Potential infinite loop in MetricSearcher::FindOffset(xxx)

[sczyh30]

Issue Description

Type: bug report

Describe what happened (or what feature you want)

while (!istream.eof()) { ... } may cause infinite loop in MetricSearcher::FindOffset(xxx):

sentinel-cpp/sentinel-core/log/metric/metric_searcher.cc

Lines 57 to 65 in e4a6eb7

	while (!in.eof()) {
	in >> second >> tmp_offset;
	if (second < begin_second) {
	last_pos_.offset_in_index = in.tellg();
	} else {
	offset = tmp_offset;
	break;
	}
	}

The eof() will return false even if the failbit or badbit is true. Refer: https://stackoverflow.com/questions/13079900/file-i-o-infinite-loop-c-eof