Messages in this thread | | | From | Rasmus Villemoes <> | Subject | Re: [PATCH v1 1/8] lib/string: introduce match_string() helper | Date | Mon, 11 Jan 2016 23:10:46 +0100 |
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On Mon, Jan 11 2016, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> On Sat, 2016-01-09 at 13:57 +0200, Andy Shevchenko wrote: >> On Sat, Jan 9, 2016 at 3:12 AM, Sergey Senozhatsky >> <sergey.senozhatsky@gmail.com> wrote: >> > Andy Shevchenko wrote: >> > [..] >> > > > >> > > > strncmp() case seems to be quite common. >> > > >> > > Like I answered to Rasmus, please, provide real examples. >> > >> > [..] >> > > > int nmatch_string(array, array_size, string, string_len) >> > > > { >> > > > do { >> > > > strncmp(); >> > > > } while (); >> > > > } >> > > > >> > > > int match_string(array, array_size, string) >> > > > { >> > > > return nmatch_string(array, array_size, string, >> > > > strlen(string)); >> > > > } >> > > >> > > See above. >> > >> > after some quick and inaccurate grepping, well, probably you're >> > right - not worth it. >> >> Good grep anyway, it clearly shows that there is hard to generalize >> which limit to use: a) length of a first argument / item from a list, >> b) length of a second argument or a constant. >> >> > arch/mips/bcm63xx/boards/board_bcm963xx.c void __init >> > board_prom_init(void) >> > net/irda/irnet/irnet_irda.c irnet_dname_to_daddr() >> > arch/powerpc/sysdev/ppc4xx_cpm.c static ssize_t cpm_idle_store() >> > arch/x86/ras/mce_amd_inj.c static int __set_inj >> > drivers/hwtracing/intel_th/msu.c mode_store >> > drivers/pci/pcie/aer/ecrc.c void pcie_ecrc_get_policy >> > drivers/pci/pcie/aspm.c pcie_aspm_set_policy >> > drivers/scsi/aic7xxx/aic7xxx_osm.c aic7xxx_setup >> > drivers/scsi/aic7xxx/aic79xx_osm.c aic79xx_setup >> > drivers/scsi/scsi_transport_fc.c static int get_fc_##title##_match >> > drivers/staging/android/ion/hisilicon/hi6220_ion.c get_type_by_name >> > drivers/staging/lustre/lustre/lmv/lproc_lmv.c placement_name2policy >> > drivers/xen/sys-hypervisor.c pmu_mode_store > > Thought more about those cases. > > If you would like you may introduce something like > > int nmatch_string(array, array_size, string, int len) > { > if (len < 0) > return match_string(); > > for (...) { > size_t itemlen = (len > 0) ? len : strlen(array[index]); > ... > if (!strncmp(array[index], string, itemlen)) > return index; > } > return -EINVAL; > }
Yeah, a separate function is probably better. But why not a more explicit name, match_prefix, match_string_prefix, match_string_starts?
I like the idea of passing the string length if one wants the "is this a prefix of some array element" semantics, and a sentinel otherwise. But I don't see any case where one would want match_string() semantics (why not call match_string directly instead?), so why not let len < 0 mean "is some array element a prefix of this string" and "len >= 0" be the other case. I don't see why one shouldn't be able to ask "is the empty string a prefix of some array element" (that is, are there any elements in the array); both the array and the string might be run-time things, so this could occur. And it's not up to a generic library routine like this to impose restrictions like "the empty string makes no sense, go away".
Rasmus
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