ykxmz/_tests/java/B64Diag.java

import com.lanremote.watch.B64;
import com.lanremote.watch.Json;

import java.util.Arrays;
import java.util.Map;

/** 定位 Base64 在哪些长度下往返出错。 */
public class B64Diag {

    public static void main(String[] args) {
        int failures = 0;
        int firstBad = -1;

        // 1. 穷举 0..2000，找出所有长度相关的缺陷
        for (int len = 0; len <= 2000; len++) {
            byte[] data = pattern(len);
            byte[] back = B64.decode(B64.encode(data));
            if (!Arrays.equals(data, back)) {
                failures++;
                if (firstBad < 0) {
                    firstBad = len;
                }
                if (failures <= 5) {
                    System.out.println("  长度 " + len + " 往返不一致  encoded="
                            + B64.encode(data).length() + " decoded=" + back.length);
                    report(data, back);
                }
            }
        }
        System.out.println("1) 0..2000 穷举：失败 " + failures + " 个长度，首个 " + firstBad);

        // 2. 实际用到的分块长度
        int[] sizes = {256 * 1024, 300 * 1024 + 7 - 256 * 1024, 300 * 1024 + 7,
                64 * 1024, 202, 1024, 45063, 262144};
        for (int size : sizes) {
            byte[] data = pattern(size);
            byte[] back = B64.decode(B64.encode(data));
            System.out.println("2) 长度 " + size + " -> " + (Arrays.equals(data, back) ? "OK" : "不一致"));
            if (!Arrays.equals(data, back)) {
                report(data, back);
            }
        }

        // 3. 走一遍真实的 JSON 内嵌流程（模拟协议报文）
        byte[] data = pattern(262144);
        Map<String, Object> msg = Json.obj("cmd", "file_push", "name", "x.bin",
                "seq", 0, "last", false, "data", B64.encode(data));
        String wire = Json.write(msg);
        Map<String, Object> parsed = Json.parseObject(wire);
        byte[] back = B64.decode(Json.str(parsed, "data", ""));
        System.out.println("3) 经 JSON 编解码后: " + (Arrays.equals(data, back) ? "OK" : "不一致"));
        if (!Arrays.equals(data, back)) {
            report(data, back);
        }

        System.exit(failures == 0 ? 0 : 1);
    }

    private static byte[] pattern(int len) {
        byte[] data = new byte[len];
        for (int i = 0; i < len; i++) {
            data[i] = (byte) ((i * 31 + 7) & 0xFF);
        }
        return data;
    }

    private static void report(byte[] expected, byte[] actual) {
        int limit = Math.min(expected.length, actual.length);
        for (int i = 0; i < limit; i++) {
            if (expected[i] != actual[i]) {
                System.out.println("     首个差异 @ " + i
                        + "  期望=" + (expected[i] & 0xFF) + " 实际=" + (actual[i] & 0xFF));
                return;
            }
        }
        System.out.println("     前缀相同，但长度不同: 期望 " + expected.length
                + " 实际 " + actual.length);
    }
}