No need to liknk with lhapdf, pythia6 and microcern libraries
[u/mrichter/AliRoot.git] / RAW / AliBitPacking.cxx
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3ea47630 1/**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
3 * *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
6 * *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
15
16/* $Id$ */
17
18///////////////////////////////////////////////////////////////////////////////
19///
20/// This is a service class for packing and unpacking bits in a 32 bit word.
21///
22///////////////////////////////////////////////////////////////////////////////
23
24#include <TError.h>
25
26#include "AliBitPacking.h"
27
28
29ClassImp(AliBitPacking)
30
31
32//_____________________________________________________________________________
33Bool_t AliBitPacking::PackWord(UInt_t data, UInt_t &word,
34 Int_t startBit, Int_t stopBit)
35{
36// Packs data into the word buffer from startBit bit up to stopBit bit
37
38 // check that startBit and stopBit are reasonable
39 if (startBit > stopBit) {
40 ::Error("AliBitPacking::PackWord",
41 "startBit is larger than stopBit");
42 return kFALSE;
43 }
44 if (stopBit > 31) {
45 ::Error("AliBitPacking::PackWord",
46 "stopBit exceeds valid range of 32 bits");
47 return kFALSE;
48 }
49
50 // create a word with the bits 0 to (stopBit-startBit) set
51 UInt_t bits = 0xFFFFFFFF;
52 if (stopBit-startBit < 31) bits = (1 << (stopBit-startBit+1)) - 1;
53
54 // check that the data fits into the given bit range
55 if (data > bits){
56 ::Error("AliBitPacking::PackWord",
57 "Word to be filled is not within desired length");
58 return kFALSE;
59 }
60
61 // clear the bits from startBit to stopBit
62 word &= (0xFFFFFFFF ^ (bits << startBit));
63
64 // fill in the data bits
65 word |= (data << startBit);
66
67 return kTRUE;
68}
69
70//_____________________________________________________________________________
71UInt_t AliBitPacking::UnpackWord(UInt_t word, Int_t startBit, Int_t stopBit)
72{
73// Unpacks data of stopBit-startBit+1 bits from word buffer starting from
74// the position indicated by startBit
75
76 // check that startBit and stopBit are reasonable
77 if (startBit > stopBit) {
78 ::Error("AliBitPacking::UnpackWord",
79 "startBit is larger than stopBit");
80 return 0xFFFFFFFF;
81 }
82 if (stopBit > 31) {
83 ::Error("AliBitPacking::UnpackWord",
84 "stopBit exceeds valid range of 32 bits");
85 return 0xFFFFFFFF;
86 }
87
88 // create a word with the bits 0 to (stopBit-startBit) set
89 UInt_t bits = 0xFFFFFFFF;
90 if (stopBit-startBit < 31) bits = (1 << (stopBit-startBit+1)) - 1;
91
92 // pick out the requested bits
93 return ((word >> startBit) & bits);
94}