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AP_Common: correctly bound bitmask datatypes 

Probably won't work correctly (and of questionable use) if less than 1.
The `first_set()` function might not be able to return a valid value if
greater than INT16_MAX.

unsigned int needs to be >= uint32_t so that the shift ops are in range.
This commit is contained in:
Thomas Watson 2024-07-07 14:58:07 -05:00 committed by Andrew Tridgell
parent 0b320fe303
commit b030b8e789
1 changed files with 9 additions and 18 deletions
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25
libraries/AP_Common/Bitmask.h
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@ -25,6 +25,12 @@
template<uint16_t num_bits>
class Bitmask {
static_assert(num_bits > 0, "must store something");
// for first_set()'s return value
static_assert(num_bits <= INT16_MAX, "must fit in int16_t");
// so that 1U << bits is in range
static_assert(sizeof(unsigned int) >= sizeof(uint32_t), "int too small");
public:
Bitmask() :
numbits(num_bits),
@ -122,13 +128,7 @@ public:
uint16_t count() const {
uint16_t sum = 0;
for (uint16_t i=0; i<numwords; i++) {
if (sizeof(bits[i]) <= sizeof(int)) {
sum += __builtin_popcount(bits[i]);
} else if (sizeof(bits[i]) <= sizeof(long)) {
sum += __builtin_popcountl(bits[i]);
} else {
sum += __builtin_popcountll(bits[i]);
}
}
return sum;
}
@ -136,18 +136,9 @@ public:
// return first bit set, or -1 if none set
int16_t first_set() const {
for (uint16_t i=0; i<numwords; i++) {
if (bits[i] == 0) {
continue;
if (bits[i] != 0) {
return i*32 + __builtin_ffs(bits[i]) - 1;
}
int fs;
if (sizeof(bits[i]) <= sizeof(int)) {
fs = __builtin_ffs(bits[i]);
} else if (sizeof(bits[i]) <= sizeof(long)) {
fs = __builtin_ffsl(bits[i]);
} else {
fs = __builtin_ffsll(bits[i]);
}
return i*32 + fs - 1;
}
return -1;
}