feat(libzigc): implement the drand48 family

* also remove their musl implementation

lib/c/stdlib.zig

@@ -8,6 +8,7 @@ const lldiv_t = std.c.lldiv_t;
 
 comptime {
     _ = @import("stdlib/rand.zig");
+    _ = @import("stdlib/drand48.zig");
 
     if (builtin.target.isMuslLibC() or builtin.target.isWasiLibC()) {
         // Functions specific to musl and wasi-libc.

lib/c/stdlib/drand48.zig

@@ -0,0 +1,147 @@
+//! drand48 functions are based off a 48-bit lcg prng: https://pubs.opengroup.org/onlinepubs/9799919799/functions/drand48.html
+
+const std = @import("std");
+const common = @import("../common.zig");
+const builtin = @import("builtin");
+const Lcg = std.Random.lcg.Wrapping(u48);
+
+comptime {
+    if (builtin.target.isMuslLibC() or builtin.target.isWasiLibC()) {
+        @export(&erand48, .{ .name = "erand48", .linkage = common.linkage, .visibility = common.visibility });
+        @export(&jrand48, .{ .name = "jrand48", .linkage = common.linkage, .visibility = common.visibility });
+        @export(&nrand48, .{ .name = "nrand48", .linkage = common.linkage, .visibility = common.visibility });
+        @export(&drand48, .{ .name = "drand48", .linkage = common.linkage, .visibility = common.visibility });
+        @export(&lrand48, .{ .name = "lrand48", .linkage = common.linkage, .visibility = common.visibility });
+        @export(&mrand48, .{ .name = "mrand48", .linkage = common.linkage, .visibility = common.visibility });
+        @export(&lcong48, .{ .name = "lcong48", .linkage = common.linkage, .visibility = common.visibility });
+        @export(&seed48, .{ .name = "seed48", .linkage = common.linkage, .visibility = common.visibility });
+        @export(&srand48, .{ .name = "srand48", .linkage = common.linkage, .visibility = common.visibility });
+    }
+}
+
+// NOTE: all "magic" numbers and tests are extracted and adapted from the source above
+
+const default_multiplier = 0x5DEECE66D;
+const default_addend = 0xB;
+
+var lcg: Lcg = .init(0, default_multiplier, default_addend);
+var seed48_xi: [3]c_ushort = undefined;
+
+fn erand48(xsubi: *[3]c_ushort) callconv(.c) f64 {
+    const xi = @as(u48, @as(u16, @truncate(xsubi[0])) | (@as(u48, @as(u16, @truncate(xsubi[1])))) << 16) | (@as(u48, @as(u16, @truncate(xsubi[2]))) << 32);
+
+    var separate_lcg: Lcg = .init(xi, lcg.a, lcg.c);
+    const next_xi = separate_lcg.next();
+
+    xsubi.* = .{ @truncate(next_xi & 0xFFFF), @truncate((next_xi >> 16) & 0xFFFF), @truncate((next_xi >> 32) & 0xFFFF) };
+    return @as(f64, next_xi) / @as(f64, std.math.maxInt(u48));
+}
+
+fn jrand48(xsubi: *[3]c_ushort) callconv(.c) c_long {
+    const xi = @as(u48, @as(u16, @truncate(xsubi[0])) | (@as(u48, @as(u16, @truncate(xsubi[1])))) << 16) | (@as(u48, @as(u16, @truncate(xsubi[2]))) << 32);
+
+    var separate_lcg: Lcg = .init(xi, lcg.a, lcg.c);
+    const next_xi = separate_lcg.next();
+
+    xsubi.* = .{ @truncate(next_xi & 0xFFFF), @truncate((next_xi >> 16) & 0xFFFF), @truncate((next_xi >> 32) & 0xFFFF) };
+    return @as(i32, @bitCast(@as(u32, @truncate(next_xi >> 16))));
+}
+
+fn nrand48(xsubi: *[3]c_ushort) callconv(.c) c_long {
+    const xi = @as(u48, @as(u16, @truncate(xsubi[0])) | (@as(u48, @as(u16, @truncate(xsubi[1])))) << 16) | (@as(u48, @as(u16, @truncate(xsubi[2]))) << 32);
+
+    var separate_lcg: Lcg = .init(xi, lcg.a, lcg.c);
+    const next_xi = separate_lcg.next();
+
+    xsubi.* = .{ @truncate(next_xi & 0xFFFF), @truncate((next_xi >> 16) & 0xFFFF), @truncate((next_xi >> 32) & 0xFFFF) };
+    return @intCast(next_xi >> 17); // a c_long is always at least 32-bits, this is never UB
+}
+
+fn drand48() callconv(.c) f64 {
+    return 2e-48 * @as(f64, lcg.next());
+}
+
+fn lrand48() callconv(.c) c_long {
+    return @intCast(lcg.next() >> 17);
