf[512];
+static uint16_t g_len;
+static uint8_t g_crc;
+
+static int sync_buf(Fat* fat) {
+    // checks whether the flag is active. If not, we 
+    if(fat->flags & 0x01) {
+        // if write fails for whatever reason
+        if(!fat->ops.write(fat->buf, fat->sect)) {
+            return FAT_ERR_IO;
+        }
+    }
+}
+static int update_buf(Fat* fat, uint32_t sect) {
+    // if fat->sect already is sect, we are good
+    if(fat->sect != sect) {
+
+    }
+}
+// attempts to sync the filesystem to fat32. Returns error code assuming one happens.
+static int sync_fs(Fat* fat)
+{
+    int error = sync_buf(fat);
+    if (error) {
+        return error;
+    }
+    FsInfo* info = (FsInfo*)fat->buf;
+    fat->flags |= 
+
+}
+
+static int get_fat(Fat* fat, uint32_t clust, uint32_t* out_val, uint8_t* out_flags) {
+
+}
+