mirror of
https://github.com/ecency/ecency-mobile.git
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258 lines
7.3 KiB
C++
258 lines
7.3 KiB
C++
/*
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* Copyright 2016 Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <glog/logging.h>
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#include <sys/types.h>
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#include <algorithm>
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#include <array>
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#include <cstring>
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#include <string>
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#include <type_traits>
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#include <folly/Conv.h>
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#include <folly/detail/IPAddress.h>
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// BSDish platforms don't provide standard access to s6_addr16
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#ifndef s6_addr16
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#if defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__) || \
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defined(__OpenBSD__)
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#define s6_addr16 __u6_addr.__u6_addr16
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#endif
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#endif
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namespace folly {
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namespace detail {
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/**
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* Helper for working with unsigned char* or uint8_t* ByteArray values
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*/
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struct Bytes {
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// mask the values from two byte arrays, returning a new byte array
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template <std::size_t N>
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static std::array<uint8_t, N> mask(
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const std::array<uint8_t, N>& a,
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const std::array<uint8_t, N>& b) {
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static_assert(N > 0, "Can't mask an empty ByteArray");
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std::size_t asize = a.size();
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std::array<uint8_t, N> ba{{0}};
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for (std::size_t i = 0; i < asize; i++) {
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ba[i] = a[i] & b[i];
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}
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return ba;
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}
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template <std::size_t N>
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static std::pair<std::array<uint8_t, N>, uint8_t> longestCommonPrefix(
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const std::array<uint8_t, N>& one,
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uint8_t oneMask,
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const std::array<uint8_t, N>& two,
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uint8_t twoMask) {
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static constexpr auto kBitCount = N * 8;
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static constexpr std::array<uint8_t, 8> kMasks{{
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0x80, // /1
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0xc0, // /2
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0xe0, // /3
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0xf0, // /4
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0xf8, // /5
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0xfc, // /6
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0xfe, // /7
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0xff // /8
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}};
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if (oneMask > kBitCount || twoMask > kBitCount) {
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throw std::invalid_argument(folly::to<std::string>(
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"Invalid mask "
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"length: ",
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oneMask > twoMask ? oneMask : twoMask,
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". Mask length must be <= ",
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kBitCount));
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}
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auto mask = std::min(oneMask, twoMask);
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uint8_t byteIndex = 0;
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std::array<uint8_t, N> ba{{0}};
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// Compare a byte at a time. Note - I measured compared this with
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// going multiple bytes at a time (8, 4, 2 and 1). It turns out
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// to be 20 - 25% slower for 4 and 16 byte arrays.
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while (byteIndex * 8 < mask && one[byteIndex] == two[byteIndex]) {
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ba[byteIndex] = one[byteIndex];
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++byteIndex;
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}
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auto bitIndex = std::min(mask, (uint8_t)(byteIndex * 8));
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// Compute the bit up to which the two byte arrays match in the
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// unmatched byte.
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// Here the check is bitIndex < mask since the 0th mask entry in
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// kMasks array holds the mask for masking the MSb in this byte.
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// We could instead make it hold so that no 0th entry masks no
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// bits but thats a useless iteration.
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while (bitIndex < mask && ((one[bitIndex / 8] & kMasks[bitIndex % 8]) ==
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(two[bitIndex / 8] & kMasks[bitIndex % 8]))) {
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ba[bitIndex / 8] = one[bitIndex / 8] & kMasks[bitIndex % 8];
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++bitIndex;
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}
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return {ba, bitIndex};
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}
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// create an in_addr from an uint8_t*
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static inline in_addr mkAddress4(const uint8_t* src) {
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union {
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in_addr addr;
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uint8_t bytes[4];
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} addr;
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std::memset(&addr, 0, 4);
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std::memcpy(addr.bytes, src, 4);
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return addr.addr;
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}
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// create an in6_addr from an uint8_t*
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static inline in6_addr mkAddress6(const uint8_t* src) {
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in6_addr addr;
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std::memset(&addr, 0, 16);
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std::memcpy(addr.s6_addr, src, 16);
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return addr;
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}
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// convert an uint8_t* to its hex value
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static std::string toHex(const uint8_t* src, std::size_t len) {
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static const char* const lut = "0123456789abcdef";
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std::string out(len * 2, 0);
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for (std::size_t i = 0; i < len; i++) {
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const unsigned char c = src[i];
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out[i * 2 + 0] = lut[c >> 4];
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out[i * 2 + 1] = lut[c & 15];
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}
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return out;
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}
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private:
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Bytes() = delete;
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~Bytes() = delete;
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};
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//
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// Write a maximum amount of base-converted character digits, of a
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// given base, from an unsigned integral type into a byte buffer of
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// sufficient size.
