在PHP中读取文件的一部分时的多字节指针 [英] Multibyte pointer when reading part of a file in PHP

问题描述

我使用PHP.

下面的函数加载一个大的多字节部分，输入一个单独的CSV文件，并在数组中返回pointer(结束位置)和content.使用pointer，我以后可以再次运行.它的工作原理:

The function below loads part of a big multibyte enter separated CSV file and return a pointer (the end position) and the content in an array. With the pointer I can later do another run. It works:

function part($path, $offset, $rows) {
    $buffer = array();
    $buffer['content'] = '';
    $buffer['pointer'] = array();
    $handle = fopen($path, "r");
    fseek($handle, $offset);
    if( $handle ) {
        for( $i = 0; $i < $rows; $i++ ) {
            $buffer['content'] .= fgets($handle);
            $buffer['pointer'] = mb_strlen($buffer['content']);
        }
    }
    fclose($handle);
    return($buffer);
}

// Buffer first part
$buffer = part($path_to_file, 0, 100);

// Buffer second part
$buffer = part($path_to_file, $buffer['pointer'], 100);

print_r($buffer);

如果我将$buffer['pointer']行更改为:

If I change the $buffer['pointer'] line to:

$buffer['pointer'] = mb_strlen($buffer['content'], "UTF-8");

...它不再起作用...我知道当我使用UTF-8而不是默认值时，它将使用不同的编码，但是为什么它不能与UTF-8一起使用?

...it does not work anymore... I understand that it uses the different encoding when I use UTF-8 instead of the default, but why doesn't it work with UTF-8?

UTF-8是否应与外来字符兼容?

因为当我在不使用"UTF-8"的情况下使用上述功能时，我想我可以在不使用UTF-8的情况下使用它.

Because the function above works when I use it without "UTF-8" I guess I could just use it without UTF-8.

我仍然担心在某些情况下它会给出错误的指针?

是否有更安全的方法来获取正确的指针?

执行此操作时，我得到UTF-8:

When I do this I get UTF-8:

echo mb_detect_encoding($buffer['content']);

推荐答案

这与UTF-8无关.文件系统功能(如fseek()，fread()等)对单个字节进行操作.他们根本不关心编码. (您可能正在写入/读取二进制数据).

This has little to do with UTF-8. Filesystem functions (like fseek(), fread(), etc.) operate on individual bytes. They don't care about the encoding at all. (You could be writing / reading binary data).

如果以后要存储指向fseek()的指针，请使用 ftell() 找出当前位置:

If you want to store a pointer to fseek() to at a later time, use ftell() to find out the current position:

$buffer['pointer'] = ftell($handle);

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