b085ee13e0
Summary:
In the adapter class `WritableFileStringStreamAdapter`, which wraps WritableFile to be used for std::ostream, previouly only `std::endl` is considered a special case because `endl` is written by `os.put()` directly without going through `xsputn()`. `os.put()` will call `sputc()` and if we further check the internal implementation of `sputc()`, we will see it is
```
int_type __CLR_OR_THIS_CALL sputc(_Elem _Ch) { // put a character
return 0 < _Pnavail() ? _Traits::to_int_type(*_Pninc() = _Ch) : overflow(_Traits::to_int_type(_Ch));
```
As we explicitly disabled buffering, _Pnavail() is always 0. Thus every write, not captured by xsputn, becomes an overflow.
When I run tests on Windows, I found not only `std::endl` will drop into this case, writing an unsigned long long will also call `os.put()` then followed by `sputc()` and eventually call `overflow()`. Therefore, instead of only checking `std::endl`, we should try to append other characters as well unless the appending operation fails.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7991
Reviewed By: jay-zhuang
Differential Revision: D26615692
Pulled By: ajkr
fbshipit-source-id: 4c0003de1645b9531545b23df69b000e07014468
RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key-value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it especially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/master/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Design discussions are conducted in https://www.facebook.com/groups/rocksdb.dev/ and https://rocksdb.slack.com/
License
RocksDB is dual-licensed under both the GPLv2 (found in the COPYING file in the root directory) and Apache 2.0 License (found in the LICENSE.Apache file in the root directory). You may select, at your option, one of the above-listed licenses.