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AP_Common: fix bitmask setall() 

Fixes an issue where the last word was not set to all 1s if the number
of bits evenly divided the word size.

Also fixes UB if there were 31 valid bits.
This commit is contained in:
Thomas Watson 2024-07-07 14:50:07 -05:00 committed by Andrew Tridgell
parent 122cd72d9c
commit 9a89223531
1 changed files with 6 additions and 4 deletions
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10
libraries/AP_Common/Bitmask.h
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@ -65,13 +65,15 @@ public:
// set all bits
void setall(void) {
// set all words to 111... except the last one.
for (uint16_t i=0; i<numwords-1; i++) {
// set all words to 111...
for (uint16_t i=0; i<numwords; i++) {
bits[i] = 0xffffffff;
}
// set most of the last word to 111.., leaving out-of-range bits to be 0
// ensure out-of-range bits in the last word, if any exist, are 0
uint16_t num_valid_bits = numbits % 32;
bits[numwords-1] = (1 << num_valid_bits) - 1;
if (num_valid_bits) { // word has out of range bits
bits[numwords-1] = (1U << num_valid_bits) - 1;
}
}
// clear given bitnumber