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arcfour: small speedup

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This commit is contained in:
Mirek Kratochvil 2012-12-25 21:32:15 +01:00
parent 52a7ce08cf
commit d4ba7793f2
1 changed files with 11 additions and 12 deletions
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23
src/arcfour.h
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@ -27,29 +27,28 @@ template<class inttype> class arcfour
{
std::vector<inttype> S;
inttype I, J;
size_t mod;
inttype mask;
public:
bool init (size_t bits) {
bool init (unsigned bits) {
if (bits > 8 * sizeof (inttype) ) return false;
I = J = 0;
S.resize (1 << bits);
mod = 1 << bits;
for (size_t i = 0; i < (1 << bits); ++i) {
S[i] = i;
}
mask = ~ (inttype) 0;
if ( (inttype) (1 << bits) ) mask %= 1 << bits;
for (size_t i = 0; i < (1 << bits); ++i) S[i] = i;
return true;
}
void clear() {
I = J = 0;
mod = 0;
mask = 0;
S.clear();
}
void load_key (const std::vector<inttype>&K) {
inttype j = 0, t;
for (size_t i = 0; i < mod; ++i) {
j = (j + S[i] + K[i % K.size()]) % mod;
for (size_t i = 0; i <= mask; ++i) {
j = (j + S[i] + K[i % K.size()]) & mask;
t = S[j];
S[j] = S[i];
S[i] = t;
@ -57,15 +56,15 @@ public:
}
inttype gen() {
I = (I + 1) % mod;
J = (J + S[I]) % mod;
I = (I + 1) & mask;
J = (J + S[I]) & mask;
register inttype t;
t = S[J];
S[J] = S[I];
S[I] = t;
return S[ (S[I] + S[J]) % mod];
return S[ (S[I] + S[J]) & mask];
}
void discard (size_t n) {