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fix wraparound bitshifting in OctalCode class

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This commit is contained in:
Stephen Birarda 2013-03-18 13:14:06 -07:00
parent 64ec16c62f
commit 32b52f474f
2 changed files with 23 additions and 5 deletions
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26
shared/src/OctalCode.cpp
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@ -18,19 +18,35 @@ int numberOfThreeBitSectionsInCode(unsigned char * octalCode) {
}
}
void printOctalCode(unsigned char * octalCode) {
for (int i = 1; i < bytesRequiredForCodeLength(*octalCode); i++) {
outputBits(octalCode[i]);
}
}
char sectionValue(unsigned char * startByte, char startIndexInByte) {
char rightShift = 8 - startIndexInByte - 3;
if (rightShift < 0) {
return ((startByte[0] << -rightShift) & 7) + (startByte[1] >> 7);
} else {
return (startByte[0] >> rightShift) & 7;
}
}
int bytesRequiredForCodeLength(unsigned char threeBitCodes) {
if (threeBitCodes == 0) {
return 1;
} else {
return 1 + (int)ceilf((threeBitCodes * 3) / 8.0);
}
}
void printOctalCode(unsigned char * octalCode) {
for (int i = 1; i < bytesRequiredForCodeLength(*octalCode); i++) {
outputBits(octalCode[i]);
}
char branchIndexWithDescendant(unsigned char * ancestorOctalCode, unsigned char * descendantOctalCode) {
int parentSections = numberOfThreeBitSectionsInCode(ancestorOctalCode);
int branchStartBit = parentSections * 3;
return sectionValue(descendantOctalCode + 1 + (branchStartBit / 8), branchStartBit % 8);
}
unsigned char * childOctalCode(unsigned char * parentOctalCode, char childNumber) {

2
shared/src/OctalCode.h
View file

@ -13,6 +13,8 @@
void printOctalCode(unsigned char * octalCode);
int bytesRequiredForCodeLength(unsigned char threeBitCodes);
bool isDirectParentOfChild(unsigned char *parentOctalCode, unsigned char * childOctalCode);
char branchIndexWithDescendant(unsigned char * ancestorOctalCode, unsigned char * descendantOctalCode);
unsigned char * childOctalCode(unsigned char * parentOctalCode, char childNumber);
#endif /* defined(__hifi__OctalCode__) */