Architecture Guide

The SRCINFO parser consists of two or three different steps (depending on desired output) to get to a well-formed and well-structured data representation.

graph TD;
    A[SRCINFO File] -->|Parse| B
    B[SourceInfoContent] -->|Normalize & Validate| SourceInfo
    subgraph SourceInfo
        C1[PackageBase]
        C2[Vec#lt;Package#gt;]
    end
    SourceInfo -->|Merge for Architecture| D[MergedPackage]

Parsing

The first step is low-level parsing of a SRCINFO file. This logic happens in the parser module.

The entry point for this is the SourceInfoContent::parser, which receives the reference to the SRCINFO file’s content. This parser returns a line-based, raw, but already typed representation of the SRCINFO data.

This representation ensures that only valid keywords are found in the respective sections of the SRCINFO file and already transforms them into the respective [alpm_types] equivalents.

However, this step does not yet validates the file and does no sanity checking.

SourceInfo

The next step is the conversion of the raw SourceInfoContent into a SourceInfo struct by calling SourceInfo::from_raw.

This process validates the input, performs error checking and linting and converts the raw content into the well-formed SourceInfo struct. The SourceInfo struct is an accurate representation of the SRCINFO file, however for most use cases it’s still not very ergonomic to use.

The SourceInfo struct contains:

• A PackageBase struct that contains the defaults for all packages in this SRCINFO file.
  • The PackageBase::architecture_properties field contains additional defaults that are architecture specific.
• A list of Packages that contains package specific information as well as overrides for the PackageBase defaults.
  • The Package::architecture_properties field contains additional data that provides overrides for the respective defaults found in PackageBase::architecture_properties.

Although already fully validated, this representation is not easy to use if one is interested in the properties of a specific package for a specific architecture. For that, we have the MergedPackage representation.

MergedPackage

To get a MergedPackage, the SourceInfo::packages_for_architecture function is used, which creates an iterator that merges the Package specific overrides with the defaults from the PackageBase and applies any architecture specific additions on top of it.

The way the merging works is as follows:

1. Take the PackageBase non-architecture default values.
2. Apply the Package non-architecture override values.
3. Take the PackageBase architecture-specific default values.
4. Apply the Package architecture-specific override values.
5. Merge the final architecture-specific values into the non-architecture specific values.