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// Copyright (C) 2004-2021 Artifex Software, Inc.
//
// This file is part of MuPDF.
//
// MuPDF is free software: you can redistribute it and/or modify it under the
// terms of the GNU Affero General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// MuPDF is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
// details.
//
// You should have received a copy of the GNU Affero General Public License
// along with MuPDF. If not, see <https://www.gnu.org/licenses/agpl-3.0.en.html>
//
// Alternative licensing terms are available from the licensor.
// For commercial licensing, see <https://www.artifex.com/> or contact
// Artifex Software, Inc., 39 Mesa Street, Suite 108A, San Francisco,
// CA 94129, USA, for further information.
#include "mupdf/fitz.h"
/* The pseudo-random number generator in this file is based on the MIT licensed
* implementation in musl libc. */
#include <string.h>
/* The seed is initialized in context.c as follows:
* static uint16_t __seed48[7] = { 0, 0, 0, 0xe66d, 0xdeec, 0x5, 0xb };
*/
static uint64_t fz_rand48_step(uint16_t *xi, uint16_t *lc)
{
uint64_t a, x;
x = xi[0] | (xi[1]+0U)<<16 | (xi[2]+0ULL)<<32;
a = lc[0] | (lc[1]+0U)<<16 | (lc[2]+0ULL)<<32;
x = a*x + lc[3];
xi[0] = x;
xi[1] = x>>16;
xi[2] = x>>32;
return x & 0xffffffffffffull;
}
double fz_erand48(fz_context *ctx, uint16_t s[3])
{
union {
uint64_t u;
double f;
} x = { 0x3ff0000000000000ULL | fz_rand48_step(s, ctx->seed48+3)<<4 };
return x.f - 1.0;
}
/*
Pseudo-random numbers using a linear congruential algorithm and 48-bit
integer arithmetic.
*/
double fz_drand48(fz_context *ctx)
{
return fz_erand48(ctx, ctx->seed48);
}
int32_t fz_nrand48(fz_context *ctx, uint16_t s[3])
{
return fz_rand48_step(s, ctx->seed48+3) >> 17;
}
int32_t fz_lrand48(fz_context *ctx)
{
return fz_nrand48(ctx, ctx->seed48);
}
int32_t fz_jrand48(fz_context *ctx, uint16_t s[3])
{
return (int32_t)(fz_rand48_step(s, ctx->seed48+3) >> 16);
}
int32_t fz_mrand48(fz_context *ctx)
{
return fz_jrand48(ctx, ctx->seed48);
}
void fz_lcong48(fz_context *ctx, uint16_t p[7])
{
memcpy(ctx->seed48, p, sizeof ctx->seed48);
}
uint16_t *fz_seed48(fz_context *ctx, uint16_t *s)
{
static uint16_t p[3];
memcpy(p, ctx->seed48, sizeof p);
memcpy(ctx->seed48, s, sizeof p);
return p;
}
void fz_srand48(fz_context *ctx, int32_t seed)
{
uint16_t p[3] = { 0x330e, seed, seed>>16 };
fz_seed48(ctx, p);
}
void fz_memrnd(fz_context *ctx, unsigned char *data, int len)
{
#ifdef CLUSTER
memset(data, 0x55, len);
#else
while (len-- > 0)
*data++ = (unsigned char)fz_lrand48(ctx);
#endif
}
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