ScotlandPHP 2016

Funciones de Bzip2

Tabla de contenidos

  • bzclose — Cierra un fichero bzip2
  • bzcompress — Comprime una cadena en datos codificados en bzip2
  • bzdecompress — Descomprime datos codificados con bzip2
  • bzerrno — Devuelve el número de erro de bzip2
  • bzerror — Devuelve el número de error y la cadena del error de bzip2 en un array
  • bzerrstr — Devuelve una cadena de error de bzip2
  • bzflush — Fuerza la escritura de todos los datos del búfer
  • bzopen — Abre un fichero comprimido con bzip2
  • bzread — Lectura segura de ficheros bzip2
  • bzwrite — Escribe en un fichero bzip2 de forma segura binariamente
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User Contributed Notes 2 notes

up
3
ec10 at gmx dot net
12 years ago
<?php
/**
* @return bool
* @param string $in
* @param string $out
* @desc compressing the file with the bzip2-extension
*/
function bzip2 ($in, $out)
{
    if (!
file_exists ($in) || !is_readable ($in))
        return
false;
    if ((!
file_exists ($out) && !is_writeable (dirname ($out)) || (file_exists($out) && !is_writable($out)) ))
        return
false;
   
   
$in_file = fopen ($in, "rb");
   
$out_file = bzopen ($out, "wb");
   
    while (!
feof ($in_file)) {
       
$buffer = fgets ($in_file, 4096);
        
bzwrite ($out_file, $buffer, 4096);
    }

   
fclose ($in_file);
   
bzclose ($out_file);
   
    return
true;
}

/**
* @return bool
* @param string $in
* @param string $out
* @desc uncompressing the file with the bzip2-extension
*/
function bunzip2 ($in, $out)
{
    if (!
file_exists ($in) || !is_readable ($in))
        return
false;
    if ((!
file_exists ($out) && !is_writeable (dirname ($out)) || (file_exists($out) && !is_writable($out)) ))
        return
false;

   
$in_file = bzopen ($in, "rb");
   
$out_file = fopen ($out, "wb");

    while (
$buffer = bzread ($in_file, 4096)) {
       
fwrite ($out_file, $buffer, 4096);
    }

   
bzclose ($in_file);
   
fclose ($out_file);
   
    return
true;
}
?>
up
0
salsi at icosaedro dot it
7 months ago
<?php
/*
* Reading a BZIP2 file can be tricky, and I never seen a complete example of
* code that account for any possible failure that may happen accessing a file
* in general, and decoding compressed data in this specific case.
* The example that follows is my attempt to address this gap.
* Some things that worth noting are:
* - Encoding/decoding errors must be detected with bzerrno().
* - bzopen() may fail returning FALSE if the file cannot be created or read,
*   but succeeds also if the file is not properly encoded.
* - bzread() may fail returning FALSE if it fails reading from the source, but
*   it returns the empty string on end of file and on encoding error.
* - bzread() may still return corrupted data with no error whatsoever until the
*   BZIP2 algo encounters the first hash code, so data retrieved cannot be
*   trusted until the very end of the file has been reached.
*/

// Safety first:
error_reporting(-1);
// On error, set $php_errormsg:
ini_set("track_errors", "1");

/**
* Reads and displays on stdout the content of a BZIP2 compressed file with
* full error detection.
* @param string $fn Filename.
* @return void
*/
function displaysBZIP2File($fn)
{
    echo
"Reading $fn:\n";
   
$bz = @bzopen($fn, "r");
    if(
$bz === FALSE ){
        echo
"ERROR: bzopen() failed: $php_errormsg\n";
        return;
    }
   
$errno = bzerrno($bz);
    if(
$errno != 0 ){
       
// May detect "DATA_ERROR_MAGIC" (not a BZIP2 file), or "DATA_ERROR"
        // (BZIP2 decoding error) and maybe others BZIP2 errors too.
       
echo "ERROR: bzopen(): BZIP2 decoding failed: ", bzerrstr($bz), "\n";
        @
bzclose($bz);
        return;
    }
    while(!
feof($bz) ) {
       
$s = bzread($bz, 100);
        if(
$s === FALSE ){
            echo
"ERROR: bzread() failed: $php_errormsg\n";
            @
bzclose($bz);
            return;
        }
       
$errno = bzerrno($bz);
        if(
$errno != 0 ){
           
// May detect "DATA_ERROR" (BZIP2 decoding error) and maybe others
            // BZIP2 errors too.
           
echo "ERROR: bzread(): BZIP2 decoding failed: ", bzerrstr($bz), "\n";
            @
bzclose($bz);
            return;
        }
        echo
"read: ", var_export($s, true), "\n";
    }
    if( !
bzclose($bz) ){
        echo
"ERROR: bzclose() failed: $php_errormsg\n";
    }
}

// Target file:
$fn = "test.bz2";

// Test 1: writes and read a good BZIP2 file:
file_put_contents($fn, bzcompress("Content of the file."));
displaysBZIP2File($fn); // works ok.

// Test 2: invalid content, not a BZIP2 file:
file_put_contents($fn, "This ia plain text file, no compression at all!");
displaysBZIP2File($fn); // ERROR: bzread(): BZIP2 decoding failed: DATA_ERROR_MAGIC

// Test 3: creates a corrupted BZIP2 file:
$plain = str_repeat("Quite random string. ", 1000);
$compressed = bzcompress($plain);
$compressed_corrupted = $compressed;
$compressed_corrupted[(int)(strlen($compressed)/2)] = 'X'; // put random char in middle
file_put_contents($fn, $compressed_corrupted);
displaysBZIP2File($fn);
// Only after some Kbytes of garbage, it tells:
// ERROR: bzread(): BZIP2 decoding failed: DATA_ERROR

// Safe coding against headache, ever.
?>
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