[Solved] Error allocating memory for a 6 MB file

[jchd]

The mentionned doc dissects the file format. The part of interest here is the 7z header named SignatureHeader. All we have to do is read the header section (binary of course) and copy that into a C-like structure to access the offset and size of the next header. Reading past that we get the trailer you appended.

Note that zip-style archives can be built in several steps, adding new headers and packed data at the end of the file. If you use such "add to existing archive" feature, you'll have to reiterate the process until last header is found (something not yet done in my sample [simple] code).

 

[TheDcoder]

@jchd Oh

I don't have to worry because the file is not tampered by any external program

[TheDcoder]

@jchd Just tested your snippet in my application... Here are the results:

Your code: 0.169343761563984 ms

My code: 0.342108609220169 ms (50.5% slower)

 

Very happy with the results

[TheDcoder]

@jchd Sorry for bugging you again but your script is suddenly not working for me ...

Download Test File: https://we.tl/zYIHvAKj04 (Expiry in 7 days)

#include <FileConstants.au3>

Local Const $7zHeaderSize = 32
Local $filename = @ScriptDir & "\MC Snapshot Testing World.mcmap"
Local $filehdl = FileOpen($filename, $FO_BINARY)
Local $fileheader = FileRead($filehdl, $7zHeaderSize)
If BinaryMid($fileheader, 1, 6) <> Binary('0x377ABCAF271C') Then
    MsgBox(0, '', 'File is not a 7z archive')
    Exit
EndIf
Local $blockheader = DllStructCreate("byte[" & $7zHeaderSize & "]")
DllStructSetData($blockheader, 1, $fileheader)
Local $header = DllStructCreate("align 1;byte tag[6];byte major;byte minor;uint crc1;uint64 offset;uint64 size;uint crc2", DllStructGetPtr($blockheader))
FileSetPos($filehdl, DllStructGetData($header, 'offset') + DllStructGetData($header, 'size'), $FILE_CURRENT)
Local $sTrailer = BinaryToString(FileRead($filehdl))
ConsoleWrite($sTrailer)

Sleep(1000)

I only get "M" as the console output... Thanks in advance, TD

[jchd]

My contribution only covers part of the file format specifications. Archive files can be built in more than one step, in which case there is a series of headers and archive parts. You'll have to work thru the specifications to adapt my little sample code for support of the full file format.

[TheDcoder]

@jchd Yes, That indeed is true but that file is generated normally as the first provided file... Why is it not working? Does it have multiple headers?

[jchd]

Can't tell. Dissect the file from specs. Maybe archive uses some max block size of something. I currently don't have the free time to dig further.

[TheDcoder]

Just now, jchd said:

Dissect the file from specs

The specs are too complex for me to understand

1 minute ago, jchd said:

I currently don't have the free time to dig further

Oh ... Ok then... can you please look while once you are free? I don't want to use my chunk by chunk search system