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const std = @import("std");
const bencode = @import("bencode.zig");
// https://wiki.theory.org/BitTorrentSpecification#Tracker_Response
pub const TrackerResp = struct {
// interval: u64,
peers: []std.net.Address,
pub fn parse(a: std.mem.Allocator, b: bencode.BValue) !TrackerResp {
var ipl = std.ArrayList(std.net.Address).init(a);
defer ipl.deinit();
var d = b.asDict() catch return error.Malformatted;
var pb = d.get("peers") orelse return error.Malformatted;
var ps = pb.asString() catch return error.Malformatted;
if ((ps.len % 6) != 0) return error.Malformatted;
for (0..ps.len / 6) |ix| {
const start = ix * 6;
const port = std.mem.readInt(u16, ps[start + 4 .. start + 6][0..2], .big);
var ip = [_]u8{0} ** 4;
@memcpy(&ip, ps[start .. start + 4]);
try ipl.append(std.net.Address.initIp4(ip, port));
}
return .{
.peers = try ipl.toOwnedSlice(),
};
}
pub fn deinit(self: *TrackerResp, a: std.mem.Allocator) void {
a.free(self.peers);
}
};
pub fn trackerRequestUrl(a: std.mem.Allocator, info_hash: [20]u8, peer_id: [20]u8, left: usize, announce: []const u8) ![]const u8 {
var q = std.StringHashMap([]const u8).init(a);
defer q.deinit();
try q.put("info_hash", &info_hash);
try q.put("peer_id", &peer_id);
try q.put("port", "6881");
try q.put("uploaded", "0");
try q.put("downloaded", "0");
var buf_left = [_]u8{0} ** 1024;
try q.put("left", try std.fmt.bufPrint(&buf_left, "{}", .{left}));
try q.put("compact", "1");
var qs = try toqs(a, q);
defer a.free(qs);
return try std.fmt.allocPrint(a, "{s}?{s}", .{ announce, qs });
}
fn toqs(a: std.mem.Allocator, hm: std.StringHashMap([]const u8)) ![]const u8 {
var al = std.ArrayList(u8).init(a);
defer al.deinit();
var w = al.writer();
var it = hm.iterator();
var first = true;
while (it.next()) |entry| {
if (!first) try w.writeByte('&');
try std.Uri.writeEscapedQuery(w, entry.key_ptr.*);
try w.writeByte('=');
try std.Uri.writeEscapedQuery(w, entry.value_ptr.*);
first = false;
}
return try al.toOwnedSlice();
}
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