diff options
Diffstat (limited to 'stdlib/random_r.c')
| -rw-r--r-- | stdlib/random_r.c | 45 |
1 files changed, 33 insertions, 12 deletions
diff --git a/stdlib/random_r.c b/stdlib/random_r.c index b6297fe..b49f03f 100644 --- a/stdlib/random_r.c +++ b/stdlib/random_r.c @@ -1,5 +1,5 @@ /* - Copyright (C) 1995-2024 Free Software Foundation, Inc. + Copyright (C) 1995-2025 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 @@ -55,6 +55,7 @@ #include <limits.h> #include <stddef.h> #include <stdlib.h> +#include <string.h> /* An improved random number generation package. In addition to the standard @@ -146,7 +147,21 @@ static const struct random_poly_info random_poly_info = { DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 } }; +static inline int32_t +read_state (int32_t *b, int idx) +{ + int32_t r; + memcpy (&r, (char *) b + idx * 4, sizeof (int32_t)); + return r; +} +static inline void +write_state (int32_t *b, int idx, int32_t v) +{ + /* Use literal 4 to avoid conversion to an unsigned type and pointer + wraparound. */ + memcpy ((char *) b + idx * 4, &v, 4); +} /* Initialize the random number generator based on the given seed. If the @@ -177,7 +192,7 @@ __srandom_r (unsigned int seed, struct random_data *buf) /* We must make sure the seed is not 0. Take arbitrarily 1 in this case. */ if (seed == 0) seed = 1; - state[0] = seed; + write_state (state, 0, seed); if (type == TYPE_0) goto done; @@ -194,7 +209,7 @@ __srandom_r (unsigned int seed, struct random_data *buf) word = 16807 * lo - 2836 * hi; if (word < 0) word += 2147483647; - *++dst = word; + write_state (++dst, 0, word); } buf->fptr = &state[buf->rand_sep]; @@ -238,9 +253,10 @@ __initstate_r (unsigned int seed, char *arg_state, size_t n, { int old_type = buf->rand_type; if (old_type == TYPE_0) - old_state[-1] = TYPE_0; + write_state (old_state, -1, TYPE_0); else - old_state[-1] = (MAX_TYPES * (buf->rptr - old_state)) + old_type; + write_state (old_state, -1, (MAX_TYPES * (buf->rptr - old_state)) + + old_type); } int type; @@ -270,9 +286,9 @@ __initstate_r (unsigned int seed, char *arg_state, size_t n, __srandom_r (seed, buf); - state[-1] = TYPE_0; + write_state (state, -1, TYPE_0); if (type != TYPE_0) - state[-1] = (buf->rptr - state) * MAX_TYPES + type; + write_state (state, -1, (buf->rptr - state) * MAX_TYPES + type); return 0; @@ -307,9 +323,10 @@ __setstate_r (char *arg_state, struct random_data *buf) old_type = buf->rand_type; old_state = buf->state; if (old_type == TYPE_0) - old_state[-1] = TYPE_0; + write_state (old_state, -1, TYPE_0); else - old_state[-1] = (MAX_TYPES * (buf->rptr - old_state)) + old_type; + write_state (old_state, -1, (MAX_TYPES * (buf->rptr - old_state)) + + old_type); type = new_state[-1] % MAX_TYPES; if (type < TYPE_0 || type > TYPE_4) @@ -361,8 +378,9 @@ __random_r (struct random_data *buf, int32_t *result) if (buf->rand_type == TYPE_0) { - int32_t val = ((state[0] * 1103515245U) + 12345U) & 0x7fffffff; - state[0] = val; + int32_t val = ((read_state(state, 0) * 1103515245U) + 12345U) + & 0x7fffffff; + write_state (state, 0, val); *result = val; } else @@ -372,7 +390,10 @@ __random_r (struct random_data *buf, int32_t *result) int32_t *end_ptr = buf->end_ptr; uint32_t val; - val = *fptr += (uint32_t) *rptr; + /* Avoid integer overflow with uint32_t arihmetic. */ + val = read_state (fptr, 0); + val += read_state (rptr, 0); + write_state (fptr, 0, val); /* Chucking least random bit. */ *result = val >> 1; ++fptr; |