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Diffstat (limited to 'REORG.TODO/stdlib/random_r.c')
| -rw-r--r-- | REORG.TODO/stdlib/random_r.c | 401 |
1 files changed, 401 insertions, 0 deletions
diff --git a/REORG.TODO/stdlib/random_r.c b/REORG.TODO/stdlib/random_r.c new file mode 100644 index 0000000000..c3f6f9aede --- /dev/null +++ b/REORG.TODO/stdlib/random_r.c @@ -0,0 +1,401 @@ +/* + Copyright (C) 1995-2017 Free Software Foundation, Inc. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +/* + Copyright (C) 1983 Regents of the University of California. + All rights reserved. + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions + are met: + + 1. Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + 2. Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in the + documentation and/or other materials provided with the distribution. + 4. Neither the name of the University nor the names of its contributors + may be used to endorse or promote products derived from this software + without specific prior written permission. + + THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + SUCH DAMAGE.*/ + +/* + * This is derived from the Berkeley source: + * @(#)random.c 5.5 (Berkeley) 7/6/88 + * It was reworked for the GNU C Library by Roland McGrath. + * Rewritten to be reentrant by Ulrich Drepper, 1995 + */ + +#include <errno.h> +#include <limits.h> +#include <stddef.h> +#include <stdlib.h> + + +/* An improved random number generation package. In addition to the standard + rand()/srand() like interface, this package also has a special state info + interface. The initstate() routine is called with a seed, an array of + bytes, and a count of how many bytes are being passed in; this array is + then initialized to contain information for random number generation with + that much state information. Good sizes for the amount of state + information are 32, 64, 128, and 256 bytes. The state can be switched by + calling the setstate() function with the same array as was initialized + with initstate(). By default, the package runs with 128 bytes of state + information and generates far better random numbers than a linear + congruential generator. If the amount of state information is less than + 32 bytes, a simple linear congruential R.N.G. is used. Internally, the + state information is treated as an array of longs; the zeroth element of + the array is the type of R.N.G. being used (small integer); the remainder + of the array is the state information for the R.N.G. Thus, 32 bytes of + state information will give 7 longs worth of state information, which will + allow a degree seven polynomial. (Note: The zeroth word of state + information also has some other information stored in it; see setstate + for details). The random number generation technique is a linear feedback + shift register approach, employing trinomials (since there are fewer terms + to sum up that way). In this approach, the least significant bit of all + the numbers in the state table will act as a linear feedback shift register, + and will have period 2^deg - 1 (where deg is the degree of the polynomial + being used, assuming that the polynomial is irreducible and primitive). + The higher order bits will have longer periods, since their values are + also influenced by pseudo-random carries out of the lower bits. The + total period of the generator is approximately deg*(2**deg - 1); thus + doubling the amount of state information has a vast influence on the + period of the generator. Note: The deg*(2**deg - 1) is an approximation + only good for large deg, when the period of the shift register is the + dominant factor. With deg equal to seven, the period is actually much + longer than the 7*(2**7 - 1) predicted by this formula. */ + + + +/* For each of the currently supported random number generators, we have a + break value on the amount of state information (you need at least this many + bytes of state info to support this random number generator), a degree for + the polynomial (actually a trinomial) that the R.N.G. is based on, and + separation between the two lower order coefficients of the trinomial. */ + +/* Linear congruential. */ +#define TYPE_0 0 +#define BREAK_0 8 +#define DEG_0 0 +#define SEP_0 0 + +/* x**7 + x**3 + 1. */ +#define TYPE_1 1 +#define BREAK_1 32 +#define DEG_1 7 +#define SEP_1 3 + +/* x**15 + x + 1. */ +#define TYPE_2 2 +#define BREAK_2 64 +#define DEG_2 15 +#define SEP_2 1 + +/* x**31 + x**3 + 1. */ +#define TYPE_3 3 +#define BREAK_3 128 +#define DEG_3 31 +#define SEP_3 3 + +/* x**63 + x + 1. */ +#define TYPE_4 4 +#define BREAK_4 256 +#define DEG_4 63 +#define SEP_4 1 + + +/* Array versions of the above information to make code run faster. + Relies on fact that TYPE_i == i. */ + +#define MAX_TYPES 5 /* Max number of types above. */ + +struct random_poly_info +{ + int seps[MAX_TYPES]; + int degrees[MAX_TYPES]; +}; + +static const struct random_poly_info random_poly_info = +{ + { SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 }, + { DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 } +}; + + + + +/* Initialize the random number generator based on the given seed. If the + type is the trivial no-state-information type, just remember the seed. + Otherwise, initializes state[] based on the given "seed" via a linear + congruential generator. Then, the pointers are set to known locations + that are exactly rand_sep places apart. Lastly, it cycles the state + information a given number of times to get rid of any initial dependencies + introduced by the L.C.R.N.G. Note that the initialization of randtbl[] + for default usage relies on values produced by this routine. */ +int +__srandom_r (unsigned int seed, struct random_data *buf) +{ + int type; + int32_t *state; + long int i; + int32_t word; + int32_t *dst; + int kc; + + if (buf == NULL) + goto