CS456 - Systems Programming

Displaying exercises/e6/files/lex.c

#include "lex.h"

char *input;	// Input string
int pos = 0;	// Position within the string

void startlex(char *s)
{
  input = s;
  pos = 0;
}

// Gets the next character, or a -1 on end of input.
int get(void)
{
  if (input[pos] == '\0') return -1;
  return input[pos++];
}

// Unget a character (as long as it is not the end of input):
int unget(int c)
{
  if (pos > 0 && c != -1) pos--;
}

/**
 * If the next character is c, then move past it and return TRUE, otherwise
 * do nothing and return FALSE.  You will likely not need this function for this
 * assignment.
 */
bool next(int c)
{
  if (input[pos] == c) {
    pos++;
    return TRUE;
  }
  return FALSE;
}

// Keywords, true, false and null defined for you, if you choose to use this
// structure.
static struct keyword {
  char *name;
  token_t tval;
} keywords[] = {
  {"true", T_TRUE},
  {"false", T_FALSE},
  {"null", T_NULL},
  {NULL, T_UNKNOWN}
};


/**
 * JSON strings are always double-quoted and may contain 0 or more characters
 * with the following allowed for characters:
 * char	  : any-Unicode-character-except-"-or-\-or-control-character
 *	  | \" | \\ | \/ | \b | \f | \n | \r | \t| \u four-hex-digits 
 * For this assignment you do not need to support \u hex sequences, although
 * you may.
 */

static token_t lexstring(char *word)
{


}

/**
 * Returns the next token.  Place strings and numbers in the word buffer.
 */
token_t lex(char *word)
{


}