Reduced memory consumption by not duplicating spaces and comments

CHANGELOG.md

@@ -5,6 +5,7 @@ HEAD
 ----
 
 * Added operator `==` to compare `JsonVariant` and strings (issue #402)
+* Reduced memory consumption by not duplicating spaces and comments
 
 v5.7.3
 ------

include/ArduinoJson/Data/StringFuncs.hpp

@@ -30,6 +30,17 @@ template <typename TString>
 struct StringFuncs<TString&> : StringFuncs<TString> {};
 
 struct CharPtrFuncs {
+  class Iterator {
+    const char* _ptr;
+
+   public:
+    Iterator(const char* ptr) : _ptr(ptr ? ptr : "") {}
+
+    char next() {
+      return *_ptr++;
+    }
+  };
+
   static bool equals(const char* str, const char* expected) {
     return strcmp(str, expected) == 0;
   }
@@ -71,6 +82,10 @@ struct StdStringFuncs {
     return static_cast<char*>(dup);
   }
 
+  struct Iterator : CharPtrFuncs::Iterator {
+    Iterator(const TString& str) : CharPtrFuncs::Iterator(str.c_str()) {}
+  };
+
   static bool equals(const TString& str, const char* expected) {
     return str == expected;
   }
@@ -99,6 +114,18 @@ struct StringFuncs<std::string> : StdStringFuncs<std::string> {};
 #if ARDUINOJSON_ENABLE_PROGMEM
 template <>
 struct StringFuncs<const __FlashStringHelper*> {
+  class Iterator {
+    const char* _ptr;
+
+   public:
+    Iterator(const __FlashStringHelper* ptr)
+        : _ptr(reinterpret_cast<const char*>(ptr)) {}
+
+    char next() {
+      return pgm_read_byte_near(_ptr++);
+    }
+  };
+
   static bool equals(const __FlashStringHelper* str, const char* expected) {
     return strcmp_P(expected, (PGM_P)str) == 0;
   }

include/ArduinoJson/Deserialization/Comments.hpp

@@ -12,51 +12,51 @@ namespace Internals {
 template <typename TInput>
 void skipSpacesAndComments(TInput& input) {
   for (;;) {
-    switch (input.peek()) {
+    switch (input.current()) {
       // spaces
       case ' ':
       case '\t':
       case '\r':
       case '\n':
-        input.skip();
+        input.move();
         continue;
 
       // comments
       case '/':
-        switch (input.peekNext()) {
+        switch (input.next()) {
           // C-style block comment
           case '*':
-            input.skip();  // skip '/'
-            input.skip();  // skip '*'
+            input.move();  // skip '/'
+            input.move();  // skip '*'
             for (;;) {
-              switch (input.peek()) {
+              switch (input.current()) {
                 case '\0':
                   return;
                 case '*':
-                  input.skip();  // skip '*'
-                  if (input.peek() == '/') {
-                    input.skip();  // skip '/'
+                  input.move();  // skip '*'
+                  if (input.current() == '/') {
+                    input.move();  // skip '/'
                     return;
                   }
                   break;
                 default:
-                  input.skip();
+                  input.move();
               }
             }
             break;
 
           // C++-style line comment
           case '/':
-            input.skip();  // skip '/'
+            input.move();  // skip '/'
             for (;;) {
-              switch (input.peek()) {
+              switch (input.current()) {
                 case '\0':
                   return;
                 case '\n':
-                  input.skip();
+                  input.move();
                   return;
                 default:
-                  input.skip();
+                  input.move();
               }
             }
             return;

include/ArduinoJson/Deserialization/JsonParser.hpp

@@ -18,12 +18,14 @@ namespace Internals {
 // Parse JSON string to create JsonArrays and JsonObjects
 // This internal class is not indended to be used directly.
 // Instead, use JsonBuffer.parseArray() or .parseObject()
+template <typename TReader, typename TWriter>
 class JsonParser {
  public:
-  JsonParser(JsonBuffer *buffer, char *json, uint8_t nestingLimit)
+  JsonParser(JsonBuffer *buffer, TReader reader, TWriter writer,
+             uint8_t nestingLimit)
       : _buffer(buffer),
-        _reader(json),
-        _writer(json),
+        _reader(reader),
+        _writer(writer),
         _nestingLimit(nestingLimit) {}
 
   JsonArray &parseArray();
@@ -36,7 +38,9 @@ class JsonParser {
   }
 
  private:
-  static bool eat(StringReader &, char charToSkip);
+  JsonParser &operator=(const JsonParser &);  // non-copiable
+
+  static bool eat(TReader &, char charToSkip);
   FORCE_INLINE bool eat(char charToSkip) {
     return eat(_reader, charToSkip);
   }
@@ -63,9 +67,42 @@ class JsonParser {
   }
 
   JsonBuffer *_buffer;
-  StringReader _reader;
-  StringWriter _writer;
+  TReader _reader;
+  TWriter _writer;
   uint8_t _nestingLimit;
 };
+
+template <typename TJsonBuffer, typename TString>
+struct JsonParserBuilder {
+  typedef typename Internals::StringFuncs<TString>::Iterator InputIterator;
+  typedef JsonParser<StringReader<InputIterator>, TJsonBuffer &> TParser;
+
+  static TParser makeParser(TJsonBuffer *buffer, const TString &json,
+                            uint8_t nestingLimit) {
+    return TParser(buffer, InputIterator(json), *buffer, nestingLimit);
+  }
+};
+
+template <typename TJsonBuffer>
+struct JsonParserBuilder<TJsonBuffer, char *> {
+  typedef typename Internals::StringFuncs<char *>::Iterator InputIterator;
+  typedef JsonParser<StringReader<InputIterator>, StringWriter> TParser;
+
+  static TParser makeParser(TJsonBuffer *buffer, char *json,
+                            uint8_t nestingLimit) {
+    return TParser(buffer, InputIterator(json), json, nestingLimit);
+  }
+};
+
+template <typename TJsonBuffer, typename TChar, size_t N>
+struct JsonParserBuilder<TJsonBuffer, TChar[N]>
+    : JsonParserBuilder<TJsonBuffer, TChar *> {};
+
+template <typename TJsonBuffer, typename TString>
+inline typename JsonParserBuilder<TJsonBuffer, TString>::TParser makeParser(
+    TJsonBuffer *buffer, TString &json, uint8_t nestingLimit) {
+  return JsonParserBuilder<TJsonBuffer, TString>::makeParser(buffer, json,
+                                                             nestingLimit);
+}
 }
 }