bool ( __stdcall *pfnFFBase64Open )( char* );
int  ( __stdcall *pfnFFBase64Get512Bytes )( char* );
int  ( __stdcall *pfnFFBase64Encode )( char* );
void ( __stdcall *pfnFFBase64Close )( void );

• prepare the attachment
• open the attachment (FFBase64Open)
• enter a loop to get 512 encoded bytes at a time (FFBase64Get512Bytes) and print the bytes directly to the socket
• close the attachment

FFBase64Encode is a general purpose encoder, but I have developed it to encode username and password when the mail client is connecting to an ESMTP server which requires the AUTH LOGIN and, you know, you must encode those two strings. Again: see the example.

• FFBase64Open:
  • complete path and filename of the attachment file
• FFBase64Get512Bytes:
  • pointer to the 512 bytes buffer: this function automatically reads 384 bytes from the opened file and fills with 512 bytes of encoded data the buffer pointed to by this parameter; this function adds a NULL character (0x00) at the end of the 512 encoded bytes, making the buffer an ASCIIZ string; at the end of the file this function reads 384 bytes or less (and the buffer is filled accordingly to the number of read bytes; the NULL character is put just after the last encoded byte); in the given example the buffer is declared some bytes more (char szMessage [ 516 ];) because it is necessary to add a carriage return & line feed pair
• FFBase64Encode:
  • pointer to the string to encode: the string should be max 384 characters; but remember to allocate 4/3 space more, because the encoded result is given in the same place pointed to by this parameter and, as you know, base-64 encoding expands the source stream by a factor of 4/3
• FFBase64Close:
  • (no parameters)

• FFBase64Open:
  • true: the file has been opened
  • false: the file has not been opened
• FFBase64Get512Bytes:
  • true: the buffer contains encoded data to print to the socket
  • false: the buffer is empty (the input file is finished), stop printing to the socket
• FFBase64Encode:
  • the length of the encoded data
• FFBase64Close:
  • (no return value)