General string into circular buffer code

[ElecDesigner]

In C, what's the best way write a generalized function to get various strings into a circular character array buffer?

Is there a better (more efficient) way that looping one byte at a time, bearing in mind that we (may) have to deal with buffer wrap around halfway though the string.

 

[andre_luis]

You only need to create a header structure to store the pointer index and the String lenght.
Everything else consists of the queue control and monitoring mechanism.

 

[doraemon]

Hello!
It very much depends on what you want to do.
Here are 2 examples:
-----------
0 This
1 is
2 an
3 example
-----------
This corresponds to your phrasing: circular character array buffer because it's a
buffer of (pointers to) character arrays.
This represents a circular buffer of 4 terms. Buf[0] = this. etc.... In this case.
Supposing this buffer effectively has 4 string spaces only, if you add another string,
Buf[0] (the string "This") will be replaced.

Now another representation of a "circular character array buffer" would be for example
char buf[32];
"This_is_an_example. "
NB: "_" means space, " " means 0.
This buffer also corresponds to your definition, it's a buffer containing a character array.
If you add a character, it will be appended at the end, and if you add from index 32, then
you will be back to buffer[0].

Dora.

 

[KlausST]

Hi

If you add a character, it will be appended at the end,

in best case the new character is placed after the "." and the " " is shifted one position right.

Usual strings are delimited by a "\0".
But since the ring buffer has a read_pointer and a write_pointer it does not necessarily need the "\0" deleimiter.

To give more detailed answers we need to have more detailed informations about your problem:
* which microcontroller
* which language and compiler
* your code
* a detailed description of what you want to achieve

Klaus

 

[doraemon]

Hello!

in best case the new character is placed after the "." and the " " is shifted one position right.

None of the circular buffers I used so far performed any shifting. Maybe we are not talking about the
same thing.

char buf[32];
uint8 pos
Let's rewrite the buffer similarily as above. But lets rewrite @ instead of the 0. We are talking here
of an array of characters, not a string. If we put "This is an example." in the buffer, then it becomse

[This_is_an_example.@@@@@@@@@@@@@]
pos = 19

If I then push "This is another one" into it, it becomes:

[er_ones_an_example.This_is_anoth]
pos = 6

But nothing is shifted.

Similarily, if it's an array of 6 pointers to string:

"This"
"is"
"an"
"example."
0
0

The above should be understood as pointer to strings, i.e. each component
is a pointer (4 bytes for instance on an STM32) to the memory location containing each string.

would become after adding "This is another one":

"another"
"one"
"an"
"example."
"This"
"is"

but there would be no shift, no copy either

Dora.

 

[KlausST]

Hi,

"This_is_an_example. "
NB: "_" means space, " " means 0.
This buffer also corresponds to your definition, it's a buffer containing a character array.
If you add a character, it will be appended at the end, and if you add from index 32, then
you will be back to buffer[0].

"This_is_an_example. "
now add an "X"
the "X" is not simply added to: "This_is_an_example. X"
but it results in : "This_is_an_example.X " (mind: the position of "X" and " " is the other way round)
So the "X" will be set in the place of the " " and the initial " " now is one byte more right.
(like a simple keyboard buffer, for example)

Again: A usual ring buffer does not necessarily need a delimiter like '\0'
--> we need a more clear definition by the OP to give more focussed answers.


Klaus