Make extEEPROM::update() first class citizen method

examples/eepromTest_Update/eepromTest_Update.ino

@@ -0,0 +1,84 @@
+// Test extEEPROM library - update() method.
+// Damian Wrobel <dwrobel@ertelnet.rybnik.pl>
+
+#include <extEEPROM.h>
+
+extEEPROM ep(kbits_256, 1, 64); // device size, number of devices, page size
+
+void test_update() {
+  Serial.println("\n(0) Test Started");
+
+  constexpr auto addr  = 0;
+  constexpr int length = (BUFFER_LENGTH * 2) + 13;
+
+  byte writeBuf[length];
+
+  for (auto i = 0; i < length; i++) {
+    writeBuf[i] = i;
+  }
+
+  auto rv = ep.update(addr, writeBuf, length);
+  if (rv) {
+    Serial.print("(1) Error updating: ");
+    Serial.println(rv);
+  }
+
+  byte readBuf[length];
+  for (auto i = 0; i < length; i++) {
+    readBuf[i] = ~writeBuf[i];
+  }
+
+  rv = ep.read(addr, readBuf, length);
+  if (rv) {
+    Serial.print("(2) Error reading: ");
+    Serial.println(rv);
+  }
+
+  rv = memcmp(writeBuf, readBuf, length);
+  if (rv) {
+    Serial.print("(3) Error comparing: ");
+    Serial.println(rv);
+  }
+
+  for (auto i = 0; i < length; i++) {
+    if (i % 2 || i % 3)
+      writeBuf[i] = i;
+  }
+
+  rv = ep.update(addr, writeBuf, length);
+  if (rv) {
+    Serial.print("(4) Error updating: ");
+    Serial.println(rv);
+  }
+
+  rv = ep.read(addr, readBuf, length);
+  if (rv) {
+    Serial.print("(5) Error reading: ");
+    Serial.println(rv);
+  }
+
+  rv = memcmp(writeBuf, readBuf, length);
+  if (rv) {
+    Serial.print("(6) Error comparing: ");
+    Serial.println(rv);
+  }
+
+  Serial.println("(7) Test OK");
+}
+
+void setup(void) {
+  Serial.begin(115200);
+
+  const auto eepStatus = ep.begin(ep.twiClock100kHz);
+  if (eepStatus) {
+    Serial.print("extEEPROM.begin() failed, status = ");
+    Serial.println(eepStatus);
+    while (1)
+      ;
+  }
+
+  test_update();
+}
+
+void loop(void) {
+}

extEEPROM.cpp

@@ -114,7 +114,7 @@ byte extEEPROM::begin(twiClockFreq_t twiFreq, TwoWire *_comm)
 //If the I/O would extend past the top of the EEPROM address space,
 //a status of EEPROM_ADDR_ERR is returned. For I2C errors, the status
 //from the Arduino Wire library is passed back through to the caller.
-byte extEEPROM::write(unsigned long addr, byte *values, unsigned int nBytes)
+byte extEEPROM::write(unsigned long addr, const byte *values, unsigned int nBytes)
 {
     uint8_t ctrlByte;       //control byte (I2C device address & chip/block select bits)
     uint8_t txStatus = 0;   //transmit status
@@ -217,13 +217,48 @@ int extEEPROM::read(unsigned long addr)
 
 //Update bytes to external EEPROM.
 //For I2C errors, the status from the Arduino Wire library is passed back through to the caller.
-byte extEEPROM::update(unsigned long addr, byte *values, unsigned int nBytes)
+byte extEEPROM::update(unsigned long addr, const byte *values, unsigned int nBytes)
 {
-    if (nBytes == 1) {
-        return update(addr, values[0]);
+    decltype(nBytes) off = 0;
+
+    while (nBytes > 0) {
+        byte tmpBuf[BUFFER_LENGTH];
+        static_assert(BUFFER_LENGTH < UINT8_MAX, "BUFFER_LENGTH value has to fit into uint8_t");
+        const uint8_t readBytes = min(nBytes, static_cast<decltype(nBytes)>(BUFFER_LENGTH));
+        const auto currAddress = addr + off;
+        const auto rv = read(currAddress, tmpBuf, readBytes);
+        if (rv != 0)
+            return rv;
+
+        auto startDiff = 0;
+
+        while (startDiff < readBytes) {
+            if (tmpBuf[startDiff] == values[currAddress + startDiff]) {
+                startDiff++;
+                continue;
+            }
+
+            auto endDiff = startDiff + 1;
+
+            while (endDiff < readBytes) {
+                if (tmpBuf[endDiff] != values[currAddress + endDiff]) {
+                    endDiff++;
+                    continue;
+                }
+            }
+
+            const auto wv = write(currAddress + startDiff, &values[off + startDiff], endDiff - startDiff);
+            if (wv)
+                return wv;
+
+            startDiff = endDiff;
+        }
+
+        off    += readBytes;
+        nBytes -= readBytes;
     }
 
-    return false;
+    return 0;
 }
 
 //Update a single byte to external EEPROM.

extEEPROM.h

@@ -47,9 +47,12 @@
  * 29Mar2013 v2 - Updated to span page boundaries (and therefore also          *
  * device boundaries, assuming an integral number of pages per device)         *
  * 08Jul2014 v3 - Generalized for 2kb - 2Mb EEPROMs.                           *
- * 																			   *
- * Paolo Paolucci 22-10-2015 v3.2											   *
- * 09-01-2016 v3.2 Add update function.										   *
+ *                                                                             *
+ * Paolo Paolucci 22-10-2015 v3.2                                              *
+ * 09-01-2016 v3.2 Add update function.                                        *
+ *                                                                             *
+ * Damian Wrobel <dwrobel@ertelnet.rybnik.pl>                                  *
+ * 29-04-2019 v3.4.2 Implement update() method.                                *
  *                                                                             *
  * External EEPROM Library by Jack Christensen is licensed under CC BY-SA 4.0, *
  * http://creativecommons.org/licenses/by-sa/4.0/                              *
@@ -93,11 +96,11 @@ class extEEPROM
         // It is ready for every I2C Sercom, by default use the main Wire
         byte begin(twiClockFreq_t twiFreq = twiClock100kHz, TwoWire *_comm=&Wire); 
 
-        byte write(unsigned long addr, byte *values, unsigned int nBytes);
+        byte write(unsigned long addr, const byte *values, unsigned int nBytes);
         byte write(unsigned long addr, byte value);
         byte read(unsigned long addr, byte *values, unsigned int nBytes);
         int read(unsigned long addr);
-        byte update(unsigned long addr, byte *values, unsigned int nBytes);
+        byte update(unsigned long addr, const byte *values, unsigned int nBytes);
         byte update(unsigned long addr, byte value);
         unsigned long length();