A number of bugfixes:

- Added DB::CompactRange() method.

  Changed manual compaction code so it breaks up compactions of
  big ranges into smaller compactions.

  Changed the code that pushes the output of memtable compactions
  to higher levels to obey the grandparent constraint: i.e., we
  must never have a single file in level L that overlaps too
  much data in level L+1 (to avoid very expensive L-1 compactions).

  Added code to pretty-print internal keys.

- Fixed bug where we would not detect overlap with files in
  level-0 because we were incorrectly using binary search
  on an array of files with overlapping ranges.

  Added "leveldb.sstables" property that can be used to dump
  all of the sstables and ranges that make up the db state.

- Removing post_write_snapshot support.  Email to leveldb mailing
  list brought up no users, just confusion from one person about
  what it meant.

- Fixing static_cast char to unsigned on BIG_ENDIAN platforms.

  Fixes	Issue 35 and Issue 36.

- Comment clarification to address leveldb Issue 37.

- Change license in posix_logger.h to match other files.

- A build problem where uint32 was used instead of uint32_t.

Sync with upstream @24408625

include/leveldb/db.h

@@ -112,6 +112,8 @@ class DB {
   //     where <N> is an ASCII representation of a level number (e.g. "0").
   //  "leveldb.stats" - returns a multi-line string that describes statistics
   //     about the internal operation of the DB.
+  //  "leveldb.sstables" - returns a multi-line string that describes all
+  //     of the sstables that make up the db contents.
   virtual bool GetProperty(const Slice& property, std::string* value) = 0;
 
   // For each i in [0,n-1], store in "sizes[i]", the approximate
@@ -125,8 +127,17 @@ class DB {
   virtual void GetApproximateSizes(const Range* range, int n,
                                    uint64_t* sizes) = 0;
 
-  // Possible extensions:
-  // (1) Add a method to compact a range of keys
+  // Compact the underlying storage for the key range [*begin,*end].
+  // In particular, deleted and overwritten versions are discarded,
+  // and the data is rearranged to reduce the cost of operations
+  // needed to access the data.  This operation should typically only
+  // be invoked by users who understand the underlying implementation.
+  //
+  // begin==NULL is treated as a key before all keys in the database.
+  // end==NULL is treated as a key after all keys in the database.
+  // Therefore the following call will compact the entire database:
+  //    db->CompactRange(NULL, NULL);
+  virtual void CompactRange(const Slice* begin, const Slice* end) = 0;
 
  private:
   // No copying allowed

include/leveldb/env.h

@@ -160,6 +160,8 @@ class SequentialFile {
   // Read up to "n" bytes from the file.  "scratch[0..n-1]" may be
   // written by this routine.  Sets "*result" to the data that was
   // read (including if fewer than "n" bytes were successfully read).
+  // May set "*result" to point at data in "scratch[0..n-1]", so
+  // "scratch[0..n-1]" must be live when "*result" is used.
   // If an error was encountered, returns a non-OK status.
   //
   // REQUIRES: External synchronization
@@ -184,8 +186,10 @@ class RandomAccessFile {
   // Read up to "n" bytes from the file starting at "offset".
   // "scratch[0..n-1]" may be written by this routine.  Sets "*result"
   // to the data that was read (including if fewer than "n" bytes were
-  // successfully read).  If an error was encountered, returns a
-  // non-OK status.
+  // successfully read).  May set "*result" to point at data in
+  // "scratch[0..n-1]", so "scratch[0..n-1]" must be live when
+  // "*result" is used.  If an error was encountered, returns a non-OK
+  // status.
   //
   // Safe for concurrent use by multiple threads.
   virtual Status Read(uint64_t offset, size_t n, Slice* result,

include/leveldb/options.h

@@ -177,21 +177,8 @@ struct WriteOptions {
   // Default: false
   bool sync;
 
-  // If "post_write_snapshot" is non-NULL, and the write succeeds,
-  // *post_write_snapshot will be modified to point to a snapshot of
-  // the DB state immediately after this write.  The caller must call
-  // DB::ReleaseSnapshot(*post_write_snapshotsnapshot) when the
-  // snapshot is no longer needed.
-  //
-  // If "post_write_snapshot" is non-NULL, and the write fails,
-  // *post_write_snapshot will be set to NULL.
-  //
-  // Default: NULL
-  const Snapshot** post_write_snapshot;
-
   WriteOptions()
-      : sync(false),
-        post_write_snapshot(NULL) {
+      : sync(false) {
   }
 };