添加bt与tracker交互
Change-Id: I1327c2ed89a76bee8e2abeb8cb3014b56357689a
diff --git a/src/main/java/com/pt/utils/BencodeCodec.java b/src/main/java/com/pt/utils/BencodeCodec.java
new file mode 100644
index 0000000..2117d43
--- /dev/null
+++ b/src/main/java/com/pt/utils/BencodeCodec.java
@@ -0,0 +1,216 @@
+package com.pt.utils;
+
+import java.io.*;
+import java.net.InetAddress;
+import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
+import java.util.*;
+
+public class BencodeCodec {
+
+ /* ------------- 编码部分 ------------- */
+
+ public static void encode(Object obj, OutputStream out) throws IOException {
+ if (obj instanceof String) {
+ encodeString((String) obj, out);
+ } else if (obj instanceof Number) {
+ encodeInteger(((Number) obj).longValue(), out);
+ } else if (obj instanceof byte[]) {
+ encodeBytes((byte[]) obj, out);
+ } else if (obj instanceof List) {
+ encodeList((List<?>) obj, out);
+ } else if (obj instanceof Map) {
+ encodeMap((Map<String, Object>) obj, out);
+ } else {
+ throw new IllegalArgumentException("Unsupported type: " + obj.getClass());
+ }
+ }
+
+ public static byte[] encode(Object obj) {
+ try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
+ encode(obj, baos);
+ return baos.toByteArray();
+ } catch (IOException e) {
+ throw new RuntimeException(e);
+ }
+ }
+
+ private static void encodeString(String s, OutputStream out) throws IOException {
+ byte[] bytes = s.getBytes(StandardCharsets.UTF_8);
+ out.write(String.valueOf(bytes.length).getBytes(StandardCharsets.US_ASCII));
+ out.write(':');
+ out.write(bytes);
+ }
+
+ private static void encodeBytes(byte[] bytes, OutputStream out) throws IOException {
+ out.write(String.valueOf(bytes.length).getBytes(StandardCharsets.US_ASCII));
+ out.write(':');
+ out.write(bytes);
+ }
+
+ private static void encodeInteger(long value, OutputStream out) throws IOException {
+ out.write('i');
+ out.write(Long.toString(value).getBytes(StandardCharsets.US_ASCII));
+ out.write('e');
+ }
+
+ private static void encodeList(List<?> list, OutputStream out) throws IOException {
+ out.write('l');
+ for (Object item : list) {
+ encode(item, out);
+ }
+ out.write('e');
+ }
+
+ private static void encodeMap(Map<String, Object> map, OutputStream out) throws IOException {
+ out.write('d');
+ List<String> keys = new ArrayList<>(map.keySet());
+ Collections.sort(keys); // bencode字典必须按key排序
+ for (String key : keys) {
+ encodeString(key, out);
+ encode(map.get(key), out);
+ }
+ out.write('e');
+ }
+
+ /* ------------- 解码部分 ------------- */
+
+ public static Object decode(byte[] data) throws IOException {
+ try (ByteArrayInputStream in = new ByteArrayInputStream(data)) {
+ in.mark(data.length);
+ return decodeNext(in);
+ }
+ }
+
+ private static Object decodeNext(InputStream in) throws IOException {
+ int prefix = in.read();
+ if (prefix == -1) {
+ throw new IOException("Unexpected end of stream");
+ }
+
+ in.mark(1024);
+
+ if (prefix >= '0' && prefix <= '9') {
+ in.reset();
+ return parseString(in);
+ } else if (prefix == 'i') {
+ return parseInteger(in);
+ } else if (prefix == 'l') {
+ return parseList(in);
+ } else if (prefix == 'd') {
+ return parseDict(in);
+ } else {
+ throw new IOException("Invalid bencode prefix: " + (char) prefix);
+ }
+ }
+
+ private static String parseString(InputStream in) throws IOException {
+ StringBuilder lenStr = new StringBuilder();
+ int b;
+ while ((b = in.read()) != -1 && b != ':') {
+ if (b < '0' || b > '9') {
+ throw new IOException("Invalid string length character: " + (char) b);
+ }
+ lenStr.append((char) b);
+ }
+ if (b == -1) {
+ throw new IOException("Unexpected end of stream reading string length");
+ }
+ int length = Integer.parseInt(lenStr.toString());
+
+ byte[] buf = new byte[length];
+ int offset = 0;
+ while (offset < length) {
+ int read = in.read(buf, offset, length - offset);
+ if (read == -1) {
+ throw new IOException("Unexpected end of stream reading string data");
+ }
+ offset += read;
+ }
+
+ return new String(buf, StandardCharsets.UTF_8);
+ }
+
+ private static long parseInteger(InputStream in) throws IOException {
+ StringBuilder intStr = new StringBuilder();
+ int b;
+ while ((b = in.read()) != -1 && b != 'e') {
+ intStr.append((char) b);
+ }
+ if (b == -1) {
+ throw new IOException("Unexpected end of stream reading integer");
+ }
+ return Long.parseLong(intStr.toString());
+ }
+
+ private static List<Object> parseList(InputStream in) throws IOException {
+ List<Object> list = new ArrayList<>();
+ int b;
+ while (true) {
+ in.mark(1);
+ b = in.read();
+ if (b == -1) {
+ throw new IOException("Unexpected end of stream reading list");
+ }
+ if (b == 'e') {
+ break;
+ }
+ in.reset();
+ list.add(decodeNext(in));
+ }
+ return list;
+ }
+
+ private static Map<String, Object> parseDict(InputStream in) throws IOException {
+ Map<String, Object> map = new LinkedHashMap<>();
+ int b;
+ while (true) {
+ in.mark(1);
+ b = in.read();
+ if (b == -1) {
+ throw new IOException("Unexpected end of stream reading dictionary");
+ }
+ if (b == 'e') {
+ break;
+ }
+ in.reset();
+ String key = (String) decodeNext(in);
+ Object value = decodeNext(in);
+ map.put(key, value);
+ }
+ return map;
+ }
+
+ /* ------------- 其他辅助方法 ------------- */
+
+ // 构造单个compact peer的二进制格式 (4字节IP + 2字节端口)
+ public static byte[] buildCompactPeer(String ip, int port) {
+ try {
+ InetAddress addr = InetAddress.getByName(ip);
+ ByteBuffer buffer = ByteBuffer.allocate(6);
+ buffer.put(addr.getAddress());
+ buffer.putShort((short) port);
+ return buffer.array();
+ } catch (IOException e) {
+ throw new RuntimeException(e);
+ }
+ }
+
+ // 构造多个compact peer的二进制拼接
+ public static byte[] buildCompactPeers(List<String> ips, List<Integer> ports) {
+ if (ips.size() != ports.size()) throw new IllegalArgumentException("IPs and ports list size mismatch");
+ ByteArrayOutputStream out = new ByteArrayOutputStream();
+ for (int i = 0; i < ips.size(); i++) {
+ out.write(buildCompactPeer(ips.get(i), ports.get(i)), 0, 6);
+ }
+ return out.toByteArray();
+ }
+
+ // 构造tracker响应字典，至少包含interval和peers
+ public static byte[] buildTrackerResponse(int interval, byte[] peersCompact) {
+ Map<String, Object> dict = new LinkedHashMap<>();
+ dict.put("interval", interval);
+ dict.put("peers", peersCompact);
+ return encode(dict);
+ }
+}