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//
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// This function does not append null terminators.
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//
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// Output buffer size must be guaranteed by caller (indirectly
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// controlled by DigitCount template parameter).
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//
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// Having these parameters at compile time allows compiler to
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// precompute several of the values, use smaller instructions, and
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// better optimize surrounding code.
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//
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// IntegralType:
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// - Something like uint8_t, uint16_t, etc
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//
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// DigitCount is the maximum number of digits to be printed
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// - This is tied to IntegralType and Base. For example:
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// - uint8_t in base 10 will print at most 3 digits ("255")
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// - uint16_t in base 16 will print at most 4 hex digits ("FFFF")
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//
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// Base is the desired output base of the string
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// - Base 10 will print [0-9], base 16 will print [0-9a-f]
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//
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// PrintAllDigits:
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// - Whether or not leading zeros should be printed
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//
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template <
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class IntegralType,
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IntegralType DigitCount,
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IntegralType Base = 10,
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bool PrintAllDigits = false,
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class = typename std::enable_if<
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std::is_integral<IntegralType>::value &&
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std::is_unsigned<IntegralType>::value,
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bool>::type>
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inline void writeIntegerString(IntegralType val, char** buffer) {
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char* buf = *buffer;
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if (!PrintAllDigits && val == 0) {
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*(buf++) = '0';
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*buffer = buf;
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return;
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}
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IntegralType powerToPrint = 1;
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for (int i = 1; i < DigitCount; ++i) {
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powerToPrint *= Base;
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}
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bool found = PrintAllDigits;
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while (powerToPrint) {
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if (found || powerToPrint <= val) {
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IntegralType value = val / powerToPrint;
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if (Base == 10 || value < 10) {
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value += '0';
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} else {
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value += ('a' - 10);
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}
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*(buf++) = value;
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val %= powerToPrint;
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found = true;
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}
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powerToPrint /= Base;
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}
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*buffer = buf;
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}
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inline std::string fastIpv4ToString(const in_addr& inAddr) {
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const uint8_t* octets = reinterpret_cast<const uint8_t*>(&inAddr.s_addr);
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char str[sizeof("255.255.255.255")];
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char* buf = str;
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writeIntegerString<uint8_t, 3>(octets[0], &buf);
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*(buf++) = '.';
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writeIntegerString<uint8_t, 3>(octets[1], &buf);
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*(buf++) = '.';
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writeIntegerString<uint8_t, 3>(octets[2], &buf);
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*(buf++) = '.';
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writeIntegerString<uint8_t, 3>(octets[3], &buf);
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return std::string(str, buf - str);
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}
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inline std::string fastIpv6ToString(const in6_addr& in6Addr) {
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#ifdef _MSC_VER
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const uint16_t* bytes = reinterpret_cast<const uint16_t*>(&in6Addr.u.Word);
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#else
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const uint16_t* bytes = reinterpret_cast<const uint16_t*>(&in6Addr.s6_addr16);
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#endif
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char str[sizeof("2001:0db8:0000:0000:0000:ff00:0042:8329")];
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char* buf = str;
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for (int i = 0; i < 8; ++i) {
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writeIntegerString<
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uint16_t,
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4, // at most 4 hex digits per ushort
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16, // base 16 (hex)
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true>(htons(bytes[i]), &buf);
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if (i != 7) {
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*(buf++) = ':';
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}
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}
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return std::string(str, buf - str);
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}
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}
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}
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