/*
 * Copyright (c)2013-2020 ZeroTier, Inc.
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file in the project's root directory.
 *
 * Change Date: 2024-01-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2.0 of the Apache License.
 */
/****/

#ifndef ZT_UTILS_HPP
#define ZT_UTILS_HPP

#include <cstdio>
#include <cstdlib>
#include <cstdint>
#include <cstring>
#include <ctime>
#include <stdexcept>
#include <vector>
#include <map>

#include "Constants.hpp"

#if (defined(__amd64) || defined(__amd64__) || defined(__x86_64) || defined(__x86_64__) || defined(__AMD64) || defined(__AMD64__) || defined(_M_X64))
#include <emmintrin.h>
#include <xmmintrin.h>
#include <immintrin.h>
#endif

namespace ZeroTier {

namespace Utils {

#if (defined(__amd64) || defined(__amd64__) || defined(__x86_64) || defined(__x86_64__) || defined(__AMD64) || defined(__AMD64__) || defined(_M_X64))
struct CPUIDRegisters
{
	uint32_t eax,ebx,ecx,edx;
	bool rdrand;
	bool aes;
	CPUIDRegisters();
};
extern const CPUIDRegisters CPUID;
#endif

/**
 * 256 zero bits / 32 zero bytes
 */
extern const uint64_t ZERO256[4];

/**
 * Hexadecimal characters 0-f
 */
extern const char HEXCHARS[16];

/**
 * Perform a time-invariant binary comparison
 *
 * @param a First binary string
 * @param b Second binary string
 * @param len Length of strings
 * @return True if strings are equal
 */
bool secureEq(const void *a,const void *b,unsigned int len) noexcept;

/**
 * Be absolutely sure to zero memory
 *
 * This uses some hacks to be totally sure the compiler does not optimize it out.
 *
 * @param ptr Memory to zero
 * @param len Length of memory in bytes
 */
void burn(void *ptr,unsigned int len);

/**
 * @param n Number to convert
 * @param s Buffer, at least 24 bytes in size
 * @return String containing 'n' in base 10 form
 */
char *decimal(unsigned long n,char s[24]) noexcept;

/**
 * Convert an unsigned integer into hex
 *
 * @param i Any unsigned integer
 * @param s Buffer to receive hex, must be at least (2*sizeof(i))+1 in size or overflow will occur.
 * @return Pointer to s containing hex string with trailing zero byte
 */
char *hex(uint8_t i,char s[3]) noexcept;
char *hex(uint16_t i,char s[5]) noexcept;
char *hex(uint32_t i,char s[9]) noexcept;
char *hex(uint64_t i,char s[17]) noexcept;

/**
 * Decode an unsigned integer in hex format
 *
 * @param s String to decode, non-hex chars are ignored
 * @return Unsigned integer
 */
uint64_t unhex(const char *s) noexcept;

/**
 * Convert the least significant 40 bits of a uint64_t to hex
 *
 * @param i Unsigned 64-bit int
 * @param s Buffer of size [11] to receive 10 hex characters
 * @return Pointer to buffer
 */
char *hex10(uint64_t i,char s[11]) noexcept;

/**
 * Convert a byte array into hex
 *
 * @param d Bytes
 * @param l Length of bytes
 * @param s String buffer, must be at least (l*2)+1 in size or overflow will occur
 * @return Pointer to filled string buffer
 */
char *hex(const void *d,unsigned int l,char *s) noexcept;

/**
 * Decode a hex string
 *
 * @param h Hex C-string (non hex chars are ignored)
 * @param hlen Maximum length of string (will stop at terminating zero)
 * @param buf Output buffer
 * @param buflen Length of output buffer
 * @return Number of written bytes
 */
unsigned int unhex(const char *h,unsigned int hlen,void *buf,unsigned int buflen) noexcept;

/**
 * Generate secure random bytes
 *
 * This will try to use whatever OS sources of entropy are available. It's
 * guarded by an internal mutex so it's thread-safe.
 *
 * @param buf Buffer to fill
 * @param bytes Number of random bytes to generate
 */
void getSecureRandom(void *buf,unsigned int bytes) noexcept;

/**
 * @return Secure random 64-bit integer
 */
uint64_t getSecureRandomU64() noexcept;

