美好的一天!我有这个软件来加密和解密文件。我是实时操作系统的新手,因为我通常对微 Controller 进行编程,前一段时间我正在对操作系统中的基本内容进行编程,包括这个项目。 Codeblocks gnu C 可移植编译器 IDE 告诉我没有错误,只有警告。但是当我执行代码时,它运行到某个点,然后给出程序意外停止并且命令提示符需要关闭的错误。
代码和警告在这里。从命令提示符处我得到:Process returned 255 0xFF
。也许变量定义需要超过 8 位。
#include <stdio.h>
#include <stdlib.h>
void main ()
{
char *f1;
char *f2;
printf ("Please enter file for encryption\n");
scanf ("%s", f1);
printf ("Please enter the name of the file after encryption\n");
scanf ("%s", f2);
Encrypt(f1, f2);
}
int Encrypt(char * FILENAME, char * NEW_FILENAME)
{ /********VARIABLE DEFINITION BLOCK*******/
printf("Encryption started\n");
FILE *inFile; //Declare inFile
FILE *outFile; //Declare outFile
char *key;
char *process;
char Byte;
char newByte;
/*int n;*/
/******USER INPUT BLOCK*******/
printf ("Please enter 'encryption or decryption'\n");
scanf ("%s", process);
printf ("Please enter the key\n");
scanf ("%s", key);
printf("Opening files\n");
/*int i=0;*/
/******FILE OPEN BLOCK********/
inFile = fopen(FILENAME,"rb");
outFile = fopen(NEW_FILENAME, "w");
/*****MAIN PROGRAM BLOCK******/
if(inFile == NULL) /* check if the input file is empy */
{
printf("Error: Can't Open inFile\n");
}
/* check if the output file is empty */
if(outFile == NULL)
{
printf("Error: Can't open outFile\n");
}
/* if both files are not empty output "Encrypting" and begin encryption */
else
{
printf("File Opened, Encrypting\n");
/* encrypting cycle */
while(1)
{
printf("."); /* loading symbol */
/* if the current byte is not the "End of file" byte and the process is encryption */
if(Byte!=EOF && process == 1)
{ /* Byte = function get char from "inFile" */
Byte = fgetc (inFile);
// printf("%d",Byte); /* the new byte = old byte plus 1 byte from the key */
newByte = Byte + key;
/* we put the new byte in the new already encrypted file */
fputc(newByte, outFile);
}
/* if the current file is not the "End of file" byte and the process is decryption */
if(Byte!=EOF && process == 2)
{ /* we read 1 byte with the function get char from the file recorded in the string (pointer) "inFile */
Byte = fgetc (inFile);
// printf("%d",Byte); /* 1 new byte, equals the old byte plus 1 byte from the key */
newByte = Byte + key;
/* we put the new byte with the function put char in the string (pointer) in which the output file is */
fputc(newByte, outFile);
}
/* if the two "while conditions" are not true we print "End of file" */
else
{
printf("End of File\n");
}
return 1;
}
}
}
构建输出:
||=== Build: Debug in Encryption-software (compiler: GNU GCC Compiler) ===|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|7|warning: return type of 'main' is not 'int' [-Wmain]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c||In function 'main':|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|17|warning: implicit declaration of function 'Encrypt' [-Wimplicit-function-declaration]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c||In function 'Encrypt':|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|65|warning: comparison between pointer and integer|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|69|warning: assignment makes integer from pointer without a cast|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|75|warning: comparison between pointer and integer|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|79|warning: assignment makes integer from pointer without a cast|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|92|warning: control reaches end of non-void function [-Wreturn-type]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|34|warning: 'process' is used uninitialized in this function [-Wuninitialized]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|36|warning: 