summaryrefslogtreecommitdiff
path: root/utils/indices_after.h
blob: 2891563c2d9c250902ed1e0e1a694116498e5dec (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
#ifndef INDICES_AFTER_REMOVING_H
#define INDICES_AFTER_REMOVING_H

//TODO: instead of making REMOVED a constant, make it class state (defaults to -1 as before, of course).

#include <assert.h>
#include <boost/config.hpp> // STATIC_CONSTANT
#include <algorithm> //swap
#include <iterator>

// iterator wrapper.  inverts boolean value.
template <class AB>
struct keep_not_marked
{
    typedef keep_not_marked<AB> self_type;
    AB i;
    bool operator *() const
    {
        return !*i;
    }
    void operator++()
    {
        ++i;
    }
    bool operator ==(self_type const& o)
    {
        return i==o.i;
    }
};

// outputs sequence to out iterator, of new indices for each element i, corresponding to deleting element i from an array when remove[i] is true (-1 if it was deleted, new index otherwise), returning one-past-end of out (the return value = # of elements left after deletion)
template <class KEEP,class KEEPe,class O>
unsigned new_indices_keep(KEEP i, KEEPe end,O out) {
    unsigned f=0;
    while (i!=end)
      *out++ = *i++ ? f++ : (unsigned)-1;
    return f;
};

template <class It,class KeepIf,class O>
unsigned new_indices_keep_if_n(unsigned n,It i,KeepIf const& r,O out)
{
    unsigned f=0;
    while(n--)
      *out++ = r(*i++) ? f++ : (unsigned)-1;
    return f;
}

template <class KEEP,class O>
unsigned new_indices(KEEP keep,O out) {
  return new_indices(keep.begin(),keep.end(),out);
}

template <class V,class Out,class Permi>
void copy_perm_to(Out o,V const& from,Permi i,Permi e) {
  for (;i!=e;++i)
    *o++=from[*i];
}

//to cannot be same as from, for most permutations.  for to==from, use indices_after::init_inverse_order instead.
template <class Vto,class Vfrom,class Perm>
void remap_perm_to(Vto &to,Vfrom const& from,Perm const& p) {
  to.resize(p.size());
  copy_perm_to(to.begin(),from,p.begin(),p.end());
}

// given a vector and a parallel sequence of bools where true means keep, keep only the marked elements while maintaining order.
// this is done with a parallel sequence to the input, marked with positions the kept items would map into in a destination array, with removed items marked with the index -1.  the reverse would be more compact (parallel to destination array, index of input item that goes into it) but would require the input sequence be random access.
struct indices_after
{
  BOOST_STATIC_CONSTANT(unsigned,REMOVED=(unsigned)-1);
  unsigned *map; // map[i] == REMOVED if i is deleted
  unsigned n_kept; // important to init this.
  unsigned n_mapped;
  template <class AB,class ABe>
  indices_after(AB i, ABe end) {
    init(i,end);
  }

  template <class Order>
  void init_inverse_order(unsigned from_sz,Order const& order) {
    init_inverse_order(from_sz,order.begin(),order.end());
  }
  template <class OrderI>
  void init_inverse_order(unsigned from_sz,OrderI i,OrderI end) {
    init_alloc(from_sz);
    unsigned d=0;
    n_kept=0;
    for(;i!=end;++i) {
      assert(d<from_sz);
      map[d++]=*i;
      ++n_kept;
    }
    for(;d<from_sz;++d)
      map[d]=REMOVED;
  }

  template <class Vec,class R>
  void init_keep_if(Vec v,R const& r)
  {
    n_mapped=v.size();
    if ( !n_mapped ) return;
    map=(unsigned *)::operator new(sizeof(unsigned)*n_mapped);
    n_kept=new_indices_keep_if_n(n_mapped,r,map);
  }
  // contents uninit.
  void init_alloc(unsigned n) {
    free();
    n_mapped=n;
    map=n_mapped>0 ?
      (unsigned *)::operator new(sizeof(unsigned)*n_mapped)
      : 0;
  }
  void init_const(unsigned n,unsigned map_all_to) {
    init_alloc(n);
    for (unsigned i=0;i<n;++i)
      map[i]=map_all_to;
    n_kept=(map_all_to==REMOVED)?0:n;
  }

  void init_keep_none(unsigned n) {
    init_const(n,REMOVED);
    n_kept=0;
  }

  template <class AB,class ABe>
  void init(AB i, ABe end) {
    n_mapped=end-i;
    if (n_mapped>0) {
      map=(unsigned *)::operator new(sizeof(unsigned)*n_mapped);
      n_kept=new_indices_keep(i,end,map);
    } else
      map=NULL;
  }
  template <class A>
  void init(A const& a)
  {
    init(a.begin(),a.end());
  }

  template <class A>
  indices_after(A const& a)
  {
    init(a.begin(),a.end());
  }
  indices_after() : n_mapped(0) {}
  ~indices_after()
  {
    free();
  }
  void free() {
    if (n_mapped)
      ::operator delete((void*)map);
    n_mapped=0;
  }

  bool removing(unsigned i) const
  {
    return map[i] == REMOVED;
  }
  bool keeping(unsigned i) const
  {
    return map[i] != REMOVED;
  }

  unsigned operator[](unsigned i) const
  {
    return map[i];
  }

  template <class Vec>
  void do_moves(Vec &v) const
  {
    assert(v.size()==n_mapped);
    unsigned i=0;
    for (;i<n_mapped&&keeping(i);++i) ;
    for(;i<n_mapped;++i)
      if (keeping(i))
        v[map[i]]=v[i];
    v.resize(n_kept);
  }

  template <class Vec>
  void do_moves_swap(Vec &v) const
  {
    using std::swap;
    assert(v.size()==n_mapped);
    unsigned i=0;
    for (;i<n_mapped&&keeping(i);++i) ;
    for(;i<n_mapped;++i)
      if (keeping(i))
        std::swap(v[map[i]],v[i]);
    v.resize(n_kept);
  }

  template <class Vecto,class Vecfrom>
  void copy_to(Vecto &to,Vecfrom const& v) const {
    to.resize(n_kept);
    for (unsigned i=0;i<n_mapped;++i)
      if (keeping(i))
        to[map[i]]=v[i];
  }

  //transform collection of indices into what we're remapping.  (input/output iterators)
  template <class IndexI,class IndexO>
  void reindex(IndexI i,IndexI const end,IndexO o) const {
    for(;i<end;++i) {
      unsigned m=map[*i];
      if (m!=REMOVED)
        *o++=m;
    }
  }

  template <class VecI,class VecO>
  void reindex_push_back(VecI const& i,VecO &o) const {
    reindex(i.begin(),i.end(),std::back_inserter(o));
  }

private:
  indices_after(indices_after const&)
  {
    map=NULL;
  }
};

#endif