в 15:31, 26 мая 2010

2010-05-26T15:31:53Z

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2010-05-26T12:20:27Z

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==Binary File Reading through FileStream==

<source lang="csharp">using System;
using System.Collections.Generic;
using System.ruponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.IO;
public class MainClass {
public static void Main() {
int nCols = 16;
FileStream inStream = new FileStream("c:\\a.txt", FileMode.Open, FileAccess.Read);
long nBytesToRead = inStream.Length;
if (nBytesToRead > 65536 / 4)
nBytesToRead = 65536 / 4;
int nLines = (int)(nBytesToRead / nCols) + 1;
string[] lines = new string[nLines];
int nBytesRead = 0;
for (int i = 0; i < nLines; i++) {
StringBuilder nextLine = new StringBuilder();
nextLine.Capacity = 4 * nCols;
for (int j = 0; j < nCols; j++) {
int nextByte = inStream.ReadByte();
nBytesRead++;
if (nextByte < 0 || nBytesRead > 65536)
break;
char nextChar = (char)nextByte;
if (nextChar < 16)
nextLine.Append(" x0" + string.Format("{0,1:X}", (int)nextChar));
else if
(char.IsLetterOrDigit(nextChar) || char.IsPunctuation(nextChar))
nextLine.Append(" " + nextChar + " ");
else
nextLine.Append(" x" + string.Format("{0,2:X}", (int)nextChar));
}
}
inStream.Close();

}
}</source>

==Demonstrate random access file==

<source lang="csharp">using System;
using System.IO;

class MainClass {
public static void Main() {
FileStream f;
char ch;

try {
f = new FileStream("random.dat", FileMode.Create);
}
catch(IOException exc) {
Console.WriteLine(exc.Message);
return ;
}

// Write the alphabet.
for(int i=0; i < 26; i++) {
try {
f.WriteByte((byte)("A"+i));
}
catch(IOException exc) {
Console.WriteLine(exc.Message);
return ;
}
}

try {
f.Seek(0, SeekOrigin.Begin); // seek to first byte
ch = (char) f.ReadByte();
Console.WriteLine("First value is " + ch);

f.Seek(1, SeekOrigin.Begin); // seek to second byte
ch = (char) f.ReadByte();
Console.WriteLine("Second value is " + ch);

f.Seek(4, SeekOrigin.Begin); // seek to 5th byte
ch = (char) f.ReadByte();
Console.WriteLine("Fifth value is " + ch);

Console.WriteLine();

}
catch(IOException exc) {
Console.WriteLine(exc.Message);
}

Console.WriteLine();
f.Close();
}
}</source>
<pre class=codeResult>First value is A
Second value is B
Fifth value is E</pre>

==Is a stream seekable==

<source lang="csharp">using System;
using System.IO;
public class MainClass {
public static void Main() {
byte[] buf2 = new byte[] { 97, 112, 112, 108, 101, 115, 97, 117, 99, 101 };
FileStream s = new FileStream("Foo.txt", FileMode.Open);
Console.WriteLine("Length: {0}, Position: {1}", s.Length, s.Position);
if (s.CanSeek) {
s.Seek(13, SeekOrigin.Begin);
Console.WriteLine(
"Position: {0}", s.Position);
s.Write(buf2, 0, buf2.Length);
}
}
}</source>

==Move file pointer to beginning of file==

<source lang="csharp">using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
class Program
{
static void Main(string[] args)
{
FileStream aFile = new FileStream("Temp.txt", FileMode.Create);
char[] charData = "this is a test.".ToCharArray();
byte[] byData = new byte[charData.Length];
Encoder e = Encoding.UTF8.GetEncoder();
e.GetBytes(charData, 0, charData.Length, byData, 0, true);
// Move file pointer to beginning of file.
aFile.Seek(0, SeekOrigin.Begin);
aFile.Write(byData, 0, byData.Length);
}
}</source>

==Open a file with exception handling==

<source lang="csharp">FileStream fin;

try {
fin = new FileStream("test.dat", FileMode.Open);
}
catch(FileNotFoundException exc) {
Console.WriteLine(exc.Message);
return;
}
catch {
Console.WriteLine("Cannot open file.");
return;
}</source>

==Open an existing file==

<source lang="csharp">using System;
using System.IO;
public class MainClass
{
static void Main(string[] args)
{
FileInfo MyFile = new FileInfo(@"c:\Testing.txt");
FileStream MyStream;
MyStream = MyFile.Open(FileMode.Open, FileAccess.Read, FileShare.None);
}
}</source>