+}
+
+fn mrand48() callconv(.c) c_long {
+    return @as(i32, @bitCast(@as(u32, @truncate(lcg.next() >> 16))));
+}
+
+// 0..3 is `Xi`, 3..6 is `a`, 6 is `c`
+// first low 16-bits, then mid, then high.
+fn lcong48(param: *[7]c_ushort) callconv(.c) void {
+    lcg.xi = (@as(u48, @as(u16, @truncate(param[0]))) | (@as(u48, @as(u16, @truncate(param[1])))) << 16) | (@as(u48, @as(u16, @truncate(param[2]))) << 32);
+    lcg.a = (@as(u48, @as(u16, @truncate(param[3]))) | (@as(u48, @as(u16, @truncate(param[4])))) << 16) | (@as(u48, @as(u16, @truncate(param[5]))) << 32);
+    lcg.c = @as(u16, @truncate(param[6]));
+}
+
+fn seed48(seed16v: *[3]c_ushort) callconv(.c) *[3]c_ushort {
+    seed48_xi = .{ @truncate(lcg.xi & 0xFFFF), @truncate((lcg.xi >> 16) & 0xFFFF), @truncate((lcg.xi >> 32) & 0xFFFF) };
+    const xi = (@as(u48, @as(u16, @truncate(seed16v[0]))) | (@as(u48, @as(u16, @truncate(seed16v[1])))) << 16) | (@as(u48, @as(u16, @truncate(seed16v[2]))) << 32);
+    lcg = .init(xi, default_multiplier, default_addend);
+    return &seed48_xi;
+}
+
+fn srand48(seedval: c_long) callconv(.c) void {
+    const xi = (@as(u32, @truncate(@as(c_ulong, @bitCast(seedval)))) << 16) | 0x330E;
+    lcg = .init(xi, default_multiplier, default_addend);
+}
+
+test erand48 {
+    var xsubi: [3]c_ushort = .{ 37174, 64810, 11603 };
+
+    try std.testing.expectApproxEqAbs(0.8965, erand48(&xsubi), 0.0005);
+    try std.testing.expectEqualSlices(c_ushort, &.{ 22537, 47966, 58735 }, &xsubi);
+
+    try std.testing.expectApproxEqAbs(0.3375, erand48(&xsubi), 0.0005);
+    try std.testing.expectEqualSlices(c_ushort, &.{ 37344, 32911, 22119 }, &xsubi);
+
+    try std.testing.expectApproxEqAbs(0.6475, erand48(&xsubi), 0.0005);
+    try std.testing.expectEqualSlices(c_ushort, &.{ 23659, 29872, 42445 }, &xsubi);
+
+    try std.testing.expectApproxEqAbs(0.5005, erand48(&xsubi), 0.0005);
+    try std.testing.expectEqualSlices(c_ushort, &.{ 31642, 7875, 32802 }, &xsubi);
+
+    try std.testing.expectApproxEqAbs(0.5065, erand48(&xsubi), 0.0005);
+    try std.testing.expectEqualSlices(c_ushort, &.{ 64669, 14399, 33170 }, &xsubi);
+}
+
+test jrand48 {
+    var xsubi: [3]c_ushort = .{ 25175, 11052, 45015 };
+
+    try std.testing.expectEqual(1699503220, jrand48(&xsubi));
+    try std.testing.expectEqualSlices(c_ushort, &.{ 2326, 23668, 25932 }, &xsubi);
+
+    try std.testing.expectEqual(-992276007, jrand48(&xsubi));
+    try std.testing.expectEqualSlices(c_ushort, &.{ 41577, 4569, 50395 }, &xsubi);
+
+    try std.testing.expectEqual(-19535776, jrand48(&xsubi));
+    try std.testing.expectEqualSlices(c_ushort, &.{ 31936, 59488, 65237 }, &xsubi);
+
+    try std.testing.expectEqual(79438377, jrand48(&xsubi));
+    try std.testing.expectEqualSlices(c_ushort, &.{ 40395, 8745, 1212 }, &xsubi);
+
+    try std.testing.expectEqual(-1258917728, jrand48(&xsubi));
+    try std.testing.expectEqualSlices(c_ushort, &.{ 37242, 28832, 46326 }, &xsubi);
+}
+
+test nrand48 {
+    var xsubi: [3]c_ushort = .{ 546, 33817, 23389 };
+
+    try std.testing.expectEqual(914920692, nrand48(&xsubi));
+    try std.testing.expectEqualSlices(c_ushort, &.{ 29829, 10728, 27921 }, &xsubi);
+
+    try std.testing.expectEqual(754104482, nrand48(&xsubi));
+    try std.testing.expectEqualSlices(c_ushort, &.{ 6828, 28997, 23013 }, &xsubi);
+
+    try std.testing.expectEqual(609453945, nrand48(&xsubi));
+    try std.testing.expectEqualSlices(c_ushort, &.{ 58183, 3826, 18599 }, &xsubi);
+
+    try std.testing.expectEqual(1878644360, nrand48(&xsubi));
+    try std.testing.expectEqualSlices(c_ushort, &.{ 36678, 44304, 57331 }, &xsubi);
+
+    try std.testing.expectEqual(2114923686, nrand48(&xsubi));
+    try std.testing.expectEqualSlices(c_ushort, &.{ 58585, 22861, 64542 }, &xsubi);
+}

