I'm trying to create a complete uint32_t using vector of uint8_t bytes. It should be filled iteratively. It can happen in any of the following ways:
uint32_t L = 0;
uint32_t* LPtr = &L;
std::vector<uint8_t> data1 = {0x1f, 0x23};
memcpy(LPtr, data1.data(), 2);
EXPECT_EQ(0x231f, L);
Above works fine (first two bytes). But following is not (with the two sets of bytes).
uint32_t L = 0;
uint32_t* LPtr = &L;
std::vector<uint8_t> data1 = {0x1f, 0x23};
std::vector<uint8_t> data2 = {0x3a, 0xee};
memcpy(LPtr, data1.data(), 2);
memcpy(LPtr, data2.data(), 2);
EXPECT_EQ(0x231f, L);
EXPECT_EQ(0x231fee3a, L);
The issue I feel is LPtr does not point to the next byte that should be filled next. I tried LPtr+2 which is not pointing to individual byte of uint32_t.
This should be done using memcpy and output should go to uint32_t. Any idea to get this sorted?
Endianness is not an issue as of now. It can be corrected once the uint32_t is completed (when eventually 4 bytes get copied).
Any help is appreciated!
The problem is you're using a pointer to uint32_t so incrementing it won't make it iterate by 1 byte, only by 4 bytes. Here is a version which populates all bytes of L, but it's still messing with endianness:
uint32_t gimmeInteger(std::vector<uint8_t> data1, std::vector<uint8_t> data2)
{
assert((data1.size() == 2));
assert((data2.size() == 2));
uint32_t L = 0;
uint8_t* LPtr = reinterpret_cast<uint8_t*>(&L);
memcpy(LPtr, data1.data(), 2);
memcpy(LPtr+2, data2.data(), 2);
return L;
}
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