Fix instantiation and array accesses in class base_uint<BITS>

The implementation of base_uint::operator++(int) and base_uint::operator--(int) is now safer.
Array pn is accessed via index i after bounds checking has been performed on the index, rather than before.
The logic of the while loops has also been made more clear.

A compile time assertion has been added in the class constructors to ensure that BITS is a positive multiple of 32.
This commit is contained in:
Pavlos Antoniou 2017-06-07 17:21:29 +00:00
parent 46311e792f
commit e5c616888b
2 changed files with 10 additions and 2 deletions

View File

@ -15,6 +15,8 @@
template <unsigned int BITS>
base_uint<BITS>::base_uint(const std::string& str)
{
static_assert(BITS/32 > 0 && BITS%32 == 0, "Template parameter BITS must be a positive multiple of 32.");
SetHex(str);
}

View File

@ -31,12 +31,16 @@ public:
base_uint()
{
static_assert(BITS/32 > 0 && BITS%32 == 0, "Template parameter BITS must be a positive multiple of 32.");
for (int i = 0; i < WIDTH; i++)
pn[i] = 0;
}
base_uint(const base_uint& b)
{
static_assert(BITS/32 > 0 && BITS%32 == 0, "Template parameter BITS must be a positive multiple of 32.");
for (int i = 0; i < WIDTH; i++)
pn[i] = b.pn[i];
}
@ -50,6 +54,8 @@ public:
base_uint(uint64_t b)
{
static_assert(BITS/32 > 0 && BITS%32 == 0, "Template parameter BITS must be a positive multiple of 32.");
pn[0] = (unsigned int)b;
pn[1] = (unsigned int)(b >> 32);
for (int i = 2; i < WIDTH; i++)
@ -174,7 +180,7 @@ public:
{
// prefix operator
int i = 0;
while (++pn[i] == 0 && i < WIDTH-1)
while (i < WIDTH && ++pn[i] == 0)
i++;
return *this;
}
@ -191,7 +197,7 @@ public:
{
// prefix operator
int i = 0;
while (--pn[i] == (uint32_t)-1 && i < WIDTH-1)
while (i < WIDTH && --pn[i] == (uint32_t)-1)
i++;
return *this;
}