cprover
boolbv_byte_update.cpp
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1 /*******************************************************************\
2 
3 Module:
4 
5 Author: Daniel Kroening, kroening@kroening.com
6 
7 \*******************************************************************/
8 
9 #include "boolbv.h"
10 
11 #include <iostream>
12 #include <cassert>
13 
14 #include <util/arith_tools.h>
15 #include <util/byte_operators.h>
16 #include <util/endianness_map.h>
17 
19 {
20  if(expr.operands().size()!=3)
21  throw "byte_update takes three operands";
22 
23  const exprt &op=expr.op0();
24  const exprt &offset_expr=expr.offset();
25  const exprt &value=expr.value();
26 
27  bool little_endian;
28 
29  if(expr.id()==ID_byte_update_little_endian)
30  little_endian=true;
31  else if(expr.id()==ID_byte_update_big_endian)
32  little_endian=false;
33  else
34  assert(false);
35 
36  bvt bv=convert_bv(op);
37 
38  const bvt &value_bv=convert_bv(value);
39  std::size_t update_width=value_bv.size();
40  std::size_t byte_width=8;
41 
42  if(update_width>bv.size())
43  update_width=bv.size();
44 
45  // see if the byte number is constant
46 
47  mp_integer index;
48  if(!to_integer(offset_expr, index))
49  {
50  // yes!
51  mp_integer offset=index*8;
52 
53  if(offset+update_width>mp_integer(bv.size()) || offset<0)
54  {
55  // out of bounds
56  }
57  else
58  {
59  if(little_endian)
60  {
61  for(std::size_t i=0; i<update_width; i++)
62  bv[integer2size_t(offset+i)]=value_bv[i];
63  }
64  else
65  {
66  endianness_mapt map_op(op.type(), false, ns);
67  endianness_mapt map_value(value.type(), false, ns);
68 
69  std::size_t offset_i=integer2unsigned(offset);
70 
71  for(std::size_t i=0; i<update_width; i++)
72  {
73  size_t index_op=map_op.map_bit(offset_i+i);
74  size_t index_value=map_value.map_bit(i);
75 
76  assert(index_op<bv.size());
77  assert(index_value<value_bv.size());
78 
79  bv[index_op]=value_bv[index_value];
80  }
81  }
82  }
83 
84  return bv;
85  }
86 
87  // byte_update with variable index
88  for(std::size_t offset=0; offset<bv.size(); offset+=byte_width)
89  {
90  // index condition
92  equality.lhs()=offset_expr;
93  equality.rhs()=from_integer(offset/byte_width, offset_expr.type());
94  literalt equal=convert(equality);
95 
96  endianness_mapt map_op(op.type(), little_endian, ns);
97  endianness_mapt map_value(value.type(), little_endian, ns);
98 
99  for(std::size_t bit=0; bit<update_width; bit++)
100  if(offset+bit<bv.size())
101  {
102  std::size_t bv_o=map_op.map_bit(offset+bit);
103  std::size_t value_bv_o=map_value.map_bit(bit);
104 
105  bv[bv_o]=prop.lselect(equal, value_bv[value_bv_o], bv[bv_o]);
106  }
107  }
108 
109  return bv;
110 }
BigInt mp_integer
Definition: mp_arith.h:19
Maps a big-endian offset to a little-endian offset.
virtual literalt convert(const exprt &expr) override
Definition: prop_conv.cpp:175
exprt & op0()
Definition: expr.h:84
typet & type()
Definition: expr.h:60
equality
Definition: std_expr.h:1082
const irep_idt & id() const
Definition: irep.h:189
Expression classes for byte-level operators.
virtual const bvt & convert_bv(const exprt &expr)
Definition: boolbv.cpp:115
const namespacet & ns
unsigned integer2unsigned(const mp_integer &n)
Definition: mp_arith.cpp:203
virtual bvt convert_byte_update(const byte_update_exprt &expr)
virtual literalt equality(const exprt &e1, const exprt &e2)
Definition: equality.cpp:17
Base class for all expressions.
Definition: expr.h:46
TO_BE_DOCUMENTED.
bool to_integer(const exprt &expr, mp_integer &int_value)
Definition: arith_tools.cpp:18
size_t map_bit(size_t bit) const
virtual literalt lselect(literalt a, literalt b, literalt c)=0
std::size_t integer2size_t(const mp_integer &n)
Definition: mp_arith.cpp:195
operandst & operands()
Definition: expr.h:70
constant_exprt from_integer(const mp_integer &int_value, const typet &type)
std::vector< literalt > bvt
Definition: literal.h:197