HardwareSerial::availableForWrite()

概要

Serial.availableForWrite()/HardwareSerial::availableForWrite()は、シリアル通信の送信バッファ内に書き込み可能な文字数を返します。リファレンスはこちら}。

ソースコード

HardwareSerial::availableForWrite()は、hardware/arduino/cores/arduino/HardwareSerial.cppに定義されています。以下に全ソースコードを示します。

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int HardwareSerial::availableForWrite(void)
{
  tx_buffer_index_t head;
  tx_buffer_index_t tail;

  TX_BUFFER_ATOMIC {
    head = _tx_buffer_head;
    tail = _tx_buffer_tail;
  }
  if (head >= tail) return SERIAL_TX_BUFFER_SIZE - 1 - head + tail;
  return tail - head - 1;
}

入力はありません。戻り値はintです。

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int HardwareSerial::availableForWrite(void)
{

バッファ内の有効な文字数を計算して返却します。

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  tx_buffer_index_t head;
  tx_buffer_index_t tail;
 
  TX_BUFFER_ATOMIC {
    head = _tx_buffer_head;
    tail = _tx_buffer_tail;
  }
  if (head >= tail) return SERIAL_TX_BUFFER_SIZE - 1 - head + tail;
  return tail - head - 1;
}

tx_buffer_tail ≦ tx_buffer_head の場合、tx_buffer_tail + SERIAL_TX_BUFFER_SIZE - tx_buffer_head - 1がバッファ内に書き込み可能な文字数です。

tx_buffer_tail > tx_buffer_head の場合、tx_buffer_tail - tx_buffer_head - 1がバッファ内の有効な文字数です。

バージョン

Arduino AVR Boards 1.8.6

ライセンス

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/*
  Copyright (c) 2016 garretlab.
  Added source code explanation by garretlab.
*/

/*
  HardwareSerial.cpp - Hardware serial library for Wiring
  Copyright (c) 2006 Nicholas Zambetti.  All right reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library 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
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

  Modified 23 November 2006 by David A. Mellis
  Modified 28 September 2010 by Mark Sproul
  Modified 14 August 2012 by Alarus
  Modified 3 December 2013 by Matthijs Kooijman
*/

最終更新日

July 31, 2025

inserted by FC2 system