如何读取任意文件并“分段”处理它(即逐字节或其他块大小以获得最佳读取性能),而不将整个文件加载到内存中? 处理的示例是生成文件的MD5哈希,尽管答案适用于任何操作。
我想要拥有或编写此代码,但如果我可以获得现有的代码那就太好了。(c#)
这是一个读取文件的例子,每次以1KB为单位读取文件块,而不需要将整个文件内容加载到内存中:
const int chunkSize = 1024; // read the file by chunks of 1KB
using (var file = File.OpenRead("foo.dat"))
{
int bytesRead;
var buffer = new byte[chunkSize];
while ((bytesRead = file.Read(buffer, 0, buffer.Length)) > 0)
{
// TODO: Process bytesRead number of bytes from the buffer
// not the entire buffer as the size of the buffer is 1KB
// whereas the actual number of bytes that are read are
// stored in the bytesRead integer.
}
}
bytesRead
的长度,而不是整个buffer
的长度,例如fsFileStream.Write(buffer, 0, bytesRead)
。 - antikbdSystem.IO.FileStream
不会将文件加载到内存中。
该流可寻址,并且MD5哈希算法也不必将流(文件)加载到内存中。
请用文件路径替换file_path
。
byte[] hash = null;
using (var stream = new FileStream(file_path, FileMode.Open))
{
using (var md5 = new System.Security.Cryptography.MD5CryptoServiceProvider())
{
hash = md5.ComputeHash(stream);
}
}
在这里,你的MD5哈希将被存储在hash
变量中。
int fullfilesize = 0;// full size of file
int DefaultReadValue = 10485760; //read 10 mb at a time
int toRead = 10485760;
int position =0;
// int
// byte[] ByteReadFirst = new byte[10485760];
private void Button_Click(object sender, RoutedEventArgs e)
{
using (var fs = new FileStream(@"filepath", FileMode.Open, FileAccess.Read))
{
using (MemoryStream requestStream = new MemoryStream())
{
fs.Position = position;
if (fs.Position >= fullfilesize)
{
MessageBox.Show(" all done");
return;
}
System.Diagnostics.Debug.WriteLine("file position" + fs.Position);
if (fullfilesize-position < toRead)
{
toRead = fullfilesize - position;
MessageBox.Show("last time");
}
System.Diagnostics.Debug.WriteLine("toread" + toRead);
int bytesRead;
byte[] buffer = new byte[toRead];
int offset = 0;
position += toRead;
while (toRead > 0 && (bytesRead = fs.Read(buffer, offset, toRead)) > 0)
{
toRead -= bytesRead;
offset += bytesRead;
}
toRead = DefaultReadValue;
}
}
}
按照Darin的方法,此方式将读取10MB的数据块直到文件结束。
const int MAX_BUFFER = 1024;
byte[] Buffer = new byte[MAX_BUFFER];
int BytesRead;
using (System.IO.FileStream fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read))
while ((BytesRead = fileStream.Read(Buffer, 0, MAX_BUFFER)) != 0)
{
// Process this chunk starting from offset 0
// and continuing for bytesRead bytes!
}
const long numberOfBytesToReadPerChunk = 1000;//1KB
using (BinaryReader fileData = new BinaryReader(File.OpenRead(aFullFilePath))
while (fileData.BaseStream.Position - fileData.BaseStream.Length > 0)
DoSomethingWithAChunkOfBytes(fileData.ReadBytes(numberOfBytesToReadPerChunk));
BinaryReader.ReadBytes
)不需要跟踪已读取的字节数。您只需要知道长度和当前位置以进行 while 循环 - 这是流告诉您的。
System.IO.FileStream
不会将文件加载到内存中。” - Vercas