'key' is used uninitialized in this function [-Wuninitialized]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|65|warning: 'Byte' may be used uninitialized in this function [-Wmaybe-uninitialized]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c||In function 'main':|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|13|warning: 'f1' is used uninitialized in this function [-Wuninitialized]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|15|warning: 'f2' is used uninitialized in this function [-Wuninitialized]|
||=== Build finished: 0 error(s), 12 warning(s) (0 minute(s), 1 second(s)) ===|
最佳答案
首先,让我们解决这些警告。
一些警告是针对使用未初始化的变量的。其中每一个都涉及将 char *
传递给 scanf
。 scanf
的 %s
格式说明符需要一个指向字符数组的指针。相反,您传入的是一个不指向任何地方的指针。取消引用未初始化的指针会调用 undefined behavior ,在本例中表现为崩溃。
将这些变量声明为 char
数组,并为您期望的输入提供足够的空间。另外,向 %s
添加长度说明符,指定要读取的最大字符数。
整数/指针比较错误是由于您使用process
的方式造成的。该变量是一个 char *
,预期指向一个以 null 结尾的字符串,但您将它与一个没有意义的整数进行比较。
相反,请使用strcmp
函数将其与“加密”
或“解密”
进行比较。
“赋值从指针生成整数而不进行强制转换”是因为您尝试将 key
(它是一个 char *
)添加到 Byte
,这是一个 char
。您可能想要索引 key
以从中获取特定字符,即 key[1]
。您还需要为当前键索引设置一个单独的计数器,并且当它大于或等于键的长度时,您需要将其重置为 0。
第一次进入 while
循环时,Byte
尚未设置,但您仍然将其与 EOF
进行比较。当您读取下一个字节时,您还会覆盖正在比较的 Byte
值,但随后您不会检查它是否为 EOF
。
您需要将 Byte
和 newByte
的类型更改为 int
,因为这是 fgetc
返回的内容。 EOF
值通常超出 char
的范围,因此除非更改类型,否则您永远找不到它。您还应该将读取和比较作为循环条件的一部分来执行,而不是使用 while(1)
并从循环体中删除读取。
隐式声明警告是因为您在定义或声明它之前调用了Encrypt
函数。结果,创建了 int Encrypt()
的隐式声明(即采用未知数量的参数并返回 int
的函数)。这恰好与它的定义方式一致,但仍然不匹配。
要么在 main
之前添加此函数的声明,要么将整个函数移到 main
之前。
除了警告之外,return 1
语句在 while
循环的底部执行,因此循环在退出之前仅执行一次迭代。上述测试条件中 Byte
值的建议应该可以解决这个问题。
您的解密当前与加密的操作相同。您可能想在这里进行减法而不是加法。在这两种情况下,您还需要检查是否有环绕。因此,如果加密值大于255,则减去256。解密时类似,如果值小于0,则加256。
应用这些修复后,您的代码应如下所示:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// declare function before it's called
void Encrypt(char * FILENAME, char * NEW_FILENAME);
int main ()
{
char f1[100]; // array big enough to hold expected input
char f2[100]; // array big enough to hold expected input
printf ("Please enter file for encryption\n");
scanf ("%99s", f1); // set max characters to read to prevent buffer overflow
printf ("Please enter the name of the file after encryption\n");
scanf ("%99s", f2);
Encrypt(f1, f2);
return 0;
}
void Encrypt(char * FILENAME, char * NEW_FILENAME)
{
printf("Encryption started\n");
FILE *inFile;
FILE *outFile;
char key[50]; // array big enough to hold expected input
char process[50]; // array big enough to hold expected input
int keylen, keyidx;
int Byte; // fgetc returns int, so use an int
int newByte;
printf ("Please enter 'encryption or decryption'\n");
scanf ("%49s", process);
printf ("Please enter the key\n");
scanf ("%49s", key);
keylen = strlen(key);
keyidx = 0; // starting index into key
printf("Opening files\n");
inFile = fopen(FILENAME,"rb");
outFile = fopen(NEW_FILENAME, "w");
if(inFile == NULL)
{
printf("Error: Can't Open inFile\n");
}
else if(outFile == NULL)
{
printf("Error: Can't open outFile\n");
}
else
{
printf("File Opened, Encrypting\n");
while((Byte = fgetc(inFile)) != EOF) // read a byte, check if EOF
{
if (!strcmp(process,"encryption"))
{
newByte = Byte + key[keyidx]; // use key index
if (newByte > 255) newByte -= 256; // check for overflow
}
else if (!strcmp(process,"decryption"))
{
newByte = Byte - key[keyidx];
if (newByte < 0) newByte += 256;
}
else
{
newByte = Byte;
}
fputc(newByte, outFile);
keyidx++;
// loop to the start of the key if needed
if (keyidx >= keylen) keyidx = 0;
}
}
if (inFile != null) fclose(inFile); // close your files when you're done
if (outFile != null) fclose(outFile);
}
关于c - 字节到字节加密 "C"程序逻辑错误,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/42818653/