From 8e90cbd6fd790c16acd86cba878a69160fa4f17b Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Mon, 24 May 2021 20:58:14 +0200
Subject: Finish first prototype of new filesystem

---
 src/filesystem.c | 61 ++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 46 insertions(+), 15 deletions(-)

(limited to 'src/filesystem.c')

diff --git a/src/filesystem.c b/src/filesystem.c
index 327b613..ee55dcf 100644
--- a/src/filesystem.c
+++ b/src/filesystem.c
@@ -117,7 +117,7 @@ fs_init(void) {
 void
 _fs_update_filesystem_header(void) {
     _fs_write(&filesystem, 0, offsetof(FileSystem, files));
-};
+}
 
 void
 _fs_update_file_index(u16 index) {
@@ -238,7 +238,6 @@ _fs_free_blocks(u8 blk_id) {
     _fs_free_blocks(next_block);
 }
 
-// Write to block as a new file.
 void
 _fs_write_to_block(u8 *src, u16 n_bytes, u16 blk_offset,
         u8 blk_id, u8 prev_blk, bool append) {
@@ -295,7 +294,7 @@ fs_seek(File *file, int offset, SeekMode mode) {
             new_offset = MAX((int)file_size - 1 + offset, 0);
         } break;
     }
-    if (new_offset >= file_size) {
+    if (new_offset != 0 && new_offset >= file_size) {
         return -1;
     }
     file->offset = new_offset;
@@ -365,22 +364,54 @@ fs_write(u8 *src, u16 n_bytes, File *file) {
     return n_bytes;
 }
 
+void
+_fs_read_from_block(u8 *dst, u16 n_bytes, u16 blk_offset, u8 blk_id) {
+    // Read initial block.
+    FileBlock block;
+    u16 block_pos = FILE_DATA_START + FILE_BLOCK_SIZE * blk_id;
+    _fs_read(&block, block_pos, sizeof(FileBlock));
+
+    u16 read_bytes = MIN(block.size - blk_offset, n_bytes);
+    _fs_read(dst, block_pos + blk_offset + sizeof(FileBlock), read_bytes);
+
+    u16 remaining_bytes = n_bytes - read_bytes;
+    if (block.next_block != FS_NULL && remaining_bytes > 0) {
+        _fs_read_from_block(dst + read_bytes, remaining_bytes, 0, block.next_block);
+    }
+}
+
 u16
-fs_read(u8 *dst, u16 n_bytes, u16 offset, File *file) {
-    // File *file = &filesystem.files[file_index];
+fs_read(u8 *dst, u16 n_bytes, File *file) {
+    if ((file->mode & FS_OPEN_READ) == 0) {
+        return 0;
+    }
+
+    // If there is an offset find the block index and relative offset.
+    u8 blk_id = filesystem.files[file->index].first_block;
+    u16 offset = file->offset;
 
-    // // Check if the offset is within limits.
-    // if (file->size == 0 || offset >= file->size - 1) {
-    //     return 0;
-    // }
+    // Read as much as we can from the file after the offset.
+    u16 file_size = fs_file_size(file);
+    if (offset + n_bytes >= file_size) {
+        n_bytes = file_size - offset;
+    }
 
-    // // Read as much as we can.
-    // if (offset + n_bytes > file->size) {
-    //     n_bytes = file->size - offset;
-    // }
+    if (offset >= FILE_BLOCK_CAPACITY) {
+        u16 n_blocks_offset = offset / FILE_BLOCK_CAPACITY;
+        for (size_t i = 0; i < n_blocks_offset; ++i) {
+            FileBlock block;
+            u16 block_pos = FILE_DATA_START + FILE_BLOCK_SIZE * blk_id;
+            _fs_read(&block, block_pos, sizeof(FileBlock));
+            blk_id = block.next_block;
+            if (blk_id == FS_NULL) {
+                return 0;
+            }
+        }
+        offset = offset % FILE_BLOCK_CAPACITY;
+    }
 
-    // // Copy n_bytes to destination.
-    // _fs_read(dst, FILE_DATA_OFFSET + FILE_MAX_SIZE * file_index + offset, n_bytes);
+    // Copy n_bytes to destination.
+    _fs_read_from_block(dst, n_bytes, offset, blk_id);
 
     return n_bytes;
 }
-- 
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