时间戳

首页 > 解决方案 > for 循环内的整数在每行增加 2，语句与它没有任何关系

c - for 循环内的整数在每行增加 2，语句与它没有任何关系

问题描述

我目前在我的 C 程序中遇到奇怪的结果，在一个 for 循环中，变量 hex_index 在每一行增加 2。它与时间无关或任何东西。尽管如此，即使语句与它无关，它也只会增加每一行。

ascii.c

#include <stdio.h>
#include "types.h"

int
main ()
{
  char *hex = "68747541";
  char output[4];
  hex_to_ascii(hex, output);
  printf("%s", output);
  return 0;
}

长度.c

#include <stddef.h>

/// Returns the length of the passed string based on checking the content 
/// with NULL or @\0 which end a string
int get_str_len(char *string)
{
  int len = 0;
  for (int i = 0; 1; i++)
  {
    if (string[i] == '\0' || string[i] == NULL) return len;
    len++;
  }
}

/// Returns the length of the passed hex string
int get_hex_len(char *hex)
{
  return get_str_len(hex);
}

类型.c

#include "types.h"
#include "length.h"

/// Removes inside a string all control chars and overwrites the passed string
void remove_control_chars(char* string)
{
  int len = get_str_len(string);
  char new_string[len];
  int string_index = 0;

  int i;
  for (i = 0; i < len; i++, string_index++)
  {
    if (string[i] < 127 && string[i] > 31)
    {
      new_string[i] = string[string_index];
    }
    else string_index++;
  }

  len = get_str_len(new_string);
  for (i = 0; i < len; i++)
  {
    string[i] = new_string[i];
  }
  string[i] = '\0';
}

/// Converts an hex number to an int
/// If an invalid character is inside the string it will return -1 (Control chars will be automatically removed)
/// @param str The string that should be converted
int hex_to_int(char *str)
{
  remove_control_chars(str);
  int str_len = get_str_len(str);
  int sum = 0;
  int multiplier = 1;

  // Calculating the multiplier for the biggest number (num at index 0)
  for (int i = 1; i < str_len; i++) multiplier *= 16;

  // Adding the multiplied value to the sum and then diving by the base (16)
  for (int i = 0; i < str_len; i++, multiplier /= 16)
  {
    char byte = str[i];
    if (byte >= '0' && byte <= '9') sum += (byte - '0') * multiplier;
    else if (byte >= 'A' && byte <='F') sum += (byte - 'A' + 10) * multiplier;
    else if (byte >= 'a' && byte <='f') sum += (byte - 'a' + 10) * multiplier;
    // Avoiding control characters
    else if (byte < 31) return sum;
    else return -1;
  }
  return sum;
}

bool valid_hex_char(char byte)
{
  return byte >= '0' && byte <= '9' || byte >= 'A' && byte <= 'F' || byte >= 'a' && byte <= 'f';
}

/// Converts an hex number to an dual ascii character and returns it
/// @param hex The string that should be converted
char dual_hex_to_ascii(char *hex)
{
  int value = hex_to_int(hex);
  return (char) value;
}

/// Converts an hex number to an ascii string
/// @param hex The string that should be converted
/// @param output The initialised string which will be overwritten
void hex_to_ascii(char *hex, char *output)
{
  char storage[2];
  int len = get_hex_len(hex);
  int i = 0;
  for (int hex_index = 0; hex_index < len; hex_index += 2)
  {
    if (valid_hex_char(hex[hex_index]))
    {
      storage[0] = hex[hex_index];
      if (valid_hex_char(hex[hex_index+1]))
      {
        storage[1] = hex[hex_index+1];
      }
      else
      {
        storage[1] = '\0';
      }

      output[i] = dual_hex_to_ascii(storage);
      i++;
    }
    else
    {
      return;
    }
  }
}

问题视频（观看 hex_index，会随机增加）

标签： cfunctionfor-looppointers

解决方案

我找到了导致这个的问题。调试器留下了手表，在每一行重新评估调用每行增量的值。所以代码很好，但我在调试器会话中犯了一个错误。

推荐阅读