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ZeroTierOne/node/Utils.hpp

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/*
* Copyright (c)2019 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: 2025-01-01
*
* 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 <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <time.h>
#include <string>
#include <stdexcept>
#include <vector>
#include <map>
#if defined(__FreeBSD__)
#include <sys/endian.h>
#endif
#include "Constants.hpp"
#if __BYTE_ORDER == __LITTLE_ENDIAN
#define ZT_CONST_TO_BE_UINT16(x) ((uint16_t)((uint16_t)((uint16_t)(x) << 8U) | (uint16_t)((uint16_t)(x) >> 8U)))
#define ZT_CONST_TO_BE_UINT64(x) ( \
(((uint64_t)(x) & 0x00000000000000ffULL) << 56U) | \
(((uint64_t)(x) & 0x000000000000ff00ULL) << 40U) | \
(((uint64_t)(x) & 0x0000000000ff0000ULL) << 24U) | \
(((uint64_t)(x) & 0x00000000ff000000ULL) << 8U) | \
(((uint64_t)(x) & 0x000000ff00000000ULL) >> 8U) | \
(((uint64_t)(x) & 0x0000ff0000000000ULL) >> 24U) | \
(((uint64_t)(x) & 0x00ff000000000000ULL) >> 40U) | \
(((uint64_t)(x) & 0xff00000000000000ULL) >> 56U))
#else
#define ZT_CONST_TO_BE_UINT16(x) ((uint16_t)(x))
#define ZT_CONST_TO_BE_UINT64(x) ((uint64_t)(x))
#endif
#define ZT_ROR64(x, r) (((x) >> (r)) | ((x) << (64 - (r))))
#define ZT_ROL64(x, r) (((x) << (r)) | ((x) >> (64 - (r))))
#define ZT_ROR32(x, r) (((x) >> (r)) | ((x) << (32 - (r))))
#define ZT_ROL32(x, r) (((x) << (r)) | ((x) >> (32 - (r))))
namespace ZeroTier {
/**
* Miscellaneous utility functions and global constants
*/
class Utils
{
public:
static const uint64_t ZERO256[4];
#ifdef ZT_ARCH_ARM_HAS_NEON
struct ARMCapabilities
{
ARMCapabilities() noexcept;
bool aes;
bool crc32;
bool pmull;
bool sha1;
bool sha2;
};
static const ARMCapabilities ARMCAP;
#endif
#ifdef ZT_ARCH_X64
struct CPUIDRegisters
{
CPUIDRegisters() noexcept;
bool rdrand;
bool aes;
bool avx;
bool vaes; // implies AVX
bool vpclmulqdq; // implies AVX
bool avx2;
bool avx512f;
bool sha;
bool fsrm;
};
static const CPUIDRegisters CPUID;
#endif
/**
* Compute the log2 (most significant bit set) of a 32-bit integer
*
* @param v Integer to compute
* @return log2 or 0 if v is 0
*/
static inline unsigned int log2(uint32_t v)
{
uint32_t r = (v > 0xffff) << 4; v >>= r;
uint32_t shift = (v > 0xff) << 3; v >>= shift; r |= shift;
shift = (v > 0xf) << 2; v >>= shift; r |= shift;
shift = (v > 0x3) << 1; v >>= shift; r |= shift;
r |= (v >> 1);
return (unsigned int)r;
}
/**
* 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
*/
static inline bool secureEq(const void *a,const void *b,unsigned int len)
{
uint8_t diff = 0;
for(unsigned int i=0;i<len;++i)
diff |= ( (reinterpret_cast<const uint8_t *>(a))[i] ^ (reinterpret_cast<const uint8_t *>(b))[i] );
return (diff == 0);
}
/**
* Securely zero memory, avoiding compiler optimizations and such