/**
 * Encode string to base32
 *
 * @param data Binary data to encode
 * @param length Length of data in bytes
 * @param result Result buffer
 * @param bufSize Size of result buffer
 * @return Number of bytes written
 */
int b32e(const uint8_t *data,int length,char *result,int bufSize) noexcept;

/**
 * Decode base32 string
 *
 * @param encoded C-string in base32 format (non-base32 characters are ignored)
 * @param result Result buffer
 * @param bufSize Size of result buffer
 * @return Number of bytes written or -1 on error
 */
int b32d(const char *encoded, uint8_t *result, int bufSize) noexcept;

/**
 * Get a non-cryptographic random integer
 */
uint64_t random() noexcept;

/**
 * Perform a safe C string copy, ALWAYS null-terminating the result
 *
 * This will never ever EVER result in dest[] not being null-terminated
 * regardless of any input parameter (other than len==0 which is invalid).
 *
 * @param dest Destination buffer (must not be NULL)
 * @param len Length of dest[] (if zero, false is returned and nothing happens)
 * @param src Source string (if NULL, dest will receive a zero-length string and true is returned)
 * @return True on success, false on overflow (buffer will still be 0-terminated)
 */
bool scopy(char *dest,unsigned int len,const char *src) noexcept;

/**
 * Mix bits in a 64-bit integer
 *
 * https://nullprogram.com/blog/2018/07/31/
 *
 * @param x Integer to mix
 * @return Hashed value
 */
static ZT_ALWAYS_INLINE uint64_t hash64(uint64_t x) noexcept
{
	x ^= x >> 30U;
	x *= 0xbf58476d1ce4e5b9ULL;
	x ^= x >> 27U;
	x *= 0x94d049bb133111ebULL;
	x ^= x >> 31U;
	return x;
}

/**
 * @param b Buffer to check
 * @param l Length of buffer
 * @return True if buffer is all zero
 */
static ZT_ALWAYS_INLINE bool allZero(const void *const b,const unsigned int l) noexcept
{
	const uint8_t *x = reinterpret_cast<const uint8_t *>(b);
	const uint8_t *const y = x + l;
	while (x != y) {
		if (*x != 0)
			return false;
		++x;
	}
	return true;
}

/**
 * Wrapper around reentrant strtok functions, which differ in name by platform
 *
 * @param str String to tokenize or NULL for subsequent calls
 * @param delim Delimiter
 * @param saveptr Pointer to pointer where function can save state
 * @return Next token or NULL if none
 */
static ZT_ALWAYS_INLINE char *stok(char *str,const char *delim,char **saveptr) noexcept
{
#ifdef __WINDOWS__
	return strtok_s(str,delim,saveptr);
#else
	return strtok_r(str,delim,saveptr);
#endif
}

static ZT_ALWAYS_INLINE unsigned int strToUInt(const char *s) noexcept { return (unsigned int)strtoul(s,nullptr,10); }

static ZT_ALWAYS_INLINE unsigned long long strToU64(const char *s) noexcept
{
#ifdef __WINDOWS__
	return (unsigned long long)_strtoui64(s,(char **)0,10);
#else
	return strtoull(s,nullptr,10);
#endif
}

static ZT_ALWAYS_INLINE unsigned long long hexStrToU64(const char *s) noexcept
{
#ifdef __WINDOWS__
	return (unsigned long long)_strtoui64(s,nullptr,16);
#else
	return strtoull(s,nullptr,16);
#endif
}

/**
 * Calculate a non-cryptographic hash of a byte string
 *
 * @param key Key to hash
 * @param len Length in bytes
 * @return Non-cryptographic hash suitable for use in a hash table
 */
static ZT_ALWAYS_INLINE unsigned long hashString(const void *restrict key,const unsigned int len) noexcept
{
	const uint8_t *p = reinterpret_cast<const uint8_t *>(key);
	unsigned long h = 0;
	for (unsigned int i=0;i<len;++i) {
		h += p[i];
		h += (h << 10U);
		h ^= (h >> 6U);
	}
	h += (h << 3U);
	h ^= (h >> 11U);
	h += (h << 15U);
	return h;
}

