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https://github.com/dx3mod/rpmfile

A library for reading metadata from RPM packages
https://github.com/dx3mod/rpmfile

parser rpm

Last synced: 2 months ago
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A library for reading metadata from RPM packages

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README 

        
# rpmfile



A library for reading metadata from [RPM packages][RPM] (supports version 3.0 and partially 4.0) written in OCaml.



## Usage



The `rpmfile` package only provides types and functions for easy field access.



To read RPM files, you need to use a package that implements a *reader*.



| Package        | Description                                                     | Require OCaml |

|----------------|-----------------------------------------------------------------|---------------|

| `rpmfile-unix` | Original reader (since the first version) powered by [Angstrom] | >= 4.14       |

| `rpmfile-eio`  | New [Eio]-based reader for more modern age                      | > 5.1         |



### Installation



You can install the library using OPAM package manager:



```console

$ opam install # rpmfile-unix / rpmfile-eio

```



Development version



Also, you may want to use the development (upstream) version of the library, but be careful:



```console

$ opam pin rpmfile-*.dev https://github.com/dx3mod/rpmfile.git

```



### Theoretical minimum



Each [RPM package][PackageFileFormat] consists of four sections: lead, signature, header, and payload. The first three are meta information about the package. It contains a description, a dependency list, and so on.



The information in the signature and header is stored on a key-value basis, where the key is called a tag. The value can be a number, a string or an array.



Often you don't need [all information](https://rpm-software-management.github.io/rpm/manual/tags.html) about a package, but only some tags. For this task, a selector (like predicate function) is used to determine which tags should be parsed and which should not. This greatly increases parsing speed and saves memory.



### Read package



For an example, let's use the `Rpmfile_unix`reader.



```ocaml

(* Create a reader to read all tags. *)

module Rpm_pkg_reader = Rpmfile_unix.Reader.Make (Rpmfile.Selector.All)



let () =

  let metadata =

    Rpm_pkg_reader.of_file "hello-2.12.1-1.7.x86_64.rpm"

    |> Result.get_ok

  in



  (* Get the package name by field access function. *)

  Printf.printf "Package Name: %s\n" @@ Rpmfile.name metadata

```



### Custom selector



You may write your own selector.



```ocaml

module My_custom_selector : Rpmfile.Selector.S = struct

  (* ... *)

end

```



Or just use built-in selectors



| Selector        | For                                          |

|-----------------|----------------------------------------------|

| `Selector.All`  | read all tags                                |

| `Selector.Base` | read basic tags (see docs or implementation) |



### Manual decode



You can write your own decoder if there is no convenient field access function for the tag you need.



```ocaml

let get_signature_size_field =

  Rpmfile.get_from_signature

    ~msg:"signature.size" (* Failwith message. *)

    D.int Tag.Signature.size

```



### Lwt 



For how to read from a Lwt channel, see [the example](./examples/with_lwt.ml).



### Read by chunk



See the `Angstrom.Unbuffered` module.



### Limitations



The implementation uses native OCaml int (32/64 bit depending on your machine) for some internal service values (e.g. as an offset), which may have limitations.



Also, decoding values with field access functions converts any int to native OCaml int, which may break on 32-bit systems.



### CLI



You can use the `rpmfile-unix` package as a command line utility to get basic information about the package, similar to `rpm -qi`.



Example



```console

$ rpmfile-unix test_misc/hello-2.12.1-1.7.x86_64.rpm

Name        : hello                 

Version     : 2.12.1

Release     : 1.7

Architecture: x86_64

Group       : Development/Tools/Other

Size        : 185847

License     : GPL-3.0-or-later

Source RPM  : hello-2.12.1-1.7.src.rpm

Build Date  : 2022-05-30

Build Host  : reproducible

Packager    : https://bugs.opensuse.org

Vendor      : openSUSE

URL         : https://www.gnu.org/software/hello

Summary     : A Friendly Greeting Program

Description :

The GNU hello program produces a familiar, friendly greeting.  It

allows nonprogrammers to use a classic computer science tool that would

otherwise be unavailable to them.  Because it is protected by the GNU

General Public License, users are free to share and change it.



GNU hello supports many native languages.

Distribution: openSUSE Tumbleweed

```



## Documentation



See the API references:

- 

- 

- 



## Contribution



The project is stable, but the library could be more complete. I look forward to your pull requests!

If you encounter a bug, then please create an [issue](https://github.com/dx3mod/rpmfile/issues).



See [HACKING.md](./HACKING.md) if you are interested in developing the project.



[RPM]: https://en.wikipedia.org/wiki/RPM_Package_Manager

[Angstrom]: https://github.com/inhabitedtype/angstrom

[Eio]: https://github.com/ocaml-multicore/eio

[PackageFileFormat]: https://refspecs.linuxbase.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/pkgformat.html