gzseek

(PHP 4, PHP 5)

gzseek — Seek on a gz-file pointer

说明

int gzseek ( resource $zp , int $offset [, int $whence = SEEK_SET ] )

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

zp

The gz-file pointer. It must be valid, and must point to a file successfully opened by gzopen().

offset

The seeked offset.

whence

whence values are:

SEEK_SET - Set position equal to offset bytes.
SEEK_CUR - Set position to current location plus offset.

If whence is not specified, it is assumed to be SEEK_SET.

返回值

Upon success, returns 0; otherwise, returns -1. Note that seeking past EOF is not considered an error.

范例

Example #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

PHP手册 - N: Seek on a gz-file pointer

用户评论:

dperham at wgate dot com (12-Apr-2005 04:47)

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; }