读取二进制和 txt 文件 - 一次 1 个字节

Question

我正在尝试编写一个读取 1 个字节的代码（理想目标是 n 个字节，但从 1 个字节开始 - 所以对于 n 个字节，如果它更容易，请建议）

下面是我尝试一次读取 1 个字节并以十六进制格式输出的代码。但是得到的只是一堆 FFFF

    FILE *fp;
    int stringlength,i;

    /* File can be txt or .bin */
    fp = fopen("TestFile3.txt", "r");
    if (fp == NULL) 
    {
        puts("Error: Input file cannot be read");
        return -1;
    }
    else 
    {
        size_t i, strlength, lengthOfFile,c;
        fseek(fp, 0, SEEK_END);
        lengthOfFile = ftell(fp);
        printf("length of File is ---- %d \n", lengthOfFile);
        while (lengthOfFile)
        {
            c = fgetc(fp);
            printf("%c", c);
            lengthOfFile--;
        }
        putchar('\n');

    }
    fclose(fp);
    return 0; 
}

Answer 1

您需要 fseek(fp, 0, SEEK_SET); 在 while 循环之前重置文件指针。

Answer 2

您还以 "text" 模式打开文件：

fp = fopen("TestFile3.txt", "r");

根据 C Standard, section 7.19.2:

A text stream is an ordered sequence of characters composed into lines, each line consisting of zero or more characters plus a terminating new-line character. Whether the last line requires a terminating new-line character is implementation-defined. Characters may have to be added, altered, or deleted on input and output to conform to differing conventions for representing text in the host environment. Thus, there need not be a one- to-one correspondence between the characters in a stream and those in the external representation.

使用 fseek()/ftell() 不会 return 从文本流中读取的字节数。

如果要读取文件大小的每个字节，您需要以二进制模式打开文件：

fp = fopen("TestFile3.txt", "rb");

最后，fseek()/ftell() 在二进制文件上的使用也不可靠，因为再次根据 C 标准，7.19.9.2:

A binary stream need not meaningfully support fseek calls with a whence value of SEEK_END

鉴于此，您也不能可靠地使用 fseek()/ftell() 来找出二进制文件有多大。是的，例子确实存在。

为了可靠地读取文件中的所有字节，@Weather Vane 在评论中发布了一种方法。

读取二进制和 txt 文件 - 一次 1 个字节

Read binary and txt File - 1 byte at a time

c

io

binaryfiles

file-handling

fgetc