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TFree.cxx
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1// @(#)root/io:$Id$
2// Author: Rene Brun 28/12/94
3
4/*************************************************************************
5 * Copyright (C) 1995-2000, 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#include "TFree.h"
13#include "TList.h"
14#include "TFile.h"
15#include "Bytes.h"
16#include "Riostream.h"
17
19
20/**
21\class TFree
22\ingroup IO
23Service class for TFile.
24
25Each file has a linked list of free segments. Each free segment is described
26by its firts and last address.
27When an object is written to a file, a new Key (see TKey)
28is created. The first free segment big enough to accomodate the object
29is used.
30If the object size has a length corresponding to the size of the free segment,
31the free segment is deleted from the list of free segments.
32When an object is deleted from a file, a new TFree object is generated.
33If the deleted object is contiguous to an already deleted object, the free
34segments are merged in one single segment.
35*/
36
37////////////////////////////////////////////////////////////////////////////////
38/// Default constructor.
39
41{
42 fFirst = fLast = 0;
43}
44
45////////////////////////////////////////////////////////////////////////////////
46/// Constructor for a free segment.
47
49{
50 fFirst = first;
51 fLast = last;
52 lfree->Add(this);
53}
54
55////////////////////////////////////////////////////////////////////////////////
56/// Add a new free segment to the list of free segments.
57///
58/// - if last just precedes an existing free segment, then first becomes
59/// the new starting location of the free segment.
60/// - if first just follows an existing free segment, then last becomes
61/// the new ending location of the free segment.
62/// - if first just follows an existing free segment AND last just precedes
63/// an existing free segment, these two segments are merged into
64/// one single segment.
65///
66
68{
69 TFree *idcur = this;
70 while (idcur) {
71 Long64_t curfirst = idcur->GetFirst();
72 Long64_t curlast = idcur->GetLast();
73 if (curlast == first-1) {
74 idcur->SetLast(last);
75 TFree *idnext = (TFree*)lfree->After(idcur);
76 if (idnext == 0) return idcur;
77 if (idnext->GetFirst() > last+1) return idcur;
78 idcur->SetLast( idnext->GetLast() );
79 lfree->Remove(idnext);
80 delete idnext;
81 return idcur;
82 }
83 if (curfirst == last+1) {
84 idcur->SetFirst(first);
85 return idcur;
86 }
87 if (first < curfirst) {
88 TFree * newfree = new TFree();
89 newfree->SetFirst(first);
90 newfree->SetLast(last);
91 lfree->AddBefore(idcur, newfree);
92 return newfree;
93 }
94 idcur = (TFree*)lfree->After(idcur);
95 }
96 return 0;
97}
98
99////////////////////////////////////////////////////////////////////////////////
100/// Destructor.
101
103{
104}
105
106////////////////////////////////////////////////////////////////////////////////
107/// Encode fre structure into output buffer.
108
109void TFree::FillBuffer(char *&buffer)
110{
111 Version_t version = TFree::Class_Version();
112 if (fLast > TFile::kStartBigFile) version += 1000;
113 tobuf(buffer, version);
114 // printf("TFree::fillBuffer, fFirst=%lld, fLast=%lld, version=%d\n",fFirst,fLast,version);
115 if (version > 1000) {
116 tobuf(buffer, fFirst);
117 tobuf(buffer, fLast);
118 } else {
119 tobuf(buffer, (Int_t)fFirst);
120 tobuf(buffer, (Int_t)fLast);
121 }
122}
123
124////////////////////////////////////////////////////////////////////////////////
125/// Return the best free segment where to store nbytes.
