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Hash is class that carries 160-bit digest. More...
#include <hash.h>
Public Member Functions | |
| Hash () | |
| Hash (const quint32 aHash160bits[KNumberOfIntsInHash]) | |
| Hash (const quint32 aBits1, const quint32 aBits2, const quint32 aBits3, const quint32 aBits4, const quint32 aBits5) | |
| Hash (const unsigned char aDigest[KNumberOfIntsInHash *4]) | |
| Hash (const char *aHexString, int aHexStringLen) | |
| Hash (const QSslCertificate &aSslCert) | |
| void | fromString (const unsigned char *aBuf) |
| QString | toString () const |
| void | fromQVariant (const QVariant &aQVariantHashValue) |
| QVariant | toQVariant () const |
| void | calculate (const QByteArray &aBuf) |
| bool | operator== (const Hash &aHashToCompare) const |
| bool | operator!= (const Hash &aHashToCompare) const |
| bool | operator< (const Hash &aHashToCompare) const |
| bool | operator> (const Hash &aHashToCompare) const |
| Hash & | operator= (const Hash &aHashToSubstitute) |
| Hash | distanceFrom (const Hash &aHash) |
| Hash | operator- (const Hash &aToBeSubstracted) const |
| Hash | operator+ (const Hash &aToBeAdded) const |
Public Attributes | |
| quint32 | iHash160bits [KNumberOfIntsInHash] |
Static Public Attributes | |
| static const int | KNumberOfIntsInHash = 5 |
Private Member Functions | |
| void | setFromCharArray (const unsigned char aDigest[KNumberOfIntsInHash *4]) |
Hash is class that carries 160-bit digest.
Hash number class. This is usually an encryption key fingerprint or something returned by SHA1 function. The number that this class carries identifies an object inside classified ads, such objects as "classified ad", "user", "node", "attachment file" or anything that is present in the network. Here the hash is number between 0-2^160.
| Hash::Hash | ( | ) |
constructor. produces zero-value hash.
| Hash::Hash | ( | const quint32 | aHash160bits[KNumberOfIntsInHash] | ) |
constructor.
| aHash160bits | is array of KNumberOfIntsInHash containing 32 bits each. The most-significant bits come in first, least-significant come in last. .. e.g. for constructing a hash that has value (decimal) 1 you say Hash(0,0,0,0,1). |
| Hash::Hash | ( | const quint32 | aBits1, |
| const quint32 | aBits2, | ||
| const quint32 | aBits3, | ||
| const quint32 | aBits4, | ||
| const quint32 | aBits5 | ||
| ) |
constructor.
| aBits1 | most significant bits |
| aBits2 | quite significant bits |
| aBits3 | somewhat significant bits |
| aBits4 | less significant bits |
| aBits5 | least significant bits |
| Hash::Hash | ( | const unsigned char | aDigest[KNumberOfIntsInHash *4] | ) |
constructor.
| aDigest | 160 bits in array of unsigned 8-bit octets. Most significant bits first. If you take SHA1 function of openssl library, this is the format the method returns. |
| Hash::Hash | ( | const char * | aHexString, |
| int | aHexStringLen | ||
| ) |
constructor that takes the hash in ascii string similar that printf("X... produces.
| aHexString | is the string containing hash value |
| aHexStringLen | is length of said string. if this param does not have value of 40 then a null hash will be instantiated. Purpose of this parameter is mainly to clearly distinguis this constuctor from the one that has single "unsigned char *" param but expects different lenght for the string |
| Hash::Hash | ( | const QSslCertificate & | aSslCert | ) |
constructor
| aSslCert | is ssl certificate. Its SHA1 digest is used to initialize value of this hash |
| void Hash::calculate | ( | const QByteArray & | aBuf | ) |
calculates SHA1 hash of data and sets value of this class instance to be the result
Method for calculating distance between 2 hashes.
Obligatory J.R.R. Tolkien quote belongs here.
In this program distance is defined in "number of rings to rule them all" meaning that 1) hash values roll over e.g. distance between Hash(0) and Hash(max value) is 1. Distance between Hash(1) and Hash(max value) is 2. Distance between Hash(1) and Hash(5) is 4. As is to be expected. 2) We may invent many rings to address same objects because from articles (for instance) we can record the article content hash, pgp-key fingerprint of the sender, node used to send, hash of the forum containing the article etc. and in different situations it may be useful to search through different ring. This method distanceFrom tells how far away the number we're seeking for is and notable thing here is that number may roll over when going via path of shortest distance.
| aHash | is the number from which we calculate distance |
| void Hash::fromQVariant | ( | const QVariant & | aQVariantHashValue | ) |
Sets hash value from QVariant produced by toQVariant() method of this same class.
| void Hash::fromString | ( | const unsigned char * | aBuf | ) |
Sets hash value from string produced by toString() method of this same class.
| bool Hash::operator!= | ( | const Hash & | aHashToCompare | ) | const |
Man-kinds greatest invention ever follows: bignum operations for small bignums.
Substraction operator. As our hash if you think of it as a number, is unsigned, this operator will definitely return undefined-kind-of-crap if you try to substract bigger number from a smaller one. Something you'll get but it can be anything.
Other way around it seems to do something.
| bool Hash::operator< | ( | const Hash & | aHashToCompare | ) | const |
substitution too, it might make code more readable
| bool Hash::operator== | ( | const Hash & | aHashToCompare | ) | const |
Comparison operator enabling us to use sort operations
| bool Hash::operator> | ( | const Hash & | aHashToCompare | ) | const |
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private |
| QVariant Hash::toQVariant | ( | ) | const |
Returns the hash value as a QVariant
| QString Hash::toString | ( | ) | const |
Returns the hash value as a string.
| quint32 Hash::iHash160bits[KNumberOfIntsInHash] |
this public array carries the calculated (SHA1) hash. there is 5*32 bits and in db too we're supposed to use 5 columns for storing a hash ; we can still compare and do ordering if we decide that low-order bits go into iHash160bits[0] and the highest into iHash160bits[4].
In 64-bit boxen we could fit the bits into 64-bit integers and have this thing working a bit faster - hopefully this thing will still work fast enough to work also in less-powerful 32-bit architechtures for which we don't here want to invent a separate implementation.
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static |
This constant KNumberOfIntsInHash defines size of our hash ; we take this many unsigned ints each 32bits in size so with value 5 w get 5*32=160.
1.8.8