看似小事，却极易写错

来源：互联网发布：linux限制ip访问次数编辑：程序博客网时间：2024/06/02 07:41

今天写个txt文章转换为html段落的小代码，结果一个地方搞了好一会才发现是哪个地方写错了：

#include <string>#include <stdio.h>void main(int argc, char** argv){if(argc < 2){printf("file name failed!!!\n");char k;scanf("%c", &k);return;}FILE * fp = fopen(argv[1], "r");if(fp == NULL){printf("file open failed!!!\n");char k;scanf("%c", &k);return;}fseek(fp, 0, SEEK_END);long fszie = ftell(fp);fseek(fp, 0, SEEK_SET);if(fszie == -1){printf("file size failed!!!\n");char k;scanf("%c", &k);return;}char* sz_str = new char[fszie+1];sz_str[fszie] = '\0';if(fread(sz_str, 1, fszie, fp) <= 0){printf("file size failed!!!\n");char k;scanf("%c", &k);return;}std::string text = sz_str;std::string output_str = "<p>";int i = 0;while(sz_str[i] != '\0'){while(sz_str[i] != '\0')//换行符 break{if(sz_str[i] == '\r')//换行符 break{if(sz_str[i] != '\n'){printf("file find \\r but not find \\n failed!!!\n");char k;scanf("%c", &k);return;}break;}else if(sz_str[i] == '\n')//换行符 breakbreak;//处理空格和tabif(sz_str[i] == ' ')output_str += " ";else if(sz_str[i] == '\t')output_str += "    ";else if(sz_str[i] != 0xcd)output_str += sz_str[i];i++;}if(sz_str[i] == '\0')break;else //碰到换行符了{output_str += "</br>";i++;}}output_str += "</p>";fclose(fp);fp = fopen(argv[1], "w");if(fp == NULL){printf("file open failed!!!\n");char k;scanf("%c", &k);return;}fwrite(output_str.c_str(), output_str.size(), 1, fp);fclose(fp);}

就错在了

else if(sz_str[i] != 0xcd)

这一行我用调试器看了变量值明明就是0xcd啊，那是为何呢？后来理了理头绪，改为 else if(sz_str[i] != (char)0xcd) 就好了

因为之前代码表达式由char提升为int ，结果sz_str[i]提升为int会变成一个负数，而0xcd会变成一个小整数。主要当时把他们看成原始二级制了（无符号）如果改为：

else if((unsigned char)sz_str[i] != (unsigned char)0xcd) 也是可以的

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