文件大小格式提供者
时间：2020-03-06 14:40:40 来源:igfitidea点击:
有没有简单的方法来创建使用IFormatProvider的类，该类写出用户友好的文件大小？
public static string GetFileSizeString(string filePath)
{
FileInfo info = new FileInfo(@"c:\windows\notepad.exe");
long size = info.Length;
string sizeString = size.ToString(FileSizeFormatProvider); // This is where the class does its magic...
}
它应导致字符串格式设置为" 2,5 MB"，" 3,9 GB"，" 670字节"等。
解决方案
我用这个，我从网上得到
public class FileSizeFormatProvider : IFormatProvider, ICustomFormatter
{
public object GetFormat(Type formatType)
{
if (formatType == typeof(ICustomFormatter)) return this;
return null;
}
private const string fileSizeFormat = "fs";
private const Decimal OneKiloByte = 1024M;
private const Decimal OneMegaByte = OneKiloByte * 1024M;
private const Decimal OneGigaByte = OneMegaByte * 1024M;
public string Format(string format, object arg, IFormatProvider formatProvider)
{
if (format == null || !format.StartsWith(fileSizeFormat))
{
return defaultFormat(format, arg, formatProvider);
}
if (arg is string)
{
return defaultFormat(format, arg, formatProvider);
}
Decimal size;
try
{
size = Convert.ToDecimal(arg);
}
catch (InvalidCastException)
{
return defaultFormat(format, arg, formatProvider);
}
string suffix;
if (size > OneGigaByte)
{
size /= OneGigaByte;
suffix = "GB";
}
else if (size > OneMegaByte)
{
size /= OneMegaByte;
suffix = "MB";
}
else if (size > OneKiloByte)
{
size /= OneKiloByte;
suffix = "kB";
}
else
{
suffix = " B";
}
string precision = format.Substring(2);
if (String.IsNullOrEmpty(precision)) precision = "2";
return String.Format("{0:N" + precision + "}{1}", size, suffix);
}
private static string defaultFormat(string format, object arg, IFormatProvider formatProvider)
{
IFormattable formattableArg = arg as IFormattable;
if (formattableArg != null)
{
return formattableArg.ToString(format, formatProvider);
}
return arg.ToString();
}
}
使用的一个例子是：
Console.WriteLine(String.Format(new FileSizeFormatProvider(), "File size: {0:fs}", 100));
Console.WriteLine(String.Format(new FileSizeFormatProvider(), "File size: {0:fs}", 10000));
感谢http://flimflan.com/blog/FileSizeFormatProvider.aspx
ToString()有问题，它期望实现IFormatProvider的NumberFormatInfo类型，但NumberFormatInfo类是密封的:(
如果我们使用的是C3.0，则可以使用扩展方法来获得所需的结果：
public static class ExtensionMethods
{
public static string ToFileSize(this long l)
{
return String.Format(new FileSizeFormatProvider(), "{0:fs}", l);
}
}
我们可以像这样使用它。
long l = 100000000; Console.WriteLine(l.ToFileSize());
希望这可以帮助。
好的，我不会将其包装为Format提供程序，而是要重新发明轮子，而是有一个Win32 api调用来根据我在各种应用程序中使用过很多次的提供的字节来格式化大小字符串。
[DllImport("Shlwapi.dll", CharSet = CharSet.Auto)]
public static extern long StrFormatByteSize( long fileSize, [MarshalAs(UnmanagedType.LPTStr)] StringBuilder buffer, int bufferSize );
因此，我想我们应该能够将使用该提供程序作为核心转换代码的提供程序组合在一起。
这是指向StrFormatByteSize的MSDN规范的链接。
我的代码...感谢Shaun Austin。
[DllImport("Shlwapi.dll", CharSet = CharSet.Auto)]
public static extern long StrFormatByteSize(long fileSize, [MarshalAs(UnmanagedType.LPTStr)] StringBuilder buffer, int bufferSize);
public void getFileInfo(string filename)
{
System.IO.FileInfo fileinfo = new FileInfo(filename);
this.FileName.Text = fileinfo.Name;
StringBuilder buffer = new StringBuilder();
StrFormatByteSize(fileinfo.Length, buffer, 100);
this.FileSize.Text = buffer.ToString();
}
我接受了Eduardo的回答，并将其与其他地方的类似示例进行了组合，以提供格式化的其他选项。
public class FileSizeFormatProvider : IFormatProvider, ICustomFormatter
{
public object GetFormat(Type formatType)
{
if (formatType == typeof(ICustomFormatter))
{
return this;
}
return null;
}
