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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 #include "Rtypes.h"
16 
17 namespace ROOT {
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 /// - ZSTD is recommended to be used with compression level 5 [505]
42 
44  struct EDefaults { /// Note: this is only temporarily a struct and will become a enum class hence the name convention
45  /// used.
46  enum EValues {
47  /// Use the global compression setting for this process; may be affected by rootrc.
49  /// Use the compile-time default setting
51  /// Use the default analysis setting; fast reading but poor compression ratio
52  kUseAnalysis = 404,
53  /// Use the recommended general-purpose setting; moderate read / write speed and compression ratio
55  /// Use the setting that results in the smallest files; very slow read and write
56  kUseSmallest = 207,
57  };
58  };
59  struct ELevel { /// Note: this is only temporarily a struct and will become a enum class hence the name convention
60  /// used.
61  enum EValues {
62  /// Some objects use this value to denote that the compression algorithm
63  /// should be inherited from the parent object
64  kInherit = -1,
65  // Compression level reserved for "uncompressed state"
67  // Compression level reserved when we are not sure what to use (1 is for the fastest compression)
68  kUseMin = 1,
74  };
75  };
76  struct EAlgorithm { /// Note: this is only temporarily a struct and will become a enum class hence the name
77  /// convention used.
78  enum EValues {
79  /// Some objects use this value to denote that the compression algorithm
80  /// should be inherited from the parent object (e.g., TBranch should get the algorithm from the TTree)
81  kInherit = -1,
82  /// Use the global compression algorithm
84  /// Use ZLIB compression
86  /// Use LZMA compression
88  /// Use the old compression algorithm
90  /// Use LZ4 compression
92  /// Use ZSTD compression
94  /// Undefined compression algorithm (must be kept the last of the list in case a new algorithm is added).
96  };
97  };
98 };
99 
101  /// Deprecated name, do *not* use:
103  /// Deprecated name, do *not* use:
105  /// Deprecated name, do *not* use:
107  /// Deprecated name, do *not* use:
109  /// Deprecated name, do *not* use:
111  /// Deprecated name, do *not* use:
113  /// Deprecated name, do *not* use:
115  /// Deprecated name, do *not* use:
117 };
118 
119 int CompressionSettings(RCompressionSetting::EAlgorithm algorithm, int compressionLevel);
120 /// Deprecated name, do *not* use:
121 int CompressionSettings(ROOT::ECompressionAlgorithm algorithm, int compressionLevel);
122 } // namespace ROOT
123 
124 #endif
EValues
Note: this is only temporarily a struct and will become a enum class hence the name convention used...
Definition: Compression.h:61
The global settings depend on a global variable named R__ZipMode which can be modified by a global fu...
Definition: Compression.h:43
VSD Structures.
Definition: StringConv.hxx:21
Use the setting that results in the smallest files; very slow read and write.
Definition: Compression.h:56
ECompressionAlgorithm
Definition: Compression.h:100
Use the global compression algorithm.
Definition: Compression.h:83
EValues
Note: this is only temporarily a struct and will become a enum class hence the name convention used...
Definition: Compression.h:46
Deprecated name, do not use:
Definition: Compression.h:104
Deprecated name, do not use:
Definition: Compression.h:102
Use the compile-time default setting.
Definition: Compression.h:50
EValues
Note: this is only temporarily a struct and will become a enum class hence the name.
Definition: Compression.h:78
Deprecated name, do not use:
Definition: Compression.h:112
int CompressionSettings(RCompressionSetting::EAlgorithm algorithm, int compressionLevel)
Some objects use this value to denote that the compression algorithm should be inherited from the par...
Definition: Compression.h:81
Deprecated name, do not use:
Definition: Compression.h:110
Use the default analysis setting; fast reading but poor compression ratio.
Definition: Compression.h:52
Deprecated name, do not use:
Definition: Compression.h:108
Use the global compression setting for this process; may be affected by rootrc.
Definition: Compression.h:48
Deprecated name, do not use:
Definition: Compression.h:114
Some objects use this value to denote that the compression algorithm should be inherited from the par...
Definition: Compression.h:64
Use the recommended general-purpose setting; moderate read / write speed and compression ratio...
Definition: Compression.h:54
Deprecated name, do not use:
Definition: Compression.h:116
Undefined compression algorithm (must be kept the last of the list in case a new algorithm is added)...
Definition: Compression.h:95
Deprecated name, do not use:
Definition: Compression.h:106