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md5_file()
calcule le MD5 du fichier
filename
en utilisant l'algorithme
»
RSA Data Security, Inc.
MD5 Message-Digest Algorithm
,
puis retourne la
valeur ainsi calculée. Le résultat est un nombre de 32
caractères hexadécimaux.
hash_file()
- Génère une valeur de hachage en utilisant le contenu d'un fichier donné
hash_init()
- Initialise un contexte de hachage incrémental
md5()
- Calcule le md5 d'une chaîne
Chris
¶
14 years ago
If you just need to find out if two files are identical, comparing file hashes can be inefficient, especially on large files. There's no reason to read two whole files and do all the math if the second byte of each file is different. If you don't need to store the hash value for later use, there may not be a need to calculate the hash value just to compare files. This can be much faster:
<?php
define
(
'READ_LEN'
,
4096
);
if(
files_identical
(
'file1.txt'
,
'file2.txt'
))
echo
'files identical'
;
else
echo
'files not identical'
;
function
files_identical
(
$fn1
,
$fn2
) {
if(
filetype
(
$fn1
) !==
filetype
(
$fn2
))
return
FALSE
;
if(
filesize
(
$fn1
) !==
filesize
(
$fn2
))
return
FALSE
;
if(!
$fp1
=
fopen
(
$fn1
,
'rb'
))
return
FALSE
;
if(!
$fp2
=
fopen
(
$fn2
,
'rb'
)) {
fclose
(
$fp1
);
return
FALSE
;
}
$same
=
TRUE
;
while (!
feof
(
$fp1
) and !
feof
(
$fp2
))
if(
fread
(
$fp1
,
READ_LEN
) !==
fread
(
$fp2
,
READ_LEN
)) {
$same
=
FALSE
;
break;
}
if(
feof
(
$fp1
) !==
feof
(
$fp2
))
$same
=
FALSE
;
fclose
(
$fp1
);
fclose
(
$fp2
);
return
$same
;
}
?>
lukasamd at gmail dot com
¶
12 years ago
It's faster to use md5sum than openssl md5:
<?php
$begin
=
microtime
(
true
);
$file_path
=
'../backup_file1.tar.gz'
;
$result
=
explode
(
" "
,
exec
(
"md5sum
$file_path
"
));
echo
"Hash = "
.
$result
[
0
].
"<br />"
;
$end
=
microtime
(
true
) -
$begin
;
echo
"Time =
$end
"
;
?>
About 3x faster
smartin
¶
16 years ago
In response to using exec instead for performance (Nov 13 2007 post), It looks like the performance depends on the size of the file. See the results below using the same script from the original post. The first hash is with md5_file and the second is with openssl md5.
With a 1MB file:
Hash = df1555ec0c2d7fcad3a03770f9aa238a; time = 0.005006
Hash = df1555ec0c2d7fcad3a03770f9aa238a; time = 0.01498
With a 2MB file:
Hash = 4387904830a4245a8ab767e5937d722c; time = 0.010393
Hash = 4387904830a4245a8ab767e5937d722c; time = 0.016691
With a 10MB file:
Hash = b89f948e98f3a113dc13fdbd3bdb17ef; time = 0.241907
Hash = b89f948e98f3a113dc13fdbd3bdb17ef; time = 0.037597
Performance seems to change proportionally with the file size. Judging from the previous post's default file name (.mov) he/she was probably dealing with a large file. These are just quick tests and far from a perfect benchmark, but you might want to test your own files before assuming that the openssl solution is faster (ie, if working with small text files vs. movies, etc)
