C++ C++；sscanf焊缝未按预期工作

我目前正在和Arduino Uno一起为学校做项目，遇到了C sscanf功能的问题。下面的代码正在解析通过串行接口发送到Arduino的字符数组。每个数据块用空格分隔。我还检查了有关Stackoverflow的类似问题，但没有发现任何有用的信息

    char testInput[] = "t 1 3 65 1";

    int registerIndex;
    int locoAddr;
    int locoSpeed;
    int locoDirection;

   if(sscanf(testInput, "t %d %d %d %d", &registerIndex, &locoAddr, &locoSpeed, &locoDirection) != 4) {
        return;
    }

    // print for demo:
    Serial.print(registerIndex);
    Serial.print(": ");

    Serial.print("loco:");
    Serial.print(locoAddr);

    Serial.print(" speed:");
    Serial.print(locoSpeed);

    Serial.print(" direction:");
    Serial.println(locoDirection);

// expected output: "1: loco:3 speed:65 direction:1"
// output: "-18248: loco:-18248 speed:-18248 direction:-18248"

sscanf函数返回预期的整数4，但不使用值填充变量，因此只打印默认值

我不知道这是什么问题。也许互联网上的某个人有一个解决方案

编辑1:为了更好地理解草图的复杂性，这可能有助于更好地理解代码：

.ino文件中的循环调用static Commander:：process（）

指挥官：：_readLine（…）；被调用并从串口读取数据

还进行了一些验证，但在这种情况下应该无关紧要

指挥官：：parseCommand（command）；使用命令调用

寄存器->设置油门（命令）；当命令以“t”开头时调用。寄存器是易变的，所以我可以在中断时调用它

在PackageRegisterList:：setThrottle中，是位于的sscanf方法

---

我通常使用从Linux内核偷来的这个版本：

int ASCII_vsscanf(const char * buf, const char * fmt, va_list args)
{
    const char *str = buf;
    char *next;
    char digit;
    int num = 0;
    int qualifier;
    int base;
    int field_width;
    int is_sign = 0;

    while(*fmt && *str) {
        /* skip any white space in format */
        /* white space in format matchs any amount of
         * white space, including none, in the input.
         */
        if (isspace(*fmt)) {
            while (isspace(*fmt))
                ++fmt;
            while (isspace(*str))
                ++str;
        }

        /* anything that is not a conversion must match exactly */
        if (*fmt != '%' && *fmt) {
            if (*fmt++ != *str++)
                break;
            continue;
        }

        if (!*fmt)
            break;
        ++fmt;

        /* skip this conversion.
         * advance both strings to next white space
         */
        if (*fmt == '*') {
            while (!isspace(*fmt) && *fmt)
                fmt++;
            while (!isspace(*str) && *str)
                str++;
            continue;
        }

        /* get field width */
        field_width = -1;
        if (isdigit(*fmt))
            field_width = skip_atoi(&fmt);

        /* get conversion qualifier */
        qualifier = -1;
        if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L' ||
            *fmt == 'Z' || *fmt == 'z') {
            qualifier = *fmt++;
            if (unlikely(qualifier == *fmt)) {
                if (qualifier == 'h') {
                    qualifier = 'H';
                    fmt++;
                } else if (qualifier == 'l') {
                    qualifier = 'L';
                    fmt++;
                }
            }
        }
        base = 10;
        is_sign = 0;

        if (!*fmt || !*str)
            break;

        switch(*fmt++) {
        case 'c':
        {
            char *s = (char *) va_arg(args,char*);
            if (field_width == -1)
                field_width = 1;
            do {
                *s++ = *str++;
            } while (--field_width > 0 && *str);
            num++;
        }
        continue;
        case 's':
        {
            char *s = (char *) va_arg(args, char *);
            if(field_width == -1)
                field_width = INT_MAX;
            /* first, skip leading white space in buffer */
            while (isspace(*str))
                str++;

