package yaokong;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.OutputStream;
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import java.nio.ByteBuffer;
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import java.nio.ByteOrder;
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import java.util.Objects;
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public abstract class WaitForAck {
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protected final InputStream inputStream;
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protected final OutputStream outputStream;
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protected WaitForAck(InputStream inputStream, OutputStream outputStream) {
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this.inputStream = Objects.requireNonNull(inputStream, "inputStream");
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this.outputStream = Objects.requireNonNull(outputStream, "outputStream");
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}
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// 在超时内等待下位机返回指定指令的确认帧
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protected boolean waitForAck(byte expectedCommand) throws IOException {
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long deadline = System.currentTimeMillis() + 1000L;
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while (System.currentTimeMillis() < deadline) {
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if (inputStream.available() > 0) {
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byte[] response = readResponse();
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if (response != null && parseResponse(response, expectedCommand)) {
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return true;
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}
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}
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try {
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Thread.sleep(10L);
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} catch (InterruptedException interruptedException) {
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Thread.currentThread().interrupt();
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break;
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}
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}
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return false;
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}
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// 从输入流读取完整响应帧并校验帧头帧尾
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private byte[] readResponse() throws IOException {
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ByteArrayOutputStream buffer = new ByteArrayOutputStream();
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while (true) {
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int value = inputStream.read();
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if (value == -1) {
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return buffer.size() == 0 ? null : buffer.toByteArray();
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}
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buffer.write(value);
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if (buffer.size() == 1 && buffer.toByteArray()[0] != BluetoothProtocol.FRAME_HEADER[0]) {
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buffer.reset();
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continue;
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}
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if (buffer.size() == 2) {
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byte[] header = buffer.toByteArray();
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if (header[0] != BluetoothProtocol.FRAME_HEADER[0] || header[1] != BluetoothProtocol.FRAME_HEADER[1]) {
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buffer.reset();
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continue;
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}
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}
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if ((byte) value == BluetoothProtocol.FRAME_FOOTER) {
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return buffer.toByteArray();
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}
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}
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}
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// 解析确认帧并校验CRC与指令号
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private boolean parseResponse(byte[] response, byte expectedCommand) {
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if (response.length < 7) {
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return false;
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}
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if (response[0] != BluetoothProtocol.FRAME_HEADER[0] || response[1] != BluetoothProtocol.FRAME_HEADER[1]) {
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return false;
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}
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if (response[2] != BluetoothProtocol.CMD_RESPONSE) {
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return false;
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}
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ByteBuffer wrapper = ByteBuffer.wrap(response).order(ByteOrder.LITTLE_ENDIAN);
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wrapper.position(3);
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int payloadLength = wrapper.getShort() & 0xFFFF;
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int frameLength = 2 + 1 + 2 + payloadLength + 2 + 1;
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if (response.length < frameLength) {
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return false;
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}
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if (payloadLength < 2) {
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return false;
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}
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int crcOffset = 2 + 1 + 2 + payloadLength;
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int calculatedCrc = CRC16.calculateCRC16(response, 2, 1 + 2 + payloadLength);
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int receivedCrc = ByteBuffer.wrap(response, crcOffset, 2).order(ByteOrder.LITTLE_ENDIAN).getShort() & 0xFFFF;
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if (calculatedCrc != receivedCrc) {
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return false;
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}
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byte ackCommand = response[2 + 1 + 2];
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byte status = response[2 + 1 + 2 + 1];
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if (ackCommand != expectedCommand) {
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return false;
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}
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return status == BluetoothProtocol.ERROR_SUCCESS;
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}
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}
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