fail; + type = buf->rand_type; + if ((unsigned int) type >= MAX_TYPES) + goto fail; + + state = buf->state; + /* We must make sure the seed is not 0. Take arbitrarily 1 in this case. */ + if (seed == 0) + seed = 1; + state[0] = seed; + if (type == TYPE_0) + goto done; + + dst = state; + word = seed; + kc = buf->rand_deg; + for (i = 1; i < kc; ++i) + { + /* This does: + state[i] = (16807 * state[i - 1]) % 2147483647; + but avoids overflowing 31 bits. */ + long int hi = word / 127773; + long int lo = word % 127773; + word = 16807 * lo - 2836 * hi; + if (word < 0) + word += 2147483647; + *++dst = word; + } + + buf->fptr = &state[buf->rand_sep]; + buf->rptr = &state[0]; + kc *= 10; + while (--kc >= 0) + { + int32_t discard; + (void) __random_r (buf, &discard); + } + + done: + return 0; + + fail: + return -1; +} + +weak_alias (__srandom_r, srandom_r) + +/* Initialize the state information in the given array of N bytes for + future random number generation. Based on the number of bytes we + are given, and the break values for the different R.N.G.'s, we choose + the best (largest) one we can and set things up for it. srandom is + then called to initialize the state information. Note that on return + from srandom, we set state[-1] to be the type multiplexed with the current + value of the rear pointer; this is so successive calls to initstate won't + lose this information and will be able to restart with setstate. + Note: The first thing we do is save the current state, if any, just like + setstate so that it doesn't matter when initstate is called. + Returns 0 on success, non-zero on failure. */ +int +__initstate_r (unsigned int seed, char *arg_state, size_t n, + struct random_data *buf) +{ + if (buf == NULL) + goto fail; + + int32_t *old_state = buf->state; + if (old_state != NULL) + { + int old_type = buf->rand_type; + if (old_type == TYPE_0) + old_state[-1] = TYPE_0; + else + old_state[-1] = (MAX_TYPES * (buf->rptr - old_state)) + old_type; + } + + int type; + if (n >= BREAK_3) + type = n < BREAK_4 ? TYPE_3 : TYPE_4; + else if (n < BREAK_1) + { + if (n < BREAK_0) + goto fail; + + type = TYPE_0; + } + else + type = n < BREAK_2 ? TYPE_1 : TYPE_2; + + int degree = random_poly_info.degrees[type]; + int separation = random_poly_info.seps[type]; + + buf->rand_type = type; + buf->rand_sep = separation; + buf->rand_deg = degree; + int32_t *state = &((int32_t *) arg_state)[1]; /* First location. */ + /* Must set END_PTR before srandom. */ + buf->end_ptr = &state[degree]; + + buf->state = state; + + __srandom_r (seed, buf); + + state[-1] = TYPE_0; + if (type != TYPE_0) + state[-1] = (buf->rptr - state) * MAX_TYPES + type; + + return 0; + + fail: + __set_errno (EINVAL); + return -1; +} + +weak_alias (__initstate_r, initstate_r) + +/* Restore the state from the given state array. + Note: It is important that we also remember the locations of the pointers + in the current state information, and restore the locations of the pointers + from the old state information. This is done by multiplexing the pointer + location into the zeroth word of the state information. Note that due + to the order in which things are done, it is OK to call setstate with the + same state as the current state + Returns 0 on success, non-zero on failure. */ +int +__setstate_r (char *arg_state, struct random_data *buf) +{ + int32_t *new_state = 1 + (int32_t *) arg_state; + int type; + int old_type; + int32_t *old_state; + int degree; + int separation; + + if (arg_state == NULL || buf == NULL) + goto fail; + + old_type = buf->rand_type; + old_state = buf->state; + if (old_type == TYPE_0) + old_state[-1] = TYPE_0; + else + old_state[-1] = (MAX_TYPES * (buf->rptr - old_state)) + old_type; + + type = new_state[-1] % MAX_TYPES; + if (type < TYPE_0 || type > TYPE_4) + goto fail; + + buf->rand_deg = degree = random_poly_info.degrees[type]; + buf->rand_sep = separation = random_poly_info.seps[type]; + buf->rand_type = type; + + if (type != TYPE_0) + { + int rear = new_state[-1] / MAX_TYPES; + buf->rptr = &new_state[rear]; + buf->fptr = &new_state[(rear + separation) % degree]; + } + buf->state = new_state; + /* Set end_ptr too. */ + buf->end_ptr = &new_state[degree]; + + return 0; + + fail: + __set_errno (EINVAL); + return -1; +} + +weak_alias (__setstate_r, setstate_r) + +/* If we are using the trivial TYPE_0 R.N.G., just do the old linear + congruential bit. Otherwise, we do our fancy trinomial stuff, which is the + same in all the other cases due to all the global variables that have been + set up. The basic operation is to add the number at the rear pointer into + the one at the front pointer. Then both pointers are advanced to the next + location cyclically in the table. The value returned is the sum generated, + reduced to 31 bits by throwing away the "least random" low bit. + Note: The code takes advantage of the fact that both the front and + rear pointers can't wrap on the same call by not testing the rear + pointer if the front one has wrapped. Returns a 31-bit random number. */ + +int +__random_r (struct random_data *buf, int32_t *result) +{ + int32_t *state; + + if (buf == NULL || result == NULL) + goto fail; + + state = buf->state; + + if (buf->rand_type == TYPE_0) + { + int32_t val = state[0]; + val = ((state[0] * 1103515245) + 12345) & 0x7fffffff; + state[0] = val; + *result = val; + } + else + { + int32_t *fptr = buf->fptr; + int32_t *rptr = buf->rptr; + int32_t *end_ptr = buf->end_ptr; + int32_t val; + + val = *fptr += *rptr; + /* Chucking least random bit. */ + *result = (val >> 1) & 0x7fffffff; + ++fptr; + if (fptr >= end_ptr) + { + fptr = state; + ++rptr; + } + else + { + ++rptr; + if (rptr >= end_ptr) + rptr = state; + } + buf->fptr = fptr; + buf->rptr = rptr; + } + return 0; + + fail: + __set_errno (EINVAL); + return -1; +} + +weak_alias (__random_r, random_r) |