Swift package for reading data from a PMTiles database.
This is work in progress and may still change.
Documentation is incomplete at this time.
Currently this package only exports a single PMTilesReader struct which is designed to read a range of bytes (like HTTP range headers). This code was originally written for use with the sfomuseum/swifter-protomaps package and has been made in to a standalone package so that it can be used with other HTTP server implementations.
By default it operates on PMTiles database files using the Foundation.FileHandle class. While suitable for most situations, if you are working with very large databases (like the 120GB global database) in an iOS context this will trigger "Cannot allocate memory" errors. To account for this it is possible to signal that the PMTilesReader instance should use a System.FileDescriptor instance for working with PMTiles database files.
import PMTiles
import Logging
guard let db_url = URL(string: "/path/to/db.pmtiles") else {
throw SomeErrorHere
}
var logger = Logger("label": "example")
logger.logLevel = .debug
var reader_opts = PMTilesReaderOptions(db_url, use_file_descriptor: true)
reader_opts.Logger = logger
var reader: PMTilesReader
do {
reader = try PMTilesReader(reader_opts)
} catch {
throw error
}
if case .failure(let error) = reader.Read(from: 0, to: 1024) {
throw error
}
if case .failure(let error) = reader.Size() {
throw error
}
if case .failure(let error) = reader.Close() {
throw error
}