how to convert array of uint16 into array of uint8

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to convert array of uint16 having 5 elements to array of uint8

[edit]
From OP in comment to one of the solutions (explains more thoroughly):
"thanx for replying but i want to separate both bytes of uint16 and then the total 10 bytes which , i will get should be in array of uint8"
[/edit]

Posted 8-Jun-11 0:25am

d_singh

Updated 8-Jun-11 7:31am

Albert Holguin

v2

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Comments

ThatsAlok 8-Jun-11 6:27am

it's not difficult, but there could be loss of data!

Sergey Alexandrovich Kryukov 8-Jun-11 13:21pm

OP did not explain it yet, bit I guess it should break 16-bit words into bytes with no loss. uint16 arr1[2] -> uint8 arr2[4]...
--SA

5 solutions

Solution 2

This discussion[^] may help you.

Posted 8-Jun-11 0:29am

Abhinav S

Comments

Sergey Alexandrovich Kryukov 8-Jun-11 13:25pm

There are answers inside, a 5.
--SA

Abhinav S 9-Jun-11 2:20am

Thank you.

Albert Holguin 8-Jun-11 13:38pm

the description of the union within would be perfect for this application as well, wouldn't require any looping whatsoever, my 5

Abhinav S 9-Jun-11 2:20am

Thank you.

Solution 4

Just use Alberts third line of code:

for(int i = 0; i < 10; i++)
{
  cout << ptr[i] << endl;
}

Best regards
Espen Harlinn

Posted 8-Jun-11 5:55am

Espen Harlinn

Comments

Sergey Alexandrovich Kryukov 8-Jun-11 13:25pm

What question do you ask by this post?
--SA

Espen Harlinn 8-Jun-11 14:39pm

In his reply to ThatsAlok d_singh wrote: thanx for replying but i want to separate both bytes of uint16 and then the total 10 bytes which , i will get should be in array of uint8.

My guess is that he wants a sequence of bytes, and doesn't actually need to copy the data ...

Sergey Alexandrovich Kryukov 8-Jun-11 18:21pm

I see. Thinks depend on that. For example, I saw a solution based on union: it would need extra step (or it's not good enough) if the arrays should be independent objects (clones) and not read-only. 5 for the note.
--SA

Espen Harlinn 8-Jun-11 19:46pm

Personally I prefer casting in most cases ( less work :blush: ), but a union may allow the intent of the code to become clearer. I'm well aware that littering the code with casts this way becomes a real pain if the client suddenly wants you to support communication with a system using a different byteordering :) - one workaround is to include information about senders byte order in the packet header - similar to OMG.org IIOP (corba)

Sergey Alexandrovich Kryukov 8-Jun-11 23:32pm

Sure, agree.
--SA

Solution 5

For the sake of completeness on the subject, another method:

union MB_DATA
{
  uint16 b16[5];
  uint8  b8[10];
};

MB_DATA data = {2,3,20,90,3857}; //this will already contain both 16 and 8 bit representations

Should be noted that with this solution, the two methods of accessing the data are dependent, meaning you change something in one and it changes on both.... unions don't allocate memory independently for members.

Posted 8-Jun-11 7:51am

Albert Holguin

Updated 8-Jun-11 12:38pm

v2

Comments

Espen Harlinn 8-Jun-11 19:37pm

Another 5 :)

Albert Holguin 8-Jun-11 19:42pm

thanks espen... :)

Solution 1

isn't this simple

uint16 arr[5]= some values;
uint8 arr1[5]

for(i=0 to 5)
arr1[i]=arr[i]

Posted 8-Jun-11 0:29am

ThatsAlok

Comments

d_singh 8-Jun-11 7:08am

thanx for replying but i want to separate both bytes of uint16 and then the total 10 bytes which , i will get should be in array of uint8

Richard MacCutchan 8-Jun-11 7:13am


// add another index
arr1[i] = arr[j] >> 8;
arr1[i+1] = arr[j] & 0xFF;

This is basic data manipulation using standard operators that you really should know if you are already writing code.

d_singh 8-Jun-11 8:17am

thanx

Albert Holguin 8-Jun-11 13:30pm

this probably shouldn't have been downvoted since OP hadn't quite explained himself completely yet.

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Albert Holguin · Accepted Answer · 2011-06-08T04:55:00

Solution 3

Another method is playing with the pointers...

uint16 arr1[5] = {2, 3, 20, 90, 3857};
uint8  arr2[10] = {0};

uint8* ptr = (uint8 *) &arr1; //cast the 16bit pointer to an 8bit pointer
for(int i=0; i<10; i++)
{
 arr2[i] = *ptr; //pass data to other array
 ptr++;          //move your pointer
}

Posted 8-Jun-11 4:55am

Albert Holguin

Comments

Espen Harlinn 8-Jun-11 11:51am

Good reply Albert, my 5

Albert Holguin 8-Jun-11 12:52pm

thank you espen

Sergey Alexandrovich Kryukov 8-Jun-11 13:18pm

Sure, simple effective way to break into bytes, a 5.
--SA

Albert Holguin 8-Jun-11 13:28pm

Yeah, I've used this before for data packing/unpacking... thanks SA

Sergey Alexandrovich Kryukov 8-Jun-11 18:22pm

I saw also a union-based approach, but it depends on where you need to have independent read/write "clones". Your solution already makes it separate independent objects.
--SA

Albert Holguin 8-Jun-11 18:29pm

yeah... definitely agree