// © 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__

/**

 * \file

 * \brief C++ API: Interface for writing bytes, and implementation classes.

 */

#include "unicode/utypes.h"

#if U_SHOW_CPLUSPLUS_API

#include <type_traits>

#include "unicode/uobject.h"

#include "unicode/std_string.h"

U_NAMESPACE_BEGIN

/**

 * A ByteSink can be filled with bytes.

 * @stable ICU 4.2

 */

class U_COMMON_API ByteSink : public UMemory {

public:

  /**

   * Default constructor.

   * @stable ICU 4.2

   */

  ByteSink() { }

  /**

   * Virtual destructor.

   * @stable ICU 4.2

   */

  virtual ~ByteSink();

  /**

   * Append "bytes[0,n-1]" to this.

   * @param bytes the pointer to the bytes

   * @param n the number of bytes; must be non-negative

   * @stable ICU 4.2

   */

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

  /**

   * Appends n bytes to this. Same as Append().

   * Call AppendU8() with u8"string literals" which are const char * in C++11

   * but const char8_t * in C++20.

   * If the compiler does support char8_t as a distinct type,

   * then an AppendU8() overload for that is defined and will be chosen.

   *

   * @param bytes the pointer to the bytes

   * @param n the number of bytes; must be non-negative

   * @stable ICU 67

   */

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

    Append(bytes, n);

  }

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

  /**

   * Appends n bytes to this. Same as Append() but for a const char8_t * pointer.

   * Call AppendU8() with u8"string literals" which are const char * in C++11

   * but const char8_t * in C++20.

   * If the compiler does support char8_t as a distinct type,

   * then this AppendU8() overload for that is defined and will be chosen.

   *

   * @param bytes the pointer to the bytes

   * @param n the number of bytes; must be non-negative

   * @stable ICU 67

   */

  inline void AppendU8(const char8_t* bytes, int32_t n) {

    Append(reinterpret_cast<const char*>(bytes), n);

  }

#endif

  /**

   * Returns a writable buffer for appending and writes the buffer's capacity to

   * *result_capacity. Guarantees *result_capacity>=min_capacity.

   * May return a pointer to the caller-owned scratch buffer which must have

   * scratch_capacity>=min_capacity.

   * The returned buffer is only valid until the next operation

   * on this ByteSink.

   *

   * After writing at most *result_capacity bytes, call Append() with the

   * pointer returned from this function and the number of bytes written.

   * Many Append() implementations will avoid copying bytes if this function

   * returned an internal buffer.

   *

   * Partial usage example:

   *  int32_t capacity;

   *  char* buffer = sink->GetAppendBuffer(..., &capacity);

   *  ... Write n bytes into buffer, with n <= capacity.

   *  sink->Append(buffer, n);

   * In many implementations, that call to Append will avoid copying bytes.

   *

   * If the ByteSink allocates or reallocates an internal buffer, it should use

   * the desired_capacity_hint if appropriate.

   * If a caller cannot provide a reasonable guess at the desired capacity,

   * it should pass desired_capacity_hint=0.

   *

   * If a non-scratch buffer is returned, the caller may only pass

   * a prefix to it to Append().

   * That is, it is not correct to pass an interior pointer to Append().

   *

   * The default implementation always returns the scratch buffer.

   *

   * @param min_capacity required minimum capacity of the returned buffer;

   *                     must be non-negative

   * @param desired_capacity_hint desired capacity of the returned buffer;

   *                              must be non-negative

   * @param scratch default caller-owned buffer

   * @param scratch_capacity capacity of the scratch buffer

   * @param result_capacity pointer to an integer which will be set to the

   *                        capacity of the returned buffer

   * @return a buffer with *result_capacity>=min_capacity

   * @stable ICU 4.2

   */

  virtual char* GetAppendBuffer(int32_t min_capacity,

                                int32_t desired_capacity_hint,

                                char* scratch, int32_t scratch_capacity,

                                int32_t* result_capacity);

  /**

   * Flush internal buffers.

   * Some byte sinks use internal buffers or provide buffering

   * and require calling Flush() at the end of the stream.

   * The ByteSink should be ready for further Append() calls after Flush().

   * The default implementation of Flush() does nothing.

   * @stable ICU 4.2

   */

  virtual void Flush();

private:

  ByteSink(const ByteSink &) = delete;

  ByteSink &operator=(const ByteSink &) = delete;

};

// -------------------------------------------------------------

// Some standard implementations

/** 

 * Implementation of ByteSink that writes to a flat byte array,

 * with bounds-checking:

 * This sink will not write more than capacity bytes to outbuf.

