gzseek
(PHP 4, PHP 5, PHP 7, PHP 8)
gzseek — Seek on a gz-file pointer
说明
$stream, int $offset, int $whence = SEEK_SET): int
Sets the file position indicator for the given file pointer to the
given offset byte into the file stream. Equivalent to calling (in C)
gzseek(zp, offset, SEEK_SET).
If the file is opened for reading, this function is emulated but can be extremely slow. If the file is opened for writing, only forward seeks are supported; gzseek() then compresses a sequence of zeroes up to the new starting position.
参数
-
stream -
The gz-file pointer. It must be valid, and must point to a file successfully opened by gzopen().
-
offset -
The seeked offset.
-
whence -
whencevalues are:SEEK_SET- Set position equal tooffsetbytes.SEEK_CUR- Set position to current location plusoffset.
If
whenceis not specified, it is assumed to beSEEK_SET.
返回值
Upon success, returns 0; otherwise, returns -1. Note that seeking past EOF is not considered an error.
范例
示例 #1 gzseek() example
<?php
$gz = gzopen('somefile.gz', 'r');
gzseek($gz,2);
echo gzgetc($gz);
gzclose($gz);
?>
参见
- gztell() - Tell gz-file pointer read/write position
- gzrewind() - Rewind the position of a gz-file pointer
add a note
User Contributed Notes 2 notes
Since seek after the end is not considered an error, I doubt that "while (gzseek ($fh, $eof) == 0) $eof += $d;" will get into infinite loop.
PHP/4.3.9
contrary to the notes, gzseek() returns -1 if I try to seek past the end of the file. here is a function that will return the last seekable position, and put the file pointer there.
/** sets the file pointer at the end of the file
* and returns the number of bytes in the file.
*/
function gzend($fh)
{
$d = 1<<14;
$eof = $d;
while ( gzseek($fh, $eof) == 0 ) $eof += $d;
while ( $d > 1 )
{
$d >>= 1;
$eof += $d * (gzseek($fh, $eof)? -1 : 1);
}
return $eof;
}