private const string fileSizeFormat = "FS";
private const string kiloByteFormat = "KB";
private const string megaByteFormat = "MB";
private const string gigaByteFormat = "GB";
private const string byteFormat = "B";
private const Decimal oneKiloByte = 1024M;
private const Decimal oneMegaByte = oneKiloByte * 1024M;
private const Decimal oneGigaByte = oneMegaByte * 1024M;
public string Format(string format, object arg, IFormatProvider formatProvider)
{
//
// Ensure the format provided is supported
//
if (String.IsNullOrEmpty(format) || !(format.StartsWith(fileSizeFormat, StringComparison.OrdinalIgnoreCase) ||
format.StartsWith(kiloByteFormat, StringComparison.OrdinalIgnoreCase) ||
format.StartsWith(megaByteFormat, StringComparison.OrdinalIgnoreCase) ||
format.StartsWith(gigaByteFormat, StringComparison.OrdinalIgnoreCase)))
{
return DefaultFormat(format, arg, formatProvider);
}
//
// Ensure the argument type is supported
//
if (!(arg is long || arg is decimal || arg is int))
{
return DefaultFormat(format, arg, formatProvider);
}
//
// Try and convert the argument to decimal
//
Decimal size;
try
{
size = Convert.ToDecimal(arg);
}
catch (InvalidCastException)
{
return DefaultFormat(format, arg, formatProvider);
}
//
// Determine the suffix to use and convert the argument to the requested size
//
string suffix;
switch (format.Substring(0, 2).ToUpper())
{
case kiloByteFormat:
size = size / oneKiloByte;
suffix = kiloByteFormat;
break;
case megaByteFormat:
size = size / oneMegaByte;
suffix = megaByteFormat;
break;
case gigaByteFormat:
size = size / oneGigaByte;
suffix = gigaByteFormat;
break;
case fileSizeFormat:
if (size > oneGigaByte)
{
size /= oneGigaByte;
suffix = gigaByteFormat;
}
else if (size > oneMegaByte)
{
size /= oneMegaByte;
suffix = megaByteFormat;
}
else if (size > oneKiloByte)
{
size /= oneKiloByte;
suffix = kiloByteFormat;
}
else
{
suffix = byteFormat;
}
break;
default:
suffix = byteFormat;
break;
}
//
// Determine the precision to use
//
string precision = format.Substring(2);
if (String.IsNullOrEmpty(precision))
{
precision = "2";
}
return String.Format("{0:N" + precision + "}{1}", size, suffix);
}
private static string DefaultFormat(string format, object arg, IFormatProvider formatProvider)
{
IFormattable formattableArg = arg as IFormattable;
if (formattableArg != null)
{
return formattableArg.ToString(format, formatProvider);
}
return arg.ToString();
}
}
现在我意识到我们实际上正在要求使用String.Format()的东西，我想我应该在发布;-)之前先阅读两次该问题
我不喜欢这种解决方案，在这种解决方案中，每次我从本文可以收集的内容中都必须显式传递格式提供程序，最好的方法是实现FileSize类型，实现IFormattable接口。
我继续并实现了一个支持此接口的结构，该结构可以从整数强制转换。在我自己的与文件相关的API中，我将让.FileSize属性返回一个FileSize实例。
这是代码：
using System.Globalization;
public struct FileSize : IFormattable
{
private ulong _value;
private const int DEFAULT_PRECISION = 2;
private static IList<string> Units;
static FileSize()
{
Units = new List<string>(){
"B", "KB", "MB", "GB", "TB"
};
}
public FileSize(ulong value)
{
_value = value;
}
public static explicit operator FileSize(ulong value)
{
return new FileSize(value);
}
override public string ToString()
{
return ToString(null, null);
}
public string ToString(string format)
{
return ToString(format, null);
}
public string ToString(string format, IFormatProvider formatProvider)
{
int precision;
if (String.IsNullOrEmpty(format))
return ToString(DEFAULT_PRECISION);
else if (int.TryParse(format, out precision))
return ToString(precision);
else
return _value.ToString(format, formatProvider);
}
/// <summary>
/// Formats the FileSize using the given number of decimals.
