What

I took the code at https://www.unixuser.org/~euske/doc/cdbinternals/pycdb.py.html and made it Python 3 compatible, then I converted it to Swift.

I still don't get it. What is CDB?

Some links for you:

1. https://cr.yp.to/cdb/cdb.txt and https://cr.yp.to/cdb.html
2. http://www.cse.yorku.ca/~oz/hash.html
3. https://www.unixuser.org/~euske/doc/cdbinternals/index.html

Getting started

Installing and using C library

The original C version of cdb (written by DJB) is only necessary if you want to prove to yourself that this Swift library is compatible:

brew install cdb

The Swift unit tests need cdbmake from this library.

Manual compatibility testing

Use the C library to make a test.cdb file from /etc/services:

cdbmake-sv test.cdb test.tmp < /etc/services

Query this cdb using the C version of `cdbget:

# result should be 25
cdbget smtp/tcp < test.cdb && echo ''

See Usage below for how to perform the same cdbget in swift.

Usage

Naming

Swift's package system doesn't appear to have a good way to deal with namespace conflicts, so the classes are manually prefixed with CDB. Example: CDBReader. get is also a reserved keyword, so we have to live with triply redundant cdbget().

Package.swift

// swift-tools-version:5.5
import PackageDescription

let package = Package(
    name: "MyProject",
    dependencies: [
        .package(url: "https://github.com/createthis/swift-cdb.git", from: "1.0.0"),
    ],
    targets: [
        .target(
            name: "MyProject",
            dependencies: [
                .product(name: "cdb", package: "swift-cdb")
            ]
        ),
    ]
)

CDBReader

Query it using this Swift library:

import cdb

let cdbReader = try CDBReader(filePath: "test.cdb", posHeader: 0)
let valueFromCdb = try cdbReader.cdbget(key: "smtp/tcp")
print("valueFromCdb=\(String(data: valueFromCdb, encoding: .utf8)!)")

CDBWriter

Alternatively, to create a cdb using swift, do something like this:

import cdb

let data = ["key1": "value1", "key2": "value2", "key3": "value3"]
let cdbWriter = try CDBWriter(filePath: "my.cdb")
for (key, value) in data {
  try cdbWriter.put(key: key, value: value)
}
try cdbWriter.finalize();

Automated compatibility testing

The Swift unit tests need cdbmake from the original C library, so install that first (see above).

Finally, you can test that the output of this Swift library matches the output of the original C version:

swift test