EwNewStringAnsi length problem

Question

Hello.

There was a problem converting ansi character to string.

 

typedef struct
{

  char text[32];
  char id[32];

} MyStringStruct;

...

MyStringStruct test;

test.text = "01234567890123456789012345678901";   // length = 32
test.id = "ABCDEF";

The code is a structure that stores strings.

But if I convert this data to EwNewStringAnsi like below code...

 

// embedded wizard

var string text = "";
var string id = "";

native( text, id )
{
  text = EwNewStringAnsi( test.text );
  id = EewNewStringAnsi( test.id );
}


// trace
trace text;
trace id;

/*
 
  01234567890123456789012345678901ABCDEF
  ABCDEF

*/

Convert until NULL data is found.

Is there any way to limit the length of the conversion of EwNewStringAnsi()? 

Answer 1

Hello,

the function EwNewStringAnsi() expects the string to be zero-terminated as this is usual in C. It would be thus better to adapt the MyStringStruct definition to reserve one additional char. Concrete to change the size of a string from 32 to 33. For example:

typedef struct
{
  char text[33];
  char id[33];
} MyStringStruct;

If this is not possible, then you can't use the function EwNewStringAnsi(). Instead, you have to perform a temp. copy step into an array containing an additional zero terminator sign. For example:

var string text = "";
var string id = "";

native( text, id )
{
  // temp. buffers for the strings. Per default filled with zero char.
  char tmpText[ sizeof( test.text ) + 1 ] = { 0 };
  char tmpId  [ sizeof( test.id   ) + 1 ] = { 0 };

  // copy the strings from the 'test' data structure. Use memcpy() or
  // EmWi-own EwCopy() function:
  EwCopy( tmpText, test.text, sizeof( test.text ));
  EwCopy( tmpId,   test.id,   sizeof( test.id ));

  text = EwNewStringAnsi ( tmpText );
  id   = EewNewStringAnsi( tmpId   );
}

Alternative approach omits the local arrays. Instead you have to copy the string sign by sign into a previously created EmWi string. To create such string use the function EwNewStringChar():

var string text = "";
var string id = "";

native( text, id )
{
  int i;

  // First create new EmWi string with enough capacity.
  text = EwNewStringChar( 0, sizeof( test.text ));
  id   = EwNewStringChar( 0, sizeof( id.text   ));

  // Then copy the ANSI string into the EmWi string. Sign by sign.
  for ( i = 0; i < sizeof( test.text ); i++ )
    text[i] = test.text[i];

  // Repeat the operation for the second string.
  for ( i = 0; i < sizeof( test.id ); i++ )
    id[i] = test.id[i];
}

Does it help you further?

Best regards

Paul Banach

Comments

Thank you. your comment.

Unfortunately, I cannot adjust the length of the buffer.

So I copied it to an arbitrary buffer and convert it.

However, I wish I could limit the length in the EwNewStringAnsi() functions afterwards.

---

In such case you can implement your own NewStringAnsi() function and use it wherever you need to create an EmWi-String from a non-zero terminated ANSI string. This could be the implementation:

XString NewStringAnsi( const char* aSrcString, int aStringLength )
{
  int     i;
  XString s;

  if ( aStringLength <= 0 )
    return 0;

  // First create new EmWi string with enough capacity.
  s = EwNewStringChar( 0, aStringLength );

  if ( !s )
    return 0;

  // Then copy the ANSI string into the EmWi string. Sign by sign.
  for ( i = 0; i < aStringLength; i++ )
    s[i] = aSrcString[i];

  return s;
}

Best regards

Paul banach