/// </summary>
public string ToString(int precision)
{
double pow = Math.Floor((_value > 0 ? Math.Log(_value) : 0) / Math.Log(1024));
pow = Math.Min(pow, Units.Count - 1);
double value = (double)_value / Math.Pow(1024, pow);
return value.ToString(pow == 0 ? "F0" : "F" + precision.ToString()) + " " + Units[(int)pow];
}
}
还有一个简单的单元测试，演示了其工作原理：
[Test]
public void CanUseFileSizeFormatProvider()
{
Assert.AreEqual(String.Format("{0}", (FileSize)128), "128 B");
Assert.AreEqual(String.Format("{0}", (FileSize)1024), "1.00 KB");
Assert.AreEqual(String.Format("{0:0}", (FileSize)10240), "10 KB");
Assert.AreEqual(String.Format("{0:1}", (FileSize)102400), "100.0 KB");
Assert.AreEqual(String.Format("{0}", (FileSize)1048576), "1.00 MB");
Assert.AreEqual(String.Format("{0:D}", (FileSize)123456), "123456");
// You can also manually invoke ToString(), optionally with the precision specified as an integer:
Assert.AreEqual(((FileSize)111111).ToString(2), "108.51 KB");
}
如我们所见，现在可以正确设置FileSize类型的格式，并且还可以指定小数位数，并在需要时应用常规数字格式。
我想我们可以更进一步，例如允许显式格式选择，例如" {0：KB}"强制以千字节为单位进行格式化。但是我要留在这里。
我还在下面留下我的第一篇文章，这两个人不想使用格式化API ...
剥皮猫的100种方法，但这是我为int类型添加扩展方法的方法：
public static class IntToBytesExtension
{
private const int PRECISION = 2;
private static IList<string> Units;
static IntToBytesExtension()
{
Units = new List<string>(){
"B", "KB", "MB", "GB", "TB"
};
}
/// <summary>
/// Formats the value as a filesize in bytes (KB, MB, etc.)
/// </summary>
/// <param name="bytes">This value.</param>
/// <returns>Filesize and quantifier formatted as a string.</returns>
public static string ToBytes(this int bytes)
{
double pow = Math.Floor((bytes>0 ? Math.Log(bytes) : 0) / Math.Log(1024));
pow = Math.Min(pow, Units.Count-1);
double value = (double)bytes / Math.Pow(1024, pow);
return value.ToString(pow==0 ? "F0" : "F" + PRECISION.ToString()) + " " + Units[(int)pow];
}
}
在程序集中具有此扩展名的情况下，要格式化文件大小，只需使用(1234567).ToBytes()之类的语句即可。
以下MbUnit测试准确地阐明了输出内容：
[Test]
public void CanFormatFileSizes()
{
Assert.AreEqual("128 B", (128).ToBytes());
Assert.AreEqual("1.00 KB", (1024).ToBytes());
Assert.AreEqual("10.00 KB", (10240).ToBytes());
Assert.AreEqual("100.00 KB", (102400).ToBytes());
Assert.AreEqual("1.00 MB", (1048576).ToBytes());
}
而且，我们可以轻松地将单位和精度更改为适合需求:-)
