nvs_flash: delete all duplicate entries in a page while loading

Due to previous flash write bug it was possible to create multiple duplicate entries in a single page.
Recovery logic detected that case and bailed out with an assert.
This change adds graceful recovery from this condition.
Tests included.

components/nvs_flash/src/nvs_page.cpp

@@ -301,6 +301,8 @@ esp_err_t Page::eraseEntryAndSpan(size_t index)
         }
         if (item.calculateCrc32() != item.crc32) {
             rc = alterEntryState(index, EntryState::ERASED);
+            --mUsedEntryCount;
+            ++mErasedEntryCount;
             if (rc != ESP_OK) {
                 return rc;
             }
@@ -473,7 +475,9 @@ esp_err_t Page::mLoadEntryTable()
         if (end > ENTRY_COUNT) {
             end = ENTRY_COUNT;
         }
-        for (size_t i = 0; i < end; ++i) {
+        size_t span;
+        for (size_t i = 0; i < end; i += span) {
+            span = 1;
             if (mEntryTable.get(i) == EntryState::ERASED) {
                 lastItemIndex = INVALID_ENTRY;
                 continue;
@@ -489,6 +493,9 @@ esp_err_t Page::mLoadEntryTable()
             
             mHashList.insert(item, i);
             
+            // search for potential duplicate item
+            size_t duplicateIndex = mHashList.find(0, item);
+
             if (item.crc32 != item.calculateCrc32()) {
                 err = eraseEntryAndSpan(i);
                 if (err != ESP_OK) {
@@ -498,11 +505,9 @@ esp_err_t Page::mLoadEntryTable()
                 continue;
             }
 
-            if (item.datatype != ItemType::BLOB && item.datatype != ItemType::SZ) {
-                continue;
-            }
             
-            size_t span = item.span;
+            if (item.datatype == ItemType::BLOB || item.datatype == ItemType::SZ) {
+                span = item.span;
                 bool needErase = false;
                 for (size_t j = i; j < i + span; ++j) {
                     if (mEntryTable.get(j) != EntryState::WRITTEN) {
@@ -513,8 +518,13 @@ esp_err_t Page::mLoadEntryTable()
                 }
                 if (needErase) {
                     eraseEntryAndSpan(i);
+                    continue;
+                }
+            }
+            
+            if (duplicateIndex < i) {
+                eraseEntryAndSpan(duplicateIndex);
             }
-            i += span - 1;
         }
 
         // check that last item is not duplicate

components/nvs_flash/test/test_nvs.cpp

@@ -963,22 +963,27 @@ TEST_CASE("duplicate items are removed", "[nvs][dupes]")
         p.writeItem<uint8_t>(1, "opmode", 3);
     }
     {
-        // add another one without deleting the first one
+        // add another two without deleting the first one
         nvs::Item item(1, ItemType::U8, 1, "opmode");
         item.data[0] = 2;
         item.crc32 = item.calculateCrc32();
         emu.write(3 * 32, reinterpret_cast<const uint32_t*>(&item), sizeof(item));
-        uint32_t mask = 0xFFFFFFFA;
+        emu.write(4 * 32, reinterpret_cast<const uint32_t*>(&item), sizeof(item));
+        uint32_t mask = 0xFFFFFFEA;
         emu.write(32, &mask, 4);
     }
     {
         // load page and check that second item persists
-        nvs::Page p;
-        p.load(0);
+        nvs::Storage s;
+        s.init(0, 3);
         uint8_t val;
-        p.readItem(1, "opmode", val);
+        ESP_ERROR_CHECK(s.readItem(1, "opmode", val));
         CHECK(val == 2);
-        CHECK(p.getErasedEntryCount() == 1);
+    }
+    {
+        Page p;
+        p.load(0);
+        CHECK(p.getErasedEntryCount() == 2);
         CHECK(p.getUsedEntryCount() == 1);
     }
 }
@@ -986,8 +991,7 @@ TEST_CASE("duplicate items are removed", "[nvs][dupes]")
 TEST_CASE("recovery after failure to write data", "[nvs]")
 {
     SpiFlashEmulator emu(3);
-    // TODO: remove explicit alignment
-    const char str[] __attribute__((aligned(4))) = "value 0123456789abcdef012345678value 0123456789abcdef012345678";
+    const char str[] = "value 0123456789abcdef012345678value 0123456789abcdef012345678";
 
     // make flash write fail exactly in Page::writeEntryData
     emu.failAfter(17);
@@ -1015,6 +1019,42 @@ TEST_CASE("recovery after failure to write data", "[nvs]")
     }
 }
 
+TEST_CASE("crc error in variable length item is handled", "[nvs]")
+{
+    SpiFlashEmulator emu(3);
+    const uint64_t before_val = 0xbef04e;
+    const uint64_t after_val = 0xaf7e4;
+    // write some data
+    {
+        Page p;
+        p.load(0);
+        TEST_ESP_OK(p.writeItem<uint64_t>(0, "before", before_val));
+        const char* str = "foobar";
+        TEST_ESP_OK(p.writeItem(0, ItemType::SZ, "key", str, strlen(str)));
+        TEST_ESP_OK(p.writeItem<uint64_t>(0, "after", after_val));
+    }
+    // corrupt some data
+    uint32_t w;
+    CHECK(emu.read(&w, 32 * 3 + 8, sizeof(w)));
+    w &= 0xf000000f;
+    CHECK(emu.write(32 * 3 + 8, &w, sizeof(w)));
+    // load and check
+    {
+        Page p;
+        p.load(0);
+        CHECK(p.getUsedEntryCount() == 2);
+        CHECK(p.getErasedEntryCount() == 2);
+
+        uint64_t val;
+        TEST_ESP_OK(p.readItem<uint64_t>(0, "before", val));
+        CHECK(val == before_val);
+        TEST_ESP_ERR(p.findItem(0, ItemType::SZ, "key"), ESP_ERR_NVS_NOT_FOUND);
+        TEST_ESP_OK(p.readItem<uint64_t>(0, "after", val));
+        CHECK(val == after_val);
+    }
+}
+
+
 TEST_CASE("dump all performance data", "[nvs]")
 {
     std::cout << "====================" << std::endl << "Dumping benchmarks" << std::endl;