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Introduce countDigits() function for PID and UID field widths #1561

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Introduce countDigits() function for PID and UID field widths #1561

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7ac4ac1
Do not expand GPU_TIME field width
Explorer09 Nov 11, 2024
9c9794a
Introduce countDigits() function for PID and UID field widths
Explorer09 Nov 11, 2024
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4 changes: 2 additions & 2 deletions Row.c
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Original file line number Diff line number Diff line change
Expand Up @@ -89,7 +89,7 @@ void Row_setPidColumnWidth(pid_t maxPid) {
return;
}

Row_pidDigits = (int)log10(maxPid) + 1;
Row_pidDigits = countDigits((size_t)maxPid, 10);
assert(Row_pidDigits <= ROW_MAX_PID_DIGITS);
}

Expand All @@ -99,7 +99,7 @@ void Row_setUidColumnWidth(uid_t maxUid) {
return;
}

Row_uidDigits = (int)log10(maxUid) + 1;
Row_uidDigits = countDigits((size_t)maxUid, 10);
assert(Row_uidDigits <= ROW_MAX_UID_DIGITS);
}

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15 changes: 15 additions & 0 deletions XUtils.c
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Expand Up @@ -374,6 +374,21 @@ double sumPositiveValues(const double* array, size_t count) {
return sum;
}

/* Counts the number of digits needed to print "n" with a given base.
If "n" is zero, returns 1. This function expects small numbers to
appear often, hence it uses a O(log(n)) time algorithm. */
size_t countDigits(size_t n, size_t base) {
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@Explorer09 Explorer09 Nov 13, 2024 •
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This question is a bit pedantic here. Since we plan to use countDigits for memory address, too, the more proper type for this function's input would be uintptr_t and not size_t. May I ask, is it better for this function's type be changed to uintptr_t to better indicate the intent? The output type can remain size_t as I see no reason for changing it.

Technical thing here: size_t and uintptr_t do not necessarily have the same size. In the C standard's sense, sizeof(size_t) <= sizeof(uintptr_t). On flat memory systems they are indeed the same size, but on other platforms (e.g. segmented memory) size_t can be defined to be narrower than uintptr_t.

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Use uint64_t and there's no problem (except for some potential upcasts for clang).

But I don't think we need to change this here; size_t is fine.

assert(base > 1);
size_t res = 1;
for (size_t limit = base; n >= limit; limit *= base) {
res++;
if (base && limit > SIZE_MAX / base) {
break;
}
}
return res;
}

#if !defined(HAVE_BUILTIN_CTZ)
// map a bit value mod 37 to its position
static const uint8_t mod37BitPosition[] = {
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5 changes: 5 additions & 0 deletions XUtils.h
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Expand Up @@ -141,6 +141,11 @@ int compareRealNumbers(double a, double b);
ATTR_NONNULL ATTR_ACCESS3_R(1, 2)
double sumPositiveValues(const double* array, size_t count);

/* Counts the number of digits needed to print "n" with a given base.
If "n" is zero, returns 1. This function expects small numbers to
appear often, hence it uses a O(log(n)) time algorithm. */
size_t countDigits(size_t n, size_t base);

/* Returns the number of trailing zero bits */
#if defined(HAVE_BUILTIN_CTZ)
static inline unsigned int countTrailingZeros(unsigned int x) {
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2 changes: 0 additions & 2 deletions linux/GPU.c
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Expand Up @@ -218,8 +218,6 @@ void GPU_readProcessData(LinuxProcessTable* lpt, LinuxProcess* lp, openat_arg_t
unsigned long long int gputimeDelta;
uint64_t monotonicTimeDelta;

Row_updateFieldWidth(GPU_TIME, ceil(log10(new_gpu_time)));

gputimeDelta = saturatingSub(new_gpu_time, lp->gpu_time);
monotonicTimeDelta = host->monotonicMs - host->prevMonotonicMs;
lp->gpu_percent = 100.0F * gputimeDelta / (1000 * 1000) / monotonicTimeDelta;
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