TI-BDS-PLUGIN 1.0.4 and string characteristics

Hi Pixbroker,

Since BDS doesn't tell the plugin anything about the length of the string, the plugin just makes a guess. Admittedly, it should perhaps guess 20 rather than 1 for the length of a string, but the point is the length isn't part of the service description, and at some point one has to allocate some length.

If you want to support variable length, you can simply manually change the defined length after code generation, and you can remove the check for whether length == expected length. You should also add a variable holding the latest received length.

So, in your example:

#define T_FIRST_NAME_LEN                40

uint16_t t_First_NameValLen = 0; // Dynamically updated length


bStatus_t Test_SetParameter(uint8_t param, uint8_t len, void *value)
{
  bStatus_t ret = SUCCESS;
  switch ( param )
  {
    case T_FIRST_NAME_ID:
      if ( len <= T_FIRST_NAME_LEN ) 
      {
        memcpy(t_First_NameVal, value, len);
        t_First_NameValLen = len;
  ....


bStatus_t Test_GetParameter( uint8_t param, uint16_t *len, void *value )
{
  bStatus_t ret = SUCCESS;
  switch ( param )
  {
    case T_FIRST_NAME_ID:
      *len = MIN(*len, t_First_NameValLen);
      memcpy(value, t_First_NameVal, *len);
      break;
....


static bStatus_t test_WriteAttrCB( uint16_t connHandle, gattAttribute_t *pAttr,
                                        uint8_t *pValue, uint16_t len, uint16_t offset,
                                        uint8_t method )
{
  ...

  else if ( ! memcmp(pAttr->type.uuid, t_First_NameUUID, pAttr->type.len) )
  {
    if ( offset + len > T_FIRST_NAME_LEN )
    {
      status = ATT_ERR_INVALID_OFFSET;
    }
    else
    {
      // Copy pValue into the variable we point to from the attribute table.
      memcpy(pAttr->pValue + offset, pValue, len);

      // Update length variable
      t_First_NameValLen = offset+len;

      // Always notify application. Note: Long writes are concatenated before reaching here.
      paramID = T_FIRST_NAME_ID;
    }
  }
  ...
}

static bStatus_t Cool_and_Nice_Service_ReadAttrCB( uint16_t connHandle, gattAttribute_t *pAttr, 
                                       uint8_t *pValue, uint16_t *pLen, uint16_t offset,
                                       uint16_t maxLen, uint8_t method )
{
  ... 

  if ( ! memcmp(pAttr->type.uuid, t_First_NameUUID, pAttr->type.len) )
  {
    if ( offset > t_First_NameValLen )  // Prevent malicious ATT ReadBlob offsets.
    {
      status = ATT_ERR_INVALID_OFFSET;
    }
    else
    {
      *pLen = MIN(maxLen, t_First_NameValLen - offset);  // Transmit as much as possible
      memcpy(pValue, pAttr->pValue + offset, *pLen);
    }
  }

Note that I haven't tested this. And note also the API for GetParameter has been changed. the len parameter must be a pointer to a max length, and is replaced by the actual length after returning.

I'll make an effort to make the plugin more intelligently decide whether a variable approach or a fixed size approach should be used for a char. Thanks for bringing this to our attention.

Best regards,
Aslak

Hi,

The output from the tool will probably never be adequate for an end-product, so some jiggering is to be expected.

However, there is now a new version available - 1.0.5 - which adds support for variable length characteristic attributes and also fixes some of the 1 byte long variable length fields.

Best regards,
Aslak