在Lua中读取整个文件 [英] Reading whole files in Lua

问题描述

我正在尝试读取完整的mp3文件，以便读出id3标签。就在那时我注意到那个文件：read（* a）显然不会读取整个文件而是一小部分。所以我尝试构建某种解决方法以获取整个文件的内容：

I am trying to read a full mp3 file in order to read out the id3 tags. That's when I noticed that file:read("*a") apparently does not read the full file but rather a small part. So I tried to build some kind of workaround in order to get the content of the whole file:

function readAll(file)
    local f = io.open(file, "r")
    local content = ""
    local length = 0

    while f:read(0) ~= "" do
        local current = f:read("*all")

        print(#current, length)
        length = length + #current

        content = content .. current
    end

    return content
end

对于我的测试文件，

，这表明执行了256次读取操作，总共读取了~113kB（整个文件大约为7MB）。虽然这应该足以读取大多数id3标签，但我想知道为什么Lua会以这种方式运行（特别是因为它在读取大型基于文本的文件时不会出现这种情况，例如* .oj或* .ase）。有没有对这种行为的解释，或者可能是一个可靠地读取整个文件的解决方案？

for my testfile, this shows that 256 reading operations are performed, reading a total of ~113kB (the whole file is ~7MB). Though this should be enough to read most id3 tags, I wonder why Lua behaves in this way (especially because it does not when reading large textbased files such as *.oj or *.ase). Is there any explanation for this behaviour or maybe a solution to reliably read the whole file?

推荐答案

我必须遗漏一些东西，但我无法理解为什么需要循环。这应该有效（但是如果无法打开文件，你最好添加错误处理）：

I must be missing something but I fail to see why a loop is needed. This should work (but you'd better add error handling in case the file cannot be opened):

function readAll(file)
    local f = assert(io.open(file, "rb"))
    local content = f:read("*all")
    f:close()
    return content
end

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