basic fs type stuff, fat16, removing stack segment and using data segment

1 files changed, 84 insertions, 22 deletions

diff --git a/src/kernel/fs.c b/src/kernel/fs.c
index 129e631..0d51c22 100644
--- a/src/kernel/fs.c
+++ b/src/kernel/fs.c
@@ -4,17 +4,26 @@
 #include "fat.h"
 #include <stdbool.h>
 #include "panic.h"
+#include "util.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)
 
+enum {
+  FH_DIRTY     = 0x01,
+  FH_NO_WRITE  = 0x02,
+  FH_NO_EXPAND = 0x04,
+  FH_ROOT      = 0x08
+};
+
 struct handle_info {
-  uint16_t start_cluster;
-  uint16_t seek;
+  uint16_t first_cluster;
   uint16_t loaded_cluster;
-  bool dirty;
+  uint32_t seek;
+  uint32_t length;
+  uint8_t flags;
 };
 
 struct handle_info handles[MAX_HANDLES];
@@ -22,61 +31,114 @@ struct handle_info handles[MAX_HANDLES];
 void clear_fs_handles() {
   struct handle_info *f = handles;
   while (f < handles + MAX_HANDLES)
-    (f++)->start_cluster = 0;
+    (f++)->first_cluster = 0;
 }
 
 fs_handle next_handle() {
   fs_handle r = 0;
-  while (HANDLE(++r).start_cluster)
+  while (HANDLE(++r).first_cluster)
     if (r == MAX_HANDLES)
       return 0;
   return r;
 }
 
 void write_buffer(fs_handle handle) {
-  HANDLE(handle).dirty = false;
-  panic("Not implemented (write_buffer).");
+  HANDLE(handle).flags &= ~FH_DIRTY;
+  if (HANDLE(handle).flags & FH_ROOT)
+    write_sectors(HANDLE(handle).loaded_cluster, 1, FILE_BUFFER(handle));
+  else
+    write_sectors(CTOS(HANDLE(handle).loaded_cluster), 1, FILE_BUFFER(handle));
 }
 
 void read_buffer(fs_handle handle) {
-  if (HANDLE(handle).dirty)
+  if (HANDLE(handle).flags & FH_DIRTY)
     write_buffer(handle);
-  HANDLE(handle).loaded_cluster = HANDLE(handle).seek >> 9;
-  panic("Not implemented (read_buffer).");
+  uint16_t s = HANDLE(handle).seek >> 9;
+  if (HANDLE(handle).flags & FH_ROOT) {
+    HANDLE(handle).loaded_cluster = HANDLE(handle).first_cluster + s;
+    read_sectors(HANDLE(handle).first_cluster + s, 1, FILE_BUFFER(handle));
+  }
+  else {
+    uint16_t c = HANDLE(handle).first_cluster;
+    while (s--)
+      c = FAT[c];
+    HANDLE(handle).loaded_cluster = c;
+    read_sectors(CTOS(c), 1, FILE_BUFFER(handle));
+  }
 }
 
 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)
+  struct directory_entry e;
+  if (get_entry(path, &e))
     return 0;
-  HANDLE(next).start_cluster = s;
+  HANDLE(next).first_cluster = e.first_cluster;
   HANDLE(next).seek = 0;
-  HANDLE(next).dirty = false;
+  HANDLE(next).length = e.length;
+  HANDLE(next).flags = (e.attrib & FA_READ_ONLY ? FH_NO_WRITE  : 0) |
+                       (e.attrib & FA_SYSTEM    ? FH_NO_EXPAND : 0);
   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;
+fs_handle fs_open_root() {
+  fs_handle next = next_handle();
+  if (!next)
+    return 0;
+  HANDLE(next).first_cluster = FAT_INFO->reserved_sectors + FAT_INFO->sectors_per_fat;
+  HANDLE(next).seek = 0;
+  HANDLE(next).length = FAT_INFO->root_entries * 32;
+  HANDLE(next).flags = FH_NO_EXPAND | FH_ROOT;
+  read_buffer(next);
+  return next;
+}
+
+int32_t fs_seek(fs_handle handle, int32_t by) {
+  uint32_t old = HANDLE(handle).seek;
+  uint32_t to = -by > old ? 0 : old + by > HANDLE(handle).length ? HANDLE(handle).length : old + by;
   HANDLE(handle).seek = to;
   if ((to ^ old) & 0xfe00)
     read_buffer(handle);
+  return to - old;
 }
 
-uint16_t fs_read(fs_handle handle, uint16_t max, void *buffer) {
-  panic("Not implemented (fs_read).");
+uint32_t fs_read(fs_handle handle, uint32_t max, void *buffer) {
+  max = HANDLE(handle).seek + max > HANDLE(handle).length ? HANDLE(handle).length - HANDLE(handle).seek : max;
+  uint32_t left = max, eos = 512 - (HANDLE(handle).seek & 0x1ff);
+  if (left < eos) {
+    memcpy(buffer, FILE_BUFFER(handle) + (HANDLE(handle).seek & 0x1ff), left);
+    HANDLE(handle).seek += left;
+    return max;
+  }
+  memcpy(buffer, FILE_BUFFER(handle) + (HANDLE(handle).seek & 0x1ff), eos);
+  left -= eos;
+  buffer += eos;
+  HANDLE(handle).seek += eos;
+  while (left >= 512) {
+    read_buffer(handle);
+    memcpy(buffer, FILE_BUFFER(handle), 512);
+    left -= 512;
+    buffer += 512;
+    HANDLE(handle).seek += 512;
+  }
+  if (left) {
+    read_buffer(handle);
+    memcpy(buffer, FILE_BUFFER(handle), left);
+    HANDLE(handle).seek += left;
+  }
+  return max;
 }
 
-uint16_t fs_write(fs_handle handle, uint16_t max, void *buffer) {
+uint32_t fs_write(fs_handle handle, uint32_t max, void *buffer) {
+  if (HANDLE(handle).flags & FH_NO_WRITE)
+    return 0;
   panic("Not implemented (fs_write).");
 }
 
 void fs_close(fs_handle handle) {
-  if (HANDLE(handle).dirty)
+  if (HANDLE(handle).flags & FH_DIRTY)
     write_buffer(handle);
-  HANDLE(handle).start_cluster = 0;
+  HANDLE(handle).first_cluster = 0;
 }
\ No newline at end of file