diff --git a/src/header/stdlib/lcg48.rs b/src/header/stdlib/lcg48.rs
index cba8188ca0f30e550d81343dde1c88b865220d4d..a425110b04cb5e6247e3c293f2ca72940332e81b 100644
--- a/src/header/stdlib/lcg48.rs
+++ b/src/header/stdlib/lcg48.rs
@@ -1,43 +1,86 @@
-//! Helper functions for pseudorandom number generation using LCG, see http://pubs.opengroup.org/onlinepubs/7908799/xsh/drand48.html
+//! Helper functions for pseudorandom number generation using LCG, see https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/functions/drand48.html
use platform::types::*;
-/* The current element of the linear congruential generator's sequence. Any
- * function that sets this variable must ensure that only the lower 48 bits get
- * set. */
-pub static mut XI: u64 = 0;
+/* The default element buffer for the linear congruential generator's
+ * sequence. Implemented using a c_ushort array for consistency between
+ * the drand48()/lrand48()/mrand48() and erand48()/nrand48()/jrand48()
+ * functions, and with STASHED_XI (see below). */
+pub static mut DEFAULT_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;
+// 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. */
+const A_DEFAULT_VALUE: u64 = 0x5deece66d;
+const C_DEFAULT_VALUE: u16 = 0xb;
+
+pub static mut A: u64 = A_DEFAULT_VALUE;
+pub static mut C: u16 = C_DEFAULT_VALUE;
+
+/// Used by `srand48()` and `seed48()`.
+pub unsafe fn reset_a_and_c() {
+ A = A_DEFAULT_VALUE;
+ C = C_DEFAULT_VALUE;
+}
+
+/// Build a 48-bit integer from a size-3 array of unsigned short.
+///
+/// Takes a pointer argument due to the inappropriate C function
+/// signatures generated from Rust's sized arrays, see
+/// https://github.com/eqrion/cbindgen/issues/171
+pub unsafe fn uint48_from_ushort_arr3(arr_ptr: *const c_ushort) -> u64 {
+ let arr = [*arr_ptr.offset(0), *arr_ptr.offset(1), *arr_ptr.offset(2)];
+
+ /* Cast via u16 to ensure we get only the lower 16 bits of each
+ * element, as specified by POSIX. */
+ u64::from(arr[0] as u16) | (u64::from(arr[1] as u16) << 16) | (u64::from(arr[2] as u16) << 32)
+}
+
+/// Set a size-3 array of unsigned short from a 48-bit integer.
+pub unsafe fn set_ushort_arr3_from_uint48(arr_ptr: *mut c_ushort, value: u64) {
+ *arr_ptr.offset(0) = c_ushort::from(value as u16);
+ *arr_ptr.offset(1) = c_ushort::from((value >> 16) as u16);
+ *arr_ptr.offset(2) = c_ushort::from((value >> 32) as u16);
+}
+
+/// Advances the buffer from the input argument to the next element in
+/// the linear congruential generator's sequence.
+///
+/// Modifies the passed argument in-place and returns the new value as a
+/// u64. The input argument must be a size-3 array.
+pub unsafe fn generator_step(xi_arr_ptr: *mut c_ushort) -> u64 {
+ let old_xi: u64 = uint48_from_ushort_arr3(xi_arr_ptr);
-/// Advances the linear congruential generator to the next element in its
-/// sequence.
-pub unsafe fn generator_step() {
/* The recurrence relation of the linear congruential generator,
* X_(n+1) = (a * X_n + c) % m,
- * with m = 2**48. The multiplication and addition can overflow a u64, but
- * we just let it wrap since we take mod 2**48 anyway. */
- XI = A.wrapping_mul(XI).wrapping_add(u64::from(C)) & 0xffff_ffff_ffff;
+ * with m = 2**48. The multiplication and addition can overflow a
+ * u64, but we just let it wrap since we take mod 2**48 anyway. */
+ let new_xi: u64 = A.wrapping_mul(old_xi).wrapping_add(u64::from(C)) & 0xffff_ffff_ffff;
+
+ set_ushort_arr3_from_uint48(xi_arr_ptr, new_xi);
+ new_xi
}
-/// Get a C `double` from a 48-bit integer (for `drand48()` and `erand48()`).
