// SPDX-License-Identifier: ISC

/*

 * optimized ntop, about 10x faster than libc versions [as of 2019]

 *

 * Copyright (c) 2019  David Lamparter, for NetDEF, Inc.

 */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <stdio.h>

#include <stdint.h>

#include <stdbool.h>

#include <string.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include "compiler.h"

#define pos (*posx)

static inline void putbyte(uint8_t bytex, char **posx)

  __attribute__((always_inline)) OPTIMIZE;

static inline void putbyte(uint8_t bytex, char **posx)

{

  bool zero = false;

  int byte = bytex, tmp, a, b;

  tmp = byte - 200;

  if (tmp >= 0) {

    *pos++ = '2';

    zero = true;

    byte = tmp;

  } else {

    tmp = byte - 100;

    if (tmp >= 0) {

      *pos++ = '1';

      zero = true;

      byte = tmp;

    }

  }

  /* make sure the compiler knows the value range of "byte" */

  assume(byte < 100 && byte >= 0);

  b = byte % 10;

  a = byte / 10;

  if (a || zero) {

    *pos++ = '0' + a;

    *pos++ = '0' + b;

  } else

    *pos++ = '0' + b;

}

static inline void puthex(uint16_t word, char **posx)

  __attribute__((always_inline)) OPTIMIZE;

static inline void puthex(uint16_t word, char **posx)

{

  const char *digits = "0123456789abcdef";

  if (word >= 0x1000)

    *pos++ = digits[(word >> 12) & 0xf];

  if (word >= 0x100)

    *pos++ = digits[(word >> 8) & 0xf];

  if (word >= 0x10)

    *pos++ = digits[(word >> 4) & 0xf];

  *pos++ = digits[word & 0xf];

}

#undef pos

const char *frr_inet_ntop(int af, const void * restrict src,

        char * restrict dst, socklen_t size)

  __attribute__((flatten)) OPTIMIZE;

const char *frr_inet_ntop(int af, const void * restrict src,

        char * restrict dst, socklen_t size)

{

  const uint8_t *b = src;

  /* 8 * "abcd:" for IPv6

   * note: the IPv4-embedded IPv6 syntax is only used for ::A.B.C.D,

   * which isn't longer than 40 chars either.  even with ::ffff:A.B.C.D

   * it's shorter.

   */

  char buf[8 * 5], *o = buf;

  size_t best = 0, bestlen = 0, curlen = 0, i;

  switch (af) {

  case AF_INET:

inet4:

    putbyte(b[0], &o);

    *o++ = '.';

    putbyte(b[1], &o);

    *o++ = '.';

    putbyte(b[2], &o);

    *o++ = '.';

    putbyte(b[3], &o);

    *o++ = '\0';

    break;

  case AF_INET6:

    for (i = 0; i < 8; i++) {

      if (b[i * 2] || b[i * 2 + 1]) {

        if (curlen && curlen > bestlen) {

          best = i - curlen;

          bestlen = curlen;

        }

        curlen = 0;

        continue;

      }

      curlen++;

    }

    if (curlen && curlen > bestlen) {

      best = i - curlen;

      bestlen = curlen;

    }

    /* do we want ::ffff:A.B.C.D? */

    if (best == 0 && bestlen == 6) {

      *o++ = ':';

      *o++ = ':';

      b += 12;

      goto inet4;

    }

    if (bestlen == 1)

      bestlen = 0;

    for (i = 0; i < 8; i++) {

      if (bestlen && i == best) {

        if (i == 0)

          *o++ = ':';

        *o++ = ':';

        continue;

      }

      if (i > best && i < best + bestlen) {

        continue;

      }

      puthex((b[i * 2] << 8) | b[i * 2 + 1], &o);

      if (i < 7)

        *o++ = ':';

    }

    *o++ = '\0';

    break;

  default:

    return NULL;

  }

  i = o - buf;

  if (i > size)

    return NULL;

  /* compiler might inline memcpy if it knows the length is short,

   * although neither gcc nor clang actually do this currently [2019]

   */

  assume(i <= 8 * 5);

  memcpy(dst, buf, i);

  return dst;

}

#if !defined(INET_NTOP_NO_OVERRIDE) && !defined(__APPLE__)

/* we want to override libc inet_ntop, but make sure it shows up in backtraces

 * as frr_inet_ntop (to avoid confusion while debugging)

 */

const char *inet_ntop(int af, const void *src, char *dst, socklen_t size)

  __attribute__((alias ("frr_inet_ntop")));

#endif