#ifdef __GNUC__
static ZT_ALWAYS_INLINE unsigned int countBits(const uint8_t v) noexcept { return (unsigned int)__builtin_popcount((unsigned int)v); }
static ZT_ALWAYS_INLINE unsigned int countBits(const uint16_t v) noexcept { return (unsigned int)__builtin_popcount((unsigned int)v); }
static ZT_ALWAYS_INLINE unsigned int countBits(const uint32_t v) noexcept { return (unsigned int)__builtin_popcountl((unsigned long)v); }
static ZT_ALWAYS_INLINE unsigned int countBits(const uint64_t v)  noexcept{ return (unsigned int)__builtin_popcountll((unsigned long long)v); }
#else
template<typename T>
static ZT_ALWAYS_INLINE unsigned int countBits(T v) noexcept
{
	v = v - ((v >> 1) & (T)~(T)0/3);
	v = (v & (T)~(T)0/15*3) + ((v >> 2) & (T)~(T)0/15*3);
	v = (v + (v >> 4)) & (T)~(T)0/255*15;
	return (unsigned int)((v * ((~((T)0))/((T)255))) >> ((sizeof(T) - 1) * 8));
}
#endif

#if __BYTE_ORDER == __LITTLE_ENDIAN
static ZT_ALWAYS_INLINE uint8_t hton(uint8_t n) noexcept { return n; }
static ZT_ALWAYS_INLINE int8_t hton(int8_t n) noexcept { return n; }
static ZT_ALWAYS_INLINE uint16_t hton(uint16_t n) noexcept
{
#if defined(__GNUC__)
#if defined(__FreeBSD__)
	return htons(n);
#elif (!defined(__OpenBSD__))
	return __builtin_bswap16(n);
#endif
#else
	return htons(n);
#endif
}
static ZT_ALWAYS_INLINE int16_t hton(int16_t n) noexcept { return (int16_t)Utils::hton((uint16_t)n); }
static ZT_ALWAYS_INLINE uint32_t hton(uint32_t n) noexcept
{
#if defined(__GNUC__)
#if defined(__FreeBSD__)
	return htonl(n);
#elif (!defined(__OpenBSD__))
	return __builtin_bswap32(n);
#endif
#else
	return htonl(n);
#endif
}
static ZT_ALWAYS_INLINE int32_t hton(int32_t n) noexcept { return (int32_t)Utils::hton((uint32_t)n); }
static ZT_ALWAYS_INLINE uint64_t hton(uint64_t n) noexcept
{
#if defined(__GNUC__)
#if defined(__FreeBSD__)
	return bswap64(n);
#elif (!defined(__OpenBSD__))
	return __builtin_bswap64(n);
#endif
#else
	return (
		((n & 0x00000000000000FFULL) << 56) |
		((n & 0x000000000000FF00ULL) << 40) |
		((n & 0x0000000000FF0000ULL) << 24) |
		((n & 0x00000000FF000000ULL) <<  8) |
		((n & 0x000000FF00000000ULL) >>  8) |
		((n & 0x0000FF0000000000ULL) >> 24) |
		((n & 0x00FF000000000000ULL) >> 40) |
		((n & 0xFF00000000000000ULL) >> 56)
	);
#endif
}
static ZT_ALWAYS_INLINE int64_t hton(int64_t n) noexcept { return (int64_t)hton((uint64_t)n); }
#else
template<typename T>
static ZT_ALWAYS_INLINE T hton(T n) noexcept { return n; }
#endif

#if __BYTE_ORDER == __LITTLE_ENDIAN
static ZT_ALWAYS_INLINE uint8_t ntoh(uint8_t n) noexcept { return n; }
static ZT_ALWAYS_INLINE int8_t ntoh(int8_t n) noexcept { return n; }
static ZT_ALWAYS_INLINE uint16_t ntoh(uint16_t n) noexcept
{
#if defined(__GNUC__)
#if defined(__FreeBSD__)
	return htons(n);
#elif (!defined(__OpenBSD__))
	return __builtin_bswap16(n);
#endif
#else
	return htons(n);
#endif
}
static ZT_ALWAYS_INLINE int16_t ntoh(int16_t n) noexcept { return (int16_t)Utils::ntoh((uint16_t)n); }
static ZT_ALWAYS_INLINE uint32_t ntoh(uint32_t n) noexcept
{
#if defined(__GNUC__)
#if defined(__FreeBSD__)
	return ntohl(n);
#elif (!defined(__OpenBSD__))
	return __builtin_bswap32(n);
#endif
#else
	return ntohl(n);
#endif
}
static ZT_ALWAYS_INLINE int32_t ntoh(int32_t n) noexcept { return (int32_t)Utils::ntoh((uint32_t)n); }
static ZT_ALWAYS_INLINE uint64_t ntoh(uint64_t n) noexcept
{
#if defined(__GNUC__)
#if defined(__FreeBSD__)
	return bswap64(n);
#elif (!defined(__OpenBSD__))
	return __builtin_bswap64(n);
#endif
#else
	return (
		((n & 0x00000000000000FFULL) << 56) |
		((n & 0x000000000000FF00ULL) << 40) |
		((n & 0x0000000000FF0000ULL) << 24) |
		((n & 0x00000000FF000000ULL) <<  8) |
		((n & 0x000000FF00000000ULL) >>  8) |
		((n & 0x0000FF0000000000ULL) >> 24) |
		((n & 0x00FF000000000000ULL) >> 40) |
		((n & 0xFF00000000000000ULL) >> 56)
	);
#endif
}
static ZT_ALWAYS_INLINE int64_t ntoh(int64_t n) noexcept { return (int64_t)ntoh((uint64_t)n); }
#else
template<typename T>
static ZT_ALWAYS_INLINE T ntoh(T n) noexcept { return n; }
#endif

