Improved random number generation (lacking the Windows implementation which will come next).

src/common/common.cpp

@@ -60,6 +60,7 @@ using namespace libebml;
 #include "error.h"
 #include "hacks.h"
 #include "mm_io.h"
+#include "random.h"
 
 int verbose = 1;
 bool suppress_warnings = false;
@@ -185,10 +186,7 @@ bitvalue_c::data()
 
 void
 bitvalue_c::generate_random() {
-  int i;
-
-  for (i = 0; i < bitsize / 8; i++)
-    value[i] = (unsigned char)(255.0 * rand() / RAND_MAX);
+  random_c::generate_bytes(value, bitsize / 8);
 }
 
 /*
@@ -597,7 +595,6 @@ init_cc_stdio() {
 */
 
 static vector<uint32_t> ru_numbers[4];
-static bool random_seeded = false;
 
 void
 clear_list_of_unique_uint32(unique_id_category_e category) {
@@ -661,7 +658,7 @@ remove_unique_uint32(uint32_t number,
 
 uint32_t
 create_unique_uint32(unique_id_category_e category) {
-  uint32_t rnumber, half;
+  uint32_t rnumber;
 
   assert((category >= UNIQUE_TRACK_IDS) &&
          (category <= UNIQUE_ATTACHMENT_IDS));
@@ -671,16 +668,8 @@ create_unique_uint32(unique_id_category_e category) {
     return ru_numbers[category].size();
   }
 
-  if (!random_seeded) {
-    srand(time(NULL));
-    random_seeded = true;
-  }
-
   do {
-    half = (uint32_t)(65535.0 * rand() / RAND_MAX);
-    rnumber = half;
-    half = (uint32_t)(65535.0 * rand() / RAND_MAX);
-    rnumber |= (half << 16);
+    rnumber = random_c::generate_32bits();
   } while ((rnumber == 0) || !is_unique_uint32(rnumber, category));
   add_unique_uint32(rnumber, category);
 

src/common/random.cpp

@@ -0,0 +1,118 @@
+/*
+   mkvmerge -- utility for splicing together matroska files
+   from component media subtypes
+
+   Distributed under the GPL
+   see the file COPYING for details
+   or visit http://www.gnu.org/copyleft/gpl.html
+
+   $Id$
+
+   random number generating functions
+
+   Written by Moritz Bunkus <moritz@bunkus.org>.
+*/
+
+#include "os.h"
+
+#if !defined(SYS_WINDOWS)
+# include <sys/time.h>
+# include <time.h>
+#endif
+
+#include "mm_io.h"
+#include "random.h"
+
+#if defined(SYS_WINDOWS)
+
+#else  // defined(SYS_WINDOWS)
+
+bool random_c::m_seeded = false;
+auto_ptr<mm_file_io_c> random_c::m_dev_urandom;
+bool random_c::m_tried_dev_urandom = false;
+
+void
+random_c::generate_bytes(void *destination,
+                         int num_bytes) {
+  int i;
+
+  try {
+    if (!m_tried_dev_urandom) {
+      m_tried_dev_urandom = true;
+      m_dev_urandom =
+        auto_ptr<mm_file_io_c>(new mm_file_io_c("/dev/urandom", MODE_READ));
+    }
+    if ((NULL != m_dev_urandom.get()) &&
+        (m_dev_urandom->read(destination, num_bytes) == num_bytes))
+      return;
+  } catch(...) {
+  }
+
+  if (!m_seeded) {
+    struct timeval tv;
+
+    gettimeofday(&tv, NULL);
+    srand(tv.tv_usec + tv.tv_sec);
+    m_seeded = true;
+  }
+
+  for (i = 0; i < num_bytes; ++i)
+    ((unsigned char *)destination)[i] =
+      (unsigned char)(256.0 * rand() / (RAND_MAX + 1.0));
+}
+
+#endif // defined(SYS_WINDOWS)
+
+void
+random_c::test() {
+  uint32_t n, ranges[16], i, k;
+  const int num = 1000000;
+  bool found;
+
+  for (i = 0; i < 16; i++)
+    ranges[i] = 0;
+
+  for (i = 0; i < num; i++) {
+    n = random_c::generate_32bits();
+    found = false;
+    for (k = 1; k <= 15; ++k)
+      if (n < (k * 0x10000000)) {
+        ++ranges[k - 1];
+        found = true;
+        break;
+      }
+    if (!found)
+      ++ranges[15];
+  }
+
+  for (i = 0; i < 16; i++)
+    printf("%0d: %d (%.2f%%)\n", i, ranges[i],
+           (double)ranges[i] * 100.0 / num);
+
+#if !defined(SYS_WINDOWS)
+  m_tried_dev_urandom = true;
+  m_dev_urandom = auto_ptr<mm_file_io_c>(NULL);
+
+  for (i = 0; i < 16; i++)
+    ranges[i] = 0;
+
+  for (i = 0; i < num; i++) {
+    n = random_c::generate_32bits();
+    found = false;
+    for (k = 1; k <= 15; ++k)
+      if (n < (k * 0x10000000)) {
+        ++ranges[k - 1];
+        found = true;
+        break;
+      }
+    if (!found)
+      ++ranges[15];
+  }
+
+  for (i = 0; i < 16; i++)
+    printf("%0d: %d (%.2f%%)\n", i, ranges[i],
+           (double)ranges[i] * 100.0 / num);
+#endif
+
+  exit(0);
+}

