Complex multidimensional array in C++

Daniel Pfeffer

If you have an two-dimensional array where each row has a differing number of elements, why not use a std::vector?

std::vector foo2DArray[];

Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.

Lost User

I think you meant this answer for Vaclav.

Daniel Pfeffer

:-O

Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.

Vaclav_

Thanks, just what the doctor ordered. Then I can add another member to the struct if I want. Nice and clean solution.

k5054

If your single element is unique, then maybe a map of vectors might be a better choice e.g.

map>

There is a requirement that obj_a implement operator<(). Basically if its not a basic type (e.g. int, double, string, etc), you need to add a

bool operator<(const foo& other) const {}

method to the object, which is usually straight forward.

Lost User

Yes, if you are using a struct you can have many different items inside it. Also, as Daniel mentions below (to me) you may want to use a std::vector rather than a simple array.

Vaclav_

Here is my test code. It is not very "dynamic" but will do for now. I may add the "Command" as a first element in Data array to make sure they match. Actually it would simplify things (a little ) - using just multidimensional array with first element being "Command". But I like the struct for future.... Now I need to modify usage of Command /Data....

#define COMMAND_ARRAY 16
struct ILI9341 {
int Command; // ILI9341 commands
int* Data; // ILI9341 data
} ILI9341Array[COMMAND_ARRAY];

// define/ assign Command
int index = 0;
int dataIndex = 0;
int DefineCommand\[COMMAND\_ARRAY\] = { 0x0, 0x1, 0x4 };
int DefineData\[\]\[10\] = { { 1, 2, 3, 4 }, { 5, 6, 7 }, { 9, 10, 11, 12, 13,
		14 } };
for (index = 0; index != 3; index++) {
	ILI9341Array\[index\].Command = DefineCommand\[index\];

#ifdef DEBUG
cout << "ILI9341Array[" << dec << +index << "] Command 0x" << hex
<< ILI9341Array[index].Command << endl;
#endif
ILI9341Array[index].Data = DefineData[index];
#ifdef DEBUG
do {
cout << "ILI9341Array[" << dec << +index << "] Data[" << dec
<< +dataIndex << "] 0x" << hex
<< ILI9341Array[index].Data[dataIndex] << endl;

	} while (ILI9341Array\[index\].Data\[++dataIndex\]);
	dataIndex = 0;

#endif

k5054

That's way too much typing. Consider:

#include <iostream>
#include <iomanip>
#include <map>
#include <vector>

using namespace std;

#define DEBUG

int main()
{
map<int,vector<int>> IL9341Command = {{ {0x0, {{ 1, 2, 3, 4 }} },
{0x1, {{ 4, 6, 7, }} },
{0x4, {{ 9, 10, 11, 12, 13, 14 }} },
{0xff, {{ 44, 55, 66, 77 }} } }};

#ifdef DEBUG
for(auto iter : IL9341Command) {
cout << "IL9341Comand [ 0x" << hex << iter.first << " ] =";
for(auto cmd : iter.second)
cout << " 0x" << hex << cmd;
cout << endl;
}

int \*data = IL9341Command\[0xff\].data(); // get access to raw vector data

cout << "\\nCommand\[0xff\] data :";
for(size\_t i = 0; i < IL9341Command\[0xff\].size(); i++)
    cout <<  " 0x" << data\[i\];
cout << endl;

#endif // DEBUG

return 0;

}

You can access the command data directly if you know the key via IL941Command[key], without having to iterate through the array, and as shown above, access to the "raw data" can be gained by calling data() on the vector. If you have C++17 then you can simplify the for(auto iter ...) loop as follows

for(auto [key, data] : IL9341Command) {
cout << "IL9341Comand [ 0x" << hex << key << " ] =";
for(auto cmd : data)
cout << " 0x" << hex << cmd;
cout << endl;
}

k5054

Hmm. Not sure why the code didn't format properly within the <pre code="C++"> tags. I looked closely and there wasn't any tags in the code as posted. Also, how does one post code with preprocessor directives in column one without them turning into (h1) header lines? Edit: the format issue with the code was because I needed to convert "<" into <.

Vaclav_

Well , I realize my way is too crude for today's standards. Yes, the "command(s)' are unique and direct access to data would be much cleaner than scanning. But I forgot that the command is actually "top level" - the same data can be actual "command" or "data" ( to be read). The clocking of the command (command or data) is different so I need some identifier for that. I need to rethink the method how to accomplish that - so far plain two dimensional array with "command" , " command or data flag " , "data" scheme looks simpler. Minor issue is - the "data" can be 0x0 - such as "0x4, 0x0, 0x7" etc.so plain scanning won't do. I need a break. Later.

Stefan_Lang

Vaclav_ wrote:

PS I did try std:array , but it conflicts with "boost" - can't do for now.

I'm using both boost functinality and std::array without any problems, ever. What is the problem you are experiencing? Maybe you were too gracious with using statements and contaminating your global namespace?

GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)

Vaclav_

Richard, I finally decided to use your suggestion and having a hard time initializing the pointer in the struct. Here is how it looks as of today

struct ILI9341 {
	uint8\_t index;  // tracking index
	uint8\_t Command; //
	uint8\_t c\_d;    // flag 0 command 1 data
	uint8\_t \*Data;  // data array
// data array format
// valid data count
// data...
// end marker
	char \*Name;     // command name
	char \*Function; // brief function description
	uint32\_t delay = 0; // delay in uS after command
	char \*RefPage;  // ILI9341 manual reference page
	char \*Notes;    // misc notes
	uint8\_t temp\[COMMAND\_ARRAY\] = {}; // kluge 
} ILI9341\_CommandList\[COMMAND\_ARRAY\];

I did try this (C sample I found) , but that obviously does not work initializing multiple struct and I feel it defeats the pointer by making the temp array fixed length.

uint8_t temp[3] = { 0x1, 0x0, 0xFF };
//int g_thing1array[3] = { 3, 4, 5 }; C example
//thing g_thing1 = { 1, 2, g_thing1array };
ILI9341_CommandList[4].Data = temp;

Lost User

You cannot add initialisers to the struct definition, but only to actual instances of it. So it should rather be something like:

struct ILI9341 { // definition of the struct starts here
uint8_t index; // tracking index
uint8_t Command; //
uint8_t c_d; // flag 0 command 1 data
uint8_t *Data; // data array
// data array format
// valid data count
// data...
// end marker
char *Name; // command name
char *Function; // brief function description
uint32_t delay; // delay in uS after command
char *RefPage; // ILI9341 manual reference page
char *Notes; // misc notes
uint8_t* temp; // this should be a pointer to allow for variable length entries
} ILI9341_CommandList[COMMAND_ARRAY] =
{ // actual instances in the array are initialised here
{ // first entry in the structure array
0, // tracking index
0, // Command
0, // flag 0 command 1 data
buffer, // data array buffer declared elsewhere as BYTE buffer[some number]
"command name" // command name
"Function", // brief function description
100, // delay in uS after command
RefPage, // ILI9341 manual reference page
Notes, // misc notes
{ 0x1, 0x0, 0xFF } // command array - you may need a counter somewhere to indicate
// how many entries are in this array
}, // end of the first entry
{
// other entries up to a maximum of COMMAND_ARRAY
}
};

And you can also fill in any of the fields later in the executable code by addressing struct entries as ILI9341_CommandList[n] where n is in the range [0..COMMAND_ARRAY-1].