流读入

private int readBytes(InputStream in, byte[] buf, int offset, int len)
throws IOException {
int readLen = 0;
while (readLen < len) {
try {
int offSize = in.read(buf, offset + readLen, len - readLen);
if (offSize == 0 || offSize == -1) {
break;
}
readLen = readLen + offSize;
} catch (java.io.IOException e) {
break;
}
}
return readLen;
}