Added contains24 method which checks whether an id is in the database…

… based on the low 24-bits.

This is useful when using Wiegand26 readers with full 32 bit ids in the database.

README.md

@@ -144,4 +144,18 @@ if (db.contains(10042)) {
 } else {
   Serial.println("Not in database");
 }
+```
+
+## contains24
+Returns 2 if the low order 24-bits of the specified id match the low order
+24 bits of any id in the databse. This us useful if 32 bit ids are stored in
+the database and the ids are read using a Wiegand26 reader which returns
+24 bits.
+
+```c++
+if (db.contains24(10042)) {
+  Serial.println("In database");
+} else {
+  Serial.println("Not in database");
+}
 ```

RfidDb.cpp

@@ -112,11 +112,29 @@ bool RfidDb::contains(uint32_t id) {
   return posOf(id) != -1;
 }
 
-// Returns the position of given id in the database or -1
-// if the id is not in the database
+bool RfidDb::contains24(uint32_t id) {
+  return posOf24(id) != -1;
+}
+
+// Returns the position of the given id in the database or -1 if the id is 
+// not in the database
 int16_t RfidDb::posOf(uint32_t id) {
+  return posOf(id, 0xFFFFFFFF);
+}
+
+// Returns the position of the given id in the database when compared on the
+// low 24 bits of the id.
+int16_t RfidDb::posOf24(uint32_t id) {
+  return posOf(id, 0x00FFFFFF);
+}
+
+// Returns the position of the given id when compared with ids in the datbase
+// after both the database id and the given id are bit masked with the given
+// mask
+int16_t RfidDb::posOf(uint32_t id, uint32_t mask) {
+  uint32_t maskedId = id & mask;
   for (uint8_t i = 0, n = count(); i < n; i++) {
-    if (id == getId(i)) {
+    if (maskedId == (getId(i) & mask)) {
       return i;
     }
   }

RfidDb.h

@@ -80,12 +80,20 @@ class RfidDb {
     // Returns whether the database contains the given identifier.
     bool contains(uint32_t id);
 
+    // Returns whether the database contains an indentifier where the low 24
+    // bits matches the low 24 bits of the given identifier. This is useful
+    // when reading from a Wiegand 26 device (that returns a 24 bit id) with
+    // identifers stored as 32 vit ids.
+    bool contains24(uint32_t id);
+
   private:
     uint16_t _eepromOffset;
     uint8_t _maxSize;
     uint8_t _maxNameLength;
 
     int16_t posOf(uint32_t id);
+    int16_t posOf24(uint32_t id);
+    int16_t posOf(uint32_t id, uint32_t mask);
     uint32_t getId(uint8_t pos);
     void writeId(uint8_t pos, uint32_t id);
     void writeName(uint8_t pos, const char* name);

examples/RfidDbTest/RfidDbTest.ino

@@ -3,11 +3,11 @@
 
 RfidDb db = RfidDb(4, 0, 4);
 
-uint32_t id1 = 1000000001;
-uint32_t id2 = 1000000002;
-uint32_t id3 = 1000000003;
-uint32_t id4 = 1000000004;
-uint32_t id5 = 1000000005;
+uint32_t id1 = 0xFFFFFF01;
+uint32_t id2 = 0xFFFFFF02;
+uint32_t id3 = 0xFFFFFF03;
+uint32_t id4 = 0xFFFFFF04;
+uint32_t id5 = 0xFFFFFF05;
 
 void setup() {
   Serial.begin(9600);
@@ -25,51 +25,61 @@ void setup() {
   Serial.println(db.insert(id1, "AAA"));
   dumpState();
   dumpContains();
+  dumpContains24();
 
   Serial.print("Inserting id2 = ");
   Serial.println(db.insert(id2, "BBB"));
   dumpState();
   dumpContains();
+  dumpContains24();
 
   Serial.print("Inserting id3 = ");
   Serial.println(db.insert(id3, "CCC"));
   dumpState();
   dumpContains();
+  dumpContains24();
 
   Serial.print("Inserting id4 = ");
   Serial.println(db.insert(id4, "DDD"));
   dumpState();
   dumpContains();
+  dumpContains24();
 
   Serial.print("Inserting id5 = ");
   Serial.println(db.insert(id5, "EEE"));
   dumpState();
   dumpContains();
+  dumpContains24();
 
   Serial.println("Removing id5");
   db.remove(id5);
   dumpState();
   dumpContains();
+  dumpContains24();
 
   Serial.println("Removing id1");
   db.remove(id1);
   dumpState();
   dumpContains();
+  dumpContains24();
 
   Serial.println("Removing id3");
   db.remove(id3);
   dumpState();
   dumpContains();
+  dumpContains24();
 
   Serial.println("Removing id2");
   db.remove(id2);
   dumpState();
   dumpContains();
+  dumpContains24();
 
   Serial.println("Removing id4");
   db.remove(id4);
   dumpState();
   dumpContains();
+  dumpContains24();
 }
 
 void loop() {
@@ -110,4 +120,17 @@ void dumpContains() {
   Serial.println(db.contains(id4));
   Serial.print("Contains id5 = ");
   Serial.println(db.contains(id5));  
+}
+
+void dumpContains24() {
+  Serial.print("Contains (24 bit) id1 = ");
+  Serial.println(db.contains(id1));
+  Serial.print("Contains (24 bit) id2 = ");
+  Serial.println(db.contains(id2));
+  Serial.print("Contains (24 bit) id3 = ");
+  Serial.println(db.contains(id3));
+  Serial.print("Contains (24 bit) id4 = ");
+  Serial.println(db.contains(id4));
+  Serial.print("Contains (24 bit) id5 = ");
+  Serial.println(db.contains(id5));  
 }