Replace rnd macros with STL alternatives

src/engine/master.cpp

@@ -244,7 +244,7 @@ void reqauth(masterclient &c, uint id, char *name, char *hostname)
     a.reqtime = totalmillis;
     a.id = id;
     copystring(a.hostname, host);
-    uint seed[3] = { uint(starttime), uint(totalmillis), randomMT() };
+    uint seed[3] = { uint(starttime), uint(totalmillis), tmprnd() };
     static vector<char> buf;
     buf.setsize(0);
     a.answer = genchallenge(u->pubkey, seed, sizeof(seed), buf);
@@ -270,7 +270,7 @@ void reqserverauth(masterclient &c, char *name)
 
     c.serverauthreq.user = u;
     c.serverauthreq.reqtime = totalmillis;
-    uint seed[3] = { uint(starttime), uint(totalmillis), randomMT() };
+    uint seed[3] = { uint(starttime), uint(totalmillis), tmprnd() };
     static vector<char> buf;
     buf.setsize(0);
     c.serverauthreq.answer = genchallenge(u->pubkey, seed, sizeof(seed), buf);

src/engine/renderparticles.cpp

@@ -1552,8 +1552,8 @@ static inline vec offsetvec(vec o, int dir, int dist)
         }
         else if(dir < 27) // flat plane
         {
-            to[dir%3] = float(rndscale(2*radius)-radius);
-            to[(dir+1)%3] = float(rndscale(2*radius)-radius);
+            to[dir%3] = float(rndfloat(2*radius)-radius);
+            to[(dir+1)%3] = float(rndfloat(2*radius)-radius);
             to[(dir+2)%3] = 0.0;
             to.add(p);
             from = to;
@@ -1599,7 +1599,7 @@ void regularflame(int type, const vec &p, float radius, float height, int color,
     float collidez = collide ? p.z - raycube(p, vec(0, 0, -1), collide >= 0 ? COLLIDERADIUS : max(p.z, 0.0f), RAY_CLIPMAT) + (collide >= 0 ? COLLIDEERROR : 0) : -1;
     loopi(density)
     {
-        vec q = vec(p).add(vec(rndscale(radius*2.f)-radius, rndscale(radius*2.f)-radius, 0));
+        vec q = vec(p).add(vec(rndfloat(radius*2.f)-radius, rndfloat(radius*2.f)-radius, 0));
         newparticle(q, v, rnd(max(int(fade*height), 1))+1, type, color, s, blend, grav, collide)->val = collidez;
     }
 }

src/shared/tools.cpp

@@ -1,41 +1,36 @@
 // implementation of generic tools
 
+#include <random>
 #include "cube.h"
 
 ////////////////////////// rnd numbers ////////////////////////////////////////
 
-#define N (624)
-#define M (397)
-#define K (0x9908B0DFU)
+// Seed stored statically to avoid excessive syscall overhead
+static std::random_device rndseed;
+static std::mt19937 rndalg(rndseed());
 
-static uint state[N];
-static int next = N;
+// Generate a random number up to a certain value and do so starting from 0
+int rnd(int value) {
+    std::uniform_int_distribution<> rndint(0, value - 1);
+    return rndint(rndalg);
+}
 
-void seedMT(uint seed)
-{
-    state[0] = seed;
-    for(uint i = 1; i < N; i++)
-        state[i] = seed = 1812433253U * (seed ^ (seed >> 30)) + i;
-    next = 0;
+// Like rnd(), but generate a floating point number instead
+float rndfloat(int value) {
+    std::uniform_real_distribution<> rndreal(0, value - 1);
+    return rndreal(rndalg);
 }
 
-uint randomMT()
-{
-    int cur = next;
-    if(++next >= N)
-    {
-        if(next > N) { seedMT(5489U + time(NULL)); cur = next++; }
-        else next = 0;
-    }
-    uint y = (state[cur] & 0x80000000U) | (state[next] & 0x7FFFFFFFU);
-    state[cur] = y = state[cur < N-M ? cur + M : cur + M-N] ^ (y >> 1) ^ (-int(y & 1U) & K);
-    y ^= (y >> 11);
-    y ^= (y <<  7) & 0x9D2C5680U;
-    y ^= (y << 15) & 0xEFC60000U;
-    y ^= (y >> 18);
-    return y;
+// Deterministic RNG: used to generate closer results by specifying the seed
+int detrnd(int seed, int value) {
+    std::mt19937 algseed(seed);
+    std::uniform_int_distribution<> rnddet(0, value - 1);
+    return rnddet(algseed);
 }
 
+// Generate a positive, ad-hoc random number
+uint tmprnd() { return rndalg(); }
+
 ///////////////////////// network ///////////////////////
 
 // all network traffic is in 32bit ints, which are then compressed using the following simple scheme (assumes that most values are small).

src/shared/tools.h

@@ -81,9 +81,6 @@ static inline int bitscan(uint mask)
 #endif
 #endif
 
-#define rnd(x) ((int)(randomMT()&0x7FFFFFFF)%(x))
-#define rndscale(x) (float((randomMT()&0x7FFFFFFF)*double(x)/double(0x7FFFFFFF)))
-#define detrnd(s, x) ((int)(((((uint)(s))*1103515245+12345)>>16)%(x)))
 #define isnumeric(c) (isdigit(c) || c == '+' || c == '-')
 
 #define loop(v,m) for(int v = 0; v < int(m); ++v)
@@ -1685,8 +1682,10 @@ extern int listzipfiles(const char *dir, const char *ext, vector<char *> &files)
 extern void backup(const char *fname, const char *ext, int revision = 0, int start = 1, bool store = false, bool full = true);
 
 extern void endianswap(void *, int, int);
-extern void seedMT(uint seed);
-extern uint randomMT();
+extern int rnd(int);
+extern float rndfloat(int);
+extern int detrnd(int, int);
+extern uint tmprnd();
 extern void putint(ucharbuf &p, int n);
 extern void putint(packetbuf &p, int n);
 extern void putint(vector<uchar> &p, int n);