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File Input / Output

Loading files

Load a text file into a String

val fileContent = File("/path/to/file.txt").readText()

Load a text file into a List<String>

val lines = File("/path/to/file.txt").readLines()

Load binary content into a ByteArray

val bytes = File("/path/to/file.txt").readBytes()

For loading large text files one can use File.bufferedReader().

Saving files

Save a String

File("/path/to/file.txt").writeText("Hello")

Save a ByteArray

File("/path/to/file.txt").writeBytes(myByteArray)

For saving large text files one can use File.bufferedWriter().

JSON

The GSON library makes it possible to convert JSON files to Kotlin objects and objects back to JSON files. To enable the library:

  1. Find the build.gradle.kts file in your openrndr-template.
  2. Uncomment the line implementation(libs.gson).
  3. Reload gradle.

Loading / converting JSON to an object

// An object matching the JSON file.
// Notice how optional properties are nullable.
data class Entry(var time: Double, var easing: String, var rotx: Double?, var roty: Double?, var x: Double?, var y: Double?, var scale: Double?, var jitter: Double?)

// from disk
// val json = File("/path/to/a/file.json").readFile()

// from a string
val json = """
        [
            {
                "time": 0.0,
                "easing": "cubic-in-out",
                "rotx": 0.0,
                "roty": 30.0,
                "x": 0.0,
                "y": 0.0,
                "scale": 1.0,
                "jitter": 0.0
            },
            {
                "time": 1.0,
                "easing": "cubic-in-out",
                "rotx": 0.0,
                "x": 20.0,
                "y": 0.0,
                "scale": 1.0
            },
            {
                "time": 1.3,
                "easing": "cubic-in-out"
            }
        ]
        """.trimIndent()

fun main() = application {
    program {
        val gson = Gson()
        // The TypeToken type must match the file's structure
        val typeToken = object : TypeToken<List<Entry>>() {}
        val entries: List<Entry> = gson.fromJson(json, typeToken.type)
        
        entries.forEachIndexed { i, entry ->
            println(i)
            println(entry)
        }
    }
}

Saving an object as a JSON file

fun main() = application {
    program {
        val points = List(20) {
            Vector2.uniform(drawer.bounds)
        }
        //val gson = GsonBuilder().setPrettyPrinting().create()
        val gson = Gson()
        val json = gson.toJson(points)
        File("data/points.json").writeText(json)
    }
}

CSV

The kotlin-csv library enables loading and saving CSV files. To enable the library:

  1. Find the build.gradle.kts file in your openrndr-template.
  2. Uncomment the line implementation(libs.csv).
  3. Reload gradle.

Load a CSV file

fun main() = application {
    program {
        // read from `String`
        val csvData = "a,b,c\nd,e,f"
        val rowsA = csvReader().readAll(csvData)
        
        // read from `java.io.File`
        val file = File("test.csv")
        val rowsB = csvReader().readAll(file)
    }
}

Save a CSV file

fun main() = application {
    program {
        val rows = listOf(listOf("a", "b", "c"), listOf("d", "e", "f"))
        csvWriter().writeAll(rows, "data/test.csv")
    }
}

XML / HTML

The jsoup library enables loading and parsing XML and HTML files. To enable the library:

  1. Find the build.gradle.kts file in your openrndr-template.
  2. Uncomment the line implementation(libs.jsoup).
  3. Reload gradle.

Get Wikipedia home page and parse news headlines

fun main() = application {
    program {
        val doc = Jsoup.connect("https://en.wikipedia.org/").get()
        println(doc.title())
        
        val newsHeadlines = doc.select("#mp-itn b a")
        newsHeadlines.forEach {
            println(it.attr("title"))
            println(it.absUrl("href"))
        }
    }
}

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