src/library/crandom.cpp

   1 #include "crandom.hpp"
   2 #include <stdexcept>
   3 #include <iostream>
   4
   5 #if defined(_WIN32) || defined(_WIN64)
   6 #include <windows.h>
   7
   8 namespace
   9 {
  10         typedef BOOLEAN (WINAPI *rtlgenrandom_t)(PVOID buf, ULONG buflen);
  11         HMODULE advapi;
  12         rtlgenrandom_t rtlgenrandom_fn;
  13 }
  14
  15 namespace crandom
  16 {
  17 void init()
  18 {
  19         if(rtlgenrandom_fn) return;
  20         advapi = LoadLibraryA("advapi32.dll");
  21         if(!advapi)
  22                 throw std::runtime_error("Can't load advapi32.dll");
  23         rtlgenrandom_fn = (rtlgenrandom_t)GetProcAddress(advapi, "SystemFunction036");
  24         if(!rtlgenrandom_fn)
  25                 throw std::runtime_error("Can't find rtlgenrandom");
  26 }
  27
  28 void generate(void* buffer, size_t buffersize)
  29 {
  30         if(!rtlgenrandom_fn)
  31                 init();
  32         while(!rtlgenrandom_fn(buffer, buffersize));
  33 }
  34 }
  35
  36 #else
  37 #include <unistd.h>
  38 #include <fcntl.h>
  39 #include <cerrno>
  40
  41 namespace
  42 {
  43         int fd = -1;
  44         void try_file(const char* name)
  45         {
  46                 int err = 0;
  47                 while(fd < 0 && err != ENOENT && err != ENXIO) {
  48                         fd = open(name, O_RDONLY);
  49                         if(fd < 0) err = errno;
  50                 }
  51         }
  52 }
  53
  54 namespace crandom
  55 {
  56 void init()
  57 {
  58         if(fd < 0) try_file("/dev/urandom");
  59         if(fd < 0) try_file("/dev/random");
  60         if(fd < 0) throw std::runtime_error("Can't open /dev/urandom");
  61 }
  62
  63 void generate(void* buffer, size_t buffersize)
  64 {
  65         if(fd < 0)
  66                 init();
  67         size_t out = 0;
  68         while(out < buffersize) {
  69                 ssize_t r = read(fd, (char*)buffer + out, buffersize - out);
  70                 if(r > 0) out += r;
  71         }
  72 }
  73 }
  74
  75 #endif