build: don't call xxd from build.zig

build.zig

@@ -142,7 +142,43 @@ pub fn build(b: *std.build.Builder) !void {
 
     const server_assets = [_][]const u8{ "index.html", "index.js", "completion.js", "json-schema-to-grammar.mjs" };
     for (server_assets) |asset| {
-        const gen_hpp = b.addSystemCommand(&.{ "bash", "-c", b.fmt("cd examples/server/public && xxd -i {s} ../{s}.hpp", .{ asset, asset }) });
-        server.step.dependOn(&gen_hpp.step);
+        const input_path = b.fmt("examples/server/public/{s}", .{asset});
+        const output_path = b.fmt("examples/server/{s}.hpp", .{asset});
+
+        const input_file = try std.fs.cwd().openFile(input_path, .{});
+        defer input_file.close();
+        const input = try input_file.readToEndAlloc(b.allocator, std.math.maxInt(usize));
+        defer b.allocator.free(input);
+
+        const hex = try b.allocator.alloc(u8, input.len * 6);
+        defer b.allocator.free(hex);
+        var i: usize = 0;
+        for (input) |byte| {
+            const high = byte >> 4;
+            const low = byte & 0xF;
+            hex[i] = '0';
+            hex[i + 1] = 'x';
+            hex[i + 2] = if (high < 10) high + '0' else high - 10 + 'A';
+            hex[i + 3] = if (low < 10) low + '0' else low - 10 + 'A';
+            hex[i + 4] = ',';
+            hex[i + 5] = ' ';
+            i += 6;
+        }
+
+        const output_file = try std.fs.cwd().createFile(output_path, .{});
+        defer output_file.close();
+
+        const name = try b.allocator.alloc(u8, asset.len);
+        defer b.allocator.free(name);
+        std.mem.copy(u8, name, asset);
+        std.mem.replaceScalar(u8, name, '-', '_');
+        std.mem.replaceScalar(u8, name, '.', '_');
+
+        try output_file.writeAll(b.fmt(
+            "unsigned char {s}[] = {{{s}}};\nunsigned int {s}_len = {d};\n",
+            .{ name, hex, name, input.len },
+        ));
+
+        std.debug.print("Dumped hex of \"{s}\" ({s}) to {s}\n", .{ input_path, name, output_path });
     }
 }