Bytes.h

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/*
 * This is a part of the Uniot project.
 * Copyright (C) 2016-2023 Uniot <contact@uniot.io>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include <Common.h>
#include <Logger.h>
#include <WString.h>
#include <stdio.h>
 
#include <functional>
#include <type_traits>

class Bytes {
 public:
  using Filler = std::function<size_t(uint8_t *buf, size_t size)>;

  Bytes() : Bytes(nullptr, 0) {}

  Bytes(const uint8_t *data, size_t size) {
    _init();
    if (data) {
      _copy(data, size);
    } else if (size) {
      _reserve(size);
    }
  }

  Bytes(const char *str) : Bytes((uint8_t *)str, strlen(str) + 1)  // + 1 null terminator
  {}

  template <typename T>
  Bytes(T value) : Bytes(((uint8_t *)&value), sizeof(T)) {
    static_assert(std::is_integral<T>::value, "only integral types are allowed");
  }

  Bytes(const Bytes &value) {
    _init();
    *this = value;
  }

  Bytes(const String &value) {
    _init();
    *this = value;
  }

  virtual ~Bytes() {
    _invalidate();
  }

  Bytes &operator=(const Bytes &rhs) {
    if (this != &rhs) {
      if (rhs.mBuffer) {
        _copy(rhs.mBuffer, rhs.mSize);
      } else {
        _invalidate();
      }
    }
    return *this;
  }

  Bytes &operator=(const String &rhs) {
    if (rhs.length()) {
      _copy((const uint8_t *)rhs.c_str(), rhs.length());
    } else {
      _invalidate();
    }
    return this->terminate();
  }
 
  // template <typename T>
  // operator T() {
  //   return *((T *)mBuffer);
  // }

  static Bytes fromHexString(const String &hexStr) {
    size_t len = hexStr.length();
    if (len % 2 != 0) {
      UNIOT_LOG_ERROR("invalid hex string length");
      return Bytes();
    }
 
    Bytes bytes;
    bytes._reserve(len / 2);
    for (size_t i = 0; i < len; i += 2) {
      char buf[3] = {hexStr.charAt(i), hexStr.charAt(i + 1), '\0'};
      uint8_t b = strtol(buf, nullptr, 16);
      bytes.mBuffer[i / 2] = b;
    }
    return bytes;
  }

  size_t fill(Filler filler) {
    if (filler) {
      return filler(mBuffer, mSize);
    }
    return 0;
  }

  Bytes &prune(size_t newSize) {
    if (newSize < mSize) {
      _reserve(newSize);
    }
    return *this;
  }

  const uint8_t *raw() const {
    return mBuffer;
  }

  Bytes &terminate() {
    if (!mSize) {
      _reserve(1);
      return *this;
    }
 
    if (mBuffer[mSize - 1] != '\0') {
      _reserve(mSize + 1);
      mBuffer[mSize - 1] = '\0';
    }
    return *this;
  }

  const char *c_str() const {
    return (const char *)mBuffer;
  }

  String toString() const {
    return String(this->c_str());
  }

  String toHexString() const {
    String result = "";
    for (size_t i = 0; i < mSize; i++) {
      char buf[3];
      snprintf(buf, sizeof(buf), "%02X", mBuffer[i]);
      result += buf;
    }
    return result;
  }

  size_t size() const {
    return mSize;
  }

  void clean() {
    _invalidate();
  }

  uint32_t checksum() const {
    return CRC32(mBuffer, mSize);
  }
 
 private:
  inline void _init(void) {
    mBuffer = nullptr;
    mSize = 0;
  }

  void _invalidate(void) {
    if (mBuffer) {
      free(mBuffer);
    }
    _init();
  }

  bool _reserve(size_t newSize) {
    mBuffer = (uint8_t *)realloc(mBuffer, newSize);
    if (mBuffer && (newSize > mSize)) {
      memset(mBuffer + mSize, 0, newSize - mSize);
    }
    mSize = newSize;
    return mBuffer;
  }

  Bytes &_copy(const uint8_t *data, size_t size) {
    if (_reserve(size)) {
      memcpy(mBuffer, data, size);
    } else {
      _invalidate();
    }
    return *this;
  }
 
  uint8_t *mBuffer;  
  size_t mSize;      
};