Added isKey method to Preferences (#4441)

Checks to see if a string is a key in the namespace. 

Fixes #4440

Author: lbernstone

libraries/Preferences/src/Preferences.cpp

@@ -15,7 +15,7 @@
 
 #include "nvs.h"
 
-const char * nvs_errors[] = { "OTHER", "NOT_INITIALIZED", "NOT_FOUND", "TYPE_MISMATCH", "READ_ONLY", "NOT_ENOUGH_SPACE", "INVALID_NAME", "INVALID_HANDLE", "REMOVE_FAILED", "KEY_TOO_LONG", "PAGE_FULL", "INVALID_STATE", "INVALID_LENGHT"};
+const char * nvs_errors[] = { "OTHER", "NOT_INITIALIZED", "NOT_FOUND", "TYPE_MISMATCH", "READ_ONLY", "NOT_ENOUGH_SPACE", "INVALID_NAME", "INVALID_HANDLE", "REMOVE_FAILED", "KEY_TOO_LONG", "PAGE_FULL", "INVALID_STATE", "INVALID_LENGTH"};
 #define nvs_error(e) (((e)>ESP_ERR_NVS_BASE)?nvs_errors[(e)&~(ESP_ERR_NVS_BASE)]:nvs_errors[0])
 
 Preferences::Preferences()
@@ -280,6 +280,30 @@ size_t Preferences::putBytes(const char* key, const void* value, size_t len){
     return len;
 }
 
+PreferenceType Preferences::getType(const char* key) {
+    if(!_started || !key || strlen(key)>15){
+        return PT_INVALID;
+    }
+    int8_t mt1; uint8_t mt2; int16_t mt3; uint16_t mt4;
+    int32_t mt5; uint32_t mt6; int64_t mt7; uint64_t mt8;
+    size_t len = 0;
+    if(nvs_get_i8(_handle, key, &mt1) == ESP_OK) return PT_I8;
+    if(nvs_get_u8(_handle, key, &mt2) == ESP_OK) return PT_U8;
+    if(nvs_get_i16(_handle, key, &mt3) == ESP_OK) return PT_I16;
+    if(nvs_get_u16(_handle, key, &mt4) == ESP_OK) return PT_U16;
+    if(nvs_get_i32(_handle, key, &mt5) == ESP_OK) return PT_I32;
+    if(nvs_get_u32(_handle, key, &mt6) == ESP_OK) return PT_U32;
+    if(nvs_get_i64(_handle, key, &mt7) == ESP_OK) return PT_I64;
+    if(nvs_get_u64(_handle, key, &mt8) == ESP_OK) return PT_U64;
+    if(nvs_get_str(_handle, key, NULL, &len) == ESP_OK) return PT_STR;
+    if(nvs_get_blob(_handle, key, NULL, &len) == ESP_OK) return PT_BLOB;
+    return PT_INVALID;
+}
+
+bool Preferences::isKey(const char* key) {
+    return getType(key) != PT_INVALID;
+}
+
 /*
  * Get a key value
  * */

libraries/Preferences/src/Preferences.h

@@ -16,6 +16,10 @@
 
 #include "Arduino.h"
 
+typedef enum {
+    PT_I8, PT_U8, PT_I16, PT_U16, PT_I32, PT_U32, PT_I64, PT_U64, PT_STR, PT_BLOB, PT_INVALID
+} PreferenceType;
+
 class Preferences {
     protected:
         uint32_t _handle;
@@ -48,6 +52,8 @@ class Preferences {
         size_t putString(const char* key, String value);
         size_t putBytes(const char* key, const void* value, size_t len);
 
+        bool isKey(const char* key);
+        PreferenceType getType(const char* key);
         int8_t getChar(const char* key, int8_t defaultValue = 0);
         uint8_t getUChar(const char* key, uint8_t defaultValue = 0);
         int16_t getShort(const char* key, int16_t defaultValue = 0);
@@ -63,7 +69,7 @@ class Preferences {
         bool getBool(const char* key, bool defaultValue = false);
         size_t getString(const char* key, char* value, size_t maxLen);
         String getString(const char* key, String defaultValue = String());
-	size_t getBytesLength(const char* key);
+        size_t getBytesLength(const char* key);
         size_t getBytes(const char* key, void * buf, size_t maxLen);
         size_t freeEntries();
 };