/*

 * string2.lex: An example of using scanning strings

 *              by using start states.

 */

%{

#include <ctype.h>

#include <malloc.h>

#define isodigit(x) ((x) >= '0' && (x) <= '7') 

#define hextoint(x) (isdigit((x)) ? (x) - '0' : ((x) - 'A') + 10)  

char *buffer      = NULL;

int  buffer_size  = 0;

void yyerror(char *message)

{

  printf("\nError: %s\n",message);

}

%}

%x STRING

hex (x|X)[0-9a-fA-F]{1,2}

oct [0-7]{1,3}

%%

\"                 { 

                     buffer      = malloc(1); 

                     buffer_size = 1; strcpy(buffer,"");

                     BEGIN(STRING);

                   }

<STRING>\n         {

                      yyerror("Unterminated string");       

                      free(buffer);

                      BEGIN(INITIAL);

                   }

<STRING><<EOF>>    {

                      yyerror("EOF in string");       

                      free(buffer);

                      BEGIN(INITIAL);

                   }

<STRING>[^\\\n"]   {

                     buffer = realloc(buffer,buffer_size+yyleng+1);

                     buffer_size += yyleng;

                     strcat(buffer,yytext);

                   }

<STRING>\\\n       /* ignore this */

<STRING>\\{hex}    {

                     int temp =0,loop = 0;

                     for(loop=yyleng-2; loop>0; loop--){

                       temp  <<= 4;

                       temp  += hextoint(toupper(yytext[yyleng-loop]));

                     } 

                     buffer = realloc(buffer,buffer_size+1);

                     buffer[buffer_size-1] = temp;

                     buffer[buffer_size]   = '\0';

                     buffer_size += 1;

                   }

<STRING>\\{oct}    {

                     int temp =0,loop = 0;

                     for(loop=yyleng-1; loop>0; loop--){

                       temp  <<= 3;

                       temp  += (yytext[yyleng-loop] - '0');

                     } 

                     buffer = realloc(buffer,buffer_size+1);

                     buffer[buffer_size-1] = temp;

                     buffer[buffer_size]   = '\0';

                     buffer_size += 1;

                   }

<STRING>\\[^\n]    {

                     buffer = realloc(buffer,buffer_size+1);

                     switch(yytext[yyleng-1]){

                     case 'b' : buffer[buffer_size-1] = '\b';  break;

                     case 't' : buffer[buffer_size-1] = '\t';  break;

                     case 'n' : buffer[buffer_size-1] = '\n';  break;

                     case 'v' : buffer[buffer_size-1] = '\v';  break;

                     case 'f' : buffer[buffer_size-1] = '\f';  break;

                     case 'r' : buffer[buffer_size-1] = '\r';  break;

                     default  : buffer[buffer_size-1] = yytext[yyleng-1];

                     }

                     buffer[buffer_size] = '\0';

                     buffer_size += 1;

                   }

<STRING>\"         {

                     printf("string = \"%s\"",buffer); 

                     free(buffer);

                     BEGIN(INITIAL);

                   }

%%