为什么当存在异常时，RealBufferedSource（FixedLengthSource）的BufferSize从65536变为2048字节？
我在下载管理员代码上遇到的2个问题如下:(我是这个论坛的新手。如果需要更多输入，请告诉我）
问题1：
android的DownloadManager（a.k.a DownloadThread）更新一次，读取65536字节4次。这个实现在哪里完成？对不起，我找不到它完成的地方。这次更新的任何特定原因是DownloadThread一次4次读取？在错误情况下，如果我从DownloadManager执行部分HTTP提取请求，则Range：请求将使用上次更新的currentBytes值。因此，如果中间发生错误（例如，第4次读取中的第2次），则Range：请求将使用先前更新的currentBytes，这可能会再次重新读取相同的字节。
// HC：是HttpConnection.java，FixedLengthSource＃读取添加打印的位置。
19:09:10.374 System.out: (HTTPLog)-Thread-270-223795676: Content-Length : 70610220
19:09:10.684 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70610220,65536
19:09:10.694 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70593836,65536
19:09:10.704 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70577452,65536
19:09:10.704 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70561068,65536
19:09:10.714 DownloadManager: currentBytes : 65536,mLastUpdateBytes : 0
19:09:10.714 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70544684,65536
19:09:10.714 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70528300,65536
19:09:10.724 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70511916,65536
19:09:10.754 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70495532,65536
19:09:10.774 DownloadManager: currentBytes : 131072,mLastUpdateBytes : 131072
19:09:10.774 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70479148,65536
19:09:10.784 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70462764,65536
19:09:10.784 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70446380,65536
19:09:10.784 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70429996,65536
19:09:10.794 DownloadManager: currentBytes : 196608,mLastUpdateBytes : 131072
19:09:10.794 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70413612,65536
19:09:10.814 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70397228,65536
19:09:10.814 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70380844,65536
19:09:10.824 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70364460,65536
19:09:10.834 DownloadManager: currentBytes : 262144,mLastUpdateBytes : 131072
示例：
19:09:10.794 DownloadManager: currentBytes : 196608,mLastUpdateBytes : 131072
// 1st read
19:09:10.794 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70413612,65536
// 2nd read
19:09:10.814 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 70397228,65536
// If error happens here, the range: request for partial fetch happens using the
// currentBytes variable as follows
System.out: (HTTPLog)-Thread-270-51176450: Range : bytes=196608-
// Ideally, it should be { [currentBytes : 196608] + [1st Read : 65536] + [2nd Read : 65536]}
System.out: (HTTPLog)-Thread-270-51176450: Range : bytes=327680-
问题2：
当发生类似SSLException的IOException时，自动将获取大小从65536减少到2048.这个实现完成了什么？对不起，我找不到它完成的地方。 降级的任何具体原因 - 避免拥堵都是这样的？
19:10:11.244 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13905628,65536 19:10:11.244 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13889244,65536 19:10:11.254 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13872860,65536 19:10:11.254 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13856476,65536 19:10:11.254 DownloadManager: currentBytes : 56754176, mLastUpdateBytes : 56360960 19:10:11.254 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13840092,65536 19:10:11.264 System.out: (HTTPLog)-Static: FixedLengthSource#read:: SSLException caught... 19:10:11.264 System.out: (HTTPLog)-Static: FixedLengthSource#read, Bytes remaining to be downloaded : 13840092 19:10:11.264 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13840092,2048 19:10:11.284 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13838044,2048 19:10:11.284 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13835996,2048 19:10:11.284 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13833948,2048 19:10:11.294 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13831900,2048 19:10:11.294 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13829852,2048 19:10:11.294 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13827804,2048 19:10:11.294 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13825756,2048 19:10:11.304 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13823708,2048 19:10:11.304 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13821660,2048 19:10:11.304 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13819612,2048 19:10:11.314 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13817564,2048 19:10:11.314 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13815516,2048 19:10:11.314 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13813468,2048 19:10:11.314 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13811420,2048 19:10:11.314 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13809372,2048 19:10:11.314 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13807324,2048 19:10:11.324 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13805276,2048 19:10:11.324 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13803228,2048 19:10:11.324 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13801180,2048 19:10:11.324 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13799132,2048 19:10:11.324 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13797084,2048 19:10:11.324 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13795036,2048 19:10:11.334 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13792988,2048 19:10:11.334 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13790940,2048 19:10:11.334 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13788892,2048 19:10:11.334 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13786844,2048 19:10:11.334 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13784796,2048 19:10:11.334 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13782748,2048 19:10:11.344 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13780700,2048 19:10:11.344 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13778652,2048 19:10:11.354 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13776604,2048 19:10:11.364 System.out: (HTTPLog)-Static: HC:: bytesRemaining, byteCount ::: 13774556,2048
在这种情况下，也不会更新有关此2048XM字节下载的currentThread的currentBytes。
因此，如果DownloadThread使用可用的currentBytes进行部分提取，它最终将从服务器重新读取相同的字节，从而导致更多的数据使用。
请帮助我理解我是否遗漏任何基本内容。
谢谢 拉姆