*/
static 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
*/
static char *decimal(unsigned long n,char s[24]);
static inline char *hex(uint64_t i,char s[17])
{
s[0] = HEXCHARS[(i >> 60) & 0xf];
s[1] = HEXCHARS[(i >> 56) & 0xf];
s[2] = HEXCHARS[(i >> 52) & 0xf];
s[3] = HEXCHARS[(i >> 48) & 0xf];
s[4] = HEXCHARS[(i >> 44) & 0xf];
s[5] = HEXCHARS[(i >> 40) & 0xf];
s[6] = HEXCHARS[(i >> 36) & 0xf];
s[7] = HEXCHARS[(i >> 32) & 0xf];
s[8] = HEXCHARS[(i >> 28) & 0xf];
s[9] = HEXCHARS[(i >> 24) & 0xf];
s[10] = HEXCHARS[(i >> 20) & 0xf];
s[11] = HEXCHARS[(i >> 16) & 0xf];
s[12] = HEXCHARS[(i >> 12) & 0xf];
s[13] = HEXCHARS[(i >> 8) & 0xf];
s[14] = HEXCHARS[(i >> 4) & 0xf];
s[15] = HEXCHARS[i & 0xf];
s[16] = (char)0;
return s;
}
static inline char *hex10(uint64_t i,char s[11])
{
s[0] = HEXCHARS[(i >> 36) & 0xf];
s[1] = HEXCHARS[(i >> 32) & 0xf];
s[2] = HEXCHARS[(i >> 28) & 0xf];
s[3] = HEXCHARS[(i >> 24) & 0xf];
s[4] = HEXCHARS[(i >> 20) & 0xf];
s[5] = HEXCHARS[(i >> 16) & 0xf];
s[6] = HEXCHARS[(i >> 12) & 0xf];
s[7] = HEXCHARS[(i >> 8) & 0xf];
s[8] = HEXCHARS[(i >> 4) & 0xf];
s[9] = HEXCHARS[i & 0xf];
s[10] = (char)0;
return s;
}
static inline char *hex(uint32_t i,char s[9])
{
s[0] = HEXCHARS[(i >> 28) & 0xf];
s[1] = HEXCHARS[(i >> 24) & 0xf];
s[2] = HEXCHARS[(i >> 20) & 0xf];
s[3] = HEXCHARS[(i >> 16) & 0xf];
s[4] = HEXCHARS[(i >> 12) & 0xf];
s[5] = HEXCHARS[(i >> 8) & 0xf];
s[6] = HEXCHARS[(i >> 4) & 0xf];
s[7] = HEXCHARS[i & 0xf];
s[8] = (char)0;
return s;
}
static inline char *hex(uint16_t i,char s[5])
{
s[0] = HEXCHARS[(i >> 12) & 0xf];
s[1] = HEXCHARS[(i >> 8) & 0xf];
s[2] = HEXCHARS[(i >> 4) & 0xf];
s[3] = HEXCHARS[i & 0xf];
s[4] = (char)0;
return s;
}
static inline char *hex(uint8_t i,char s[3])
{
s[0] = HEXCHARS[(i >> 4) & 0xf];
s[1] = HEXCHARS[i & 0xf];
s[2] = (char)0;
return s;
}
static inline char *hex(const void *d,unsigned int l,char *s)
{
char *const save = s;
for(unsigned int i=0;i<l;++i) {
const unsigned int b = reinterpret_cast<const uint8_t *>(d)[i];
*(s++) = HEXCHARS[b >> 4];
*(s++) = HEXCHARS[b & 0xf];
}
*s = (char)0;
return save;
}
static inline unsigned int unhex(const char *h,void *buf,unsigned int buflen)
{
unsigned int l = 0;
while (l < buflen) {
uint8_t hc = *(reinterpret_cast<const uint8_t *>(h++));
if (!hc) break;
uint8_t c = 0;
if ((hc >= 48)&&(hc <= 57)) // 0..9
c = hc - 48;
else if ((hc >= 97)&&(hc <= 102)) // a..f
c = hc - 87;
else if ((hc >= 65)&&(hc <= 70)) // A..F
c = hc - 55;
hc = *(reinterpret_cast<const uint8_t *>(h++));
if (!hc) break;
c <<= 4;
if ((hc >= 48)&&(hc <= 57))
c |= hc - 48;
else if ((hc >= 97)&&(hc <= 102))
c |= hc - 87;
else if ((hc >= 65)&&(hc <= 70))
c |= hc - 55;
reinterpret_cast<uint8_t *>(buf)[l++] = c;
}
return l;
}
static inline unsigned int unhex(const char *h,unsigned int hlen,void *buf,unsigned int buflen)
