// Copyright (c) 2004-present, Facebook, Inc.
// All Rights Reserved.
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.

// convert.h - conversion utility methods
// no-check-code

#ifndef FBHGEXT_CLIB_CONVERT_H
#define FBHGEXT_CLIB_CONVERT_H

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

#ifdef __cplusplus
#include <string>
#endif

static const size_t BIN_NODE_SIZE = 20;
static const size_t HEX_NODE_SIZE = 40;

static const char* const NULLID = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
static const char* const HEXNULLID = "0000000000000000000000000000000000000000";

static const int8_t hextable[256] = {
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0,  1,  2,  3,  4,  5,
    6,  7,  8,  9,  -1, -1, -1, -1, -1, -1, /*0-9*/
    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*A-F*/
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 10,
    11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*a-f*/
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1};

static char chartable[16] = {'0',
                             '1',
                             '2',
                             '3',
                             '4',
                             '5',
                             '6',
                             '7',
                             '8',
                             '9',
                             'a',
                             'b',
                             'c',
                             'd',
                             'e',
                             'f'};

/*
 * Turn a hex-encoded string into binary.  Returns false on failure.
 */
static inline bool unhexlify(const char* input, int len, uint8_t* dst) {
  if (len % 2 != 0) {
    return false;
  }

  for (size_t ix = 0; ix < (size_t)len; ix += 2, dst++) {
    int hi = hextable[(unsigned char)input[ix]];
    int lo = hextable[(unsigned char)input[ix + 1]];

    if (hi < 0 || lo < 0) {
      return false;
    }
    *dst = (hi << 4) | lo;
  }

  return true;
}

/*
 * Turn binary data into a hex-encoded string.
 */
static inline void hexlify(const uint8_t* input, int len, char* dst) {
  for (size_t ix = 0; ix < (size_t)len; ix++, dst += 2) {
    unsigned char ch = (unsigned char)input[ix];
    char hi = chartable[ch >> 4];
    char lo = chartable[ch & 0xf];

    *dst = hi;
    *(dst + 1) = lo;
  }
}

#ifdef __cplusplus

/**
 * Converts a given 40-byte hex string into a 20-byte hgid.
 */
static inline void appendbinfromhex(const char* hgid, std::string& output) {
  for (size_t i = 0; i < HEX_NODE_SIZE;) {
    int8_t hi = hextable[(unsigned char)hgid[i++]];
    int8_t lo = hextable[(unsigned char)hgid[i++]];
    output.push_back((hi << 4) | lo);
  }
}

/**
 * Converts a given 40-byte hex string into a 20-byte hgid.
 */
static inline std::string binfromhex(const char* hgid) {
  std::string result;

  result.reserve(BIN_NODE_SIZE);
  appendbinfromhex(hgid, result);
  return result;
}

/**
 * Converts a given 20-byte hgid into a 40-byte hex string.
 */
static inline void hexfrombin(const char* binnode, std::string& output) {
  for (size_t ix = 0; ix < BIN_NODE_SIZE; ix++) {
    unsigned char ch = (unsigned char)binnode[ix];
    char hi = chartable[ch >> 4];
    char lo = chartable[ch & 0xf];

    output.push_back(hi);
    output.push_back(lo);
  }
}

#endif /* __cplusplus */

#endif /* FBHGEXT_CLIB_CONVERT_H */