How do I copy the contents of one stream to another

Question

What is the best way to copy the contents of one stream to another  Is there a standard utility method for this

User · Answer

if you want a procdure to copy a stream to other the one that nick posted is fine but it is missing the position reset, it should be

public static void CopyStream(Stream input, Stream output)
{
    byte[] buffer = new byte[32768];
    long TempPos = input.Position;
    while (true)    
    {
        int read = input.Read (buffer, 0, buffer.Length);
        if (read <= 0)
            return;
        output.Write (buffer, 0, read);
    }
    input.Position = TempPos;// or you make Position = 0 to set it at the start
}

but if it is in runtime not using a procedure you shpuld use memory stream

Stream output = new MemoryStream();
byte[] buffer = new byte[32768]; // or you specify the size you want of your buffer
long TempPos = input.Position;
while (true)    
{
    int read = input.Read (buffer, 0, buffer.Length);
    if (read <= 0)
        return;
    output.Write (buffer, 0, read);
 }
    input.Position = TempPos;// or you make Position = 0 to set it at the start

User · Answer

I use the following extension methods  They have optimized overloads for when one stream is a MemoryStream       public static void CopyTo this Stream src  Stream dest                int size    src CanSeek    Math Min  int  src Length - src Position   0x2000    0x2000          byte   buffer   new byte size           int n          do                       n   src Read buffer  0  buffer Length               dest Write buffer  0  n             while  n    0                         public static void CopyTo this MemoryStream src  Stream dest                dest Write src GetBuffer     int src Position   int  src Length - src Position               public static void CopyTo this Stream src  MemoryStream dest                if  src CanSeek                        int pos    int dest Position              int length    int  src Length - src Position    pos              dest SetLength length                 while pos  lt  length                                  pos    src Read dest GetBuffer    pos  length - pos                     else             src CopyTo  Stream dest

User · Answer

There is actually  a less heavy-handed way of doing a stream copy  Take note however  that this implies that you can store the entire file in memory  Don t try and use this if you are working with files that go into the hundreds of megabytes or more  without caution  public static void CopySmallTextStream Stream input  Stream output      using  StreamReader reader   new StreamReader input     using  StreamWriter writer   new StreamWriter output           writer Write reader ReadToEnd            NOTE  There may also be some issues concerning binary data and character encodings

User · Answer

The following code to solve the issue copy the Stream to MemoryStream using CopyTo Stream stream   new MemoryStream       any function require input the stream  In mycase to save the PDF file as stream document Save stream   MemoryStream newMs    MemoryStream stream   byte   getByte   newMs ToArray       Note - please dispose the stream in the finally block instead of inside using block as it will throw an error  Access denied as the stream is closed

User · Answer

Unfortunately  there is no really simple solution  You can try something like that   Stream s1  s2  byte   buffer   new byte 4096   int bytesRead   0  while  bytesRead   s1 Read buffer  0  buffer Length   gt  0  s2 Write buffer  0  bytesRead   s1 Close    s2 Close      But the problem with that that different implementation of the Stream class might behave differently if there is nothing to read  A stream reading a file from a local harddrive will probably block until the read operaition has read enough data from the disk to fill the buffer and only return less data if it reaches the end of file  On the other hand  a stream reading from the network might return less data even though there are more data left to be received   Always check the documentation of the specific stream class you are using before using a generic solution

User · Answer

The following code to solve the issue copy the Stream to MemoryStream using CopyTo Stream stream   new MemoryStream       any function require input the stream  In mycase to save the PDF file as stream document Save stream   MemoryStream newMs    MemoryStream stream   byte   getByte   newMs ToArray       Note - please dispose the stream in the finally block instead of inside using block as it will throw an error  Access denied as the stream is closed

User · Answer

There may be a way to do this more efficiently  depending on what kind of stream you re working with   If you can convert one or both of your streams to a MemoryStream  you can use the GetBuffer method to work directly with a byte array representing your data   This lets you use methods like Array CopyTo  which abstract away all the issues raised by fryguybob   You can just trust  NET to know the optimal way to copy the data

User · Answer

From  NET 4 5 on  there is the Stream CopyToAsync method  input CopyToAsync output     This will return a Task that can be continued on when completed  like so   await input CopyToAsync output      Code from here on will be run in a continuation    Note that depending on where the call to CopyToAsync is made  the code that follows may or may not continue on the same thread that called it   The SynchronizationContext that was captured when calling await will determine what thread the continuation will be executed on   Additionally  this call  and this is an implementation detail subject to change  still sequences reads and writes  it just doesn t waste a threads blocking on I O completion    From  NET 4 0 on  there s is the Stream CopyTo method  input CopyTo output     For  NET 3 5 and before  There isn t anything baked into the framework to assist with this  you have to copy the content manually  like so   public static void CopyStream Stream input  Stream output        byte   buffer   new byte 32768       int read      while   read   input Read buffer  0  buffer Length    gt  0                output Write  buffer  0  read             Note 1  This method will allow you to report on progress  x bytes read so far      Note 2  Why use a fixed buffer size and not input Length  Because that Length may not be available  From the docs      If a class derived from Stream does not support seeking  calls to Length  SetLength  Position  and Seek throw a NotSupportedException

User · Answer

NET Framework 4 introduce new  CopyTo  method of Stream Class of System IO namespace  Using this method we can copy one stream to another stream of different stream class    Here is example for this       FileStream objFileStream   File Open Server MapPath  TextFile txt    FileMode Open       Response Write string Format  FileStream Content length   0    objFileStream Length ToString           MemoryStream objMemoryStream   new MemoryStream            Copy File Stream to Memory Stream using CopyTo method     objFileStream CopyTo objMemoryStream       Response Write   lt br  gt  lt br  gt         Response Write string Format  MemoryStream Content length   0    objMemoryStream Length ToString          Response Write   lt br  gt  lt br  gt

User · Answer

NET Framework 4 introduce new  CopyTo  method of Stream Class of System IO namespace  Using this method we can copy one stream to another stream of different stream class    Here is example for this       FileStream objFileStream   File Open Server MapPath  TextFile txt    FileMode Open       Response Write string Format  FileStream Content length   0    objFileStream Length ToString           MemoryStream objMemoryStream   new MemoryStream            Copy File Stream to Memory Stream using CopyTo method     objFileStream CopyTo objMemoryStream       Response Write   lt br  gt  lt br  gt         Response Write string Format  MemoryStream Content length   0    objMemoryStream Length ToString          Response Write   lt br  gt  lt br  gt

User · Answer

Unfortunately  there is no really simple solution  You can try something like that   Stream s1  s2  byte   buffer   new byte 4096   int bytesRead   0  while  bytesRead   s1 Read buffer  0  buffer Length   gt  0  s2 Write buffer  0  bytesRead   s1 Close    s2 Close      But the problem with that that different implementation of the Stream class might behave differently if there is nothing to read  A stream reading a file from a local harddrive will probably block until the read operaition has read enough data from the disk to fill the buffer and only return less data if it reaches the end of file  On the other hand  a stream reading from the network might return less data even though there are more data left to be received   Always check the documentation of the specific stream class you are using before using a generic solution

User · Answer

There may be a way to do this more efficiently  depending on what kind of stream you re working with   If you can convert one or both of your streams to a MemoryStream  you can use the GetBuffer method to work directly with a byte array representing your data   This lets you use methods like Array CopyTo  which abstract away all the issues raised by fryguybob   You can just trust  NET to know the optimal way to copy the data

User · Answer

The basic questions that differentiate implementations of  CopyStream  are    size of the reading buffer size of the writes Can we use more than one thread  writing while we are reading     The answers to these questions result in vastly different implementations of CopyStream and are dependent on what kind of streams you have and what you are trying to optimize   The  best  implementation would even need to know what specific hardware the streams were reading and writing to

User · Answer

Easy and safe - make new stream from original source       MemoryStream source   new MemoryStream byteArray       MemoryStream copy   new MemoryStream byteArray

