From 9ae226d50b929828fc9dd571cb406a773f1758e8 Mon Sep 17 00:00:00 2001
From: H1ghBre4k3r <h1ghbre4k3r@dev.bre4k3r.de>
Date: Wed, 14 Apr 2021 18:47:55 +0200
Subject: [PATCH] Implement correct read using crc and deleted flag and
 implement deletion

---
 src/ens/ens_fs.c | 47 +++++++++++++++++++++++++++++++++++------------
 src/ens/ens_fs.h |  4 +++-
 2 files changed, 38 insertions(+), 13 deletions(-)

diff --git a/src/ens/ens_fs.c b/src/ens/ens_fs.c
index c1444f6..8d51d4b 100644
--- a/src/ens/ens_fs.c
+++ b/src/ens/ens_fs.c
@@ -1,6 +1,7 @@
 #include <drivers/flash.h>
 #include <storage/flash_map.h>
 #include <sys/crc.h>
+#include <string.h>
 
 #include "ens_fs.h"
 
@@ -9,17 +10,27 @@
 int ens_fs_init(ens_fs_t* fs, uint8_t id, uint64_t entry_size) {
     int rc = flash_area_open(id, &fs->area);
     if (rc) {
-        return rc;
+        goto end;
     }
 
+    // Check, if entry size is multiple of flash_area_align
+    if((entry_size % flash_area_align(fs->area)) != 0) {
+        flash_area_close(fs->area);
+        // TODO lome: set custom error code
+        rc = -1;
+        goto end;
+    }
+    fs->entry_size = entry_size;
+
     const struct device* dev = flash_area_get_device(fs->area);
 
     fs->sector_count = flash_get_page_count(dev);
     struct flash_pages_info info;
     rc = flash_get_page_info_by_offs(dev, fs->area->fa_off, &info);
     fs->sector_size = info.size;
-    fs->entry_size = entry_size;
-    return 0;
+
+end:
+    return rc;
 }
 
 int ens_fs_read(ens_fs_t* fs, uint64_t id, void* dist) {
@@ -31,7 +42,14 @@ int ens_fs_read(ens_fs_t* fs, uint64_t id, void* dist) {
        goto end;
     }
 
-    // TODO lome: Read deleted flag and CRC
+    uint8_t* obj = dist;
+    uint8_t metadata = crc7_be(SEED, obj, fs->entry_size - 1) | 1;
+    int isInvalid = memcmp(&obj[fs->entry_size - 1], &metadata, 1);
+    if(isInvalid) {
+        // If checksum is not equal to calculated checksum or if deleted flag is not 1, set memory to 0
+        rc = -1;
+        memset(dist, 0, fs->entry_size);
+    }
 end:
 
     return rc;
@@ -55,15 +73,20 @@ end:
 
 int ens_fs_delete(ens_fs_t* fs, uint64_t id) {
 
-    // TODO lome: Maybe overwrite last 4 bytes? Or make it file system dependend?    
-    // uint8_t data = 0;
-    // uint64_t offset = (id + 1) * fs->entry_size - 1;
+    uint8_t data[fs->entry_size];
 
-    // int rc = flash_area_write(fs->area, offset, &data, 0);
-    // if(rc) {
-    //     goto end;
-    // }
-    return 0;
+    uint64_t offset = id * fs->entry_size;
+    int rc = flash_area_read(fs->area, offset, data, fs->entry_size);
+    if(rc) {
+        goto end;
+    }
+
+    // set memory to 0, so not-deleted flag is 0
+    memset(data, 0, fs->entry_size);
+    rc = flash_area_write(fs->area, offset, data, fs->entry_size);
+
+end:
+    return rc;
 }
 
 int ens_fs_page_erase(ens_fs_t* fs, uint64_t offset, uint64_t sector_count) {
diff --git a/src/ens/ens_fs.h b/src/ens/ens_fs.h
index 8b147ab..567f580 100644
--- a/src/ens/ens_fs.h
+++ b/src/ens/ens_fs.h
@@ -15,7 +15,9 @@ typedef struct ens_fs {
     const struct flash_area* area;
     /**
      * Size of each individual entry. The last byte will be used by 
-     * ens_fs to store metadata about each individual entry.
+     * ens_fs to store metadata about each individual entry. 
+     * 
+     * @attention has to be multiple of drivers write size
      */
     size_t entry_size;
     /**