nsIOutputStream

Un flux de sortie peut être «bloquant» ou «non-bloquant" (voir le IsNonBlocking() méthode). Un flux de sortie bloquant peut suspendre le thread appelant afin de satisfaire un appel à Close(), Flush(), write(), writeFrom(), ou writeSegments(). Un flux de sortie non-bloquant, d'autre part, ne bloque pas l'exécution du thread appelant .

Méthode

Methods

close()

Close the stream. Forces the output stream to flush() any buffered data.

void close();

Parameters

None.

Exceptions thrown

NS_BASE_STREAM_WOULD_BLOCK

Indicates that closing the output stream would block the calling thread for an indeterminate amount of time. This exception may only be thrown if isNonBlocking() returns true.

flush()

Cette méthode peut être appelée pour demander le flux de sortie pour écrire le contenu de tous les tampons internes à un collecteur de données de bas niveau, comme un fichier sur le disque. Cependant, la méthode flush peut tout simplement ne rien faire en fonction de la mise en œuvre du flux de sortie.

void flush();

Parameters

None.

Exceptions thrown

NS_BASE_STREAM_WOULD_BLOCK

Indicates that flushing the output stream would block the calling thread for an indeterminate amount of time. This exception may only be thrown if isNonBlocking() returns true.

isNonBlocking()

boolean isNonBlocking();

Parameters

None.

Return value

true if stream is non-blocking.

Exceptions thrown

NS_BASE_STREAM_WOULD_BLOCK

A non-blocking stream may throw this exception when written to if space for the data is not immediately available.

write()

Cette méthode copies des données à partir d'un tampon dans le flux.

unsigned long write(
  in string aBuf,
  in unsigned long aCount
);

Parameters

aBuf

The buffer containing the data to be written.

aCount

The size of the buffer, or the maximum number of bytes to copy from the buffer.

Return value

This method returns the number of bytes copied from the buffer (may be less than aCount).

Exceptions thrown

NS_BASE_STREAM_WOULD_BLOCK

If writing to the output stream would block the calling thread (non-blocking mode only)

writeFrom()

Cette méthode copies des données à partir d'une nsIInputStream à notre nsIOutputStream.

A nsIOutputStream is not required to implement this method. In some contexts, writeFrom may be guaranteed to be implemented, but in general it is not. This method serves as an optimization.

unsigned long writeFrom(
  in nsIInputStream aFromStream,
  in unsigned long aCount
);

Parameters

aFromStream

An nsIInputStream containing the data to be written.

aCount

The maximum number of bytes to write to the stream.

Return value

This method returns the number of bytes written to the stream (may be less than aCount).

Exceptions thrown

NS_BASE_STREAM_WOULD_BLOCK

Indicates that writing to the output stream would block the calling thread for an indeterminate amount of time. This exception may only be thrown if isNonBlocking() returns true.

NS_ERROR_NOT_IMPLEMENTED

Indicates that the stream does not implement this method. Typically, output streams that do not have an internal buffer will not implement this method since such an implementation would require an intermediate buffer unless aFromStream supported nsIInputStream.readSegments(), but that is not guaranteed.

Méthode d'écriture de bas niveau qui a accès à un tampon sous-jacente du flux. La fonction de lecteur peut être appelée plusieurs fois pour les tampons segmentés. Cette méthode devrait continuer à appeler le lecteur jusqu'à ce qu'il n'y a plus rien à écrire ou le lecteur renvoie une erreur. Cette méthode ne devrait pas appeler le lecteur avec zéro octets à fournir.

unsigned long writeSegments(
  in nsReadSegmentFun aReader,
  in voidPtr aClosure,
  in unsigned long aCount
);

Parameters

aReader

A callback function that may be called multiple times. See nsReadSegmentFun for more details on this function.

aClosure

A parameter that is passed to aReader each time it is called.

aCount

The maximum number of bytes to write to the stream.

Return value

This method returns the number of bytes written to the stream (may be less than aCount).

Exceptions thrown

NS_BASE_STREAM_WOULD_BLOCK

Indicates that writing to the output stream would block the calling thread for an indeterminate amount of time. This exception may only be thrown if isNonBlocking() returns true.

NS_ERROR_NOT_IMPLEMENTED

Indicates that the stream does not have an internal buffer that can be written to directly.

Example

writeSegments() example

 // Copy data from a string to a stream

 static NS_METHOD CopySegment(nsIInputStream* aStream,
                              void* aClosure,
                              char* aToSegment,
                              PRUint32 aFromOffset,
                              PRUint32 aCount,
                              PRUint32* aReadCount)
 {
   // aFromSegment now contains aCount bytes of data.

   nsACString* pBuf = (nsACString*) aClosure;

   const char* data;
   PRUint32 len = NS_CStringGetData(&data);

   data += aFromOffset;
   len -= aFromOffset;

   if (len > aCount)
     len = aCount;
   memcpy(aToSegment, data, len);

   // Indicate that we have copied len bytes to the segment
   *aReadCount = len;
   return NS_OK;
 }

 // Write the contents of aSource into aStream, using WriteSegments
 // to avoid intermediate buffer copies.
 nsresult WriteStream(const nsACString& aSource, nsIInputStream* aStream)
 {
   PRUint32 num;
   return aStream->WriteSegments(CopySegment, (void*) &aSource,
                                 aSource.Length(), &num);
 }

Remarks

This interface was frozen for Gecko 1.0. See bug 124465 for details. From Gecko 2.0 interfaces are no longer frozen.

See also

• nsIInputStream
• nsReadSegmentFun