sys/base64: api change (const + void*)

[pwillem]

Contribution description

This merge request changes the api of the base64 functions:

• add const to input arguments
• use void * for the raw (byte) data (input for base64_encode(), output for base64_decode())

Testing procedure

make BOARD=native -C tests/unittests tests-base64 test still compiles and passes

Issues/PRs references

None

[smlng]

@pwillem I agree we[with] making the input const and I tend to agree to use void * to avoid (😉 ) casting when passing around buffers, see #5497 too. @kaspar030 what's your assessment on this here?

[kaspar030]

is this variable necesary?

[smlng]

mhm, right I mean thats the point of using void right, to not hassle with casts.

[pwillem]

if I try to use the void. I get the following errors:

RIOT/sys/base64/base64.c: In function ‘base64_encode’:
RIOT/sys/base64/base64.c:89:28: error: pointer of type ‘void *’ used in arithmetic [-Werror=pointer-arith]
         tmpval = *(data_in + i);
                            ^
RIOT/sys/base64/base64.c:89:18: error: dereferencing ‘void’ pointer [-Werror]
         tmpval = *(data_in + i);
                  ^~~~~~~~~~~~~~
RIOT/sys/base64/base64.c:89:16: error: void value not ignored as it ought to be
         tmpval = *(data_in + i);
                ^

[jcarrano]

That's right, void* cannot be used in pointer arithmetic.

[kaspar030]

@kaspar030 what's your assessment on this here?

+1!

[jcarrano]

Looks good, and the test passes.