bytestream.h

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// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
// Copyright (C) 2009-2012, International Business Machines
// Corporation and others. All Rights Reserved.
//
// Copyright 2007 Google Inc. All Rights Reserved.
// Author: sanjay@google.com (Sanjay Ghemawat)
//
// Abstract interface that consumes a sequence of bytes (ByteSink).
//
// Used so that we can write a single piece of code that can operate
// on a variety of output string types.
//
// Various implementations of this interface are provided:
//   ByteSink:
//      CheckedArrayByteSink    Write to a flat array, with bounds checking
//      StringByteSink          Write to an STL string

// This code is a contribution of Google code, and the style used here is
// a compromise between the original Google code and the ICU coding guidelines.
// For example, data types are ICU-ified (size_t,int->int32_t),
// and API comments doxygen-ified, but function names and behavior are
// as in the original, if possible.
// Assertion-style error handling, not available in ICU, was changed to
// parameter "pinning" similar to UnicodeString.
//
// In addition, this is only a partial port of the original Google code,
// limited to what was needed so far. The (nearly) complete original code
// is in the ICU svn repository at icuhtml/trunk/design/strings/contrib
// (see ICU ticket 6765, r25517).

#ifndef __BYTESTREAM_H__
#define __BYTESTREAM_H__

#include "unicode/utypes.h"

#if U_SHOW_CPLUSPLUS_API

#include <type_traits>

#include "unicode/uobject.h"
#include "unicode/std_string.h"

U_NAMESPACE_BEGIN

class U_COMMON_API ByteSink : public UMemory {
public:
  ByteSink() { }
  virtual ~ByteSink();

  virtual void Append(const char* bytes, int32_t n) = 0;

  inline void AppendU8(const char* bytes, int32_t n) {
    Append(bytes, n);
  }

#if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN)

  inline void AppendU8(const char8_t* bytes, int32_t n) {
    Append(reinterpret_cast<const char*>(bytes), n);
  }
#endif

  virtual char* GetAppendBuffer(int32_t min_capacity,
                                int32_t desired_capacity_hint,
                                char* scratch, int32_t scratch_capacity,
                                int32_t* result_capacity);

  virtual void Flush();

private:
  ByteSink(const ByteSink &) = delete;
  ByteSink &operator=(const ByteSink &) = delete;
};

// -------------------------------------------------------------
// Some standard implementations

class U_COMMON_API CheckedArrayByteSink : public ByteSink {
public:
  CheckedArrayByteSink(char* outbuf, int32_t capacity);
  virtual ~CheckedArrayByteSink();
  virtual CheckedArrayByteSink& Reset();
  virtual void Append(const char* bytes, int32_t n) override;
  virtual char* GetAppendBuffer(int32_t min_capacity,
                                int32_t desired_capacity_hint,
                                char* scratch, int32_t scratch_capacity,
                                int32_t* result_capacity) override;
  int32_t NumberOfBytesWritten() const { return size_; }
  UBool Overflowed() const { return overflowed_; }
  int32_t NumberOfBytesAppended() const { return appended_; }
private:
  char* outbuf_;
  const int32_t capacity_;
  int32_t size_;
  int32_t appended_;
  UBool overflowed_;

  CheckedArrayByteSink() = delete;
  CheckedArrayByteSink(const CheckedArrayByteSink &) = delete;
  CheckedArrayByteSink &operator=(const CheckedArrayByteSink &) = delete;
};

namespace prv {
template<typename StringClass, typename = void>
struct value_type_or_char {
  using type = char;
};
template<typename StringClass>
struct value_type_or_char<StringClass, std::void_t<typename StringClass::value_type>> {
  using type = typename StringClass::value_type;
};
template<typename StringClass>
using value_type_or_char_t = typename value_type_or_char<StringClass>::type;
}

template<typename StringClass>
class StringByteSink : public ByteSink {
  using Unit = typename prv::value_type_or_char_t<StringClass>;
 public:
  StringByteSink(StringClass* dest) : dest_(dest) { }
  StringByteSink(StringClass* dest, int32_t initialAppendCapacity) : dest_(dest) {
    if (initialAppendCapacity > 0 &&
        static_cast<uint32_t>(initialAppendCapacity) > dest->capacity() - dest->length()) {
      dest->reserve(dest->length() + initialAppendCapacity);
    }
  }
  virtual void Append(const char* data, int32_t n) override {
    if constexpr (std::is_same_v<Unit, char>) {
      dest_->append(data, n);
    } else {
      dest_->append(reinterpret_cast<const Unit*>(data), n);
    }
  }
 private:
  StringClass* dest_;

  StringByteSink() = delete;
  StringByteSink(const StringByteSink &) = delete;
  StringByteSink &operator=(const StringByteSink &) = delete;
};

U_NAMESPACE_END

#endif /* U_SHOW_CPLUSPLUS_API */

#endif  // __BYTESTREAM_H__