mapleFU commented on code in PR #1839:
URL: https://github.com/apache/kvrocks/pull/1839#discussion_r1365808687
##########
src/common/rdb_stream.cc:
##########
@@ -50,20 +50,18 @@ Status RdbFileStream::Open() {
return Status::OK();
}
-StatusOr<size_t> RdbFileStream::Read(char *buf, size_t len) {
- size_t n = 0;
+Status RdbFileStream::Read(char *buf, size_t len) {
while (len) {
size_t read_bytes = std::min(max_read_chunk_size_, len);
ifs_.read(buf, static_cast<std::streamsize>(read_bytes));
if (!ifs_.good()) {
- return Status(Status::NotOK, fmt::format("read failed: {}:",
strerror(errno)));
+ return {Status::NotOK, fmt::format("read failed: {}:", strerror(errno))};
}
check_sum_ = crc64(check_sum_, reinterpret_cast<const unsigned char
*>(buf), read_bytes);
- buf = (char *)buf + read_bytes;
+ buf = buf + read_bytes;
+ DCHECK(len >= read_bytes);
len -= read_bytes;
total_read_bytes_ += read_bytes;
- n += read_bytes;
}
-
- return n;
+ return Status::OK();
Review Comment:
```c++
ifs_.read(buf, static_cast<std::streamsize>(read_bytes));
if (!ifs_.good()) {
if (!ifs_.eof()) {
return {Status::NotOK, fmt::format("read failed: {}:",
strerror(errno))};
}
auto eof_read_bytes = static_cast<size_t>(ifs_.gcount());
if (read_bytes != eof_read_bytes) {
return {Status::NotOK, fmt::format("read failed: {}:",
strerror(errno))};
}
}
```
I've update it to code like this. In `read(2)`, if file reaches EOF, the
`read` would return `0`. And return `-1` when meets error. So I think previous
code is ok. But I don't get what the `ifstream` works even after I gothrough
the cppreference. So I change it to the code above.
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