编译器优化和memcpy

时间:2018-12-14 14:03:07

标签: c++ arduino avr-gcc

我有一个Arduino Pro Mini和一个通过SPI连接的ESP32。 Arduino应该制作数据包并将其发送到ESP32,反之亦然。

以下是Arduino的草图:

#include <stdint.h>
#include <time.h>
#include "SPI.h"

#define ChipSelect 10
#define Handshake  14
#define FF_PACKET_FIXED_LENGTH 5
#define SPI_BUFFER_SIZE 128

static const uint16_t crc16_table[256] = {
0x0000,0xC0C1,0xC181,0x0140,0xC301,0x03C0,0x0280,0xC241,
0xC601,0x06C0,0x0780,0xC741,0x0500,0xC5C1,0xC481,0x0440,
0xCC01,0x0CC0,0x0D80,0xCD41,0x0F00,0xCFC1,0xCE81,0x0E40,
0x0A00,0xCAC1,0xCB81,0x0B40,0xC901,0x09C0,0x0880,0xC841,
0xD801,0x18C0,0x1980,0xD941,0x1B00,0xDBC1,0xDA81,0x1A40,
0x1E00,0xDEC1,0xDF81,0x1F40,0xDD01,0x1DC0,0x1C80,0xDC41,
0x1400,0xD4C1,0xD581,0x1540,0xD701,0x17C0,0x1680,0xD641,
0xD201,0x12C0,0x1380,0xD341,0x1100,0xD1C1,0xD081,0x1040,
0xF001,0x30C0,0x3180,0xF141,0x3300,0xF3C1,0xF281,0x3240,
0x3600,0xF6C1,0xF781,0x3740,0xF501,0x35C0,0x3480,0xF441,
0x3C00,0xFCC1,0xFD81,0x3D40,0xFF01,0x3FC0,0x3E80,0xFE41,
0xFA01,0x3AC0,0x3B80,0xFB41,0x3900,0xF9C1,0xF881,0x3840,
0x2800,0xE8C1,0xE981,0x2940,0xEB01,0x2BC0,0x2A80,0xEA41,
0xEE01,0x2EC0,0x2F80,0xEF41,0x2D00,0xEDC1,0xEC81,0x2C40,
0xE401,0x24C0,0x2580,0xE541,0x2700,0xE7C1,0xE681,0x2640,
0x2200,0xE2C1,0xE381,0x2340,0xE101,0x21C0,0x2080,0xE041,
0xA001,0x60C0,0x6180,0xA141,0x6300,0xA3C1,0xA281,0x6240,
0x6600,0xA6C1,0xA781,0x6740,0xA501,0x65C0,0x6480,0xA441,
0x6C00,0xACC1,0xAD81,0x6D40,0xAF01,0x6FC0,0x6E80,0xAE41,
0xAA01,0x6AC0,0x6B80,0xAB41,0x6900,0xA9C1,0xA881,0x6840,
0x7800,0xB8C1,0xB981,0x7940,0xBB01,0x7BC0,0x7A80,0xBA41,
0xBE01,0x7EC0,0x7F80,0xBF41,0x7D00,0xBDC1,0xBC81,0x7C40,
0xB401,0x74C0,0x7580,0xB541,0x7700,0xB7C1,0xB681,0x7640,
0x7200,0xB2C1,0xB381,0x7340,0xB101,0x71C0,0x7080,0xB041,
0x5000,0x90C1,0x9181,0x5140,0x9301,0x53C0,0x5280,0x9241,
0x9601,0x56C0,0x5780,0x9741,0x5500,0x95C1,0x9481,0x5440,
0x9C01,0x5CC0,0x5D80,0x9D41,0x5F00,0x9FC1,0x9E81,0x5E40,
0x5A00,0x9AC1,0x9B81,0x5B40,0x9901,0x59C0,0x5880,0x9841,
0x8801,0x48C0,0x4980,0x8941,0x4B00,0x8BC1,0x8A81,0x4A40,
0x4E00,0x8EC1,0x8F81,0x4F40,0x8D01,0x4DC0,0x4C80,0x8C41,
0x4400,0x84C1,0x8581,0x4540,0x8701,0x47C0,0x4680,0x8641,
0x8201,0x42C0,0x4380,0x8341,0x4100,0x81C1,0x8081,0x4040};

// Вычисление контрольной суммы
uint16_t ffCrc16(const uint8_t *data, uint16_t data_size) {
    if (!data || !data_size) {
        return 0;
    }

    uint16_t crc = 0;
    uint8_t *buf = (uint8_t *) data;

    while (data_size--) {
        crc = (crc >> 8) ^ crc16_table[(uint8_t)crc ^ *buf++];
    }
    return crc;
}

