/*
 * Original code by Paul Vixie. "curlified" by Gisle Vanem.
 */

#include "setup.h"

#ifndef HAVE_INET_NTOP

#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#include <string.h>
#include <errno.h>

#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>

#include "inet_ntop.h"

#if defined( HAVE_INET_NTOA_R ) && !defined( HAVE_INET_NTOA_R_DECL )
/* this platform has a inet_ntoa_r() function, but no proto declared anywhere
   so we include our own proto to make compilers happy */
#include "inet_ntoa_r.h"
#endif

#define IN6ADDRSZ       16
#define INADDRSZ         4
#define INT16SZ          2

#ifdef WIN32
#define EAFNOSUPPORT    WSAEAFNOSUPPORT
#define SET_ERRNO( e )    WSASetLastError( errno = ( e ) )
#else
#define SET_ERRNO( e )    errno = e
#endif

/*
 * Format an IPv4 address, more or less like inet_ntoa().
 *
 * Returns `dst' (as a const)
 * Note:
 *  - uses no statics
 *  - takes a u_char* not an in_addr as input
 */
static const char *inet_ntop4( const u_char *src, char *dst, size_t size ) {
#ifdef HAVE_INET_NTOA_R
	return inet_ntoa_r( *(struct in_addr*)src, dst, size );
#else
	const char *addr = inet_ntoa( *(struct in_addr*)src );

	if ( strlen( addr ) >= size ) {
		SET_ERRNO( ENOSPC );
		return ( NULL );
	}
	return strcpy( dst, addr );
#endif
}

#ifdef ENABLE_IPV6
/*
 * Convert IPv6 binary address into presentation (printable) format.
 */
static const char *inet_ntop6( const u_char *src, char *dst, size_t size ) {
	/*
	 * Note that int32_t and int16_t need only be "at least" large enough
	 * to contain a value of the specified size.  On some systems, like
	 * Crays, there is no such thing as an integer variable with 16 bits.
	 * Keep this in mind if you think this function should have been coded
	 * to use pointer overlays.  All the world's not a VAX.
	 */
	char tmp [sizeof( "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255" )];
	char *tp;
	struct {
		long base;
		long len;
	} best, cur;
	u_long words [IN6ADDRSZ / INT16SZ];
	int i;

	/* Preprocess:
	 *  Copy the input (bytewise) array into a wordwise array.
	 *  Find the longest run of 0x00's in src[] for :: shorthanding.
	 */
	memset( words, 0, sizeof( words ) );
	for ( i = 0; i < IN6ADDRSZ; i++ )
		words[i / 2] |= ( src[i] << ( ( 1 - ( i % 2 ) ) << 3 ) );

	best.base = -1;
	cur.base  = -1;
	for ( i = 0; i < ( IN6ADDRSZ / INT16SZ ); i++ )
	{
		if ( words[i] == 0 ) {
			if ( cur.base == -1 ) {
				cur.base = i, cur.len = 1;
			} else {
				cur.len++;
			}
		} else if ( cur.base != -1 )     {
			if ( best.base == -1 || cur.len > best.len ) {
				best = cur;
			}
			cur.base = -1;
		}
	}
	if ( ( cur.base != -1 ) && ( best.base == -1 || cur.len > best.len ) ) {
		best = cur;
	}
	if ( best.base != -1 && best.len < 2 ) {
		best.base = -1;
	}

	/* Format the result.
	 */
	tp = tmp;
	for ( i = 0; i < ( IN6ADDRSZ / INT16SZ ); i++ )
	{
		/* Are we inside the best run of 0x00's?
		 */
		if ( best.base != -1 && i >= best.base && i < ( best.base + best.len ) ) {
			if ( i == best.base ) {
				*tp++ = ':';
			}
			continue;
		}

		/* Are we following an initial run of 0x00s or any real hex?
		 */
		if ( i != 0 ) {
			*tp++ = ':';
		}

		/* Is this address an encapsulated IPv4?
		 */
		if ( i == 6 && best.base == 0 &&
			 ( best.len == 6 || ( best.len == 5 && words[5] == 0xffff ) ) ) {
			if ( !inet_ntop4( src + 12, tp, sizeof( tmp ) - ( tp - tmp ) ) ) {
				SET_ERRNO( ENOSPC );
				return ( NULL );
			}
			tp += strlen( tp );
			break;
		}
		tp += snprintf( tp, 5, "%lx", words[i] );
	}

	/* Was it a trailing run of 0x00's?
	 */
	if ( best.base != -1 && ( best.base + best.len ) == ( IN6ADDRSZ / INT16SZ ) ) {
		*tp++ = ':';
	}
	*tp++ = '\0';

	/* Check for overflow, copy, and we're done.
	 */
	if ( (size_t)( tp - tmp ) > size ) {
		SET_ERRNO( ENOSPC );
		return ( NULL );
	}
	return strcpy( dst, tmp );
}
#endif  /* ENABLE_IPV6 */

/*
 * Convert a network format address to presentation format.
 *
 * Returns pointer to presentation format address (`dst'),
 * Returns NULL on error (see errno).
 */
const char *Curl_inet_ntop( int af, const void *src, char *buf, size_t size ) {
	switch ( af ) {
	case AF_INET:
		return inet_ntop4( (const u_char*)src, buf, size );
#ifdef ENABLE_IPV6
	case AF_INET6:
		return inet_ntop6( (const u_char*)src, buf, size );
#endif
	default:
		SET_ERRNO( EAFNOSUPPORT );
		return NULL;
	}
}
#endif  /* HAVE_INET_NTOP */