c - 为什么unsigned char变量包含EOF？

Question

我开发了一种加密算法，它从 .txt 文件中逐字符获取文本并对其进行加密，然后将其写回另一个 .txt 文件。问题是当我读取加密文件时，像箭头这样的字符充当 EOF，并且我的循环在原始 EOF 之前终止。这是我的代码:

static void ECB_ENCRYPTION(void)
{
    uint8_t i = 0, j = 0, c, buf1[16]


    uint8_t plain_text[16];

    // File pointers for file operations.
    FILE *f, *f1;


    // Encrypts the file [plaintext.txt].
    f = fopen("plaintext.txt", "r");
    f1 = fopen("ciphertext.txt", "w");
    while(1)
    {
        i = 0;
        while(i < 16)
        {
            c = getc(f);
            if(feof(f))
            {
                break;
            }
            else
            {
                plain_text[i] = c;
                ++i;
            }
        }

        if(i != 16)
        {
            while(i < 16)
            {
                plain_text[i] = ' ';
                ++i;
            }
        }

        // Encrypts plain text.
        AES128_ENCRYPT(plain_text, buf1);

        i = 0;
        while(i < 16)
        {
            putc(buf1[i], f1);
            ++i;
        }

        if(feof(f))
            break;

    }

    fclose(f);
    fclose(f1);
}

static void ECB_DECRYPTION(void)
{

    uint8_t i = 0, j = 0, c, buf1[16];

    uint8_t cipher_text[16];

    // File pointers for file operations.
    FILE *f, *f1;

    // Encrypts the file [plaintext.txt].
    f = fopen("ciphertext.txt", "r");
    f1 = fopen("decryptedtext.txt", "w");
    while(1)
    {
        i = 0;
        while(i < 16)
        {
            c = getc(f);
            if(feof(f))
            {
                break;
            }
            else
            {
                cipher_text[i] = c;
                ++i;
            }
        }

        if(feof(f))
            break;

        // Decrypts cipher text.
        AES128_DECRYPT(cipher_text, buf1);

        i = 0;
        while(i < 16)
        {
            putc(buf1[i], f1);
            ++i;
        }

    }

    fclose(f);
    fclose(f1);
}

Answer 1

使用uint8_t c而不是int c混淆了真正的问题:以二进制模式与文本模式打开文件。 @Klas Lindbäck

int c会更好。还是OP使用uint8_t; c = getc(f); if(feof(f)) 几乎正确。发生读取错误时失败。

static void ECB_DECRYPTION(void) {
    uint8_t cipher_text[16];
    uint8_t buf1[16];

    FILE *f = fopen("ciphertext.txt", "rb");  // add 'b'
    assert(f);
    FILE *f1 = fopen("decryptedtext.txt", "wb"); // add 'b'
    assert(f1);
    while(1)
    {
        int c;
        for (unsigned i=0; i<16; i++) {
            c = getc(f);
            if (c == EOF) break;
            cipher_text[i] = (uint8_t) c;
        }

        if(c == EOF) break;  // exit loop on end-of-file or input error

        AES128_DECRYPT(cipher_text, buf1);

        for (unsigned i=0; i<16; i++) {
            putc(buf1[i], f1);
        }
    }

    fclose(f);
    fclose(f1);
}