stream_set_write_buffer

(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

stream_set_write_bufferSets write file buffering on the given stream

Descrizione

stream_set_write_buffer(resource $stream, int $size): int

Sets the buffering for write operations on the given stream to size bytes.

Elenco dei parametri

stream

The file pointer.

size

The number of bytes to buffer. If size is 0 then write operations are unbuffered. This ensures that all writes with fwrite() are completed before other processes are allowed to write to that output stream.

Valori restituiti

Returns 0 on success, or another value if the request cannot be honored.

Esempi

Example #1 stream_set_write_buffer() example

The following example demonstrates how to use stream_set_write_buffer() to create an unbuffered stream.

<?php
$fp
= fopen($file, "w");
if (
$fp) {
if (
stream_set_write_buffer($fp, 0) !== 0) {
// changing the buffering failed
}
fwrite($fp, $output);
fclose($fp);
}
?>

Vedere anche:

  • fopen() - Apre un file o un URL
  • fwrite() - Scrive un file salvaguardando la corrispondenza binaria
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User Contributed Notes 2 notes

up
1
MOX
2 years ago
The stream_set_write_buffer() function has been broken since PHP 4.3.0. As a workaround, I would suggest using a php_user_filter as an output buffer. By using the following class I have measured over 50% performance improvements with scripts that generate large text files by writing them one line at a time:

class my_output_buffer extends php_user_filter
{
protected static $BUFFER_SIZE = 4096;

function onCreate( ) {
$this->bff = [];
$this->len = 0;
return true;
}

public function filter($in, $out, &$consumed, $closing)
{
$rv = PSFS_FEED_ME; /* assume no output */

/* process input */
while ($bucket = stream_bucket_make_writeable($in)) {

/* bucket is too big for the buffer? */
$space = static::$BUFFER_SIZE - $this->len;

if ($bucket->datalen >= $space) {
/* consume data by placing it into internal buffers */
$this->bff[] = substr($bucket->data, 0, $space);
$this->len += $space;
$overflow = substr($bucket->data, $space);
$ovfl_len = $bucket->datalen - $space;
$consumed += $bucket->datalen;

assert($this->len == static::$BUFFER_SIZE);

/* make one big bucket */
$bucket->data = implode('', $this->bff);
$bucket->datalen = static::$BUFFER_SIZE;
stream_bucket_append($out, $bucket);
$rv = PSFS_PASS_ON; /* we have output! */

/* handle overflow */
$this->bff = [$overflow];
$this->len = $ovfl_len;
}
else {
/* consume data by placing it into internal buffers */
$this->bff[] = $bucket->data;
$this->len += $bucket->datalen;
$consumed += $bucket->datalen;
}
}

/* stream is closing and we have data? */
if ($closing && $this->len > 0) {
/* make one last bucket */
$data = implode('', $this->bff);
$bucket = stream_bucket_new($this->stream, $data);
stream_bucket_append($out, $bucket);
$rv = PSFS_PASS_ON; /* we have output! */

/* clear internal buffer */
$this->bff = [];
$this->len = 0;
}

return $rv;
}
}

$fp = fopen('foobar.txt', 'w');

/* enable filtering */
stream_filter_register('output.buffer', 'my_output_buffer');
stream_filter_append($fp, 'output.buffer');

/* a lot of small writes */
for ($i = 0; $i < 10000; $i++) {
fwrite($fp, 'x');
}

fclose($fp);
up
1
kevin at bonnevillessei dot com
5 years ago
Trying to use stream_set_write_buffer on a local file will always fail according to this note from 2003.

http://grokbase.com/t/php/php-internals/0351gp6xtn/stream-set-write-buffer-does-not-work

Example:

$fp = fopen("localfile.txt", "w");
if (stream_set_write_buffer($fp, 0) !== 0) {
// changing the buffering failed is always true on local files
}
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