Stream (Geo)JSON file and get startByte and endByte of each JSON record in the file

To stream a GeoJSON file and get the startByte and endByte positions of each JSON record in the file, you can use Node.js and its built-in fs (File System) and readline modules. The readline module provides an interface for reading a file line by line, which is useful for processing large files efficiently.

Here's a step-by-step approach to achieve this:

1. Install Required Packages: First, create a new Node.js project and install the necessary packages.

   bashCopy code
   npm init -y
   npm install readline fs
   

2. Create the Streaming Script: Create a JavaScript file (e.g., streamGeoJSON.js) and add the following code:

   javascriptCopy code
   const fs = require('fs');
   const readline = require('readline');
   
   // Replace 'your_geojson_file.json' with the path to your GeoJSON file
   const filePath = 'your_geojson_file.json';
   
   const readStream = fs.createReadStream(filePath);
   const lineReader = readline.createInterface({
     input: readStream,
   });
   
   let startByte = 0;
   let endByte = 0;
   
   lineReader.on('line', (line) => {
     // Increment the endByte by the number of bytes read from the line (including the newline character)
     endByte += Buffer.byteLength(line) + 1;
   
     try {
       const jsonRecord = JSON.parse(line);
       // Process the JSON record as needed
       console.log('JSON Record:', jsonRecord);
   
       // Start the next JSON record at the current endByte position
       startByte = endByte;
     } catch (error) {
       console.error('Error parsing JSON:', error);
     }
   });
   
   lineReader.on('close', () => {
     console.log('Stream processing complete.');
   });
   

3. Run the Script: Replace 'your_geojson_file.json' in the code with the path to your GeoJSON file. Then, run the script using Node.js:

   bashCopy code
   node streamGeoJSON.js
   

The script will read the GeoJSON file line by line and parse each line as a JSON record. It will log the JSON records and update the startByte and endByte positions to indicate the byte range of each JSON record in the file. By doing this, you can obtain the start and end positions of each JSON record as the stream processes the file.

Keep in mind that the GeoJSON file must contain one valid JSON record per line for this approach to work correctly. If the GeoJSON records span multiple lines or are not separated by newlines, you'll need to adapt the script to handle multi-line JSON records appropriately.