Implement lcong48() and seed48()

src/header/stdlib/lcg48.rs

@@ -7,10 +7,16 @@ use platform::types::*;
  * set. */
 pub static mut XI: u64 = 0;
 
+// Used by seed48() (returns a pointer to this array).
+pub static mut STASHED_XI: [c_ushort; 3] = [0; 3];
+
 /* Multiplier and addend, which may be set through lcong48(). Default values as
  * specified in POSIX. */
-pub static mut A: u64 = 0x5deece66d;
-pub static mut C: u16 = 0xb;
+const A_DEFAULT: u64 = 0x5deece66d;
+const C_DEFAULT: u16 = 0xb;
+
+pub static mut A: u64 = A_DEFAULT;
+pub static mut C: u16 = C_DEFAULT;
 
 /// Gets the next element in the linear congruential generator's
 /// sequence.
@@ -61,3 +67,9 @@ pub unsafe fn set_ushort_arr3_from_uint48(arr_ptr: *mut c_ushort, value: u64) {
     *arr_ptr.offset(1) = c_ushort::from((value >> 16) as u16);
     *arr_ptr.offset(2) = c_ushort::from((value >> 32) as u16);
 }
+
+/// Used by `srand48()` and `seed48()`.
+pub unsafe fn reset_a_and_c() {
+    A = A_DEFAULT;
+    C = C_DEFAULT;
+}

src/header/stdlib/mod.rs

@@ -382,9 +382,12 @@ pub extern "C" fn labs(i: c_long) -> c_long {
     i.abs()
 }
 
-// #[no_mangle]
-pub extern "C" fn lcong48(param: [c_ushort; 7]) {
-    unimplemented!();
+#[no_mangle]
+pub unsafe extern "C" fn lcong48(param: *mut c_ushort) {
+    // Input should be a size-7 array.
+    lcg48::XI = lcg48::ushort_arr3_to_uint48(param.offset(0));
+    lcg48::A = lcg48::ushort_arr3_to_uint48(param.offset(3));
+    lcg48::C = *param.offset(6) as u16; // c_ushort may be more than 16 bits
 }
 
 #[repr(C)]
@@ -703,9 +706,17 @@ pub unsafe extern "C" fn realpath(pathname: *const c_char, resolved: *mut c_char
     ptr
 }
 
-// #[no_mangle]
-pub extern "C" fn seed48(seed16v: [c_ushort; 3]) -> c_ushort {
-    unimplemented!();
+#[no_mangle]
+pub unsafe extern "C" fn seed48(seed16v: *mut c_ushort) -> *mut c_ushort {
+    lcg48::reset_a_and_c();
+    
+    //lcg48::STASHED_XI = lcg48::XI;
+    //lcg48::set_ushort_arr3_from_uint48(&mut lcg48::STASHED_XI[0] as *mut c_ushort, lcg48::XI);
+    lcg48::set_ushort_arr3_from_uint48(lcg48::STASHED_XI.as_mut_ptr(), lcg48::XI);
+    lcg48::XI = lcg48::ushort_arr3_to_uint48(seed16v);
+    
+    //&mut lcg48::STASHED_XI[0]
+    lcg48::STASHED_XI.as_mut_ptr()
 }
 
 #[no_mangle]
@@ -792,10 +803,12 @@ pub unsafe extern "C" fn srand(seed: c_uint) {
 
 #[no_mangle]
 pub unsafe extern "C" fn srand48(seedval: c_long) {
+    lcg48::reset_a_and_c();
+    
     /* Set the high 32 bits of the 48-bit X_i value to the lower 32 bits
      * of the input argument, and the lower 16 bits to 0x330e, as
      * specified in POSIX. */
-    lcg48::XI = (((seedval & 0xffff_ffff) as u64) << 16) | 0x330e_u64;
+    lcg48::XI = (((seedval as u32) as u64) << 16) | 0x330e_u64;
 }
 
 // #[no_mangle]

tests/expected/stdlib/lcg48.stdout

@@ -1,7 +1,14 @@
 lrand48 (uninitialized): 0 2116118 89401895 379337186 782977366 196130996 198207689 1046291021 1131187612 975888346
-drand48: 0.750266 0.607593 0.567593 0.799563 0.984984 0.205670 0.625922 0.794426 0.369416 0.854100
-lrand48: 1611183183 1304796356 1218897288 1717049088 2115236938 441672110 1344158015 1706017430 793314380 1834165927
-mrand48: -1072600929 -1685374584 -1857172720 -860869119 -64493420 883344220 -1606651266 -882932436 1586628760 -626635441
+drand48 (seeded with srand48): 0.750266 0.607593 0.567593 0.799563 0.984984 0.205670 0.625922 0.794426 0.369416 0.854100
+lrand48 (seeded with srand48): 1611183183 1304796356 1218897288 1717049088 2115236938 441672110 1344158015 1706017430 793314380 1834165927
+mrand48 (seeded with srand48): -1072600929 -1685374584 -1857172720 -860869119 -64493420 883344220 -1606651266 -882932436 1586628760 -626635441
 erand48: 0.210555 0.014158 0.111353 0.658369 0.103767 0.180385 0.945033 0.745768 0.290272 0.111716
 nrand48: 514983590 590935818 1480794144 1496813112 2133865028 1816766485 2095074020 126058208 909762120 14734916
 jrand48: -1066398599 903693914 -1922375113 -2090140830 1218074962 1662411059 -722435322 764426686 -874142666 -1454656015
+seed48_return: [40c0, 4d4f, daa6]
+lrand48 (seeded with seed48): 386486647 2049879217 706208537 1265096744 1586830881 1884641178 1566935266 1256810805 875501172 1670187935
+xsubi restored froom seed48 return value: [40c0, 4d4f, daa6]
+nrand48 (from xsubi value returned by seed48): 1654466549 509433115 2007628085 1022767111 1935848687 967444157 1967758021 686622820 989863078 1688030308
+lrand48 (with parameters from lcong48): 2015972364 2009368981 971134301 317520085 149004773 538917235 242519436 1066970146 991527304 1588277058
+lrand48 (seeded with srand48 after lcong48 call): 1611183183 1304796356 1218897288 1717049088 2115236938 441672110 1344158015 1706017430 793314380 1834165927
+lrand48 (seeded with seed48 after lcong48 call): 386486647 2049879217 706208537 1265096744 1586830881 1884641178 1566935266 1256810805 875501172 1670187935

