Zig

Decode Base64 Image String (GIF, JPG, etc.) and Save to File

I have an XML response that includes a base 64 encoded image string (UPS label). It's a huge string and I need to save it as a gif file on my users pc.

This example shows how to do it..

Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    const bd = try chilkat.BinData.init();
    defer bd.deinit();

    // I created an extra-small GIF image for this example..
    bd.loadFile("qa_data/gif/xsmall.gif") catch {
        std.debug.print("Failed to load GIF image file.\n", .{});
        return;
    };

    // Show GIF bytes as base64:
    std.debug.print("{s}\n", .{try bd.getEncoded(alloc, "base64")});

    // This particular GIF in base64 is this:
    // R0lGODlhBQAFAMQAAAAAAP////z8/PHx8evr6+jo6OHh4d7e3sPDw8LCwpqamo2NjWxsbGRkZFpaWk1NTUtLS0hISCwsLCQkJP///wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACH5BAEAABQALAAAAAAFAAUAAAUTYCAYQUBAU1lI0TIgztE8jFImIQA7

    // Let's begin with an XML string:
    const x = "<abc><def>R0lGODlhBQAFAMQAAAAAAP////z8/PHx8evr6+jo6OHh4d7e3sPDw8LCwpqamo2NjWxsbGRkZFpaWk1NTUtLS0hISCwsLCQkJP///wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACH5BAEAABQALAAAAAAFAAUAAAUTYCAYQUBAU1lI0TIgztE8jFImIQA7</def></abc>";

    const xml = try chilkat.Xml.init();
    defer xml.deinit();
    try xml.loadXml(x);

    // Get the base64 string:
    const gif_base64 = try xml.getChildContent(alloc, "def");

    std.debug.print("{s}\n", .{gif_base64});

    // Load bd with the base64 decoded bytes.
    bd.clear() catch {};
    bd.appendEncoded(gif_base64, "base64") catch {};

    // Save to a GIF file.
    try bd.writeFile("qa_output/xsmall.gif");
}