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[ftfuzzer] Replace `rand' with an xorshift algorithm.

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* src/tools/ftfuzzer/ftfuzzer.cc: Don't include `stdlib.h'.
(Random): Implement and use a 32bit `xorshift' algorithm.
This commit is contained in:
Werner Lemberg 2016-12-30 19:51:37 +01:00
parent c9de4bf6ba
commit 8fb9d22a6b
2 changed files with 20 additions and 5 deletions
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7
ChangeLog
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@ -1,3 +1,10 @@
2016-12-30 Werner Lemberg <wl@gnu.org>
[ftfuzzer] Replace `rand' with an xorshift algorithm.
* src/tools/ftfuzzer/ftfuzzer.cc: Don't include `stdlib.h'.
(Random): Implement and use a 32bit `xorshift' algorithm.
2016-12-30 Werner Lemberg <wl@gnu.org>
[ftfuzzer] Restrict number of tested bitmap strikes.

18
src/tools/ftfuzzer/ftfuzzer.cc
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@ -22,7 +22,6 @@
#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
#include <memory>
#include <vector>
@ -88,6 +87,8 @@
int t; // total number of values so far
int m; // number of selected values so far
uint32_t r; // the current pseudo-random number
Random( int n_,
int N_ )
: n( n_ ),
@ -96,10 +97,10 @@
t = 0;
m = 0;
// ideally, this should depend on the input file,
// Ideally, this should depend on the input file,
// for example, taking the sha256 as input;
// however, this is overkill for fuzzying tests
srand( 12345 );
// however, this is overkill for fuzzying tests.
r = 12345;
}
int get()
@ -108,7 +109,14 @@
return -1;
Redo:
double U = double(rand()) / RAND_MAX;
// We can't use `rand': different C libraries might provide
// different implementations of this function. As a replacement,
// we use a 32bit version of the `xorshift' algorithm.
r ^= r << 13;
r ^= r >> 17;
r ^= r << 5;
double U = double( r ) / UINT32_MAX;
if ( ( N - t ) * U >= ( n - m ) )
{