-pub fn x_to_float64(x: u64) -> c_double {
+/// Get a C `double` from a 48-bit integer (for `drand48()` and
+/// `erand48()`).
+pub fn float64_from_x(x: u64) -> c_double {
/* We set the exponent to 0, and the 48-bit integer is copied into the high
* 48 of the 52 significand bits. The value then lies in the range
* [1.0, 2.0), from which we simply subtract 1.0. */
f64::from_bits(0x3ff0_0000_0000_0000_u64 | (x << 4)) - 1.0f64
}
-/// Get the high 31 bits of a 48-bit integer (for `lrand48()` and `nrand48()`).
-pub fn x_to_uint31(x: u64) -> c_long {
+/// Get the high 31 bits of a 48-bit integer (for `lrand48()` and
+/// `nrand48()`).
+pub fn uint31_from_x(x: u64) -> c_long {
(x >> 17) as c_long
}
-/// Get the high 32 bits, signed, of a 48-bit integer (for `mrand48()` and
-/// `jrand48()`).
-pub fn x_to_int32(x: u64) -> c_long {
+/// Get the high 32 bits, signed, of a 48-bit integer (for `mrand48()`
+/// and `jrand48()`).
+pub fn int32_from_x(x: u64) -> c_long {
// Cast via i32 to ensure we get the sign correct
- (x >> 16) as i32 as c_long
+ c_long::from((x >> 16) as i32)
}
diff --git a/src/header/stdlib/mod.rs b/src/header/stdlib/mod.rs
index b1170693b6bf85749d61da9923ecac17bce9ef24..380bca304290fc447555f5d0691e1ff8b885d853 100644
--- a/src/header/stdlib/mod.rs
+++ b/src/header/stdlib/mod.rs
@@ -232,8 +232,8 @@ pub extern "C" fn div(numer: c_int, denom: c_int) -> div_t {
#[no_mangle]
pub unsafe extern "C" fn drand48() -> c_double {
- lcg48::generator_step();
- lcg48::x_to_float64(lcg48::XI)
+ let new_xi = lcg48::generator_step(lcg48::DEFAULT_XI.as_mut_ptr());
+ lcg48::float64_from_x(new_xi)
}
// #[no_mangle]
@@ -246,9 +246,10 @@ pub extern "C" fn ecvt(
unimplemented!();
}
-// #[no_mangle]
-pub extern "C" fn erand(xsubi: [c_ushort; 3]) -> c_double {
- unimplemented!();
+#[no_mangle]
+pub unsafe extern "C" fn erand48(xsubi: *mut c_ushort) -> c_double {
+ let new_xi = lcg48::generator_step(xsubi);
+ lcg48::float64_from_x(new_xi)
}
#[no_mangle]
@@ -361,9 +362,10 @@ pub extern "C" fn initstate(seec: c_uint, state: *mut c_char, size: size_t) -> *
unimplemented!();
}
-// #[no_mangle]
-pub extern "C" fn jrand48(xsubi: [c_ushort; 3]) -> c_long {
- unimplemented!();
+#[no_mangle]
+pub unsafe extern "C" fn jrand48(xsubi: *mut c_ushort) -> c_long {
+ let new_xi = lcg48::generator_step(xsubi);
+ lcg48::int32_from_x(new_xi)
}
// #[no_mangle]
@@ -376,9 +378,16 @@ 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.