==Read every other value using FileSeek==

<source lang="csharp">using System;
using System.IO;

class MainClass {
public static void Main() {
FileStream f;
char ch;

try {
f = new FileStream("random.dat", FileMode.Create);
}
catch(IOException exc) {
Console.WriteLine(exc.Message);
return ;
}

// Write the alphabet.
for(int i=0; i < 26; i++) {
try {
f.WriteByte((byte)("A"+i));
}
catch(IOException exc) {
Console.WriteLine(exc.Message);
return ;
}
}

try {
Console.WriteLine("Here is every other value: ");
for(int i=0; i < 26; i += 2) {
f.Seek(i, SeekOrigin.Begin); // seek to ith double
ch = (char) f.ReadByte();
Console.Write(ch + " ");
}

}
catch(IOException exc) {
Console.WriteLine(exc.Message);
}

Console.WriteLine();
f.Close();
}
}</source>
<pre class=codeResult>Here is every other value:
A C E G I K M O Q S U W Y</pre>

==Read file stream as an array of bytes==

<source lang="csharp">using System;
using System.IO;
public class MainClass
{
static void Main(string[] args)
{
FileStream MyFileStream1 = new FileStream(@"c:\Testing.txt", FileMode.Create);
int NumberOfBytes = 200;
byte[] MyByteArray = new Byte[NumberOfBytes];
int BytesRead = MyFileStream1.Read(MyByteArray, 0, NumberOfBytes);

MyFileStream1.Close();
}
}</source>

==Read file stream on a per byte basis==

<source lang="csharp">using System;
using System.IO;
public class MainClass
{
static void Main(string[] args)
{
FileStream MyFileStream1 = new FileStream(@"c:\Testing.txt", FileMode.Create);

int MyBytes = MyFileStream1.ReadByte();

MyFileStream1.Close();
}
}</source>

==Reset internal position for a FileStream==

<source lang="csharp">using System;
using System.IO;
public class MainClass
{
public static int Main(string[] args)
{
FileInfo f = new FileInfo(@"C:\test.txt");
FileStream s = f.Open(FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);
for(int i = 0; i < 256; i++)
{
s.WriteByte((byte)i);
}
// Reset internal position.
s.Position = 0;
for(int i = 0; i < 256; i++)
{
Console.Write(s.ReadByte());
}
s.Close();
f.Delete();
return 0;
}
}</source>

==Text File Reading with FileStream==

<source lang="csharp">using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
class Program
{
static void Main(string[] args)
{
byte[] byData = new byte[200];
char[] charData = new Char[200];
FileStream aFile = new FileStream("Program.cs", FileMode.Open);
aFile.Seek(113, SeekOrigin.Begin);
aFile.Read(byData, 0, 200);
Decoder d = Encoding.UTF8.GetDecoder();
d.GetChars(byData, 0, byData.Length, charData, 0);
Console.WriteLine(charData);
}
}</source>

==The FileMode and FileAccess==

Value
Description
FileMode.Append
append to the end of file.
FileMode.Create
create a new output file. Any preexisting file by the same name will be destroyed.
FileMode.CreateNew
create a new output file. The file must not already exist.
FileMode.Open
open a preexisting file.
FileMode.OpenOrCreate
open a file if it exists, or create the file if it does not already exist.
FileMode.Truncate
open a preexisting file, but reduce its length to zero.
<p>If you want to restrict access to just reading or just writing, use this constructor:</p>

<source lang="csharp">FileStream(string filename, FileMode mode, FileAccess how)</source>

==Use FileStream to read a file byte by byte==

<source lang="csharp">using System;
using System.Windows.Forms;
using System.IO;
class MainClass
{
public static void Main()
{
OpenFileDialog dlgOpen = new OpenFileDialog();
dlgOpen.Title="Select file to back up";
if (dlgOpen.ShowDialog() == DialogResult.OK)
{
FileStream inStream = File.OpenRead(dlgOpen.FileName);
FileStream outStream = File.OpenWrite(dlgOpen.FileName + ".bak");
int b;
while ((b = inStream.ReadByte()) > -1)
outStream.WriteByte( (byte) b);
outStream.Flush();
outStream.Close();
inStream.Close();
}
}
}</source>