{
unsigned int l = 0;
const char *hend = h + hlen;
while (l < buflen) {
if (h == hend) break;
uint8_t hc = *(reinterpret_cast<const uint8_t *>(h++));
if (!hc) break;
uint8_t c = 0;
if ((hc >= 48)&&(hc <= 57))
c = hc - 48;
else if ((hc >= 97)&&(hc <= 102))
c = hc - 87;
else if ((hc >= 65)&&(hc <= 70))
c = hc - 55;
if (h == hend) break;
hc = *(reinterpret_cast<const uint8_t *>(h++));
if (!hc) break;
c <<= 4;
if ((hc >= 48)&&(hc <= 57))
c |= hc - 48;
else if ((hc >= 97)&&(hc <= 102))
c |= hc - 87;
else if ((hc >= 65)&&(hc <= 70))
c |= hc - 55;
reinterpret_cast<uint8_t *>(buf)[l++] = c;
}
return l;
}
static inline float normalize(float value, float bigMin, float bigMax, float targetMin, float targetMax)
{
float bigSpan = bigMax - bigMin;
float smallSpan = targetMax - targetMin;
float valueScaled = (value - bigMin) / bigSpan;
return targetMin + valueScaled * smallSpan;
}
/**
* 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
*/
static void getSecureRandom(void *buf,unsigned int bytes);
/**
* Tokenize a string (alias for strtok_r or strtok_s depending on platform)
*
* @param str String to split
* @param delim Delimiters
* @param saveptr Pointer to a char * for temporary reentrant storage
*/
static inline char *stok(char *str,const char *delim,char **saveptr)
{
#ifdef __WINDOWS__
return strtok_s(str,delim,saveptr);
#else
return strtok_r(str,delim,saveptr);
#endif
}
static inline unsigned int strToUInt(const char *s) { return (unsigned int)strtoul(s,(char **)0,10); }
static inline int strToInt(const char *s) { return (int)strtol(s,(char **)0,10); }
static inline unsigned long strToULong(const char *s) { return strtoul(s,(char **)0,10); }
static inline long strToLong(const char *s) { return strtol(s,(char **)0,10); }
static inline double strToDouble(const char *s) { return strtod(s,NULL); }
static inline unsigned long long strToU64(const char *s)
{
#ifdef __WINDOWS__
return (unsigned long long)_strtoui64(s,(char **)0,10);
#else
return strtoull(s,(char **)0,10);
#endif
}
static inline long long strTo64(const char *s)
{
#ifdef __WINDOWS__
return (long long)_strtoi64(s,(char **)0,10);
#else
return strtoll(s,(char **)0,10);
#endif
}
static inline unsigned int hexStrToUInt(const char *s) { return (unsigned int)strtoul(s,(char **)0,16); }
static inline int hexStrToInt(const char *s) { return (int)strtol(s,(char **)0,16); }
static inline unsigned long hexStrToULong(const char *s) { return strtoul(s,(char **)0,16); }
static inline long hexStrToLong(const char *s) { return strtol(s,(char **)0,16); }
static inline unsigned long long hexStrToU64(const char *s)
{
#ifdef __WINDOWS__
return (unsigned long long)_strtoui64(s,(char **)0,16);
#else
return strtoull(s,(char **)0,16);
#endif
}
static inline long long hexStrTo64(const char *s)
{