User · Answer

Since none of the answers have covered an asynchronous way of copying from one stream to another  here is a pattern that I ve successfully used in a port forwarding application to copy data from one network stream to another  It lacks exception handling to emphasize the pattern   const int BUFFER SIZE   4096   static byte   bufferForRead   new byte BUFFER SIZE   static byte   bufferForWrite   new byte BUFFER SIZE    static Stream sourceStream   new MemoryStream    static Stream destinationStream   new MemoryStream     static void Main string   args           Initial read from source stream     sourceStream BeginRead bufferForRead  0  BUFFER SIZE  BeginReadCallback  null      private static void BeginReadCallback IAsyncResult asyncRes           Finish reading from source stream     int bytesRead   sourceStream EndRead asyncRes          Make a copy of the buffer as we ll start another read immediately     Array Copy bufferForRead  0  bufferForWrite  0  bytesRead          Write copied buffer to destination stream     destinationStream BeginWrite bufferForWrite  0  bytesRead  BeginWriteCallback  null          Start the next read  looks like async recursion I guess      sourceStream BeginRead bufferForRead  0  BUFFER SIZE  BeginReadCallback  null      private static void BeginWriteCallback IAsyncResult asyncRes           Finish writing to destination stream     destinationStream EndWrite asyncRes

User · Answer

Easy and safe - make new stream from original source       MemoryStream source   new MemoryStream byteArray       MemoryStream copy   new MemoryStream byteArray

User · Answer

The basic questions that differentiate implementations of  CopyStream  are    size of the reading buffer size of the writes Can we use more than one thread  writing while we are reading     The answers to these questions result in vastly different implementations of CopyStream and are dependent on what kind of streams you have and what you are trying to optimize   The  best  implementation would even need to know what specific hardware the streams were reading and writing to

User · Answer

From  NET 4 5 on  there is the Stream CopyToAsync method  input CopyToAsync output     This will return a Task that can be continued on when completed  like so   await input CopyToAsync output      Code from here on will be run in a continuation    Note that depending on where the call to CopyToAsync is made  the code that follows may or may not continue on the same thread that called it   The SynchronizationContext that was captured when calling await will determine what thread the continuation will be executed on   Additionally  this call  and this is an implementation detail subject to change  still sequences reads and writes  it just doesn t waste a threads blocking on I O completion    From  NET 4 0 on  there s is the Stream CopyTo method  input CopyTo output     For  NET 3 5 and before  There isn t anything baked into the framework to assist with this  you have to copy the content manually  like so   public static void CopyStream Stream input  Stream output        byte   buffer   new byte 32768       int read      while   read   input Read buffer  0  buffer Length    gt  0                output Write  buffer  0  read             Note 1  This method will allow you to report on progress  x bytes read so far      Note 2  Why use a fixed buffer size and not input Length  Because that Length may not be available  From the docs      If a class derived from Stream does not support seeking  calls to Length  SetLength  Position  and Seek throw a NotSupportedException

User · Answer

I use the following extension methods  They have optimized overloads for when one stream is a MemoryStream       public static void CopyTo this Stream src  Stream dest                int size    src CanSeek    Math Min  int  src Length - src Position   0x2000    0x2000          byte   buffer   new byte size           int n          do                       n   src Read buffer  0  buffer Length               dest Write buffer  0  n             while  n    0                         public static void CopyTo this MemoryStream src  Stream dest                dest Write src GetBuffer     int src Position   int  src Length - src Position               public static void CopyTo this Stream src  MemoryStream dest                if  src CanSeek                        int pos    int dest Position              int length    int  src Length - src Position    pos              dest SetLength length                 while pos  lt  length                                  pos    src Read dest GetBuffer    pos  length - pos                     else             src CopyTo  Stream dest

User · Answer

There is actually  a less heavy-handed way of doing a stream copy  Take note however  that this implies that you can store the entire file in memory  Don t try and use this if you are working with files that go into the hundreds of megabytes or more  without caution  public static void CopySmallTextStream Stream input  Stream output      using  StreamReader reader   new StreamReader input     using  StreamWriter writer   new StreamWriter output           writer Write reader ReadToEnd            NOTE  There may also be some issues concerning binary data and character encodings

