Bzip2 Functions

    Table of Contents

    • bzclose — Close a bzip2 file
    • bzcompress — Compress a string into bzip2 encoded data
    • bzdecompress — Decompresses bzip2 encoded data
    • bzerrno — Returns a bzip2 error number
    • bzerror — Returns the bzip2 error number and error string in an array
    • bzerrstr — Returns a bzip2 error string
    • bzflush — Do nothing
    • bzopen — Opens a bzip2 compressed file
    • bzread — Binary safe bzip2 file read
    • bzwrite — Binary safe bzip2 file write

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    User Contributed Notes 2 notes

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    2
    ec10 at gmx dot net
    20 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
    2
    salsi at icosaedro dot it
    8 years 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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