#ifdef __WINDOWS__
return (long long)_strtoi64(s,(char **)0,16);
#else
return strtoll(s,(char **)0,16);
#endif
}
/**
* 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)
*/
static inline bool scopy(char *dest,unsigned int len,const char *src)
{
if (!len)
return false; // sanity check
if (!src) {
*dest = (char)0;
return true;
}
char *end = dest + len;
while ((*dest++ = *src++)) {
if (dest == end) {
*(--dest) = (char)0;
return false;
}
}
return true;
}
/**
* Count the number of bits set in an integer
*
* @param v 32-bit integer
* @return Number of bits set in this integer (0-32)
*/
static inline uint32_t countBits(uint32_t v)
{
v = v - ((v >> 1) & (uint32_t)0x55555555);
v = (v & (uint32_t)0x33333333) + ((v >> 2) & (uint32_t)0x33333333);
return ((((v + (v >> 4)) & (uint32_t)0xF0F0F0F) * (uint32_t)0x1010101) >> 24);
}
/**
* Count the number of bits set in an integer
*
* @param v 64-bit integer
* @return Number of bits set in this integer (0-64)
*/
static inline uint64_t countBits(uint64_t v)
{
v = v - ((v >> 1) & (uint64_t)~(uint64_t)0/3);
v = (v & (uint64_t)~(uint64_t)0/15*3) + ((v >> 2) & (uint64_t)~(uint64_t)0/15*3);
v = (v + (v >> 4)) & (uint64_t)~(uint64_t)0/255*15;
return (uint64_t)(v * ((uint64_t)~(uint64_t)0/255)) >> 56;
}
/**
* Check if a memory buffer is all-zero
*
* @param p Memory to scan
* @param len Length of memory
* @return True if memory is all zero
*/
static inline bool isZero(const void *p,unsigned int len)
{
for(unsigned int i=0;i<len;++i) {
if (((const unsigned char *)p)[i])
return false;
}
return true;
}
/**
* Unconditionally swap bytes regardless of host byte order
*
* @param n Integer to swap
* @return Integer with bytes reversed
*/
static ZT_INLINE uint64_t swapBytes(const uint64_t n) noexcept
{
#ifdef __GNUC__
return __builtin_bswap64(n);
#else
#ifdef _MSC_VER
return (uint64_t)_byteswap_uint64((unsigned __int64)n);
#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
#endif
}
/**
* Unconditionally swap bytes regardless of host byte order
*
* @param n Integer to swap
* @return Integer with bytes reversed
*/
static ZT_INLINE uint32_t swapBytes(const uint32_t n) noexcept
{
#if defined(__GNUC__)
return __builtin_bswap32(n);
#else
#ifdef _MSC_VER
return (uint32_t)_byteswap_ulong((unsigned long)n);
#else
return htonl(n);
#endif
#endif
}
/**
* Unconditionally swap bytes regardless of host byte order
*
* @param n Integer to swap
* @return Integer with bytes reversed
*/
static ZT_INLINE uint16_t swapBytes(const uint16_t n) noexcept
{
#if defined(__GNUC__)
return __builtin_bswap16(n);
#else
#ifdef _MSC_VER
return (uint16_t)_byteswap_ushort((unsigned short)n);
#else
return htons(n);
#endif
#endif
}
// These are helper adapters to load and swap integer types special cased by size
// to work with all typedef'd variants, signed/unsigned, etc.
