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added utility to dump leveldb files

Fix corruption bug found and analyzed by [email protected]

https://groups.google.com/d/msg/leveldb/Kc9JxuIUu5A/9P0N9RL4ar8J

Fixes issues:

• #153 - thanks feniksgordonfreeman
• #159
• #162
• #172

Additionally,

• Remove calls to exit(1).
• Fix unused-variable warnings from clang.
• Fix possible overflow error related to num_restart value >= (2^32/4).
• Add leveldbutil to .gitignore.
• Add better log messages when Write is stalled on a compaction.

Fixes issues:

• #167
• #180
• #184

As well as the issue reported by [email protected] about MissingSSTFile unit test failing on windows.

1. Remove obsolete android port files.
2. Remove static initializer
3. Fix endian-ness detection
4. Fix build on various platforms
5. Improve android port speed.

Non-functional changes only:

1. Add Kevin Regan to the AUTHORS file
2. Add standard license header to issues/issue178_test.cc

Fix issues #83, #93, #188, #196.

Additionally, fix the bug described in https://groups.google.com/d/msg/leveldb/yL6h1mAOc20/vLU64RylIdMJ where a large contiguous keyspace of deleted data was not getting compacted.

Also fix a bug where options.max_open_files was not getting clamped properly.

Fix issues #206, #207

Also,

• Fix link to bigtable paper in docs.
• New sstables will have the file extension .ldb. .sst files will continue to be recognized.
• When building for iOS, use xcrun to execute the compiler. This may affect issue #183.

• Make Log::Reader not report a corruption when the last record in a log file is truncated.
• Fix issue #230: variable created but not utilized.
• Remove comment that referenced a removed feature.

• switched from mmap based writing to simpler stdio based writing. Has a minor impact (0.5 microseconds) on microbenchmarks for asynchronous writes. Synchronous writes speed up from 30ms to 10ms on linux/ext4. Should be much more reliable on diverse platforms.
• compaction errors now immediately put the database into a read-only mode (until it is re-opened). As a downside, a disk going out of space and then space being created will require a re-open to recover from, whereas previously that would happen automatically. On the plus side, many corruption possibilities go away.
• force the DB to enter an error-state so that all future writes fail when a synchronous log write succeeds but the sync fails.
• repair now regenerates sstables that exhibit problems
• fix issue #224 - Use native memory barriers on OSX
• fix issue #218 - QNX build is broken
• fix build on iOS with xcode 5
• make tests compile and pass on windows