            /* now copy until next white space */
            while (*str && !isspace(*str) && field_width--) {
                *s++ = *str++;
            }
            *s = '\0';
            num++;
        }
        continue;
        case 'n':
            /* return number of characters read so far */
        {
            int *i = (int *)va_arg(args,int*);
            *i = str - buf;
        }
        continue;
        case 'o':
            base = 8;
            break;
        case 'x':
        case 'X':
            base = 16;
            break;
        case 'i':
                        base = 0;
        case 'd':
            is_sign = 1;
        case 'u':
            break;
        case '%':
            /* looking for '%' in str */
            if (*str++ != '%')
                return num;
            continue;
        default:
            /* invalid format; stop here */
            return num;
        }

        /* have some sort of integer conversion.
         * first, skip white space in buffer.
         */
        while (isspace(*str))
            str++;

        digit = *str;
        if (is_sign && digit == '-')
            digit = *(str + 1);

        if (!digit
                    || (base == 16 && !isxdigit(digit))
                    || (base == 10 && !isdigit(digit))
                    || (base == 8 && (!isdigit(digit) || digit > '7'))
                    || (base == 0 && !isdigit(digit)))
                break;

        switch(qualifier) {
        case 'H':   /* that's 'hh' in format */
            if (is_sign) {
                signed char *s = (signed char *) va_arg(args,signed char *);
                *s = (signed char) ASCII_simple_strtol(str,&next,base);
            } else {
                unsigned char *s = (unsigned char *) va_arg(args, unsigned char *);
                *s = (unsigned char) ASCII_simple_strtoul(str, &next, base);
            }
            break;
        case 'h':
            if (is_sign) {
                short *s = (short *) va_arg(args,short *);
                *s = (short) ASCII_simple_strtol(str,&next,base);
            } else {
                unsigned short *s = (unsigned short *) va_arg(args, unsigned short *);
                *s = (unsigned short) ASCII_simple_strtoul(str, &next, base);
            }
            break;
        case 'l':
            if (is_sign) {
                long *l = (long *) va_arg(args,long *);
                *l = ASCII_simple_strtol(str,&next,base);
            } else {
                unsigned long *l = (unsigned long*) va_arg(args,unsigned long*);
                *l = ASCII_simple_strtoul(str,&next,base);
            }
            break;
        case 'L':
            if (is_sign) {
                long long *l = (long long*) va_arg(args,long long *);
                *l = ASCII_simple_strtoll(str,&next,base);
            } else {
                unsigned long long *l = (unsigned long long*) va_arg(args,unsigned long long*);
                *l = ASCII_simple_strtoull(str,&next,base);
            }
            break;
        case 'Z':
        case 'z':
        {
            size_t *s = (size_t*) va_arg(args,size_t*);
            *s = (size_t) ASCII_simple_strtoul(str,&next,base);
        }
        break;
        default:
            if (is_sign) {
                int *i = (int *) va_arg(args, int*);
                *i = (int) ASCII_simple_strtol(str,&next,base);
            } else {
                unsigned int *i = (unsigned int*) va_arg(args, unsigned int*);
                *i = (unsigned int) ASCII_simple_strtoul(str,&next,base);
            }
            break;
        }
        num++;

        if (!next)
            break;
        str = next;
    }
    return num;
}

---

有限但对我来说足够小和好。

“每个数据块都用空格隔开。”尝试在格式规范的边缘放一个空格，因为

“t%d%d%d%d”

。无法通过将代码段复制到C程序中来进行复制，该程序使用

fprintf

@WeatherVane输出提供的代码示例不起作用。提供的输入的第一个字符是“t”，后跟空格。在switch语句中使用了“t”来确定在调用sscanf之前它是什么类型的输入。请不要责怪Arduino。99.9999%的人拥有代码或理解。由于

Serial.print

被重载，可以使用

char*

或

int

参数，这显然与C无关。应该删除C标记。C++是一种不同的语言。请停止在

C++

主题中使用名称

C

。