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package topojsone
Module TopojsoneSource
A library for manipulating large TopoJSON documents without reading the whole document into memory using the Jsone streaming, JSON parser.
module Jsone = Geojsone.Jsonemodule Ezjsone = Geojsone.EzjsoneTopojsone comes with an implementation of a TopoJSON parser using Ezjsone. This is like Ezjsonm but uses Jsone for providing a non-blocking interface.
Sources and Sinks
Topojsone is intended to be used with a non-blocking IO library using OCaml 5's effect support to provide a direct-style buffer filling and buffer writing functions.
Here's an example using the Eio library:
let src_of_flow ?(size = 2048) flow =
let buff = Cstruct.create size in
fun () ->
let got = Eio.Flow.(single_read flow buff) in
let t = Cstruct.sub buff 0 got in
t
let with_src cwd f func =
Eio.Path.(with_open_in (cwd / f)) @@ fun ic -> func @@ src_of_flow ic
let buffer_to_dst buf bs =
Eio.Flow.(copy (cstruct_source [ bs ]) (Eio.Flow.buffer_sink buf))Mapping
Maps are functions that allow you to manipulate common structure in TopoJson objects. These will be written directly back to the destination that you provide.
Source
val map_object :
((string * Topojson.Geometry.t) -> string * Topojson.Geometry.t) ->
Jsone.src ->
Jsone.dst ->
(unit, Err.t) resultmap_object f src dst will apply f to all TopoJson objects. The map will recurse into TopoJson Object. Note for the moment if you have a single geometry object as your document, this will not work.
Folding
Source
val fold_object :
('acc -> (string * Topojson.Geometry.t) -> 'acc) ->
'acc ->
Jsone.src ->
('acc, Err.t) resultfold_object f initial_acc src is much like map_object but allows you to accumulate some result that is then returned to you.
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