+
+ /* Go through this ptr -> u64 -> ptr conversion to ensure we only
+ * get the lower 16 bits of each element. */
+ let new_xi = lcg48::uint48_from_ushort_arr3(param.offset(0));
+ lcg48::set_ushort_arr3_from_uint48(lcg48::DEFAULT_XI.as_mut_ptr(), new_xi);
+ lcg48::A = lcg48::uint48_from_ushort_arr3(param.offset(3));
+ lcg48::C = *param.offset(6) as u16; // c_ushort may be more than 16 bits
}
#[repr(C)]
@@ -416,8 +425,8 @@ pub extern "C" fn lldiv(numer: c_longlong, denom: c_longlong) -> lldiv_t {
#[no_mangle]
pub unsafe extern "C" fn lrand48() -> c_long {
- lcg48::generator_step();
- lcg48::x_to_uint31(lcg48::XI)
+ let new_xi = lcg48::generator_step(lcg48::DEFAULT_XI.as_mut_ptr());
+ lcg48::uint31_from_x(new_xi)
}
#[no_mangle]
@@ -573,13 +582,14 @@ pub extern "C" fn mkstemps(name: *mut c_char, suffix_len: c_int) -> c_int {
#[no_mangle]
pub unsafe extern "C" fn mrand48() -> c_long {
- lcg48::generator_step();
- lcg48::x_to_int32(lcg48::XI)
+ let new_xi = lcg48::generator_step(lcg48::DEFAULT_XI.as_mut_ptr());
+ lcg48::int32_from_x(new_xi)
}
-// #[no_mangle]
-pub extern "C" fn nrand48(xsubi: [c_ushort; 3]) -> c_long {
- unimplemented!();
+#[no_mangle]
+pub unsafe extern "C" fn nrand48(xsubi: *mut c_ushort) -> c_long {
+ let new_xi = lcg48::generator_step(xsubi);
+ lcg48::uint31_from_x(new_xi)
}
#[no_mangle]
@@ -719,9 +729,16 @@ 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::DEFAULT_XI;
+
+ let new_xi = lcg48::uint48_from_ushort_arr3(seed16v);
+ lcg48::set_ushort_arr3_from_uint48(lcg48::DEFAULT_XI.as_mut_ptr(), new_xi);
+
+ lcg48::STASHED_XI.as_mut_ptr()
}
#[no_mangle]
@@ -808,10 +825,13 @@ 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;
+ let new_xi = (((seedval as u32) as u64) << 16) | 0x330e_u64;
+ lcg48::set_ushort_arr3_from_uint48(lcg48::DEFAULT_XI.as_mut_ptr(), new_xi);
}
// #[no_mangle]
diff --git a/tests/expected/stdlib/lcg48.stdout b/tests/expected/stdlib/lcg48.stdout
index 14522ff60bc904344273f0d18ce229d04b20ca00..fa871030baa911d47a02c434e66f92db34c033f6 100644
--- a/tests/expected/stdlib/lcg48.stdout
+++ b/tests/expected/stdlib/lcg48.stdout
@@ -1,4 +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
diff --git a/tests/stdlib/lcg48.c b/tests/stdlib/lcg48.c
index da8c76a46ab55ca529348ab7ba03d81b4c830247..a1685f27fd207ec9f19615bd89fbb95bdfa85bc2 100644
--- a/tests/stdlib/lcg48.c
+++ b/tests/stdlib/lcg48.c
@@ -7,7 +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++)
{
@@ -16,8 +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();
@@ -26,7 +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();
@@ -35,11 +42,96 @@ int main(void) {
printf("\n");
srand48(seedval);
- printf("mrand48:");
+ printf("mrand48 (seeded with srand48):");
for (int i = 0; i < 10; i++)
{
x_m = mrand48();
printf(" %ld", x_m);
}
printf("\n");
+
+ /* Test corresponding functions taking user-supplied X_i, with
+ * default multiplier and addend */
+ printf("erand48:");
+ for (int i = 0; i < 10; i++)
+ {
+ x_d = erand48(xsubi);
+ printf(" %lf", x_d);
+ }
+ printf("\n");
+
+ printf("nrand48:");
+ for (int i = 0; i < 10; i++)
+ {
+ x_l = nrand48(xsubi);
+ printf(" %ld", x_l);
+ }
+ printf("\n");
+
+ printf("jrand48:");
+ for (int i = 0; i < 10; i++)
+ {
+ x_l = jrand48(xsubi);
+ 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");
}