C ++ FREAD jibberish [英] c++ fread jibberish

问题描述

出于某种原因，我的缓冲区越来越充满jibberish，我不知道为什么。我甚至检查我的文件与十六进制编辑器来验证我的角色保存在2字节的UNI code格式。我不知道什么是错的。

[在打开文件]

  fseek的（_file_pointer，0，SEEK_END）;
这 - ＆GT; _length = FTELL（这个 - ＆GT; _file_pointer）/的sizeof（CHR）;
 

[主]

  //还有一个原因，我只是
//不包括code，告诉为什么
wchar_t的类型定义CHR;
CHR *缓冲区=（CHR *）malloc的（F＆GT; _length *的sizeof（CHR））;
如果（缓冲== NULL）回报;
memset的（缓冲液，0，F-＆GT; _length * sizeof的 - （CHR））;
F-＆GT; Read_Whole_File（缓冲液）;
F-＆GT;关闭（）;
免费（缓冲）;
 

[Read_Whole_File]

 无效Read_Whole_File（CHR *缓冲区）
{
    如果（缓冲== NULL）
    {
    这 - ＆GT; _IsError = TRUE;
    返回;
    }
    fseek的（这 - ＆GT; _file_pointer，0，SEEK_SET）;
    一个诠释的sizeof =（缓冲[0]）; //用于调试目的
    FREAD（缓冲，一，_length，这 - ＆GT; _file_pointer）;
}
 

解决方案

假设你的错误处理（你说你在这里略）是合理的，我看到两个原因，可能是问题的原因：

1. 首先， wchar_t的不一定是2个字节，它的大小是实现定义。例如在Linux上它是最有可能的4个字节。




2. 这可能是因为该文件是UTF-16BE（大端），和你在一个小端平台上运行，因此 wchar_t的值在您的缓冲区有自己的字节顺序调换。

或者，它可以是两者。请了一些关于你的平台，以十六进制（如果可能）。

样本文件的细节和几个字节更新你的问题

的在任何情况下，你不应该做出有关使用UNI code文件打交道时，标准的C尺寸或C ++类型的任何假设。的

例如，如果你想读UTF16-BE，使用C99 uint16_t 键入（或有保证的同等类型为16位），和交换字节顺序您输入的取决于你的平台字节序和文件字节序。您可以使用字节顺序标记检测文件字节序，如果它是present在文件中。

另外，使用第三部分统一code库，如 ICU 。这需要所有的平台特定的细节关怀，并会为你节省很多时间调试的一个相当大的项目。

For some reason my buffer is getting filled with jibberish, and I'm not sure why. I even checked my file with a hex editor to verify that my characters are saved in a 2 byte unicode format. I'm not sure what's wrong.

[on file open]

fseek(_file_pointer, 0, SEEK_END);
this->_length = ftell(this->_file_pointer) / sizeof(chr);

[Main]

//there is a reason for this, I just 
//didn't include the code that tells why
typedef wchar_t chr;
chr *buffer = (chr*)malloc(f->_length*sizeof(chr));
if(buffer == NULL)return;
memset(buffer,0,f->_length*sizeof(chr));
f->Read_Whole_File(buffer);
f->Close();
free(buffer);

[Read_Whole_File]

void Read_Whole_File(chr *buffer)
{
    if(buffer == NULL)
    {
    	this->_IsError = true;
    	return;
    }
    fseek(this->_file_pointer, 0, SEEK_SET);
    int a = sizeof(buffer[0]);//for debugging purposes	
    fread(buffer, a, _length, this->_file_pointer);	
}

解决方案

Assuming your error handling (that you said you've omitted here) is sound, I see two reasons that may be the cause of the problem:

1. First of all, wchar_t may not necessarily be 2 bytes, its size is implementation defined. For example on Linux it's most likely 4 bytes.

2. It may be that the file is UTF-16BE (big-endian), and you are running on a little-endian platform, so the wchar_t values in your buffer have their byte order swapped.

Or, it may be both. Please update your question with some details about your platform and a few bytes from the sample file in hex (if possible).

In any case, you should not make any assumptions about sizes of standard C or C++ types when dealing with Unicode files.

For example, If you want to read UTF16-BE, use C99 uint16_t type (or an equivalent type that's guaranteed to be 16-bit), and swap byte order of your input depending on your platform endian-ness and file endian-ness. You can detect file endian-ness using a byte order mark if it's present in the file.

Alternatively, use a third-part Unicode library, like ICU. It takes care of all platform-specific details and will save you a lot of time debugging in a sizable project.

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