Embedding files

#embed and #embed_dir read files while compiling and put their contents in the executable, so the program ships as one file.

Embed one file#

#embed("path") gives the file's contents as a String. The path is relative to the project's valk.json:

fn not_found_page() String {
    return #embed("views/404.html")
}

fn main() {
    let page = not_found_page()
    println(page.bytes > 0) // true
}

Each #embed puts its own copy in the executable. When several places need the same file, embed it once in a function, as above, and call that.

Embed a directory#

#embed_dir("path") reads a directory recursively and gives a Map[String] from each file's relative path to its contents:

fn main() {
    let views = #embed_dir("views")
    each views as content, name {
        println("%name: %{content.bytes} bytes") // 404.html: 249 bytes, ...
    }
    let page = views.get("404.html") !? ""
    println(page.bytes > 0) // true
}

Files in subdirectories use / in their name, such as blog/post.html.

Things to know#

• The path must be a string literal, and the file must exist when you build.
• Changing an embedded file needs a rebuild.
• A typical use is shipping templates or static web assets with a server.