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Reference Guide
Compression.h
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1 // @(#)root/zip:$Id$
2 // Author: David Dagenhart May 2011
3 
4 /*************************************************************************
5  * Copyright (C) 1995-2011, Rene Brun and Fons Rademakers. *
6  * All rights reserved. *
7  * *
8  * For the licensing terms see $ROOTSYS/LICENSE. *
9  * For the list of contributors see $ROOTSYS/README/CREDITS. *
10  *************************************************************************/
11 
12 #ifndef ROOT_Compression
13 #define ROOT_Compression
14 
15 #if defined(__cplusplus)
16 namespace ROOT {
17 #endif
18 
19 /// The global settings depend on a global variable named R__ZipMode which can be
20 /// modified by a global function named R__SetZipMode. Both are defined in Bits.h.
21 ///
22 /// - The default is to use the global setting and the default of the global
23 /// setting is to use the ZLIB compression algorithm.
24 /// - The LZMA algorithm (from the XZ package) is also available. The LZMA
25 /// compression usually results in greater compression factors, but takes
26 /// more CPU time and memory when compressing. LZMA memory usage is particularly
27 /// high for compression levels 8 and 9.
28 /// - Finally, the LZ4 package results in worse compression ratios
29 /// than ZLIB but achieves much faster decompression rates.
30 ///
31 /// The current algorithms support level 1 to 9. The higher the level the greater
32 /// the compression and more CPU time and memory resources used during compression.
33 /// Level 0 means no compression.
34 ///
35 /// Recommendation for the compression algorithm's levels:
36 /// - ZLIB is recommended to be used with compression level 1 [101]
37 /// - LZMA is recommended to be used with compression level 7-8 (higher is better,
38 /// since in the case of LZMA we don't care about compression/decompression speed)
39 /// [207 - 208]
40 /// - LZ4 is recommended to be used with compression level 4 [404]
41 
42 
44  /// Use the global compression setting
46  /// Use ZLIB compression
48  /// Use LZMA compression
50  /// Use the old compression algorithm
52  /// Use LZ4 compression
54  /// Undefined compression algorithm (must be kept the last of the list in case a new algorithm is added).
56 };
57 
58 /// Deprecated name, do *not* use:
60 
61 #if defined(__cplusplus)
62 
63  int CompressionSettings(ECompressionAlgorithm algorithm,
64  int compressionLevel);
65 }
66 #endif
67 
68 #endif
Namespace for new ROOT classes and functions.
Definition: StringConv.hxx:21
Use LZ4 compression.
Definition: Compression.h:53
Use LZMA compression.
Definition: Compression.h:49
ECompressionAlgorithm
The global settings depend on a global variable named R__ZipMode which can be modified by a global fu...
Definition: Compression.h:43
Use ZLIB compression.
Definition: Compression.h:47
Use the old compression algorithm.
Definition: Compression.h:51
Use the global compression setting.
Definition: Compression.h:45
static enum ECompressionAlgorithm kUseGlobalSetting
Deprecated name, do not use:
Definition: Compression.h:59
Undefined compression algorithm (must be kept the last of the list in case a new algorithm is added)...
Definition: Compression.h:55