块读错误 [英] block read error

问题描述

任何人都可以解释一下我为什么在下面的块中遇到I / O错误998？

 函数ReadBiggerFile：string; 
 var 
 greaterfile：文件的char; 
 BufArray：char的数组[1 ... 4096] //我们将一次读取4 KB 
 nrcit，i：integer; 
 sir，path：string; 
 begin 
 path：= ExtractFilePath（application.exename）; 
 assignfile（greaterfile，path +'asd.txt'）; 
重置（更大文件）; 
重复
 blockread（更大的文件，BufArray，SizeOf（BufArray），nrcit）; 
 for i：= 1 to nrcit do 
 begin 
 sir：= sir + BufArray [i]; 
 Form4.Memo1.Lines.Add（sir）; 
结束
 until（nrcit = 0）; 
 closefile（greaterfile）; 
 ReadBiggerFile：= sir; 
结束
  

解决方案

我想你错过了标签的问题，重新使用Delphi 2009+，而不是Delphi 7.我在标题栏中收到错误，尝试在Delphi 2010（unicode Delphi）上的确切代码。当你说：

  var greaterfile：Char的文件; 
  

您正在声明 greaterfile 一个记录文件，其中每个记录是一个 Char 。在Unicode Delphi这是2个字节。您稍后请求阅读 SizeOf（BufArray） 记录，而不是字节。也就是说，您要求4096 x 2 = 8192 记录。但是你的缓冲区只有4096个记录长，所以你会出现一个奇怪的错误。

我可以通过简单地替换 Char with AnsiChar ，因为 AnsiChar 的大小为$ $ c> 1 ，因此 SizeOf（）等于 Length（） p>

永久修复应该涉及从旧的Pascal风格的文件操作移到现代的 TStream 为基础。我不确定你正在试图获得什么，但是如果你只想获取一个字符串中的文件的内容，我可以建议这样的一个例子：

 函数ReadBiggerFile：AnsiString; 
 var 
 greaterfile：TFileStream; 
 begin 
 greaterfile：= TFileStream.Create（'C：\Users\Cosmin Prund\Downloads\AppWaveInstall201_385.exe'，fmOpenRead或fmShareDenyWrite）; 
 try 
 SetLength（Result，greaterfile.Size）; 
 greaterfile.Read（Result [1]，greaterfile.Size）; 
 finally greaterfile.Free; 
结束
结束
  

Can anybody please explain me why I am hitting 'I/O error 998' in the below block read?

function ReadBiggerFile: string;
var
  biggerfile: file of char;
  BufArray: array [1 .. 4096] of char; // we will read 4 KB at a time
  nrcit, i: integer;
  sir, path: string;
begin
  path := ExtractFilePath(application.exename);
  assignfile(biggerfile, path + 'asd.txt');
  reset(biggerfile);
  repeat
    blockread(biggerfile, BufArray, SizeOf(BufArray), nrcit);
    for i := 1 to nrcit do
    begin
      sir := sir + BufArray[i];
      Form4.Memo1.Lines.Add(sir);
    end;
  until (nrcit = 0);
  closefile(biggerfile);
  ReadBiggerFile := sir;
end;

解决方案

I think you miss-tagged the question and you're using Delphi 2009+, not Delphi 7. I got the error in the title bar trying your exact code on Delphi 2010 (unicode Delphi). When you say:

var biggerfile: file of Char;

You're declaring the biggerfile to be a file of "records", where each record is a Char. On Unicode Delphi that's 2 bytes. You later request to read SizeOf(BufArray) records, not bytes. That is, you request to 4096 x 2 = 8192 records. But your buffer is only 4096 records long, so you get a weird error.

I was able to fix your code by simply replacing Char with AnsiChar, since AnsiChar has a size of 1, hence the SizeOf() equals Length().

The permanent fix should involve moving from the very old Pascal-style file operations to something modern, TStream based. I'm not sure exactly what you're trying to obtain, but if you simply want to get the content of the file in a string, may I suggest something like this:

function ReadBiggerFile: AnsiString;
var
  biggerfile: TFileStream;
begin
  biggerfile := TFileStream.Create('C:\Users\Cosmin Prund\Downloads\AppWaveInstall201_385.exe', fmOpenRead or fmShareDenyWrite);
  try
    SetLength(Result, biggerfile.Size);
    biggerfile.Read(Result[1], biggerfile.Size);
  finally biggerfile.Free;
  end;
end;

这篇关于块读错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！