lib/libc/musl/src/prng/__rand48_step.c

@@ -1,14 +0,0 @@
-#include <stdint.h>
-#include "rand48.h"
-
-uint64_t __rand48_step(unsigned short *xi, unsigned short *lc)
-{
-	uint64_t a, x;
-	x = xi[0] | xi[1]+0U<<16 | xi[2]+0ULL<<32;
-	a = lc[0] | lc[1]+0U<<16 | lc[2]+0ULL<<32;
-	x = a*x + lc[3];
-	xi[0] = x;
-	xi[1] = x>>16;
-	xi[2] = x>>32;
-	return x & 0xffffffffffffull;
-}

lib/libc/musl/src/prng/__seed48.c

@@ -1,3 +0,0 @@
-#include "rand48.h"
-
-unsigned short __seed48[7] = { 0, 0, 0, 0xe66d, 0xdeec, 0x5, 0xb };

lib/libc/musl/src/prng/drand48.c

@@ -1,17 +0,0 @@
-#include <stdlib.h>
-#include <inttypes.h>
-#include "rand48.h"
-
-double erand48(unsigned short s[3])
-{
-	union {
-		uint64_t u;
-		double f;
-	} x = { 0x3ff0000000000000ULL | __rand48_step(s, __seed48+3)<<4 };
-	return x.f - 1.0;
-}
-
-double drand48(void)
-{
-	return erand48(__seed48);
-}

lib/libc/musl/src/prng/lcong48.c

@@ -1,8 +0,0 @@
-#include <stdlib.h>
-#include <string.h>
-#include "rand48.h"
-
-void lcong48(unsigned short p[7])
-{
-	memcpy(__seed48, p, sizeof __seed48);
-}

lib/libc/musl/src/prng/lrand48.c

@@ -1,13 +0,0 @@
-#include <stdlib.h>
-#include <inttypes.h>
-#include "rand48.h"
-
-long nrand48(unsigned short s[3])
-{
-	return __rand48_step(s, __seed48+3) >> 17;
-}
-
-long lrand48(void)
-{
-	return nrand48(__seed48);
-}

lib/libc/musl/src/prng/mrand48.c

@@ -1,13 +0,0 @@
-#include <stdlib.h>
-#include <inttypes.h>
-#include "rand48.h"
-
-long jrand48(unsigned short s[3])
-{
-	return (int32_t)(__rand48_step(s, __seed48+3) >> 16);
-}
-
-long mrand48(void)
-{
-	return jrand48(__seed48);
-}

lib/libc/musl/src/prng/rand48.h

@@ -1,5 +0,0 @@
-#include <stdint.h>
-#include <features.h>
-
-hidden uint64_t __rand48_step(unsigned short *xi, unsigned short *lc);
-extern hidden unsigned short __seed48[7];

lib/libc/musl/src/prng/seed48.c

@@ -1,11 +0,0 @@
-#include <stdlib.h>
-#include <string.h>
-#include "rand48.h"
-
-unsigned short *seed48(unsigned short *s)
-{
-	static unsigned short p[3];
-	memcpy(p, __seed48, sizeof p);
-	memcpy(__seed48, s, sizeof p);
-	return p;
-}

lib/libc/musl/src/prng/srand48.c

@@ -1,6 +0,0 @@
-#include <stdlib.h>
-
-void srand48(long seed)
-{
-	seed48((unsigned short [3]){ 0x330e, seed, seed>>16 });
-}

src/libs/musl.zig

@@ -1305,15 +1305,7 @@ const src_files = [_][]const u8{
     "musl/src/passwd/putgrent.c",
     "musl/src/passwd/putpwent.c",
     "musl/src/passwd/putspent.c",
-    "musl/src/prng/drand48.c",
-    "musl/src/prng/lcong48.c",
-    "musl/src/prng/lrand48.c",
-    "musl/src/prng/mrand48.c",
-    "musl/src/prng/__rand48_step.c",
     "musl/src/prng/random.c",
-    "musl/src/prng/__seed48.c",
-    "musl/src/prng/seed48.c",
-    "musl/src/prng/srand48.c",
     "musl/src/process/aarch64/vfork.s",
     "musl/src/process/arm/vfork.s",
     "musl/src/process/execl.c",

src/libs/wasi_libc.zig

@@ -885,14 +885,6 @@ const libc_top_half_src_files = [_][]const u8{
     "musl/src/network/inet_pton.c",
     "musl/src/network/ntohl.c",
     "musl/src/network/ntohs.c",
-    "musl/src/prng/drand48.c",
-    "musl/src/prng/lcong48.c",
-    "musl/src/prng/lrand48.c",
-    "musl/src/prng/mrand48.c",
-    "musl/src/prng/__rand48_step.c",
-    "musl/src/prng/__seed48.c",
-    "musl/src/prng/seed48.c",
-    "musl/src/prng/srand48.c",
     "musl/src/regex/fnmatch.c",
     "musl/src/regex/regerror.c",
     "musl/src/search/hsearch.c",