From b729d794bfcea356c360f84b5114a9946724037c Mon Sep 17 00:00:00 2001
From: H1ghBre4k3r <h1ghbre4k3r@dev.bre4k3r.de>
Date: Sun, 2 May 2021 21:50:13 +0200
Subject: [PATCH] Apply suggestions for ens_fs

---
 src/ens/ens_error.h |  3 ++-
 src/ens/ens_fs.c    | 39 ++++++++++++++++++++++++++++-----------
 src/ens/ens_fs.h    |  8 ++------
 3 files changed, 32 insertions(+), 18 deletions(-)

diff --git a/src/ens/ens_error.h b/src/ens/ens_error.h
index 2e6f91d..5f386d1 100644
--- a/src/ens/ens_error.h
+++ b/src/ens/ens_error.h
@@ -3,6 +3,7 @@
 
 #define ENS_INTERR 1  // internal error
 #define ENS_NOENT 2   // entry not found or invalid
-#define ENS_INVARG 3  // invalid argument
+#define ENS_DELENT 3  // entry got deleted
+#define ENS_INVARG 4  // invalid argument
 
 #endif
\ No newline at end of file
diff --git a/src/ens/ens_fs.c b/src/ens/ens_fs.c
index 72cdbed..7827f3e 100644
--- a/src/ens/ens_fs.c
+++ b/src/ens/ens_fs.c
@@ -8,8 +8,13 @@
 
 #define SEED 42
 
-int ens_fs_init(ens_fs_t* fs, uint8_t id, uint64_t entry_size) {
-    if (flash_area_open(id, &fs->area)) {
+// mask for metadata
+#define CRC_MASK 254
+
+#define GET_CHECKSUM(x) (x&CRC_MASK)
+
+int ens_fs_init(ens_fs_t* fs, uint8_t flash_id, uint64_t entry_size) {
+    if (flash_area_open(flash_id, &fs->area)) {
         // opening of flash area was not successful
         return -ENS_INTERR;
     }
@@ -35,21 +40,33 @@ int ens_fs_init(ens_fs_t* fs, uint8_t id, uint64_t entry_size) {
     return 0;
 }
 
-int ens_fs_read(ens_fs_t* fs, uint64_t id, void* dist) {
+int ens_fs_read(ens_fs_t* fs, uint64_t id, void* dest) {
     // read the entry from flash
     uint64_t offset = id * fs->entry_size;
-    if (flash_area_read(fs->area, offset, dist, fs->entry_size)) {
+    if (flash_area_read(fs->area, offset, dest, fs->entry_size)) {
         // opening of flash area was not successful
         return -ENS_INTERR;
     }
 
     // check, if checksum and not-deleted flag are as expected
-    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);
+    uint8_t* obj = dest;
+    
+    int isNotDeleted = obj[fs->entry_size - 1] & 1;
+    if(!isNotDeleted) {
+        // entry got deleted
+        return -ENS_DELENT;
+    }
+
+    // crc stored in entry
+    uint8_t entryCRC = GET_CHECKSUM(obj[fs->entry_size - 1]);
+
+    // calculated crc
+    uint8_t checkCRC = crc7_be(SEED, obj, fs->entry_size - 1);
+
+    int isInvalid = memcmp(&entryCRC, &checkCRC, 1);
     if (isInvalid) {
         // if checksum is not equal to calculated checksum or if deleted flag is not 1, set memory to 0
-        memset(dist, 0, fs->entry_size);
+        memset(dest, 0, fs->entry_size);
         // we do not know, if object got deleted or data is corrupt
         return -ENS_NOENT;
     }
@@ -90,9 +107,9 @@ int ens_fs_delete(ens_fs_t* fs, uint64_t id) {
     return 0;
 }
 
-int ens_fs_page_erase(ens_fs_t* fs, uint64_t offset, uint64_t sector_count) {
-    // calculate the next page start before (or at) the given offset
-    uint64_t start = (offset - offset % fs->sector_size) * fs->entry_size;
+int ens_fs_page_erase(ens_fs_t* fs, uint64_t entry_id, uint64_t sector_count) {
+    // calculate the next page start before (or at) the given entry_id
+    uint64_t start = (entry_id - entry_id % fs->sector_size) * fs->entry_size;
 
     // erase given amount of pages, starting for the given offset
     if (flash_area_erase(fs->area, start, fs->sector_size * sector_count)) {
diff --git a/src/ens/ens_fs.h b/src/ens/ens_fs.h
index 9bfb10a..b6ff097 100644
--- a/src/ens/ens_fs.h
+++ b/src/ens/ens_fs.h
@@ -27,10 +27,6 @@ typedef struct ens_fs {
      * Amount of sectors in this fs.
      */
     uint16_t sector_count;
-    /**
-     * Lock for this fs.
-     */
-    // struct k_mutex* lock;
 } ens_fs_t;
 
 /**
@@ -42,7 +38,7 @@ typedef struct ens_fs {
  *
  * @return 0 on success, -errno otherwise
  */
-int ens_fs_init(ens_fs_t* fs, uint8_t id, uint64_t entry_size);
+int ens_fs_init(ens_fs_t* fs, uint8_t flash_id, uint64_t entry_size);
 
 /**
  * Read an entry from this file system.
@@ -53,7 +49,7 @@ int ens_fs_init(ens_fs_t* fs, uint8_t id, uint64_t entry_size);
  *
  * @return 0 on success, -errno otherwise
  */
-int ens_fs_read(ens_fs_t* fs, uint64_t id, void* dist);
+int ens_fs_read(ens_fs_t* fs, uint64_t id, void* dest);
 
 /**
  * Write data to the file system.