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      1 /* Copyright libuv contributors. All rights reserved.
      2  *
      3  * Permission is hereby granted, free of charge, to any person obtaining a copy
      4  * of this software and associated documentation files (the "Software"), to
      5  * deal in the Software without restriction, including without limitation the
      6  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
      7  * sell copies of the Software, and to permit persons to whom the Software is
      8  * furnished to do so, subject to the following conditions:
      9  *
     10  * The above copyright notice and this permission notice shall be included in
     11  * all copies or substantial portions of the Software.
     12  *
     13  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     14  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     15  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     16  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     17  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     18  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
     19  * IN THE SOFTWARE.
     20  */
     21 
     22 #include "uv.h"
     23 #include "internal.h"
     24 
     25 #ifdef __linux__
     26 
     27 #define uv__random_getrandom_init() 0
     28 
     29 #else  /* !__linux__ */
     30 
     31 #include <stddef.h>
     32 #include <dlfcn.h>
     33 
     34 typedef ssize_t (*uv__getrandom_cb)(void *, size_t, unsigned);
     35 
     36 static uv__getrandom_cb uv__getrandom;
     37 static uv_once_t once = UV_ONCE_INIT;
     38 
     39 static void uv__random_getrandom_init_once(void) {
     40   uv__getrandom = (uv__getrandom_cb) dlsym(RTLD_DEFAULT, "getrandom");
     41 }
     42 
     43 static int uv__random_getrandom_init(void) {
     44   uv_once(&once, uv__random_getrandom_init_once);
     45 
     46   if (uv__getrandom == NULL)
     47     return UV_ENOSYS;
     48 
     49   return 0;
     50 }
     51 
     52 #endif  /* !__linux__ */
     53 
     54 int uv__random_getrandom(void* buf, size_t buflen) {
     55   ssize_t n;
     56   size_t pos;
     57   int rc;
     58 
     59   rc = uv__random_getrandom_init();
     60   if (rc != 0)
     61     return rc;
     62 
     63   for (pos = 0; pos != buflen; pos += n) {
     64     do {
     65       n = buflen - pos;
     66 
     67       /* Most getrandom() implementations promise that reads <= 256 bytes
     68        * will always succeed and won't be interrupted by signals.
     69        * It's therefore useful to split it up in smaller reads because
     70        * one big read may, in theory, continuously fail with EINTR.
     71        */
     72       if (n > 256)
     73         n = 256;
     74 
     75       n = uv__getrandom((char *) buf + pos, n, 0);
     76     } while (n == -1 && errno == EINTR);
     77 
     78     if (n == -1)
     79       return UV__ERR(errno);
     80 
     81     if (n == 0)
     82       return UV_EIO;
     83   }
     84 
     85   return 0;
     86 }
     87