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       lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname,
       lwres_getnamebyaddr - lightweight resolver utility functions

       #include	<lwres/lwres.h>

       lwres_result_t lwres_string_parse(lwres_buffer_t	*b, char **c,
					 uint16_t *len);

       lwres_result_t lwres_addr_parse(lwres_buffer_t *b, lwres_addr_t *addr);

       lwres_result_t lwres_getaddrsbyname(lwres_context_t *ctx,
					   const char *name,
					   uint32_t addrtypes,
					   lwres_gabnresponse_t	**structp);

       lwres_result_t lwres_getnamebyaddr(lwres_context_t *ctx,
					  uint32_t addrtype, uint16_t addrlen,
					  const	unsigned char *addr,
					  lwres_gnbaresponse_t **structp);

       lwres_string_parse() retrieves a	DNS-encoded string starting the
       current pointer of lightweight resolver buffer b: i.e.  b->current.
       When the	function returns, the address of the first byte	of the encoded
       string is returned via *c and the length	of that	string is given	by
       *len. The buffer's current pointer is advanced to point at the
       character following the string length, the encoded string, and the
       trailing	NULL character.

       lwres_addr_parse() extracts an address from the buffer b. The buffer's
       current pointer b->current is presumed to point at an encoded address:
       the address preceded by a 32-bit	protocol family	identifier and a
       16-bit length field. The	encoded	address	is copied to addr->address and
       addr->length indicates the size in bytes	of the address that was
       copied.	b->current is advanced to point	at the next byte of available
       data in the buffer following the	encoded	address.

       lwres_getaddrsbyname() and lwres_getnamebyaddr()	use the
       lwres_gnbaresponse_t structure defined below:

	   typedef struct {
		   uint32_t	     flags;
		   uint16_t	     naliases;
		   uint16_t	     naddrs;
		   char			  *realname;
		   char			 **aliases;
		   uint16_t	     realnamelen;
		   uint16_t	    *aliaslen;
		   lwres_addrlist_t	   addrs;
		   void			  *base;
		   size_t		   baselen;
	   } lwres_gabnresponse_t;

       The contents of this structure are not manipulated directly but they
       are controlled through the lwres_gabn(3)	functions.

       The lightweight resolver	uses lwres_getaddrsbyname() to perform forward
       lookups.	Hostname name is looked	up using the resolver context ctx for
       memory allocation.  addrtypes is	a bitmask indicating which type	of
       addresses are to	be looked up. Current values for this bitmask are
       LWRES_ADDRTYPE_V4 for IPv4 addresses and	LWRES_ADDRTYPE_V6 for IPv6
       addresses. Results of the lookup	are returned in	*structp.

       lwres_getnamebyaddr() performs reverse lookups. Resolver	context	ctx is
       used for	memory allocation. The address type is indicated by addrtype:
       LWRES_ADDRTYPE_V4 or LWRES_ADDRTYPE_V6. The address to be looked	up is
       given by	addr and its length is addrlen bytes. The result of the
       function	call is	made available through *structp.

       Successful calls	to lwres_string_parse()	and lwres_addr_parse() return
       LWRES_R_SUCCESS.	 Both functions	return LWRES_R_FAILURE if the buffer
       is corrupt or LWRES_R_UNEXPECTEDEND if the buffer has less space	than
       expected	for the	components of the encoded string or address.

       lwres_getaddrsbyname() returns LWRES_R_SUCCESS on success and it
       returns LWRES_R_NOTFOUND	if the hostname	name could not be found.

       LWRES_R_SUCCESS is returned by a	successful call	to

       Both lwres_getaddrsbyname() and lwres_getnamebyaddr() return
       LWRES_R_NOMEMORY	when memory allocation requests	fail and
       LWRES_R_UNEXPECTEDEND if	the buffers used for sending queries and
       receiving replies are too small.

       lwres_buffer(3),	lwres_gabn(3).

       Internet	Systems	Consortium, Inc.

       Copyright (C) 2000, 2001, 2004, 2005, 2007, 2014-2016, 2018-2021
       Internet	Systems	Consortium, Inc. ("ISC")

ISC				  2007-06-18		      LWRES_RESUTIL(3)


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