src/common/random.h

@@ -0,0 +1,78 @@
+/*
+   mkvmerge -- utility for splicing together matroska files
+   from component media subtypes
+
+   Distributed under the GPL
+   see the file COPYING for details
+   or visit http://www.gnu.org/copyleft/gpl.html
+
+   $Id$
+
+   definitions for random number generating functions
+
+   Written by Moritz Bunkus <moritz@bunkus.org>.
+*/
+
+#ifndef __RANDOM_H
+#define __RANDOM_H
+
+#include "os.h"
+
+#include "mm_io.h"
+#include "smart_pointers.h"
+
+class MTX_DLL_API random_c {
+private:
+#if !defined(SYS_WINDOWS)
+  static bool m_seeded;
+  static auto_ptr<mm_file_io_c> m_dev_urandom;
+  static bool m_tried_dev_urandom;
+#endif
+
+public:
+  static void generate_bytes(void *destination, int num_bytes);
+
+  static uint8_t generate_8bits() {
+    uint8_t b;
+
+    generate_bytes(&b, 1);
+    return b;
+  }
+
+  static int16_t generate_15bits() {
+    return (int16_t)(generate_16bits() & 0x7fff);
+  }
+
+  static uint16_t generate_16bits() {
+    uint16_t b;
+
+    generate_bytes(&b, 2);
+    return b;
+  }
+
+  static int32_t generate_31bits() {
+    return (int32_t)(generate_32bits() & 0x7fffffff);
+  }
+
+  static uint32_t generate_32bits() {
+    uint32_t b;
+
+    generate_bytes(&b, 4);
+    return b;
+  }
+
+  static int64_t generate_63bits() {
+    return (int64_t)(generate_64bits() & 0x7fffffffffffull);
+  }
+
+  static uint64_t generate_64bits() {
+    uint64_t b;
+
+    generate_bytes(&b, 8);
+    return b;
+  }
+
+  static void test();
+};
+
+#endif // __RANDOM_H

src/extract/xtr_ogg.cpp

@@ -14,6 +14,7 @@
 
 #include "common.h"
 #include "commonebml.h"
+#include "random.h"
 
 #include "xtr_ogg.h"
 
@@ -61,7 +62,7 @@ xtr_oggbase_c::create_file(xtr_base_c *_master,
   if (no_variable_data)
     ogg_stream_init(&os, 1804289383);
   else
-    ogg_stream_init(&os, rand());
+    ogg_stream_init(&os, random_c::generate_31bits());
 }
 
 void
@@ -172,7 +173,7 @@ xtr_oggflac_c::create_file(xtr_base_c *_master,
   if (no_variable_data)
     ogg_stream_init(&os, 1804289383);
   else
-    ogg_stream_init(&os, rand());
+    ogg_stream_init(&os, random_c::generate_31bits());
 
   // Handle the three header packets: Headers, comments, codec
   // setup data.

src/merge/output_control.cpp

@@ -1947,7 +1947,6 @@ setup() {
 #endif
 
   mm_file_io_c::setup();
-  srand(time(NULL));
   cc_local_utf8 = utf8_init("");
   init_cc_stdio();