tests/stdlib/lcg48.c

@@ -7,8 +7,12 @@ int main(void) {
     long x_l, x_m;
     double x_d;
     long seedval = 0xcafebeef;
+    unsigned short seed[3] = {0xfedc, 0xba98, 0x7654};
     unsigned short xsubi[3] = {0xabcd, 0xef42, 0x5678};
+    unsigned short lcong48_params[7] = {0x0123, 0x4567, 0x89ab, 0xcdef, 0x4242, 0xf000, 0xbaaa};
+    unsigned short xsubi_from_seed48[3] = {0, 0, 0};
     
+    /* Test uninitialized behavior */
     printf("lrand48 (uninitialized):");
     for (int i = 0; i < 10; i++)
     {
@@ -17,8 +21,10 @@ int main(void) {
     }
     printf("\n");
     
+    /* Test different output types with same seed, builtin X_i and
+     * default multiplier and addend */
     srand48(seedval);
-    printf("drand48:");
+    printf("drand48 (seeded with srand48):");
     for (int i = 0; i < 10; i++)
     {
         x_d = drand48();
@@ -27,7 +33,7 @@ int main(void) {
     printf("\n");
     
     srand48(seedval);
-    printf("lrand48:");
+    printf("lrand48 (seeded with srand48):");
     for (int i = 0; i < 10; i++)
     {
         x_l = lrand48();
@@ -36,7 +42,7 @@ int main(void) {
     printf("\n");
     
     srand48(seedval);
-    printf("mrand48:");
+    printf("mrand48 (seeded with srand48):");
     for (int i = 0; i < 10; i++)
     {
         x_m = mrand48();
@@ -44,6 +50,8 @@ int main(void) {
     }
     printf("\n");
     
+    /* Test corresponding functions taking user-supplied X_i, with
+     * default multiplier and addend */
     printf("erand48:");
     for (int i = 0; i < 10; i++)
     {
@@ -67,4 +75,63 @@ int main(void) {
         printf(" %ld", x_l);
     }
     printf("\n");
+    
+    /* Test seed48() "stashing" behavior.  */
+    unsigned short *seed48_return = seed48(seed);
+    printf("seed48_return: [%x, %x, %x]\n",
+        seed48_return[0], seed48_return[1], seed48_return[2]);
+    
+    /* Test seeding behavior of seed48() */
+    printf("lrand48 (seeded with seed48):");
+    for (int i = 0; i < 10; i++)
+    {
+        x_l = lrand48();
+        printf(" %ld", x_l);
+    }
+    printf("\n");
+    
+    /* Test restore from seed48()'s "stashed" value */
+    xsubi_from_seed48[0] = seed48_return[0];
+    xsubi_from_seed48[1] = seed48_return[1];
+    xsubi_from_seed48[2] = seed48_return[2];
+    printf("xsubi restored froom seed48 return value: [%x, %x, %x]\n",
+        xsubi_from_seed48[0], xsubi_from_seed48[1], xsubi_from_seed48[2]);
+    printf("nrand48 (from xsubi value returned by seed48):");
+    for (int i = 0; i < 10; i++)
+    {
+        x_l = nrand48(xsubi_from_seed48);
+        printf(" %ld", x_l);
+    }
+    printf("\n");
+    
+    /* Test behavior with all-user-defined parameters */
+    lcong48(lcong48_params);
+    printf("lrand48 (with parameters from lcong48):");
+    for (int i = 0; i < 10; i++)
+    {
+        x_l = lrand48();
+        printf(" %ld", x_l);
+    }
+    printf("\n");
+    
+    /* Test multiplier- and addend-restoring behavior of srand48() */
+    srand48(seedval);
+    printf("lrand48 (seeded with srand48 after lcong48 call):");
+    for (int i = 0; i < 10; i++)
+    {
+        x_l = lrand48();
+        printf(" %ld", x_l);
+    }
+    printf("\n");
+    
+    /* Test multiplier- and addend-restoring behavior of seed48() */
+    lcong48(lcong48_params);
+    seed48(seed);
+    printf("lrand48 (seeded with seed48 after lcong48 call):");
+    for (int i = 0; i < 10; i++)
+    {
+        x_l = lrand48();
+        printf(" %ld", x_l);
+    }
+    printf("\n");
 }