How to dynamic output a file content with replaced some bytes?

Question

I used a fuse plugin named 'concatfs'

It can virtual merge some file with a specific filename like xxx-concat-.mkv, and this file's content is a TEXT:

1.mkv
2.mkv
3.mkv

system reads xxx-concat-.mkv, it outputs a merged file with 1.mkv 2.mkv .... but the files are not merged in fact, it's a virtual output.

So, My question is :

• a static file, 1.zip > 300 MB.
• It has so many copies(publish to many people), and the difference is only 4 bytes offset: 0xa 0xb 0xc 0xd in these copies. the 4 bytes is people's id
• so I wanna make a file named '1-replaced-123.zip' like concatfs, content mostly like:(all binary)

1.zip

0xa 4 replaced-4bytes-binary-content

0x1111 10 replaced-10bytes-binary-content

• system reads 1-replaced-123.zip, the fuse will outputing the replaced content.
• It can saves so many disk space.
• And I known PHP/JSP can read and echo with replaced, but php will using a high cpu/memory to echo big file stream.

do you have some suggestion?

Thanks a lot, and sorry for my english.

Answer 1

Use merged-fuse to virtual merge/replace files (C++ 11)

https://github.com/fly-studio/merged-fuse

Example

1.txt

12345678

2.txt

abcdefghi

Make a file named 1-merged-.txt,

-merged- is a special words in the file name

content is JSON format

[
    {
        "path": "1.txt"
    },
    {
        "path": "2.txt",
        "replaces": [
             {
                 "offset": 2,
                 "length": 2,
                 "content": "MjE="
             }
        ]
    }
]

When cat 1-merged-.txt, output:

12345678ab12efghi

You can see the files were merged(virtual), and the content was replaced:

cd replaced to 12