c语言二进制文件加密

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#define  _CRT_SECURE_NO_WARNINGS//关闭安全检查#include<stdio.h>#include<stdlib.h>int getfilesize(char *path){FILE *pf = fopen(path, "r");if (pf == NULL){return -1;}else{fseek(pf, 0, SEEK_END);int length = ftell(pf);return length;//获取文件大小}}void copy(char *oldpath, char *newpath){FILE *pfr, *pfw;pfr = fopen(oldpath, "rb");pfw = fopen(newpath, "wb");//写入二进制模式if (pfr == NULL || pfw == NULL){fclose(pfr);//关闭文件fclose(pfw);return;}else{int length = getfilesize(oldpath);char *p = (char *)malloc(length*sizeof(char));//分配内存，读取文件fread(p, sizeof(char), length, pfr);//读取二进制到内存fwrite(p, sizeof(char), length, pfw);//写入二进制到文件fclose(pfr);//关闭文件fclose(pfw);}}//加密void jia(char *oldpath, char *newpath){FILE *pfr, *pfw;pfr = fopen(oldpath, "rb");pfw = fopen(newpath, "wb");//写入二进制模式if (pfr == NULL || pfw == NULL){fclose(pfr);//关闭文件fclose(pfw);return;}else{int length = getfilesize(oldpath);char *p = (char *)malloc(length*sizeof(char));//分配内存，读取文件fread(p, sizeof(char), length, pfr);//读取二进制到内存for (int i = 0; i < length; i++){p[i] ^= 'A';}fwrite(p, sizeof(char), length, pfw);//写入二进制到文件fclose(pfr);//关闭文件fclose(pfw);}}//解密void jie(char *oldpath, char *newpath){FILE *pfr, *pfw;pfr = fopen(oldpath, "rb");pfw = fopen(newpath, "wb");//写入二进制模式if (pfr == NULL || pfw == NULL){fclose(pfr);//关闭文件fclose(pfw);return;}else{int length = getfilesize(oldpath);char *p = (char *)malloc(length*sizeof(char));//分配内存，读取文件fread(p, sizeof(char), length, pfr);//读取二进制到内存for (int i = 0; i < length; i++){p[i] ^= 'A';}fwrite(p, sizeof(char), length, pfw);//写入二进制到文件fclose(pfr);//关闭文件fclose(pfw);}}void main(){   char  *oldpath = "C:\\Users\\yincheng01\\Desktop\\腾讯截图2012.exe";char  *newpath = "C:\\Users\\yincheng01\\Desktop\\腾讯截图2012A.exe";char  *newjiepath = "C:\\Users\\yincheng01\\Desktop\\腾讯截图2012B.exe";jia(oldpath, newpath);jie(newpath, newjiepath);    system("pause");}

fseek
  函数名: fseek
  功能: 重定位流上的文件指针
  用法: int fseek(FILE *stream, long offset, int fromwhere);
  描述: 函数设置文件指针stream的位置。如果执行成功，stream将指向以fromwhere为基准，偏移offset个字     节的位置。如果执行失败(比如offset超过文件自身大小)，则不改变stream指向的位置。
  返回值: 成功，返回0，否则返回其他值。
  fseek position the file position pointer for the file referenced by stream to the byte location calculated by offset.

ftell

函数 ftell 用于得到文件位置指针当前位置相对于文件首的偏移字节数

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