/**
 * Decode a big-endian value from a byte stream
 *
 * @tparam I Type to decode (should be unsigned e.g. uint32_t or uint64_t)
 * @param p Byte stream, must be at least sizeof(I) in size
 * @return Decoded integer
 */
template<typename I>
static ZT_ALWAYS_INLINE I loadBigEndian(const void *const p) noexcept
{
#ifdef ZT_NO_UNALIGNED_ACCESS
	I x = (I)0;
	for(unsigned int k=0;k<sizeof(I);++k) {
#if __BYTE_ORDER == __LITTLE_ENDIAN
		reinterpret_cast<uint8_t *>(&x)[k] = reinterpret_cast<const uint8_t *>(p)[(sizeof(I)-1)-k];
#else
		reinterpret_cast<uint8_t *>(&x)[k] = reinterpret_cast<const uint8_t *>(p)[k];
#endif
	}
	return x;
#else
	return ntoh(*reinterpret_cast<const I *>(p));
#endif
}

/**
 * Save an integer in big-endian format
 *
 * @tparam I Integer type to store (usually inferred)
 * @param p Byte stream to write (must be at least sizeof(I))
 * #param i Integer to write
 */
template<typename I>
static ZT_ALWAYS_INLINE void storeBigEndian(void *const p,const I i) noexcept
{
#ifdef ZT_NO_UNALIGNED_ACCESS
	for(unsigned int k=0;k<sizeof(I);++k) {
#if __BYTE_ORDER == __LITTLE_ENDIAN
		reinterpret_cast<uint8_t *>(p)[k] = reinterpret_cast<const uint8_t *>(&i)[(sizeof(I)-1)-k];
#else
		reinterpret_cast<uint8_t *>(p)[k] = reinterpret_cast<const uint8_t *>(&i)[k];
#endif
	}
#else
	*reinterpret_cast<I *>(p) = hton(i);
#endif
}

/**
 * Copy bits from memory into an integer type without modifying their order
 *
 * @tparam I Type to load
 * @param p Byte stream, must be at least sizeof(I) in size
 * @return Loaded raw integer
 */
template<typename I>
static ZT_ALWAYS_INLINE I loadAsIsEndian(const void *const p) noexcept
{
#ifdef ZT_NO_UNALIGNED_ACCESS
	I x = (I)0;
	for(unsigned int k=0;k<sizeof(I);++k)
		reinterpret_cast<uint8_t *>(&x)[k] = reinterpret_cast<const uint8_t *>(p)[k];
	return x;
#else
	return *reinterpret_cast<const I *>(p);
#endif
}

/**
 * Copy bits from memory into an integer type without modifying their order
 *
 * @tparam I Type to store
 * @param p Byte array (must be at least sizeof(I))
 * @param i Integer to store
 */
template<typename I>
static ZT_ALWAYS_INLINE void storeAsIsEndian(void *const p,const I i) noexcept
{
#ifdef ZT_NO_UNALIGNED_ACCESS
	for(unsigned int k=0;k<sizeof(I);++k)
		reinterpret_cast<uint8_t *>(p)[k] = reinterpret_cast<const uint8_t *>(&i)[k];
#else
	*reinterpret_cast<I *>(p) = i;
#endif
}

} // namespace Utils

} // namespace ZeroTier

#endif