refactor device value rendering (to Web, Console or MQTT) to base class #632

lib/uuid-common/src/compare_flash_string.cpp

@@ -0,0 +1,71 @@
+/*
+ * EMS-ESP - https://github.com/proddy/EMS-ESP
+ * Copyright 2020  Paul Derbyshire
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <uuid/common.h>
+
+// #ifdef ESP8266
+// #include <pgmspace.h>
+// #else
+// #include <avr/pgmspace.h>
+// #endif
+
+#include <Arduino.h>
+
+namespace uuid {
+
+// On ESP8266, pgm_read_byte() already takes care of 4-byte alignment, and
+// memcpy_P(s, p, 4) makes 4 calls to pgm_read_byte() anyway, so don't bother
+// optimizing for 4-byte alignment here.
+
+// class __FlashStringHelper;
+
+int compare_flash_string(const __FlashStringHelper * a, const __FlashStringHelper * b) {
+    const char * aa = reinterpret_cast<const char *>(a);
+    const char * bb = reinterpret_cast<const char *>(b);
+
+    while (true) {
+        uint8_t ca = pgm_read_byte(aa);
+        uint8_t cb = pgm_read_byte(bb);
+        if (ca != cb)
+            return (int)ca - (int)cb;
+        if (ca == 0)
+            return 0;
+        aa++;
+        bb++;
+    }
+}
+
+int compare_flash_string(const __FlashStringHelper * a, const __FlashStringHelper * b, size_t n) {
+    const char * aa = reinterpret_cast<const char *>(a);
+    const char * bb = reinterpret_cast<const char *>(b);
+
+    while (n > 0) {
+        uint8_t ca = pgm_read_byte(aa);
+        uint8_t cb = pgm_read_byte(bb);
+        if (ca != cb)
+            return (int)ca - (int)cb;
+        if (ca == 0)
+            return 0;
+        aa++;
+        bb++;
+        n--;
+    }
+    return 0;
+}
+
+} // namespace uuid

lib/uuid-common/src/uuid/common.h

@@ -16,6 +16,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+// compare_flash_string added by Proddy
+
 #ifndef UUID_COMMON_H_
 #define UUID_COMMON_H_
 
@@ -32,6 +34,21 @@
  */
 namespace uuid {
 
+/**
+ * String compare two flash strings
+ *
+ * The flash string must be stored with appropriate alignment for
+ * reading it on the platform.
+ *
+ * @param[in] a Pointer to string stored in flash.
+ * @param[in] b Pointer to string stored in flash.
+ * @param[in] n optional max length
+ * @return 0 for match, otherwise diff
+ * @since 1.0.0
+ */
+int compare_flash_string(const __FlashStringHelper * a, const __FlashStringHelper * b);
+int compare_flash_string(const __FlashStringHelper * a, const __FlashStringHelper * b, size_t n);
+
 /**
  * Read a string from flash and convert it to a std::string.
  *