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-rw-r--r--libgcompat/random_r.c157
1 files changed, 157 insertions, 0 deletions
diff --git a/libgcompat/random_r.c b/libgcompat/random_r.c
new file mode 100644
index 0000000..5bc7053
--- /dev/null
+++ b/libgcompat/random_r.c
@@ -0,0 +1,157 @@
+/*
+ * -------------------------------------------------------------------
+ * Copyright © 2005-2020 Rich Felker, et al.
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * -------------------------------------------------------------------
+ */
+
+/* This is an adaptation of musl's random() implementation, adding
+ * random_data buffers to make reentrant variants
+ */
+
+#include <stddef.h> /* NULL, size_t */
+#include <stdint.h> /* int32_t, uint32_t */
+#include <errno.h> /* errno */
+
+/* This code uses the same lagged fibonacci generator as the
+ * original bsd random implementation except for the seeding
+ * which was broken in the original
+ */
+
+/* This must use the same struct layout as used by glibc
+ * and specified in LSB
+ * ref: https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/libc-ddefs.html
+ */
+struct random_data {
+ int32_t *x; /* int32_t *fptr */
+ int32_t *unused_1; /* int32_t *rptr */
+ int32_t *unused_2; /* int32_t *state */
+ int n; /* int rand_type */
+ int i; /* int rand_deg */
+ int j; /* int rand_sep */
+ int32_t *unused_3; /* int32_t *end_ptr */
+};
+
+static uint32_t lcg31(uint32_t x) {
+ return (1103515245*x + 12345) & 0x7fffffff;
+}
+
+static uint64_t lcg64(uint64_t x) {
+ return 6364136223846793005ull*x + 1;
+}
+
+static void savestate_r(struct random_data *buf) {
+ buf->x[-1] = (buf->n<<16)|(buf->i<<8)|buf->j;
+}
+
+static void loadstate_r(uint32_t *state, struct random_data *buf) {
+ buf->x = (int32_t *)state + 1;
+ buf->n = buf->x[-1]>>16;
+ buf->i = (buf->x[-1]>>8)&0xff;
+ buf->j = buf->x[-1]&0xff;
+}
+
+int srandom_r(unsigned seed, struct random_data *buf) {
+ int k;
+ uint64_t s = seed;
+
+ if (buf == NULL) {
+ return -1;
+ }
+
+ if (buf->n > 63) {
+ return -1;
+ } else if (buf->n == 0) {
+ buf->x[0] = s;
+ return 0;
+ }
+ buf->i = buf->n == 31 || buf->n == 7 ? 3 : 1;
+ buf->j = 0;
+ for (k = 0; k < buf->n; k++) {
+ s = lcg64(s);
+ buf->x[k] = s>>32;
+ }
+ /* make sure x contains at least one odd number */
+ buf->x[0] |= 1;
+
+ return 0;
+}
+
+int initstate_r(unsigned seed, char *restrict state, size_t size,
+ struct random_data *restrict buf) {
+ if (size < 8) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ savestate_r(buf);
+ if (size < 32) {
+ buf->n = 0;
+ } else if (size < 64) {
+ buf->n = 7;
+ } else if (size < 128) {
+ buf->n = 15;
+ } else if (size < 256) {
+ buf->n = 31;
+ } else {
+ buf->n = 63;
+ }
+ buf->x = (int32_t*)state + 1;
+ srandom_r(seed, buf);
+ savestate_r(buf);
+ return 0;
+}
+
+int setstate_r(char *restrict state, struct random_data *restrict buf) {
+ if (!state || !buf) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ savestate_r(buf);
+ loadstate_r((uint32_t*)state, buf);
+ return 0;
+}
+
+int random_r(struct random_data *restrict buf, int32_t *restrict result) {
+ long k;
+
+ if (result == NULL || buf == NULL) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ if (buf->n == 0) {
+ k = buf->x[0] = lcg31(buf->x[0]);
+ goto end;
+ }
+ buf->x[buf->i] += buf->x[buf->j];
+ k = buf->x[buf->i]>>1;
+ if (++(buf->i) == buf->n) {
+ buf->i = 0;
+ } if (++(buf->j) == buf->n) {
+ buf->j = 0;
+ }
+end:
+ *result = k;
+ return 0;
+}