Mesh Oriented datABase  (version 5.5.1)
An array-based unstructured mesh library
moab::BitPage Class Reference

bit tag data More...

#include <BitPage.hpp>

Public Member Functions

 BitPage (int bits_per_ent, unsigned char init_val)
 Initialize memory. More...
 
void get_bits (int offset, int count, int bits_per_ent, unsigned char *data) const
 Get tag values. More...
 
void set_bits (int offset, int count, int bits_per_ent, const unsigned char *data)
 Set tag values. More...
 
void set_bits (int offset, int count, int bits_per_ent, unsigned char value)
 Set several tag values to the same value. More...
 
unsigned char get_bits (int offset, int bits_per_ent) const
 Get tag value. More...
 
void set_bits (int offset, int bits_per_ent, unsigned char data)
 Set tag value. More...
 
void search (unsigned char value, int offset, int count, int bits_per_ent, Range &results, EntityHandle start) const
 Search stored values for specified value. More...
 

Private Attributes

char byteArray [BitTag::PageSize]
 The actual array of bytes. More...
 

Detailed Description

bit tag data

This class represents a fixed-size block of memory in which bit tag values are stored.

Definition at line 17 of file BitPage.hpp.

Constructor & Destructor Documentation

◆ BitPage()

moab::BitPage::BitPage ( int  bits_per_ent,
unsigned char  init_val 
)

Initialize memory.

Parameters
bits_per_entNumber of bits in each tag value. MUST BE A POWER OF TWO.
init_valThe lower bits_per_ent bits of this byte are used to initialize each tag value.

Definition at line 22 of file BitPage.cpp.

23 {
24  unsigned char mask = (unsigned char)( 1 << per_ent ) - 1; // 2^per_ent - 1
25  init_val &= (unsigned char)mask;
26  switch( per_ent )
27  {
28  default:
29  assert( false );
30  abort();
31  break; // must be power of two
32 
33  // Note: fall through such that all bits in init_val are set, but with odd structure to avoid
34  // fall-through warnings
35  case 1:
36  init_val |= (unsigned char)( init_val << 1 );
37  // fall through
38  case 2:
39  init_val |= (unsigned char)( init_val << 2 );
40  // fall through
41  case 4:
42  init_val |= (unsigned char)( init_val << 4 );
43  // fall through
44  case 8:;
45  }
46  memset( byteArray, init_val, BitTag::PageSize );
47 }

References byteArray, and moab::BitTag::PageSize.

Member Function Documentation

◆ get_bits() [1/2]

unsigned char moab::BitPage::get_bits ( int  offset,
int  bits_per_ent 
) const
inline

Get tag value.

Get one tag value.

Parameters
offsetOffset into list of values, where a value of zero indicates the first tag value, a value of one indicates the second tag value, etc. NOTE: This is the value offset, not the bit offset.
bits_per_entNumber of bits composing each tag value. NOTE: Must be a power of two.
Returns
A byte containing the tag value in the lower bits with any unused higher bits zeroed.

Definition at line 127 of file BitPage.hpp.

128 {
129  // Assume per_ent is a power of two, which should be guaranteed
130  // by higher-level code.
131  unsigned char mask = (unsigned char)( 1 << per_ent ) - 1; // 2^per_ent - 1
132  int byte = ( offset * per_ent ) >> 3; // shifting 3 is dividing by eight
133  int bit = ( offset * per_ent ) & 7; // masking with 7 is modulo eight
134  assert( byte < BitTag::PageSize );
135  return (unsigned char)( byteArray[byte] >> bit ) & mask;
136 }

References byteArray, and moab::BitTag::PageSize.

◆ get_bits() [2/2]

void moab::BitPage::get_bits ( int  offset,
int  count,
int  bits_per_ent,
unsigned char *  data 
) const
inline

Get tag values.

Get 'count' tag values, beginning with the one at 'offset'.

Parameters
offsetOffset into list of values, where a value of zero indicates the first tag value, a value of one indicates the second tag value, etc. NOTE: This is the value offset, not the bit offset.
countNumber of consecutive tag values to get.
bits_per_entNumber of bits composing each tag value. NOTE: Must be a power of two.
dataMemory into which to copy tag values. Each value is copied into a separate byte, such that the lower bits of the bit contain the tag value and any unused higher bits are zero.

Definition at line 149 of file BitPage.hpp.

