BinaryWriter.Seek(Int32, SeekOrigin) Méthode
Définition
Important
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Définit la position dans le flux actuel.
public:
virtual long Seek(int offset, System::IO::SeekOrigin origin);public virtual long Seek (int offset, System.IO.SeekOrigin origin);abstract member Seek : int * System.IO.SeekOrigin -> int64
override this.Seek : int * System.IO.SeekOrigin -> int64Public Overridable Function Seek (offset As Integer, origin As SeekOrigin) As LongParamètres
- offset
- Int32
Offset d'octet par rapport à origin.
- origin
- SeekOrigin
Champ de SeekOrigin indiquant le point de référence à partir duquel la nouvelle position doit être obtenue.
Retours
Position dans le flux actuel.
Exceptions
Le pointeur de fichier a été déplacé vers un emplacement non valide.
La valeur SeekOrigin n’est pas valide.
Exemples
L’exemple suivant écrit une série de valeurs d’octets dans un fichier. L’exemple utilise Seek pour se déplacer vers différents emplacements dans le fichier, puis écrit des octets de marqueur à l’aide de la Write méthode .
using namespace System;
using namespace System::IO;
using namespace System::Text;
public ref class BinReadWrite
{
public:
static void Main()
{
String^ testfile = "C:\\temp\\testfile.bin";
// create a test file using BinaryWriter
FileStream^ fs = File::Create(testfile);
UTF8Encoding^ utf8 = gcnew UTF8Encoding();
BinaryWriter^ bw = gcnew BinaryWriter(fs, utf8);
// write a series of bytes to the file, each time incrementing
// the value from 0 - 127
int pos;
for (pos = 0; pos < 128; pos++)
{
bw->Write((Byte)pos);
}
// reset the stream position for the next write pass
bw->Seek(0, SeekOrigin::Begin);
// write marks in file with the value of 255 going forward
for (pos = 0; pos < 120; pos += 8)
{
bw->Seek(7, SeekOrigin::Current);
bw->Write((Byte)255);
}
// reset the stream position for the next write pass
bw->Seek(0, SeekOrigin::End);
// write marks in file with the value of 254 going backward
for (pos = 128; pos > 6; pos -= 6)
{
bw->Seek(-6, SeekOrigin::Current);
bw->Write((Byte)254);
bw->Seek(-1, SeekOrigin::Current);
}
// now dump the contents of the file using the original file stream
fs->Seek(0, SeekOrigin::Begin);
array<Byte>^ rawbytes = gcnew array<Byte>(fs->Length);
fs->Read(rawbytes, 0, (int)fs->Length);
int i = 0;
for each (Byte b in rawbytes)
{
switch (b)
{
case 254:
{
Console::Write("-%- ");
}
break;
case 255:
{
Console::Write("-*- ");
}
break;
default:
{
Console::Write("{0:d3} ", b);
}
break;
}
i++;
if (i == 16)
{
Console::WriteLine();
i = 0;
}
}
fs->Close();
}
};
int main()
{
BinReadWrite::Main();
}
//The output from the program is this:
//
// 000 001 -%- 003 004 005 006 -*- -%- 009 010 011 012 013 -%- -*-
// 016 017 018 019 -%- 021 022 -*- 024 025 -%- 027 028 029 030 -*-
// -%- 033 034 035 036 037 -%- -*- 040 041 042 043 -%- 045 046 -*-
// 048 049 -%- 051 052 053 054 -*- -%- 057 058 059 060 061 -%- -*-
// 064 065 066 067 -%- 069 070 -*- 072 073 -%- 075 076 077 078 -*-
// -%- 081 082 083 084 085 -%- -*- 088 089 090 091 -%- 093 094 -*-
// 096 097 -%- 099 100 101 102 -*- -%- 105 106 107 108 109 -%- -*-
// 112 113 114 115 -%- 117 118 -*- 120 121 -%- 123 124 125 126 127
using System;
using System.IO;
using System.Text;
public class BinReadWrite3
{
public static void Main()
{
string testfile = @"C:\temp\testfile.bin";
// create a test file using BinaryWriter
FileStream fs = File.Create(testfile);
UTF8Encoding utf8 = new UTF8Encoding();
BinaryWriter bw = new BinaryWriter(fs, utf8);
// write a series of bytes to the file, each time incrementing
// the value from 0 - 127
int pos;
for (pos = 0; pos < 128; pos++)
{
bw.Write((byte)pos);
}
// reset the stream position for the next write pass
bw.Seek(0, SeekOrigin.Begin);
// write marks in file with the value of 255 going forward
for (pos = 0; pos < 120; pos += 8)
{
bw.Seek(7, SeekOrigin.Current);
bw.Write((byte)255);
}
// reset the stream position for the next write pass
bw.Seek(0, SeekOrigin.End);
// write marks in file with the value of 254 going backward
for (pos = 128; pos > 6; pos -= 6)
{
bw.Seek(-6, SeekOrigin.Current);
bw.Write((byte)254);
bw.Seek(-1, SeekOrigin.Current);
}
// now dump the contents of the file using the original file stream
fs.Seek(0, SeekOrigin.Begin);
byte[] rawbytes = new byte[fs.Length];
fs.Read(rawbytes, 0, (int)fs.Length);
int i = 0;
foreach (byte b in rawbytes)
{
switch (b)
{
case 254:
{
Console.Write("-%- ");
}
break;
case 255:
{
Console.Write("-*- ");
}
break;
default:
{
Console.Write("{0:d3} ", b);
}
break;
}
i++;
if (i == 16)
{
Console.WriteLine();
i = 0;
}
}
fs.Close();
}
}
//The output from the program is this:
//
// 000 001 -%- 003 004 005 006 -*- -%- 009 010 011 012 013 -%- -*-
// 016 017 018 019 -%- 021 022 -*- 024 025 -%- 027 028 029 030 -*-
// -%- 033 034 035 036 037 -%- -*- 040 041 042 043 -%- 045 046 -*-
// 048 049 -%- 051 052 053 054 -*- -%- 057 058 059 060 061 -%- -*-
// 064 065 066 067 -%- 069 070 -*- 072 073 -%- 075 076 077 078 -*-
// -%- 081 082 083 084 085 -%- -*- 088 089 090 091 -%- 093 094 -*-
// 096 097 -%- 099 100 101 102 -*- -%- 105 106 107 108 109 -%- -*-
// 112 113 114 115 -%- 117 118 -*- 120 121 -%- 123 124 125 126 127
open System.IO
open System.Text
let testfile = @"C:\temp\testfile.bin"
// create a test file using BinaryWriter
let fs = File.Create testfile
let utf8 = UTF8Encoding()
let bw = new BinaryWriter(fs, utf8)
// write a series of bytes to the file, each time incrementing
// the value from 0 - 127
for pos = 0 to 127 do
bw.Write(byte pos)
// reset the stream position for the next write pass
bw.Seek(0, SeekOrigin.Begin) |> ignore
// write marks in file with the value of 255 going forward
for _ in 0..8..119 do
bw.Seek(7, SeekOrigin.Current) |> ignore
bw.Write(byte 255)
// reset the stream position for the next write pass
bw.Seek(0, SeekOrigin.End) |> ignore
// write marks in file with the value of 254 going backward
for _ in 128 .. -6 .. 6 do
bw.Seek(-6, SeekOrigin.Current) |> ignore
bw.Write(byte 254)
bw.Seek(-1, SeekOrigin.Current) |> ignore
// now dump the contents of the file using the original file stream
fs.Seek(0, SeekOrigin.Begin) |> ignore
