Buffer arguments of write functions are changed to const so that the functions cannot change the content of the buffer. Also, if the I2C device's register address are define using const rather than #define, the functions can accept those too.

Adafruit_I2CDevice.cpp

@@ -66,8 +66,8 @@ bool Adafruit_I2CDevice::detected(void) {
  *    @param  stop Whether to send an I2C STOP signal on write
  *    @return True if write was successful, otherwise false.
  */
-bool Adafruit_I2CDevice::write(uint8_t *buffer, size_t len, bool stop,
-                               uint8_t *prefix_buffer, size_t prefix_len) {
+bool Adafruit_I2CDevice::write(const uint8_t *buffer, size_t len, bool stop,
+                               const uint8_t *prefix_buffer, size_t prefix_len) {
   if ((len + prefix_len) > maxBufferSize()) {
     // currently not guaranteed to work if more than 32 bytes!
     // we will need to find out if some platforms have larger
@@ -200,7 +200,7 @@ bool Adafruit_I2CDevice::read(uint8_t *buffer, size_t len, bool stop) {
  *    @param  stop Whether to send an I2C STOP signal between the write and read
  *    @return True if write & read was successful, otherwise false.
  */
-bool Adafruit_I2CDevice::write_then_read(uint8_t *write_buffer,
+bool Adafruit_I2CDevice::write_then_read(const uint8_t *write_buffer,
                                          size_t write_len, uint8_t *read_buffer,
                                          size_t read_len, bool stop) {
   if (!write(write_buffer, write_len, stop)) {

Adafruit_I2CDevice.h

@@ -12,9 +12,9 @@ public:
   bool detected(void);
 
   bool read(uint8_t *buffer, size_t len, bool stop = true);
-  bool write(uint8_t *buffer, size_t len, bool stop = true,
-             uint8_t *prefix_buffer = NULL, size_t prefix_len = 0);
-  bool write_then_read(uint8_t *write_buffer, size_t write_len,
+  bool write(const uint8_t *buffer, size_t len, bool stop = true,
+             const uint8_t *prefix_buffer = NULL, size_t prefix_len = 0);
+  bool write_then_read(const uint8_t *write_buffer, size_t write_len,
                        uint8_t *read_buffer, size_t read_len,
                        bool stop = false);
   bool setSpeed(uint32_t desiredclk);