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C/C++: strtok Procedure

char * strtok ( char * string, const char * control )
{
	unsigned char *str;
	const unsigned char *ctrl = control;

	unsigned char map[32];
	int count;

	static char *nextoken; // Not thread safe

	// Clear control map
	for (count = 0; count < 32; count++)
		map[count] = 0;

	// Set bits in delimiter table
	do {
		map[*ctrl >> 3] |= (1 << (*ctrl & 7));
	} while (*ctrl++);

	// Initialize str. If string is NULL, set str to the saved
	// pointer (i.e., continue breaking tokens out of the string
	// from the last strtok call)
	if (string)
		str = string;
	else
		str = nextoken;

	// Find beginning of token (skip over leading delimiters). Note that
	// there is no token iff this loop sets str to point to the terminal
	// null (*str == '\0')
	while ( (map[*str >> 3] & (1 << (*str & 7))) && *str )
		str++;

	string = str;

	// Find the end of the token. If it is not the end of the string,
	// put a null there.
	for ( ; *str ; str++ )
	{
		if ( map[*str >> 3] & (1 << (*str & 7)) )
		{
			*str++ = '\0';
			break;
		}
	}

	// Update nextoken (or the corresponding field in the per-thread
	// data structure
	nextoken = str;

	// Determine if a token has been found.
	if ( string == str )
		return NULL;
	else
		return string;
}

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