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AP_Common: fix Bitmask out-of-range values

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squilter 2017-08-31 12:21:16 -04:00 committed by Randy Mackay
parent 963c9c93fe
commit 1a9bccaaa7
1 changed files with 17 additions and 8 deletions
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25
libraries/AP_Common/Bitmask.h
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@ -20,9 +20,11 @@
class Bitmask { class Bitmask {
public: public:
Bitmask(uint16_t numbits) : Bitmask(uint16_t num_bits) :
numwords((numbits+31)/32) { numbits(num_bits),
numwords((num_bits+31)/32) {
bits = new uint32_t[numwords]; bits = new uint32_t[numwords];
clearall();
} }
~Bitmask(void) { ~Bitmask(void) {
delete[] bits; delete[] bits;
@ -30,6 +32,10 @@ public:
// set given bitnumber // set given bitnumber
void set(uint16_t bit) { void set(uint16_t bit) {
// ignore an invalid bit number
if (bit >= numbits) {
return;
}
uint16_t word = bit/32; uint16_t word = bit/32;
uint8_t ofs = bit & 0x1f; uint8_t ofs = bit & 0x1f;
bits[word] |= (1U << ofs); bits[word] |= (1U << ofs);
@ -37,9 +43,13 @@ public:
// set all bits // set all bits
void setall(void) { void setall(void) {
for (uint16_t i=0; i<numwords; i++) { // set all words to 111... except the last one.
for (uint16_t i=0; i<numwords-1; i++) {
bits[i] = 0xffffffff; bits[i] = 0xffffffff;
} }
// set most of the last word to 111.., leaving out-of-range bits to be 0
uint16_t num_valid_bits = numbits % 32;
bits[numwords-1] = (1 << num_valid_bits) - 1;
} }
// clear given bitnumber // clear given bitnumber
@ -51,9 +61,7 @@ public:
// clear all bits // clear all bits
void clearall(void) { void clearall(void) {
for (uint16_t i=0; i<numwords; i++) { memset(bits, 0, numwords*sizeof(bits[0]));
bits[i] = 0;
}
} }
// return true if given bitnumber is set // return true if given bitnumber is set
@ -88,12 +96,13 @@ public:
return sum; return sum;
} }
// return number of bits available (may be slightly larger than number requested in constructor) // return number of bits available
uint16_t size() const { uint16_t size() const {
return numwords * 32; return numbits;
} }
private: private:
uint16_t numbits;
uint16_t numwords; uint16_t numwords;
uint32_t *bits; uint32_t *bits;
}; };