let rawbytes = Array.zeroCreate<byte> (int fs.Length)
fs.Read(rawbytes, 0, int fs.Length) |> ignore
let mutable i = 0
for b in rawbytes do
match b with
| 254uy ->
printf "-%%- "
| 255uy ->
printf "-*- "
| _ ->
printf $"{b:d3} "
i <- i + 1
if i = 16 then
printfn ""
i <- 0
fs.Close()
//The output from the program is this:
//
// 000 001 -%- 003 004 005 006 -*- -%- 009 010 011 012 013 -%- -*-
// 016 017 018 019 -%- 021 022 -*- 024 025 -%- 027 028 029 030 -*-
// -%- 033 034 035 036 037 -%- -*- 040 041 042 043 -%- 045 046 -*-
// 048 049 -%- 051 052 053 054 -*- -%- 057 058 059 060 061 -%- -*-
// 064 065 066 067 -%- 069 070 -*- 072 073 -%- 075 076 077 078 -*-
// -%- 081 082 083 084 085 -%- -*- 088 089 090 091 -%- 093 094 -*-
// 096 097 -%- 099 100 101 102 -*- -%- 105 106 107 108 109 -%- -*-
// 112 113 114 115 -%- 117 118 -*- 120 121 -%- 123 124 125 126 127
Imports System.IO
Imports System.Text
Public Class BinReadWrite
Public Shared Sub Main()
Dim testfile As String = "C:\temp\testfile.bin"
' create a test file using BinaryWriter
Dim fs As FileStream = File.Create(testfile)
Dim utf8 As New UTF8Encoding()
Dim bw As New BinaryWriter(fs, utf8)
' write a series of bytes to the file, each time incrementing
' the value from 0 - 127
Dim pos As Integer
For pos = 0 to 127
bw.Write(CType(pos, Byte))
Next pos
' reset the stream position for the next write pass
bw.Seek(0, SeekOrigin.Begin)
' write marks in file with the value of 255 going forward
For pos = 0 To 119 Step 8
bw.Seek(7, SeekOrigin.Current)
bw.Write(CType(255, Byte))
Next pos
' reset the stream position for the next write pass
bw.Seek(0, SeekOrigin.End)
' write marks in file with the value of 254 going backward
For pos = 128 To 7 Step -6
bw.Seek(-6, SeekOrigin.Current)
bw.Write(CType(254, Byte))
bw.Seek(-1, SeekOrigin.Current)
Next pos
' now dump the contents of the file using the original file stream
fs.Seek(0, SeekOrigin.Begin)
Console.WriteLine("Length: {0:d}", fs.Length)
Dim rawbytes(fs.Length) As Byte
fs.Read(rawbytes, 0, fs.Length)
Console.WriteLine("Length: {0:d}", rawbytes.Length)
Dim i As Integer = 0
For Each b As Byte In rawbytes
Select b
Case 254
Console.Write("-%- ")
Case 255
Console.Write("-*- ")
Case Else
Console.Write("{0:d3} ", b)
End Select
i = i + 1
If i = 16 Then
Console.WriteLine()
i = 0
End If
Next b
fs.Close()
End Sub
End Class
' The output from the program is this:
'
' 000 001 -%- 003 004 005 006 -*- -%- 009 010 011 012 013 -%- -*-
' 016 017 018 019 -%- 021 022 -*- 024 025 -%- 027 028 029 030 -*-
' -%- 033 034 035 036 037 -%- -*- 040 041 042 043 -%- 045 046 -*-
' 048 049 -%- 051 052 053 054 -*- -%- 057 058 059 060 061 -%- -*-
' 064 065 066 067 -%- 069 070 -*- 072 073 -%- 075 076 077 078 -*-
' -%- 081 082 083 084 085 -%- -*- 088 089 090 091 -%- 093 094 -*-
' 096 097 -%- 099 100 101 102 -*- -%- 105 106 107 108 109 -%- -*-
' 112 113 114 115 -%- 117 118 -*- 120 121 -%- 123 124 125 126 127
Remarques
Pour obtenir la liste des tâches d’E/S courantes, consultez Tâches courantes d’E/S.
S’applique à
Voir aussi
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