126
128{
129 TFree *idcur = this;
130 if (idcur == 0) return 0;
131 TFree *idcur1 = 0;
132 do {
133 Long64_t nleft = Long64_t(idcur->fLast - idcur->fFirst +1);
134 if (nleft == nbytes) {
135 // Found an exact match
136 return idcur;
137 }
138 if(nleft > (Long64_t)(nbytes+3)) {
139 if (idcur1 == 0) {
140 idcur1=idcur;
141 }
142 }
143 idcur = (TFree*)lfree->After(idcur);
144 } while (idcur !=0);
145
146 // return first segment >nbytes
147 if (idcur1) return idcur1;
148
149 // try big file
150 idcur = (TFree*)lfree->Last();
151 Long64_t last = idcur->fLast+1000000000LL;
152 idcur->SetLast(last);
153 return idcur;
154}
155
156////////////////////////////////////////////////////////////////////////////////
157/// List free segment contents.
158
159void TFree::ls(Option_t *) const
160{
161 std::cout <<"Free Segment: "<<fFirst<<"\t"<<fLast<<std::endl;
162}
163
164////////////////////////////////////////////////////////////////////////////////
165/// Decode one free structure from input buffer
166
167void TFree::ReadBuffer(char *&buffer)
168{
169 Version_t version;
170 frombuf(buffer, &version);
171 if (version > 1000) {
172 frombuf(buffer, &fFirst);
173 frombuf(buffer, &fLast);
174 } else {
175 Int_t first,last;
176 frombuf(buffer, &first); fFirst = (Long64_t)first;
177 frombuf(buffer, &last); fLast = (Long64_t)last;
178 }
179}
180
181////////////////////////////////////////////////////////////////////////////////
182/// return number of bytes occupied by this TFree on permanent storage
183
185{
186 // printf("TFree::Sizeof, fFirst=%lld, fLast=%lld, version=%d\n",fFirst,fLast, (fLast > TFile::kStartBigFile));
187 if (fLast > TFile::kStartBigFile) return 18;
188 else return 10;
189}
190
void frombuf(char *&buf, Bool_t *x)
Definition: Bytes.h:280
void tobuf(char *&buf, Bool_t x)
Definition: Bytes.h:57
int Int_t
Definition: RtypesCore.h:43
short Version_t
Definition: RtypesCore.h:63
long long Long64_t
Definition: RtypesCore.h:71
const char Option_t
Definition: RtypesCore.h:64
#define ClassImp(name)
Definition: Rtypes.h:361
@ kStartBigFile
Definition: TFile.h:191
Service class for TFile.
Definition: TFree.h:27
Long64_t GetLast() const
Definition: TFree.h:41
void SetFirst(Long64_t first)
Definition: TFree.h:44
virtual ~TFree()
Destructor.
Definition: TFree.cxx:102
TFree()
Default constructor.
Definition: TFree.cxx:40
Int_t Sizeof() const
return number of bytes occupied by this TFree on permanent storage
Definition: TFree.cxx:184
virtual void ReadBuffer(char *&buffer)
Decode one free structure from input buffer.
Definition: TFree.cxx:167
void SetLast(Long64_t last)
Definition: TFree.h:45
Long64_t GetFirst() const
Definition: TFree.h:40
Long64_t fLast
Last free word of segment.
Definition: TFree.h:31
virtual void FillBuffer(char *&buffer)
Encode fre structure into output buffer.
Definition: TFree.cxx:109
void ls(Option_t *="") const
List free segment contents.
Definition: TFree.cxx:159
Long64_t fFirst
First free word of segment.
Definition: TFree.h:30
TFree * AddFree(TList *lfree, Long64_t first, Long64_t last)
Add a new free segment to the list of free segments.
Definition: TFree.cxx:67
TFree * GetBestFree(TList *lfree, Int_t nbytes)
Return the best free segment where to store nbytes.
Definition: TFree.cxx:127
A doubly linked list.
Definition: TList.h:44
virtual void Add(TObject *obj)
Definition: TList.h:87
virtual TObject * After(const TObject *obj) const
Returns the object after object obj.
Definition: TList.cxx:329
virtual TObject * Remove(TObject *obj)
Remove object from the list.
Definition: TList.cxx:821
virtual TObject * Last() const
Return the last object in the list. Returns 0 when list is empty.
Definition: TList.cxx:692
virtual void AddBefore(const TObject *before, TObject *obj)
Insert object before object before in the list.
Definition: TList.cxx:195
Definition: first.py:1