template< typename I, unsigned int S >
class _swap_bytes_bysize;
template< typename I >
class _swap_bytes_bysize< I, 1 >
{
public:
static ZT_INLINE I s(const I n) noexcept
{ return n; }
};
template< typename I >
class _swap_bytes_bysize< I, 2 >
{
public:
static ZT_INLINE I s(const I n) noexcept
{ return (I)swapBytes((uint16_t)n); }
};
template< typename I >
class _swap_bytes_bysize< I, 4 >
{
public:
static ZT_INLINE I s(const I n) noexcept
{ return (I)swapBytes((uint32_t)n); }
};
template< typename I >
class _swap_bytes_bysize< I, 8 >
{
public:
static ZT_INLINE I s(const I n) noexcept
{ return (I)swapBytes((uint64_t)n); }
};
template< typename I, unsigned int S >
class _load_be_bysize;
template< typename I >
class _load_be_bysize< I, 1 >
{
public:
static ZT_INLINE I l(const uint8_t *const p) noexcept
{ return p[0]; }
};
template< typename I >
class _load_be_bysize< I, 2 >
{
public:
static ZT_INLINE I l(const uint8_t *const p) noexcept
{ return (I)(((unsigned int)p[0] << 8U) | (unsigned int)p[1]); }
};
template< typename I >
class _load_be_bysize< I, 4 >
{
public:
static ZT_INLINE I l(const uint8_t *const p) noexcept
{ return (I)(((uint32_t)p[0] << 24U) | ((uint32_t)p[1] << 16U) | ((uint32_t)p[2] << 8U) | (uint32_t)p[3]); }
};
template< typename I >
class _load_be_bysize< I, 8 >
{
public:
static ZT_INLINE I l(const uint8_t *const p) noexcept
{ return (I)(((uint64_t)p[0] << 56U) | ((uint64_t)p[1] << 48U) | ((uint64_t)p[2] << 40U) | ((uint64_t)p[3] << 32U) | ((uint64_t)p[4] << 24U) | ((uint64_t)p[5] << 16U) | ((uint64_t)p[6] << 8U) | (uint64_t)p[7]); }
};
template< typename I, unsigned int S >
class _load_le_bysize;
template< typename I >
class _load_le_bysize< I, 1 >
{
public:
static ZT_INLINE I l(const uint8_t *const p) noexcept
{ return p[0]; }
};
template< typename I >
class _load_le_bysize< I, 2 >
{
public:
static ZT_INLINE I l(const uint8_t *const p) noexcept
{ return (I)((unsigned int)p[0] | ((unsigned int)p[1] << 8U)); }
};
template< typename I >
class _load_le_bysize< I, 4 >
{
public:
static ZT_INLINE I l(const uint8_t *const p) noexcept
{ return (I)((uint32_t)p[0] | ((uint32_t)p[1] << 8U) | ((uint32_t)p[2] << 16U) | ((uint32_t)p[3] << 24U)); }
};
template< typename I >
class _load_le_bysize< I, 8 >
{
public:
static ZT_INLINE I l(const uint8_t *const p) noexcept
{ return (I)((uint64_t)p[0] | ((uint64_t)p[1] << 8U) | ((uint64_t)p[2] << 16U) | ((uint64_t)p[3] << 24U) | ((uint64_t)p[4] << 32U) | ((uint64_t)p[5] << 40U) | ((uint64_t)p[6] << 48U) | ((uint64_t)p[7]) << 56U); }
};
/**
* Convert any signed or unsigned integer type to big-endian ("network") byte order
*
* @tparam I Integer type (usually inferred)
* @param n Value to convert
* @return Value in big-endian order
*/
template< typename I >
static ZT_INLINE I hton(const I n) noexcept
{
#if __BYTE_ORDER == __LITTLE_ENDIAN
return _swap_bytes_bysize< I, sizeof(I) >::s(n);
#else
return n;
#endif
}
/**
* Convert any signed or unsigned integer type to host byte order from big-endian ("network") byte order
*
* @tparam I Integer type (usually inferred)
* @param n Value to convert
* @return Value in host byte order
*/
template< typename I >
static ZT_INLINE I ntoh(const I n) noexcept
{
#if __BYTE_ORDER == __LITTLE_ENDIAN
return _swap_bytes_bysize< I, sizeof(I) >::s(n);
#else
return n;
#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_INLINE I loadMachineEndian(const void *const p) noexcept
