From b98e1e643f98531f33404d67e23b691a7d3094d9 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Mon, 24 May 2021 18:56:59 +0200
Subject: Add append mode and fs_seek

---
 src/filesystem.c | 78 ++++++++++++++++++++------------------------------------
 1 file changed, 28 insertions(+), 50 deletions(-)

(limited to 'src')

diff --git a/src/filesystem.c b/src/filesystem.c
index cac2805..3fe95ab 100644
--- a/src/filesystem.c
+++ b/src/filesystem.c
@@ -127,14 +127,19 @@ _fs_update_file_index(u16 index) {
 }
 
 typedef enum {
-    FS_OPEN_READ,
-    FS_OPEN_WRITE,
-    FS_OPEN_APPEND,
+    FS_OPEN_READ   = (1 << 0),
+    FS_OPEN_WRITE  = (1 << 1),
+    FS_OPEN_APPEND = (1 << 2),
 } OpenMode;
 
 typedef struct File {
+    // File index offset.
     u8 index;
+    // The offset within the file. Must always be valid, and so the File struct
+    // shouldn't be manaully modified unless we are sure we know what we are
+    // doing.
     u16 offset;
+    // The mode of this file (read/write/append).
     OpenMode mode;
 } File;
 
@@ -148,7 +153,8 @@ fs_open_file(char *name, OpenMode mode) {
         }
     }
 
-    if (mode == FS_OPEN_READ) {
+    // If read only.
+    if ((mode & (FS_OPEN_WRITE | FS_OPEN_APPEND)) == 0) {
         return (File){FS_NULL, 0, mode};
     }
 
@@ -202,8 +208,6 @@ _fs_init_new_block(void) {
     return FS_NULL;
 }
 
-#include "text.h"
-
 // Recursively free blocks starting at blk_id. To improve performance, the
 // filesystem header is updated in memory but not written to disk. It is
 // responsability of the caller to perform the filesystem update.
@@ -236,7 +240,8 @@ _fs_free_blocks(u8 blk_id) {
 
 // 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) {
+_fs_write_to_block(u8 *src, u16 n_bytes, u16 blk_offset,
+        u8 blk_id, u8 prev_blk, bool append) {
     // Read initial block.
     FileBlock block;
     u16 block_pos = FILE_DATA_START + FILE_BLOCK_SIZE * blk_id;
@@ -253,7 +258,7 @@ _fs_write_to_block(u8 *src, u16 n_bytes, u16 blk_offset, u8 blk_id, u8 prev_blk)
             block.next_block = _fs_init_new_block();
         }
         _fs_write_to_block(src + block_capacity, n_bytes - block_capacity, 0,
-                block.next_block, blk_id);
+                block.next_block, blk_id, append);
     } else if (block.next_block != FS_NULL){
         // Recursively free unused blocks.
         _fs_free_blocks(block.next_block);
@@ -269,52 +274,27 @@ _fs_write_to_block(u8 *src, u16 n_bytes, u16 blk_offset, u8 blk_id, u8 prev_blk)
     _fs_write(&block, block_pos, sizeof(FileBlock));
 }
 
-// void
-// _fs_append_to_block(u8 *src, u16 n_bytes, u8 blk_id, u8 prev_block) {
-//     // Read initial block.
-//     FileBlock block;
-//     size_t block_pos = FILE_DATA_START + FILE_BLOCK_SIZE * blk_id;
-//     _fs_read(&block, block_pos, sizeof(FileBlock));
-//     u16 block_capacity = (FILE_BLOCK_SIZE - sizeof(FileBlock)) - block.size;
-
-//     // Write capacity.
-//     u16 block_bytes = MIN(block_capacity, n_bytes);
-//     _fs_write(src, block_pos + sizeof(FileBlock), block_bytes);
-
-//     // txt_printf("cap: %d\n", block_capacity);
-//     // txt_printf("bytes: %d\n", n_bytes);
-//     // txt_printf("id: %d\n", blk_id);
-//     if (n_bytes > block_capacity) {
-//         if (block.next_block == FS_NULL) {
-//             // Find new available block and initialize it.
-//             block.next_block = _fs_init_new_block();
-//             // TODO: Don't forget to set the block_prev of the next block as
-//             // this one.
-//         }
-//         _fs_write_to_block(
-//                 src + block_capacity,
-//                 n_bytes - block_capacity,
-//                 block.next_block,
-//                 blk_id);
-//     }
-
-//     // Update block header.
-//     if (prev_block != FS_NULL) {
-//         block.prev_block = prev_bloc7f8k;
-//     }
-//     block.size += block_bytes;
-//     _fs_write(&block, block_pos, sizeof(FileBlock));
-// }
+int
+fs_seek(File *file, int offset) {
+    u16 file_size = fs_file_size(file);
+    u16 new_offset = MAX((int)file->offset + offset, 0);
+    if (new_offset >= file_size) {
+        return -1;
+    }
+    file->offset = new_offset;
+    return 0;
+}
 
 u16
 fs_write(u8 *src, u16 n_bytes, File *file) {
-    if (file->mode != FS_OPEN_WRITE && file->mode != FS_OPEN_APPEND) {
+    if ((file->mode & (FS_OPEN_WRITE | FS_OPEN_APPEND)) == 0) {
         return 0;
     }
 
     FileIndex *file_idx = &filesystem.files[file->index];
 
     u8 blk_id = FS_NULL;
+    u8 blk_prev = FS_NULL;
     u16 offset = file->offset;
     if (file_idx->first_block == FS_NULL) {
         // Check how many blocks will this write requires and if we have enough
@@ -352,6 +332,7 @@ fs_write(u8 *src, u16 n_bytes, File *file) {
                 u16 block_pos = FILE_DATA_START + FILE_BLOCK_SIZE * blk_id;
                 _fs_read(&block, block_pos, sizeof(FileBlock));
                 blk_id = block.next_block;
+                blk_prev = block.prev_block;
                 if (blk_id == FS_NULL) {
                     return 0;
                 }
@@ -361,11 +342,8 @@ fs_write(u8 *src, u16 n_bytes, File *file) {
     }
 
     // Write to block.
-    if (file->mode == FS_OPEN_WRITE) {
-        _fs_write_to_block(src, n_bytes, offset, blk_id, FS_NULL);
-    } else {
-        // TODO: Append...
-    }
+    _fs_write_to_block(src, n_bytes, offset, blk_id, blk_prev,
+            file->mode == FS_OPEN_APPEND);
 
     return n_bytes;
 }
-- 
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