53 lines
1.5 KiB
C
53 lines
1.5 KiB
C
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/* udns_jran.c: small non-cryptographic random number generator
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* taken from http://burtleburtle.net/bob/rand/smallprng.html
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* by Bob Jenkins, Public domain.
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*/
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#include "udns.h"
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#define rot32(x,k) (((x) << (k)) | ((x) >> (32-(k))))
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#define rot64(x,k) (((x) << (k)) | ((x) >> (64-(k))))
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#define tr32(x) ((x)&0xffffffffu)
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unsigned udns_jranval(struct udns_jranctx *x) {
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/* This routine can be made to work with either 32 or 64bit words -
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* if JRAN_32_64 is defined when compiling the file.
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* We use if() instead of #if since there's no good
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* portable way to check sizeof() in preprocessor without
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* introducing some ugly configure-time checks.
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* Most compilers will optimize the wrong branches away anyway.
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* By default it assumes 32bit integers
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*/
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#ifdef JRAN_32_64
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if (sizeof(unsigned) == 4) {
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#endif
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unsigned e = tr32(x->a - rot32(x->b, 27));
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x->a = tr32(x->b ^ rot32(x->c, 17));
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x->b = tr32(x->c + x->d);
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x->c = tr32(x->d + e);
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x->d = tr32(e + x->a);
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#ifdef JRAN_32_64
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}
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else if (sizeof(unsigned) == 8) { /* assuming it's 64bits */
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unsigned e = x->a - rot64(x->b, 7);
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x->a = x->b ^ rot64(x->c, 13);
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x->b = x->c + rot64(x->d, 37);
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x->c = x->d + e;
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x->d = e + x->a;
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}
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else {
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unsigned e = 0;
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x->d = 1/e; /* bail */
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}
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#endif
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return x->d;
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}
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void udns_jraninit(struct udns_jranctx *x, unsigned seed) {
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unsigned i;
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x->a = 0xf1ea5eed;
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x->b = x->c = x->d = seed;
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for (i = 0; i < 20; ++i)
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(void)udns_jranval(x);
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}
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