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sys/bcd: add bcd_buf_from_u32()#21308

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mguetschow merged 4 commits intoRIOT-OS:masterfrom
benpicco:dec_as_hex
Apr 3, 2025
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sys/bcd: add bcd_buf_from_u32()#21308
mguetschow merged 4 commits intoRIOT-OS:masterfrom
benpicco:dec_as_hex

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@benpicco benpicco commented Mar 19, 2025 •
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Contribution description

This adds two helper functions to the string_utils library:

  • a reverse_buf() that inverts the order of bytes in an array
  • a bcd_buf_from_u32() that takes a number a and calculates a number a' so that the hex string representation of a' is the same as the decimal string representation of a. e.g. bcd_buf_from_u32(123) would produce 0x123.

Testing procedure

This can be used to to generate pretty MAC / IP addresses from decimal serial numbers:

static inline int _get_eui64(uint8_t index, eui64_t *addr)
{
    memset(addr, 0, sizeof(*addr));
    int res = bcd_buf_from_u32(device_get_serial(), addr, sizeof(*addr));
    if (res < 0) {
        return res;
    }
    addr->uint8[res] = index;
    reverse_buf(addr, sizeof(*addr));

    eui64_set_local(addr);
    return 0;
}
2025-03-20 10:43:11,323 # Iface  8  HWaddr: 17:12  Channel: 0  NID: 0x23  PHY: MR-O-QPSK 
2025-03-20 10:43:11,327 #            chip rate: 1000  rate mode: 2 
2025-03-20 10:43:11,331 #           Long HWaddr: 02:00:00:00:00:00:97:12 
2025-03-20 10:43:11,338 #            TX-Power: 3dBm  State: IDLE  max. Retrans.: 3  CSMA Retries: 4 
2025-03-20 10:43:11,344 #           AUTOACK  ACK_REQ  CSMA  L2-PDU:2022  MTU:1280  HL:64  RTR  
2025-03-20 10:43:11,346 #           6LO  IPHC  
2025-03-20 10:43:11,349 #           Source address length: 8
2025-03-20 10:43:11,352 #           Link type: wireless
2025-03-20 10:43:11,357 #           inet6 addr: fe80::9712  scope: link  VAL
2025-03-20 10:43:11,361 #           inet6 addr: fd40::9712  scope: global  VAL
2025-03-20 10:43:11,364 #           inet6 group: ff02::2
2025-03-20 10:43:11,367 #           inet6 group: ff02::1
2025-03-20 10:43:11,370 #           inet6 group: ff02::1:ff00:9712

Issues/PRs references

@github-actions github-actions bot added the Area: sys Area: System label Mar 19, 2025
@github-actions github-actions bot added the Area: tests Area: tests and testing framework label Mar 20, 2025
@benpicco benpicco added the CI: ready for build If set, CI server will compile all applications for all available boards for the labeled PR label Mar 20, 2025
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riot-ci commented Mar 20, 2025 •
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Murdock results

✔️ PASSED

8f4dec6 tests/unittests: add test for bcd_buf_from_u32()

Success Failures Total Runtime
10280 0 10280 10m:03s

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@benpicco benpicco requested a review from maribu March 20, 2025 09:50
@benpicco benpicco marked this pull request as ready for review March 20, 2025 09:51
@benpicco benpicco requested a review from miri64 as a code owner March 20, 2025 09:51
@benpicco benpicco requested a review from fabian18 March 20, 2025 09:53
@maribu
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maribu commented Mar 20, 2025

Isn't the dec_as_hex the same as binary coded decimals? I think there is already a helper for that.

@benpicco
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benpicco commented Mar 20, 2025

hah you are right!
But I don't think we have a helper for that yet - should I just change the name to dec_to_bcd() then?

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maribu commented Mar 20, 2025

Sounds good to me. I'd personally search such a function in the bcd module, though. How about moving it there?

@OlegHahm
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OlegHahm commented Mar 20, 2025

I also thing that such a function in a string header is somewhat misleading.

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benpicco commented Mar 21, 2025

Ok, will move it to a new bcd module, but I think the reverse buffer function can remain as it's more in the spirit of memcpy()/memchk()

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mguetschow commented Mar 21, 2025

Ok, will move it to a new bcd module

There already is https://doc.riot-os.org/group__sys__bcd.html

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benpicco commented Mar 21, 2025

Yes but that's just a header file 😉

Teufelchen1
Teufelchen1 requested changes Mar 31, 2025
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@benpicco benpicco changed the title sys/string_utils: add dec_as_hex() sys/string_utils: add bcd_buf_from_u32() Apr 2, 2025
@benpicco benpicco changed the title sys/string_utils: add bcd_buf_from_u32() sys/bcd: add bcd_buf_from_u32() Apr 2, 2025
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benpicco commented Apr 2, 2025

I renamed the function and moved it to the bcd module.

Teufelchen1
Teufelchen1 approved these changes Apr 3, 2025
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I can't shake the feeling off that there's a off-by-one error in it. Oh well, can't find it nor proof it. So looks good to me! :D

@mguetschow mguetschow added this pull request to the merge queue Apr 3, 2025
Merged via the queue into RIOT-OS:master with commit 57de45c Apr 3, 2025
26 checks passed
@benpicco benpicco deleted the dec_as_hex branch April 3, 2025 12:36
@mguetschow mguetschow added this to the Release 2025.04 milestone Apr 8, 2025
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@Teufelchen1 Teufelchen1 Teufelchen1 approved these changes

@maribu maribu Awaiting requested review from maribu

@miri64 miri64 Awaiting requested review from miri64 miri64 is a code owner

@fabian18 fabian18 Awaiting requested review from fabian18

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6 participants

@benpicco @riot-ci @maribu @OlegHahm @mguetschow @Teufelchen1