User · Answer

From  NET 4 5 on  there is the Stream CopyToAsync method  input CopyToAsync output     This will return a Task that can be continued on when completed  like so   await input CopyToAsync output      Code from here on will be run in a continuation    Note that depending on where the call to CopyToAsync is made  the code that follows may or may not continue on the same thread that called it   The SynchronizationContext that was captured when calling await will determine what thread the continuation will be executed on   Additionally  this call  and this is an implementation detail subject to change  still sequences reads and writes  it just doesn t waste a threads blocking on I O completion    From  NET 4 0 on  there s is the Stream CopyTo method  input CopyTo output     For  NET 3 5 and before  There isn t anything baked into the framework to assist with this  you have to copy the content manually  like so   public static void CopyStream Stream input  Stream output        byte   buffer   new byte 32768       int read      while   read   input Read buffer  0  buffer Length    gt  0                output Write  buffer  0  read             Note 1  This method will allow you to report on progress  x bytes read so far      Note 2  Why use a fixed buffer size and not input Length  Because that Length may not be available  From the docs      If a class derived from Stream does not support seeking  calls to Length  SetLength  Position  and Seek throw a NotSupportedException

User · Answer

There may be a way to do this more efficiently  depending on what kind of stream you re working with   If you can convert one or both of your streams to a MemoryStream  you can use the GetBuffer method to work directly with a byte array representing your data   This lets you use methods like Array CopyTo  which abstract away all the issues raised by fryguybob   You can just trust  NET to know the optimal way to copy the data

User · Answer

From  NET 4 5 on  there is the Stream CopyToAsync method  input CopyToAsync output     This will return a Task that can be continued on when completed  like so   await input CopyToAsync output      Code from here on will be run in a continuation    Note that depending on where the call to CopyToAsync is made  the code that follows may or may not continue on the same thread that called it   The SynchronizationContext that was captured when calling await will determine what thread the continuation will be executed on   Additionally  this call  and this is an implementation detail subject to change  still sequences reads and writes  it just doesn t waste a threads blocking on I O completion    From  NET 4 0 on  there s is the Stream CopyTo method  input CopyTo output     For  NET 3 5 and before  There isn t anything baked into the framework to assist with this  you have to copy the content manually  like so   public static void CopyStream Stream input  Stream output        byte   buffer   new byte 32768       int read      while   read   input Read buffer  0  buffer Length    gt  0                output Write  buffer  0  read             Note 1  This method will allow you to report on progress  x bytes read so far      Note 2  Why use a fixed buffer size and not input Length  Because that Length may not be available  From the docs      If a class derived from Stream does not support seeking  calls to Length  SetLength  Position  and Seek throw a NotSupportedException

User · Answer

MemoryStream has  WriteTo outstream   and  NET 4 0 has  CopyTo on normal stream object   NET 4 0  instream CopyTo outstream

User · Answer

Unfortunately  there is no really simple solution  You can try something like that   Stream s1  s2  byte   buffer   new byte 4096   int bytesRead   0  while  bytesRead   s1 Read buffer  0  buffer Length   gt  0  s2 Write buffer  0  bytesRead   s1 Close    s2 Close      But the problem with that that different implementation of the Stream class might behave differently if there is nothing to read  A stream reading a file from a local harddrive will probably block until the read operaition has read enough data from the disk to fill the buffer and only return less data if it reaches the end of file  On the other hand  a stream reading from the network might return less data even though there are more data left to be received   Always check the documentation of the specific stream class you are using before using a generic solution

User · Answer

There may be a way to do this more efficiently  depending on what kind of stream you re working with   If you can convert one or both of your streams to a MemoryStream  you can use the GetBuffer method to work directly with a byte array representing your data   This lets you use methods like Array CopyTo  which abstract away all the issues raised by fryguybob   You can just trust  NET to know the optimal way to copy the data