==Use FileStream to read a file selected from OpenFileDialog==

<source lang="csharp">using System;
using System.Windows.Forms;
using System.IO;
class MainClass
{
public static void Main()
{
OpenFileDialog dlgOpen = new OpenFileDialog();
dlgOpen.Title="Select file to back up";
if (dlgOpen.ShowDialog() == DialogResult.OK)
{
FileStream inStream = File.OpenRead(dlgOpen.FileName);
FileStream outStream = File.OpenWrite(dlgOpen.FileName + ".bak");
int b;
while ((b = inStream.ReadByte()) > -1)
outStream.WriteByte( (byte) b);
outStream.Flush();
outStream.Close();
inStream.Close();
}
}
}</source>

==Use FileStream to write/read a file byte by byte==

<source lang="csharp">using System;
using System.Windows.Forms;
using System.IO;
class MainClass
{
public static void Main()
{
OpenFileDialog dlgOpen = new OpenFileDialog();
dlgOpen.Title="Select file to back up";
if (dlgOpen.ShowDialog() == DialogResult.OK)
{
FileStream inStream = File.OpenRead(dlgOpen.FileName);
FileStream outStream = File.OpenWrite(dlgOpen.FileName + ".bak");
int b;
while ((b = inStream.ReadByte()) > -1)
outStream.WriteByte( (byte) b);
outStream.Flush();
outStream.Close();
inStream.Close();
}
}
}</source>

==using statement and FileStream==

<source lang="csharp">using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
class Program
{
static void Main(string[] args)
{
using (FileStream fStream = File.Open(@"C:\myMessage.dat",FileMode.Create))
{
string msg = "Hello!";
byte[] msgAsByteArray = Encoding.Default.GetBytes(msg);
fStream.Write(msgAsByteArray, 0, msgAsByteArray.Length);
fStream.Position = 0;
byte[] bytesFromFile = new byte[msgAsByteArray.Length];
for (int i = 0; i < msgAsByteArray.Length; i++)
{
bytesFromFile[i] = (byte)fStream.ReadByte();
Console.Write(bytesFromFile[i]);
}
Console.WriteLine(Encoding.Default.GetString(bytesFromFile));
}
}
}</source>

==Write byte array with FileStream==

<source lang="csharp">using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
class Program
{
static void Main(string[] args)
{
FileStream aFile = new FileStream("Temp.txt", FileMode.Create);
char[] charData = "this is a test.".ToCharArray();
byte[] byData = new byte[charData.Length];
Encoder e = Encoding.UTF8.GetEncoder();
e.GetBytes(charData, 0, charData.Length, byData, 0, true);
// Move file pointer to beginning of file.
aFile.Seek(0, SeekOrigin.Begin);
aFile.Write(byData, 0, byData.Length);
}
}</source>

==Write data to file through FileStream per byte==

<source lang="csharp">using System;
using System.IO;
public class MainClass
{
static void Main(string[] args)
{
FileStream MyFileStream1 = new FileStream(@"c:\Testing.txt", FileMode.Create);
byte MyWriteByte = 100;
MyFileStream1.WriteByte(MyWriteByte);

MyFileStream1.Close();
}
}</source>

==Write data to file through FileStream via an array==

<source lang="csharp">using System;
using System.IO;
public class MainClass
{
static void Main(string[] args)
{
FileStream MyFileStream1 = new FileStream(@"c:\Testing.txt", FileMode.Create);
int NumberOfBytesToWrite = 256;
byte[] MyWriteByteArray = new Byte[NumberOfBytesToWrite];
for (int i = 0; i < 256; i++)
{
MyWriteByteArray[i] = (byte)i;
i++;
}
MyFileStream1.Write(MyWriteByteArray, 0, NumberOfBytesToWrite);

MyFileStream1.Close();
}
}</source>

==Write/read bytes using FileStream==

<source lang="csharp">using System;
using System.IO;
public class MainClass
{
public static int Main(string[] args)
{
FileStream myFStream = new FileStream("test.dat", FileMode.OpenOrCreate, FileAccess.ReadWrite);

for(int i = 0; i < 256; i++)
myFStream.WriteByte((byte)i);
myFStream.Position = 0;
for(int i = 0; i < 256; i++)
Console.Write(myFStream.ReadByte());
Console.WriteLine();
myFStream.Close();
return 0;
}
}</source>
<pre class=codeResult>0123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354
5556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991001011021
0310410510610710810911011111211311411511611711811912012112212312412512612712812913013113213313413513
6137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169
1701711721731741751761771781791801811821831841851861871881891901911921931941951961971981992002012022
0320420520620720820921021121221321421521621721821922022122222322422522622722822923023123223323423523
6237238239240241242243244245246247248249250251252253254255</pre>

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