1479140 - File sizes in about:cache do not reflect actual file sizes as stored on disk

Status: RESOLVED INVALID

(Core :: Networking: Cache, defect)

Description

[therube]

File sizes in about:cache, about:cache?storage=disk&context=, do not reflect actual file sizes as stored on disk.

Windows XP
FF 52

Windows 7
FF 61
 
 
You've found something of interest in about:cache?storage=disk&context= & you want to find the specific entity in your /cache2/ directory.

One method to find the file might be by file size.

You can't - at least not 1 to 1, by file size, because the file size in about:cache?storage=disk&context= differs from the file size as stored on disk.

For instance the following item is listed:

> key: 	https://s-static.innovid.com/media/encoded/07_18/159112/11_source_58615_197016.mp4
> fetch count: 	1
> last fetched: 	2018-07-27 19:22:55
> last modified: 	2018-07-27 20:04:36
> expires: 	2018-07-29 22:03:20
> Data size: 	8036438 B

It shows "data size" as 8,036,438 bytes.
Yet the size of the corresponding file on disk is 8,045,341 bytes.

As it is with sizes differing, it makes it difficult to correspond something listed in about:cache with the physical entity on disk.

Ah, I see, the file in /cache2/ file includes more then just the actual "data" (aka Data size:, as evidenced by Content-Length:), it also includes, appended, stuff like the request & the response.

So the "Data size" is accurate for the data object itself, but not for the physically cached item, as the two are not the same.
 
 
Now that's a quandary...

Comment 1

[Michal Novotny [:michal]]

Data size isn't file size and there is no reason why the file size should be shown. I cannot recommend doing changes in cache2 directory manually. Why do you need to locate the entry?

Comment 2

[therube]

Forensics.
Investigating malware.

Comment 3

[Honza Bambas (:mayhemer)]

I would like to have a button to reveal a file right from about:cache too, but it's not that straightforward to get the file name.