User · Answer

The basic questions that differentiate implementations of  CopyStream  are    size of the reading buffer size of the writes Can we use more than one thread  writing while we are reading     The answers to these questions result in vastly different implementations of CopyStream and are dependent on what kind of streams you have and what you are trying to optimize   The  best  implementation would even need to know what specific hardware the streams were reading and writing to

User · Answer

MemoryStream has  WriteTo outstream   and  NET 4 0 has  CopyTo on normal stream object   NET 4 0  instream CopyTo outstream

User · Answer

Since none of the answers have covered an asynchronous way of copying from one stream to another  here is a pattern that I ve successfully used in a port forwarding application to copy data from one network stream to another  It lacks exception handling to emphasize the pattern   const int BUFFER SIZE   4096   static byte   bufferForRead   new byte BUFFER SIZE   static byte   bufferForWrite   new byte BUFFER SIZE    static Stream sourceStream   new MemoryStream    static Stream destinationStream   new MemoryStream     static void Main string   args           Initial read from source stream     sourceStream BeginRead bufferForRead  0  BUFFER SIZE  BeginReadCallback  null      private static void BeginReadCallback IAsyncResult asyncRes           Finish reading from source stream     int bytesRead   sourceStream EndRead asyncRes          Make a copy of the buffer as we ll start another read immediately     Array Copy bufferForRead  0  bufferForWrite  0  bytesRead          Write copied buffer to destination stream     destinationStream BeginWrite bufferForWrite  0  bytesRead  BeginWriteCallback  null          Start the next read  looks like async recursion I guess      sourceStream BeginRead bufferForRead  0  BUFFER SIZE  BeginReadCallback  null      private static void BeginWriteCallback IAsyncResult asyncRes           Finish writing to destination stream     destinationStream EndWrite asyncRes

User · Answer

For  NET 3 5 and before try    MemoryStream1 WriteTo MemoryStream2

User · Answer

For  NET 3 5 and before try    MemoryStream1 WriteTo MemoryStream2

User · Answer

The basic questions that differentiate implementations of  CopyStream  are    size of the reading buffer size of the writes Can we use more than one thread  writing while we are reading     The answers to these questions result in vastly different implementations of CopyStream and are dependent on what kind of streams you have and what you are trying to optimize   The  best  implementation would even need to know what specific hardware the streams were reading and writing to

User · Answer

Unfortunately  there is no really simple solution  You can try something like that   Stream s1  s2  byte   buffer   new byte 4096   int bytesRead   0  while  bytesRead   s1 Read buffer  0  buffer Length   gt  0  s2 Write buffer  0  bytesRead   s1 Close    s2 Close      But the problem with that that different implementation of the Stream class might behave differently if there is nothing to read  A stream reading a file from a local harddrive will probably block until the read operaition has read enough data from the disk to fill the buffer and only return less data if it reaches the end of file  On the other hand  a stream reading from the network might return less data even though there are more data left to be received   Always check the documentation of the specific stream class you are using before using a generic solution

User · Answer

if you want a procdure to copy a stream to other the one that nick posted is fine but it is missing the position reset, it should be

public static void CopyStream(Stream input, Stream output)
{
    byte[] buffer = new byte[32768];
    long TempPos = input.Position;
    while (true)    
    {
        int read = input.Read (buffer, 0, buffer.Length);
        if (read <= 0)
            return;
        output.Write (buffer, 0, read);
    }
    input.Position = TempPos;// or you make Position = 0 to set it at the start
}

but if it is in runtime not using a procedure you shpuld use memory stream

Stream output = new MemoryStream();
byte[] buffer = new byte[32768]; // or you specify the size you want of your buffer
long TempPos = input.Position;
while (true)    
{
    int read = input.Read (buffer, 0, buffer.Length);
    if (read <= 0)
        return;
    output.Write (buffer, 0, read);
 }
    input.Position = TempPos;// or you make Position = 0 to set it at the start

[c#] How do I copy the contents of one stream to another?

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