Speed up Snappy uncompression, new Logger interface.

- Removed one copy of an uncompressed block contents changing
  the signature of Snappy_Uncompress() so it uncompresses into a
  flat array instead of a std::string.
        
  Speeds up readrandom ~10%.

- Instead of a combination of Env/WritableFile, we now have a
  Logger interface that can be easily overridden applications
  that want to supply their own logging.

- Separated out the gcc and Sun Studio parts of atomic_pointer.h
  so we can use 'asm', 'volatile' keywords for Sun Studio.




git-svn-id: https://leveldb.googlecode.com/svn/trunk@39 62dab493-f737-651d-591e-8d6aee1b9529

1 files changed, 11 insertions, 1 deletions

diff --git a/port/port_example.h b/port/port_example.h
index 8a624f3..6bd9b49 100644
--- a/port/port_example.h
+++ b/port/port_example.h
@@ -96,11 +96,21 @@ class AtomicPointer {
 extern bool Snappy_Compress(const char* input, size_t input_length,
                             std::string* output);
 
+// If input[0,input_length-1] looks like a valid snappy compressed
+// buffer, store the size of the uncompressed data in *result and
+// return true.  Else return false.
+extern bool Snappy_GetUncompressedLength(const char* input, size_t length,
+                                         size_t* result);
+
 // Attempt to snappy uncompress input[0,input_length-1] into *output.
 // Returns true if successful, false if the input is invalid lightweight
 // compressed data.
+//
+// REQUIRES: at least the first "n" bytes of output[] must be writable
+// where "n" is the result of a successful call to
+// Snappy_GetUncompressedLength.
 extern bool Snappy_Uncompress(const char* input_data, size_t input_length,
-                              std::string* output);
+                              char* output);
 
 // ------------------ Miscellaneous -------------------