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* Description of path hashing algorithm.

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This commit is contained in:
Eelco Dolstra 2003-06-16 14:19:32 +00:00
parent 822794001c
commit a09e66da5a
2 changed files with 53 additions and 8 deletions
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8
src/hash.cc
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@ -6,14 +6,12 @@ extern "C" {
#include <iostream> #include <iostream>
/* Create a zeroed hash object. */
Hash::Hash() Hash::Hash()
{ {
memset(hash, 0, sizeof(hash)); memset(hash, 0, sizeof(hash));
} }
/* Check whether two hash are equal. */
bool Hash::operator == (Hash & h2) bool Hash::operator == (Hash & h2)
{ {
for (unsigned int i = 0; i < hashSize; i++) for (unsigned int i = 0; i < hashSize; i++)
@ -22,14 +20,12 @@ bool Hash::operator == (Hash & h2)
} }
/* Check whether two hash are not equal. */
bool Hash::operator != (Hash & h2) bool Hash::operator != (Hash & h2)
{ {
return !(*this == h2); return !(*this == h2);
} }
/* Convert a hash code into a hexadecimal representation. */
Hash::operator string() const Hash::operator string() const
{ {
ostringstream str; ostringstream str;
@ -42,7 +38,6 @@ Hash::operator string() const
} }
/* Parse a hexadecimal representation of a hash code. */
Hash parseHash(const string & s) Hash parseHash(const string & s)
{ {
Hash hash; Hash hash;
@ -61,7 +56,6 @@ Hash parseHash(const string & s)
} }
/* Verify that a reference is valid (that is, is a MD5 hash code). */
bool isHash(const string & s) bool isHash(const string & s)
{ {
if (s.length() != 32) return false; if (s.length() != 32) return false;
@ -75,7 +69,6 @@ bool isHash(const string & s)
} }
/* Compute the MD5 hash of a file. */
Hash hashString(const string & s) Hash hashString(const string & s)
{ {
Hash hash; Hash hash;
@ -84,7 +77,6 @@ Hash hashString(const string & s)
} }
/* Compute the MD5 hash of a file. */
Hash hashFile(const string & fileName) Hash hashFile(const string & fileName)
{ {
Hash hash; Hash hash;

53
src/hash.hh
View file

@ -13,9 +13,16 @@ struct Hash
static const unsigned int hashSize = 16; static const unsigned int hashSize = 16;
unsigned char hash[hashSize]; unsigned char hash[hashSize];
/* Create a zeroed hash object. */
Hash(); Hash();
/* Check whether two hash are equal. */
bool operator == (Hash & h2); bool operator == (Hash & h2);
/* Check whether two hash are not equal. */
bool operator != (Hash & h2); bool operator != (Hash & h2);
/* Convert a hash code into a hexadecimal representation. */
operator string() const; operator string() const;
}; };
@ -27,9 +34,55 @@ public:
}; };
/* Parse a hexadecimal representation of a hash code. */
Hash parseHash(const string & s); Hash parseHash(const string & s);
/* Verify that the given string is a valid hash code. */
bool isHash(const string & s); bool isHash(const string & s);
/* Compute the hash of the given string. */
Hash hashString(const string & s); Hash hashString(const string & s);
/* Compute the hash of the given file. */
Hash hashFile(const string & fileName); Hash hashFile(const string & fileName);
/* Compute the hash of the given path. The hash is defined as
follows:
hash(path) = md5(dump(path))
IF path points to a REGULAR FILE:
dump(path) = attrs(
[ ("type", "regular")
, ("contents", contents(path))
])
IF path points to a DIRECTORY:
dump(path) = attrs(
[ ("type", "directory")
, ("entries", concat(map(f, entries(path))))
])
where f(fn) = attrs(
[ ("name", fn)
, ("file", dump(path + "/" + fn))
])
where:
attrs(as) = concat(map(attr, as)) + encN(0)
attrs((a, b)) = encS(a) + encS(b)
encS(s) = encN(len(s)) + s
encN(n) = 64-bit little-endian encoding of n.
contents(path) = the contents of a regular file.
entries(path) = the entries of a directory, without `.' and
`..'.
`+' denotes string concatenation. */
Hash hashPath(const string & path);
#endif /* !__HASH_H */ #endif /* !__HASH_H */