Question

有没有办法从文件中读取特定字节？

例如，我有以下代码来读取文件的所有字节

byte[] test = File.ReadAllBytes(file);

我想读取偏移量50到偏移量60的字节并将它们放在一个数组中。

Answer 1

创建一个BinaryReader，从字节50开始读取10个字节：

byte[] test = new byte[10];
using (BinaryReader reader = new BinaryReader(new FileStream(file, FileMode.Open)))
{
    reader.BaseStream.Seek(50, SeekOrigin.Begin);
    reader.Read(test, 0, 10);
}

Answer 2

这应该这样做

var data = new byte[10];
int actualRead;

using (FileStream fs = new FileStream("c:\\MyFile.bin", FileMode.Open)) {
    fs.Position = 50;
    actualRead = 0;
    do {
        actualRead += fs.Read(data, actualRead, 10-actualRead);
    } while (actualRead != 10 && fs.Position < fs.Length);
}

完成后，data将在文件的偏移量50和60之间包含10个字节，actualRead将包含0到10之间的数字，表示实际读取了多少字节（这是有意义的当文件至少有50个但小于60个字节时）。如果文件少于50个字节，您将看到EndOfStreamException。

Answer 3

LINQ版本：

byte[] test = File.ReadAllBytes(file).Skip(50).Take(10).ToArray();

Answer 4

你需要：

寻找您想要的数据
重复调用Read，检查返回值，直到获得所需的所有数据

例如：

public static byte[] ReadBytes(string path, int offset, int count) {
    using(var file = File.OpenRead(path)) {
        file.Position = offset;
        offset = 0;
        byte[] buffer = new byte[count];
        int read;
        while(count > 0  &&  (read = file.Read(buffer, offset, count)) > 0 )
        {
            offset += read;
            count -= read;
        }
        if(count < 0) throw new EndOfStreamException();
        return buffer;     
    }
}

Answer 5

using System.IO;

public static byte[] ReadFile(string filePath)
{
    byte[] buffer;
    FileStream fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read);
    try
    {
        buffer = new byte[length];            // create buffer
        fileStream.Read(buffer, 50, 10);
     }
     finally
     {
         fileStream.Close();
     }
     return buffer;
 }

Answer 6

您可以使用filestream然后调用read

string pathSource = @"c:\tests\source.txt";

using (FileStream fsSource = new FileStream(pathSource,
    FileMode.Open, FileAccess.Read))
{

    // Read the source file into a byte array.
    byte[] bytes = new byte[fsSource.Length];
    int numBytesToRead = 10;
    int numBytesRead = 50;
    // Read may return anything from 0 to numBytesToRead.
    int n = fsSource.Read(bytes, numBytesRead, numBytesToRead);
}

Check this example MSDN

Answer 7

byte[] a = new byte[60];
byte[] b = new byte[10];
Array.Copy( a ,50, b , 0 , 10 );

c＃ - 读取文件的特定字节

7 个答案: