Reading Hex from an file - c

Question

So my knowledge of pointers is a bit rusty and I think thats where I'm getting messed up, I am trying to write a function that will grab hex values (an amount n) at a specified offset in the file. And write those values to an array.
File I'm reading from, Example
0 1 2 3 4 5 6 7 8 9 A B C D E F
0 F6 EA 9D DE D8 40 1C 44 19 24 59 D2 6A 2C 48 1D
1 FC 96 DE 94 AF 95 FC 42 9B 6D DA 15 D4 CE 88 BB
2 B8 24 99 8F 65 B5 D3 7E D9 5D 51 44 89 97 61 85
3 2D 40 1A DC D5 16 1F 70 84 F9 85 58 C8 0E 13 80
4 32 AC 10 97 61 B3 16 3B 40 67 7A CA FE E1 4F 2B
5 21 A9 07 F6 80 26 66 04 20 EC 5C E8 FA 70 68 2C
6 1C 78 C4 7E 5C DA B9 9C 41 38 66 3F 19 B6 6A 3A
Here's the function I've written thus far.
aDest point's to an array of size nBytes + 1
bAddr point's to firstbyte of the memory region
OffsetAmt is a location which is relative bAddr
nBytes is just the number of bytes that I want to copy
Heres the function
void getHexBytesAt(uint8_t* const aDest, const uint8_t* const bAddr,
uint16_t OffsetAmt, uint8_t nBytes)
{
const uint8_t *point1 = bAddr; //set he address of point1 to base address value
//front point1 shift until we get to the specified offset value
for (int i = 0; i < Offset; i++)
{
point1 = (point1 + 1);
}
//set the values of *aDest to the value of point1;
//increment point1
for (int k = 0; k < nBytes; k++)
{
*aDest = point1;
point1 = (point1 + 1);
}
The problem I'm having is im not even getting the first byte copied into the array correctly,
My output looks like this Getting 9 bytes,
starting at the offset 2C
MY OUTPUT: 84 CA CA CA CA CA CA CA CA
FILE: 89 97 61 85 2D 40 1A DC D5

Answer 1

If you want to read the data from the Memory bAddr then you must
dereference the pointer for reading
increment the Destination pointer
This would be implemented like this:
void getHexBytesAt(uint8_t* const aDest, const uint8_t* const bAddr,
uint16_t OffsetAmt, uint8_t nBytes)
{
const uint8_t *point1 = bAddr; //set he address of point1 to base address value
//front point1 shift until we get to the specified offset value
for (int i = 0; i < OffsetAmt; i++) // fixed typo
{
point1 = (point1 + 1);
}
//set the values of *aDest to the value of point1;
//increment point1
for (int k = 0; k < nBytes; k++)
{
*aDest = *point1; // copy data from address the point1 points to
aDest = aDest + 1; // increment destination pointer
point1 = (point1 + 1);
}
}
But this can be done much simpler:
void getHexBytesAt(uint8_t* const aDest, const uint8_t* const bAddr,
uint16_t OffsetAmt, uint8_t nBytes)
{
memcpy(aDest, bAddr + OffsetAmt, nBytes);
}
You should consider replacing the function with the one-liner that implements it in your code.
BTW: There is no file used in the code. You should review your question.