150 {
151  unsigned char* end = data + count;
152  while( data != end )
153  *( data++ ) = get_bits( offset++, per_ent );
154 }

Referenced by search().

◆ search()

void moab::BitPage::search ( unsigned char  value,
int  offset,
int  count,
int  bits_per_ent,
Range results,
EntityHandle  start 
) const

Search stored values for specified value.

Find the offsets n in the data at which the specified value occurs, and for each one insert 'start + n' into the passed Range.

Parameters
valueThe value to look for
offsetThe offset at which to begin searching
countThe number of values to search
bits_per_entNumber of bits composing each tag value.
resultsResult list.
startThe handle of the entity corresponding to the tag value stored at 'offset'

Definition at line 9 of file BitPage.cpp.

11 {
12  const int end = offset + count;
13  Range::iterator hint = results.begin();
14  while( offset != end )
15  {
16  if( get_bits( offset, per_ent ) == value ) hint = results.insert( hint, start );
17  ++offset;
18  ++start;
19  }
20 }

References moab::Range::begin(), get_bits(), and moab::Range::insert().

◆ set_bits() [1/3]

void moab::BitPage::set_bits ( int  offset,
int  bits_per_ent,
unsigned char  data 
)
inline

Set tag value.

Set tag value.

Parameters
offsetOffset into list of values, where a value of zero indicates the first tag value, a value of one indicates the second tag value, etc. NOTE: This is the value offset, not the bit offset.
bits_per_entNumber of bits composing each tag value. NOTE: Must be a power of two.
valueThe lower 'bits_per_ent' of this byte are used as the tag value. Any additional higher bits are ignored.

Definition at line 138 of file BitPage.hpp.

139 {
140  int byte = ( offset * per_ent ) >> 3; // shifting 3 is dividing by eight
141  int bit = ( offset * per_ent ) & 7; // masking with 7 is modulo eight
142  assert( byte < BitTag::PageSize );
143  // Assume per_ent is a power of two, which should be guaranteed
144  // by higher-level code.
145  unsigned char mask = (unsigned char)( ( 1 << per_ent ) - 1 ) << bit;
146  byteArray[byte] = (char)( ( byteArray[byte] & ~mask ) | ( ( bits << bit ) & mask ) );
147 }

References byteArray, and moab::BitTag::PageSize.

◆ set_bits() [2/3]

void moab::BitPage::set_bits ( int  offset,
int  count,
int  bits_per_ent,
const unsigned char *  data 
)
inline

Set tag values.

Set 'count' tag values, beginning with the one at 'offset'.

Parameters
offsetOffset into list of values, where a value of zero indicates the first tag value, a value of one indicates the second tag value, etc. NOTE: This is the value offset, not the bit offset.
countNumber of consecutive tag values to set.
bits_per_entNumber of bits composing each tag value. NOTE: Must be a power of two.
dataMemory from which to copy tag values. Each value is copied from a separate byte. The lower 'bits_per_ent' of each byte are used as the tag value. Any additional higher bits are ignored.

Definition at line 156 of file BitPage.hpp.

157 {
158  const unsigned char* end = data + count;
159  while( data != end )
160  set_bits( offset++, per_ent, *( data++ ) );
161 }

Referenced by set_bits().

◆ set_bits() [3/3]

void moab::BitPage::set_bits ( int  offset,
int  count,
int  bits_per_ent,
unsigned char  value 
)
inline

Set several tag values to the same value.

Set 'count' tag values to specified value.

Parameters
offsetOffset into list of values, where a value of zero indicates the first tag value, a value of one indicates the second tag value, etc. NOTE: This is the value offset, not the bit offset.
countNumber of consecutive tag values to set.
bits_per_entNumber of bits composing each tag value. NOTE: Must be a power of two.
valueThe lower 'bits_per_ent' of this byte are used as the tag value. Any additional higher bits are ignored.

Definition at line 163 of file BitPage.hpp.

164 {
165  int end = offset + count;
166  while( offset < end )
167  set_bits( offset++, per_ent, value );
168 }

References set_bits().

Member Data Documentation

◆ byteArray

char moab::BitPage::byteArray[BitTag::PageSize]
private

The actual array of bytes.

Definition at line 124 of file BitPage.hpp.

Referenced by BitPage(), get_bits(), and set_bits().


The documentation for this class was generated from the following files: