@bitblit/asyncglk/dist/common/file.js

A Typescript Glk library

/*

Common file processing functions
================================

Copyright (c) 2024 Dannii Willis
MIT licenced
https://github.com/curiousdannii/asyncglk

*/
/** Parse Base 64 into a Uint8Array */
export async function parse_base64(data) {
    // Firefox has a data URL limit of 32MB, so we have to chunk large data
    const chunk_length = 30_000_000;
    if (data.length < chunk_length) {
        return parse_base64_with_data_url(data);
    }
    const chunks = [];
    let i = 0;
    while (i < data.length) {
        chunks.push(await parse_base64_with_data_url(data.substring(i, i += chunk_length)));
    }
    const blob = new Blob(chunks);
    return new Uint8Array(await blob.arrayBuffer());
}
async function parse_base64_with_data_url(data) {
    // Parse base64 using a trick from https://stackoverflow.com/a/54123275/2854284
    const response = await fetch(`data:application/octet-stream;base64,${data}`);
    if (!response.ok) {
        throw new Error(`Could not parse base64: ${response.status}`);
    }
    return new Uint8Array(await response.arrayBuffer());
}
/** Read a response, with optional progress notifications */
export async function read_response(response, progress_callback) {
    if (!response.ok) {
        throw new Error(`Could not fetch ${response.url}, got ${response.status}`);
    }
    if (!progress_callback) {
        return new Uint8Array(await response.arrayBuffer());
    }
    // Read the response, calling the callback with each chunk
    const chunks = [];
    let length = 0;
    const reader = response.body.getReader();
    for (;;) {
        const { done, value } = await reader.read();
        if (done) {
            break;
        }
        chunks.push([length, value]);
        progress_callback(value.length);
        length += value.length;
    }
    // Join the chunks together
    const result = new Uint8Array(length);
    for (const [offset, chunk] of chunks) {
        result.set(chunk, offset);
    }
    return result;
}