Fix PersistentStorageDelegate 0-storage behavior

- Make Server's PersistentStorageDelegate and TestPersistentStorage delegate properly handle nullptr input for zero-length. - Document behavior expected of PersistentStorageDelegate interface Issue #16130
project-chip · Mar 11, 2022 · fe14524 · fe14524
1 parent 86a8444
commit fe14524
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Showing 3 changed files with 39 additions and 5 deletions.
diff --git a/src/app/server/Server.h b/src/app/server/Server.h
@@ -128,6 +128,18 @@ class Server
 
         CHIP_ERROR SyncSetKeyValue(const char * key, const void * value, uint16_t size) override
         {
+            uint8_t placeholderForEmpty = 0;
+            if (value == nullptr)
+            {
+                if (size == 0)
+                {
+                    value = &placeholderForEmpty;
+                }
+                else
+                {
+                    return CHIP_ERROR_INVALID_ARGUMENT;
+                }
+            }
             return DeviceLayer::PersistedStorage::KeyValueStoreMgr().Put(key, value, size);
         }
 

diff --git a/src/lib/core/CHIPPersistentStorageDelegate.h b/src/lib/core/CHIPPersistentStorageDelegate.h
@@ -62,11 +62,15 @@ class DLL_EXPORT PersistentStorageDelegate
 
     /**
      * @brief
-     *   Set the value for the key to a byte buffer.
+     *   Set the value for the key to a byte buffer. Empty keys can be stored
+     *   with size == 0.
      *
      * @param[in] key Key to be set
-     * @param[in] value Value to be set
-     * @param[in] size Size of the Value
+     * @param[in] value Pointer to buytes of value to be set. `value` can only be `nullptr` if size == 0.
+     * @param[in] size Size of the `value` to store.
+     *
+     * @return CHIP_NO_ERROR on success, CHIP_INVALID_ARGUMENT on bad assumptions, other
+     *         CHIP_ERROR value from implementation on failure.
      */
     virtual CHIP_ERROR SyncSetKeyValue(const char * key, const void * value, uint16_t size) = 0;
 

diff --git a/src/lib/support/TestPersistentStorageDelegate.h b/src/lib/support/TestPersistentStorageDelegate.h
@@ -59,9 +59,27 @@ class TestPersistentStorageDelegate : public PersistentStorageDelegate
         {
             return CHIP_ERROR_PERSISTED_STORAGE_FAILED;
         }
+
         const uint8_t * bytes = static_cast<const uint8_t *>(value);
-        mStorage[key]         = std::vector<uint8_t>(bytes, bytes + size);
-        return CHIP_NO_ERROR;
+
+        // Handle empty values
+        if (value == nullptr)
+        {
+            if (size == 0)
+            {
+                mStorage[key] = std::vector<uint8_t>();
+                return CHIP_NO_ERROR;
+            }
+            else
+            {
+                return CHIP_ERROR_INVALID_ARGUMENT;
+            }
+        }
+        else
+        {
+            mStorage[key] = std::vector<uint8_t>(bytes, bytes + size);
+            return CHIP_NO_ERROR;
+        }
     }
 
     CHIP_ERROR SyncDeleteKeyValue(const char * key) override