Linear Congruential Generator

LGC.asm

00000000004011b0 <my_srand>:
  4011b0:       55                      push   rbp
  4011b1:       48 89 e5                mov    rbp,rsp
  4011b4:       89 7d fc                mov    DWORD PTR [rbp-0x4],edi
  4011b7:       8b 7d fc                mov    edi,DWORD PTR [rbp-0x4]
  4011ba:       89 3c 25 3c 40 40 00    mov    DWORD PTR ds:0x40403c,edi              ; 0x40403c holds rand_state
  4011c1:       5d                      pop    rbp
  4011c2:       c3                      ret    
  4011c3:       66 2e 0f 1f 84 00 00    nop    WORD PTR cs:[rax+rax*1+0x0]
  4011ca:       00 00 00 
  4011cd:       0f 1f 00                nop    DWORD PTR [rax]

00000000004011d0 <my_rand>:
  4011d0:       55                      push   rbp
  4011d1:       48 89 e5                mov    rbp,rsp
  4011d4:       69 04 25 3c 40 40 00    imul   eax,DWORD PTR ds:0x40403c,0x19660d     ; rand_state * RNG_a
  4011db:       0d 66 19 00 
  4011df:       89 04 25 3c 40 40 00    mov    DWORD PTR ds:0x40403c,eax
  4011e6:       8b 04 25 3c 40 40 00    mov    eax,DWORD PTR ds:0x40403c
  4011ed:       05 5f f3 6e 3c          add    eax,0x3c6ef35f                         ; rand_state + RNG_c
  4011f2:       89 04 25 3c 40 40 00    mov    DWORD PTR ds:0x40403c,eax
  4011f9:       8b 04 25 3c 40 40 00    mov    eax,DWORD PTR ds:0x40403c
  401200:       25 ff 7f 00 00          and    eax,0x7fff                             ; rand_state & SHRT_MAX (32767)
  401205:       89 c0                   mov    eax,eax                                ; ORLY?
  401207:       5d                      pop    rbp
  401208:       c3                      ret    
  401209:       0f 1f 80 00 00 00 00    nop    DWORD PTR [rax+0x0]

LGC.c

#include <stdlib.h>
#include <stdint.h>
#include <limits.h>
#include <time.h>
#include <stdio.h>

#define RNG_a (1664525)     // 0x19660d
#define RNG_c (1013904223)  // 0x3c6ef35f

static uint32_t rand_state;

static void my_srand(uint32_t init)
{
  rand_state = init;
}

static uint64_t my_rand()
{
  rand_state = rand_state * RNG_a;
  rand_state = rand_state + RNG_c;
  return rand_state & SHRT_MAX;
}

int main()
{
  my_srand((uint32_t)time(NULL));
  for (int i = 0 ; i < 10 ; ++i)
    printf("0x%lx\n", my_rand());
}