{
#ifdef ZT_NO_UNALIGNED_ACCESS
I tmp;
for(int i=0;i<(int)sizeof(I);++i)
reinterpret_cast<uint8_t *>(&tmp)[i] = reinterpret_cast<const uint8_t *>(p)[i];
return tmp;
#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_INLINE void storeMachineEndian(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
}
/**
* 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_INLINE I loadBigEndian(const void *const p) noexcept
{
#ifdef ZT_NO_UNALIGNED_ACCESS
return _load_be_bysize<I,sizeof(I)>::l(reinterpret_cast<const uint8_t *>(p));
#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_INLINE void storeBigEndian(void *const p, I i) noexcept
{
#ifdef ZT_NO_UNALIGNED_ACCESS
storeMachineEndian(p,hton(i));
#else
*reinterpret_cast<I *>(p) = hton(i);
#endif
}
/**
* Decode a little-endian value from a byte stream
*
* @tparam I Type to decode
* @param p Byte stream, must be at least sizeof(I) in size
* @return Decoded integer
*/
template< typename I >
static ZT_INLINE I loadLittleEndian(const void *const p) noexcept
{
#if __BYTE_ORDER == __BIG_ENDIAN || defined(ZT_NO_UNALIGNED_ACCESS)
return _load_le_bysize<I,sizeof(I)>::l(reinterpret_cast<const uint8_t *>(p));
#else
return *reinterpret_cast<const I *>(p);
#endif
}
/**
* Save an integer in little-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_INLINE void storeLittleEndian(void *const p, const I i) noexcept
{
#if __BYTE_ORDER == __BIG_ENDIAN
storeMachineEndian(p,_swap_bytes_bysize<I,sizeof(I)>::s(i));
#else
#ifdef ZT_NO_UNALIGNED_ACCESS
storeMachineEndian(p,i);
#else
*reinterpret_cast<I *>(p) = i;
#endif
#endif
}
/**
* Copy memory block whose size is known at compile time.
*
* @tparam L Size of memory
* @param dest Destination memory
* @param src Source memory
*/
template< unsigned long L >
static ZT_INLINE void copy(void *dest, const void *src) noexcept
{
#if defined(ZT_ARCH_X64) && defined(__GNUC__)
uintptr_t l = L;
__asm__ __volatile__ ("cld ; rep movsb" : "+c"(l), "+S"(src), "+D"(dest) :: "memory");
#else
memcpy(dest, src, L);
#endif
}
/**
* Copy memory block whose size is known at run time
*
* @param dest Destination memory
* @param src Source memory
* @param len Bytes to copy
*/
static ZT_INLINE void copy(void *dest, const void *src, unsigned long len) noexcept
{
#if defined(ZT_ARCH_X64) && defined(__GNUC__)
__asm__ __volatile__ ("cld ; rep movsb" : "+c"(len), "+S"(src), "+D"(dest) :: "memory");
#else
memcpy(dest, src, len);
#endif
}
/**
* Zero memory block whose size is known at compile time
*
* @tparam L Size in bytes
* @param dest Memory to zero
*/
template< unsigned long L >
static ZT_INLINE void zero(void *dest) noexcept
{
#if defined(ZT_ARCH_X64) && defined(__GNUC__)
uintptr_t l = L;
__asm__ __volatile__ ("cld ; rep stosb" :"+c" (l), "+D" (dest) : "a" (0) : "memory");
#else
memset(dest, 0, L);
#endif
}
/**
* Zero memory block whose size is known at run time
*
* @param dest Memory to zero
* @param len Size in bytes
*/
static ZT_INLINE void zero(void *dest, unsigned long len) noexcept
{
#if defined(ZT_ARCH_X64) && defined(__GNUC__)
__asm__ __volatile__ ("cld ; rep stosb" :"+c" (len), "+D" (dest) : "a" (0) : "memory");
#else
memset(dest, 0, len);
#endif
}
/**
* Hexadecimal characters 0-f
*/
static const char HEXCHARS[16];
};
} // namespace ZeroTier
#endif
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