 * If more than capacity bytes are Append()ed, then excess bytes are ignored,

 * and Overflowed() will return true.

 * Overflow does not cause a runtime error.

 * @stable ICU 4.2

 */

class U_COMMON_API CheckedArrayByteSink : public ByteSink {

public:

  /**

   * Constructs a ByteSink that will write to outbuf[0..capacity-1].

   * @param outbuf buffer to write to

   * @param capacity size of the buffer

   * @stable ICU 4.2

   */

  CheckedArrayByteSink(char* outbuf, int32_t capacity);

  /**

   * Destructor.

   * @stable ICU 4.2

   */

  virtual ~CheckedArrayByteSink();

  /**

   * Returns the sink to its original state, without modifying the buffer.

   * Useful for reusing both the buffer and the sink for multiple streams.

   * Resets the state to NumberOfBytesWritten()=NumberOfBytesAppended()=0

   * and Overflowed()=false.

   * @return *this

   * @stable ICU 4.6

   */

  virtual CheckedArrayByteSink& Reset();

  /**

   * Append "bytes[0,n-1]" to this.

   * @param bytes the pointer to the bytes

   * @param n the number of bytes; must be non-negative

   * @stable ICU 4.2

   */

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

  /**

   * Returns a writable buffer for appending and writes the buffer's capacity to

   * *result_capacity. For details see the base class documentation.

   * @param min_capacity required minimum capacity of the returned buffer;

   *                     must be non-negative

   * @param desired_capacity_hint desired capacity of the returned buffer;

   *                              must be non-negative

   * @param scratch default caller-owned buffer

   * @param scratch_capacity capacity of the scratch buffer

   * @param result_capacity pointer to an integer which will be set to the

   *                        capacity of the returned buffer

   * @return a buffer with *result_capacity>=min_capacity

   * @stable ICU 4.2

   */

  virtual char* GetAppendBuffer(int32_t min_capacity,

                                int32_t desired_capacity_hint,

                                char* scratch, int32_t scratch_capacity,

                                int32_t* result_capacity) override;

  /**

   * Returns the number of bytes actually written to the sink.

   * @return number of bytes written to the buffer

   * @stable ICU 4.2

   */

  int32_t NumberOfBytesWritten() const { return size_; }

  /**

   * Returns true if any bytes were discarded, i.e., if there was an

   * attempt to write more than 'capacity' bytes.

   * @return true if more than 'capacity' bytes were Append()ed

   * @stable ICU 4.2

   */

  UBool Overflowed() const { return overflowed_; }

  /**

   * Returns the number of bytes appended to the sink.

   * If Overflowed() then NumberOfBytesAppended()>NumberOfBytesWritten()

   * else they return the same number.

   * @return number of bytes written to the buffer

   * @stable ICU 4.6

   */

  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 {

/** @internal */

template<typename StringClass, typename = void>

struct value_type_or_char {

  /** @internal */

  using type = char;

};

/** @internal */

template<typename StringClass>

struct value_type_or_char<StringClass, std::void_t<typename StringClass::value_type>> {

  /** @internal */

  using type = typename StringClass::value_type;

};

/** @internal */

template<typename StringClass>

using value_type_or_char_t = typename value_type_or_char<StringClass>::type;

}

/** 

 * Implementation of ByteSink that writes to a "string".

 * The StringClass is usually instantiated with a std::string or a std::u8string.

 * StringClass must have public member functions reserve(integer type), capacity(), length(), and

 * append(value type, integer type) with the same semantics as those of std::basic_string, and must

 * have an 8-bit value type.  If the value type is not char, it must be a public member type

 * StringClass::value_type.

 * @stable ICU 4.2

 */

template<typename StringClass>

class StringByteSink : public ByteSink {

  using Unit = typename prv::value_type_or_char_t<StringClass>;

 public:

  /**

   * Constructs a ByteSink that will append bytes to the dest string.

   * @param dest pointer to string object to append to

   * @stable ICU 4.2

   */

  StringByteSink(StringClass* dest) : dest_(dest) { }

  /**

   * Constructs a ByteSink that reserves append capacity and will append bytes to the dest string.

   * 

   * @param dest pointer to string object to append to

   * @param initialAppendCapacity capacity beyond dest->length() to be reserve()d

   * @stable ICU 60

   */

  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);

    }

  }

  /**

   * Append "bytes[0,n-1]" to this.

   * @param data the pointer to the bytes

   * @param n the number of bytes; must be non-negative

   * @stable ICU 4.2

   */

  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__