Info Catalog flex: Global Replacement flex: Reentrant Detail flex: Accessor Methods

flex: Init and Destroy Functions

 
 19.4.4 Init and Destroy Functions
 ---------------------------------
 
 'yylex_init' and 'yylex_destroy' must be called before and after
 'yylex', respectively.
 
          int yylex_init ( yyscan_t * ptr_yy_globals ) ;
          int yylex_init_extra ( YY_EXTRA_TYPE user_defined, yyscan_t * ptr_yy_globals ) ;
          int yylex ( yyscan_t yyscanner ) ;
          int yylex_destroy ( yyscan_t yyscanner ) ;
 
    The function 'yylex_init' must be called before calling any other
 function.  The argument to 'yylex_init' is the address of an
 uninitialized pointer to be filled in by 'yylex_init', overwriting any
 previous contents.  The function 'yylex_init_extra' may be used instead,
 taking as its first argument a variable of type 'YY_EXTRA_TYPE'.  See
 the section on yyextra, below, for more details.
 
    The value stored in 'ptr_yy_globals' should thereafter be passed to
 'yylex' and 'yylex_destroy'.  Flex does not save the argument passed to
 'yylex_init', so it is safe to pass the address of a local pointer to
 'yylex_init' so long as it remains in scope for the duration of all
 calls to the scanner, up to and including the call to 'yylex_destroy'.
 
    The function 'yylex' should be familiar to you by now.  The reentrant
 version takes one argument, which is the value returned (via an
 argument) by 'yylex_init'.  Otherwise, it behaves the same as the
 non-reentrant version of 'yylex'.
 
    Both 'yylex_init' and 'yylex_init_extra' returns 0 (zero) on success,
 or non-zero on failure, in which case errno is set to one of the
 following values:
 
    * ENOMEM Memory allocation error.  ⇒memory-management.
    * EINVAL Invalid argument.
 
    The function 'yylex_destroy' should be called to free resources used
 by the scanner.  After 'yylex_destroy' is called, the contents of
 'yyscanner' should not be used.  Of course, there is no need to destroy
 a scanner if you plan to reuse it.  A 'flex' scanner (both reentrant and
 non-reentrant) may be restarted by calling 'yyrestart'.
 
    Below is an example of a program that creates a scanner, uses it,
 then destroys it when done:
 
          int main ()
          {
              yyscan_t scanner;
              int tok;
      
              yylex_init(&scanner);
      
              while ((tok=yylex(scanner)) > 0)
                  printf("tok=%d  yytext=%s\n", tok, yyget_text(scanner));
      
              yylex_destroy(scanner);
              return 0;
          }
 

Info Catalog flex: Global Replacement flex: Reentrant Detail flex: Accessor Methods