// the setup function runs once when you press reset or power the board
void setup() {
    Serial.begin(9600);
    // set the CipSelectPin & LED as an output:
    pinMode(ChipSelect, OUTPUT);
    pinMode(LED_BUILTIN, OUTPUT);
    // initialize digital pin Handsake as an input.
    pinMode(Handshake, INPUT);
    Serial.println("Test  ESP-32");
    // initialize SPI:
    SPI.begin();
    Serial.println("SPI Init");
    digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(1000);                       // wait for a second
    digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
    delay(1000);                       // wait for a second
}

void loop() {
    Serial.println("===== Loop iter start =====");
    uint8_t data[50] = {0};
    uint8_t *dataPtr = data;
    Serial.print("sizeof(data) = ");
    Serial.println(sizeof(data));
    Serial.print("sizeof(dataPtr) = ");
    Serial.println(sizeof(dataPtr));
    uint32_t val = 1;
    Serial.print("sizeof(val) = ");
    Serial.println(sizeof(val));
    memcpy(dataPtr, &val, 4);
    dataPtr += 4;

    val = (uint32_t) time(NULL);
    memcpy(dataPtr, &val, 4);
    dataPtr += 4;

    val = 1;
    memcpy(dataPtr, &val, 1);
    dataPtr += 1;

    val = 15;
    memcpy(dataPtr, &val, 4);
    dataPtr += 4;

    Serial.print("data: ");
    printPacket(data, 13);

    uint8_t packet[50] = {0};
    uint16_t packetSize = 50;
    Serial.print("sizeof(packet) = ");
    Serial.println(sizeof(packet));
    Serial.print("sizeof(packetSize) = ");
    Serial.println(sizeof(packetSize));

    ffCreateCustomPacket(0xA0, data, 13, packet, &packetSize);
    if (packetSize > 0) {
        ffSendPacket(packet, packetSize);
    }
    Serial.println("===== Loop iter end =====");
    delay(20000);
}

void printPacket(uint8_t *packet, uint16_t packetSize) {
    uint32_t dumpSize = packetSize * 2;
    char hexDump[dumpSize];
    char *p = hexDump;
    memset(hexDump, 0, dumpSize);

    for (uint16_t i = 0; i < packetSize; ++i) {
        sprintf(p, "%02x", packet[i]);
        p += 2;
    }
    Serial.println(hexDump);
}

void ffCreateCustomPacket(uint8_t signature, uint8_t *data, uint16_t dataSize, uint8_t *buf, uint16_t *bufSize) {
    uint16_t packetSize = FF_PACKET_FIXED_LENGTH + dataSize;
    if (*bufSize < packetSize) {
        Serial.println("Not enough buffer size!");
        *bufSize = 0;
        return;
    }
    Serial.print("data2: ");
    printPacket(data, dataSize);

    uint8_t *packetStart = buf;

    // signature
    *buf = signature;
    buf++;
    Serial.print("signature: ");
    printPacket(packetStart, 50);

    // dataSize
    memcpy(buf, &dataSize, 2);
    buf += 2;
    Serial.print("size: ");
    printPacket(packetStart, 50);
    Serial.print("dataSize = ");
    Serial.println(dataSize);

    // data
    memcpy(buf, data, dataSize);
    buf += dataSize;
    Serial.print("data: ");
    printPacket(packetStart, 50);

    // CRC
    uint16_t crc = ffCrc16(packetStart, packetSize - 2);
    memcpy(buf, &crc, 2);
    buf += 2;

    *bufSize = packetSize;
    Serial.print("packet: ");
    printPacket(packetStart, 50);
}

void ffSendPacket(uint8_t *packet, uint16_t packetSize) {
    Serial.print("Send packet: ");
    printPacket(packet, packetSize);

    uint8_t spiBuffer[SPI_BUFFER_SIZE] = {0};
    memcpy(spiBuffer, packet, packetSize);
    SPI.transfer(spiBuffer, SPI_BUFFER_SIZE);

    Serial.print("Received: ");
    printPacket(spiBuffer, SPI_BUFFER_SIZE);
}

以下是日志输出:

sizeof(data) = 50
sizeof(dataPtr) = 2
sizeof(val) = 4
data: 0100000000000000010f000000
sizeof(packet) = 50
sizeof(packetSize) = 2
data2: 0100000000000000010f000000
signature: a0000000000000000000000000...
size: a00d0000000000000000000000...
dataSize = 13
data: a00d0000000000000000000000...
packet: a00d0000000000000000000000000000b57d...
Send packet: a00d0000000000000000000000000000b57d
Received: 000...
Loop iter end

实际数据包应为a00d000100000000000000010f000000xxxx(xxxx-crc),但我得到的是a00d0000000000000000000000000000b57d

如果我将编译器标志从Os切换到O0,则一切正常。是否有一些优化可以切断数据memcpy,以及如何告诉编译器不要这样做?

其他信息:如果我将数据包数组设置为静态,或者将其分配到堆上,那么它们也都按预期工作。

0 个答案:

没有答案