From 059ec45f8244ac3b01cf024c5182c77cb40c76d9 Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Sat, 21 Jan 2023 19:35:04 +0100
Subject: [PATCH] Add jrand48()/nrand48() compat functions

These functions are not available on all platforms.
---
 app/meson.build  |  2 ++
 app/src/compat.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 app/src/compat.h |  8 ++++++++
 3 files changed, 54 insertions(+)

diff --git a/app/meson.build b/app/meson.build
index 626e89f8..cc465564 100644
--- a/app/meson.build
+++ b/app/meson.build
@@ -170,6 +170,8 @@ check_functions = [
     'strdup',
     'asprintf',
     'vasprintf',
+    'nrand48',
+    'jrand48',
 ]
 
 foreach f : check_functions
diff --git a/app/src/compat.c b/app/src/compat.c
index 11ddd3cb..bb0152aa 100644
--- a/app/src/compat.c
+++ b/app/src/compat.c
@@ -51,3 +51,47 @@ int vasprintf(char **strp, const char *fmt, va_list ap) {
     return len;
 }
 #endif
+
+#if !defined(HAVE_NRAND48) || !defined(HAVE_JRAND48)
+#define SC_RAND48_MASK UINT64_C(0xFFFFFFFFFFFF) // 48 bits
+#define SC_RAND48_A UINT64_C(0x5DEECE66D)
+#define SC_RAND48_C 0xB
+static inline uint64_t rand_iter48(uint64_t x) {
+    assert((x & ~SC_RAND48_MASK) == 0);
+    return (x * SC_RAND48_A + SC_RAND48_C) & SC_RAND48_MASK;
+}
+
+static uint64_t rand_iter48_xsubi(unsigned short xsubi[3]) {
+    uint64_t x = ((uint64_t) xsubi[0] << 32)
+               | ((uint64_t) xsubi[1] << 16)
+               | xsubi[2];
+
+    x = rand_iter48(x);
+
+    xsubi[0] = (x >> 32) & 0XFFFF;
+    xsubi[1] = (x >> 16) & 0XFFFF;
+    xsubi[2] = x & 0XFFFF;
+
+    return x;
+}
+
+#ifndef HAVE_NRAND48
+long nrand48(unsigned short xsubi[3]) {
+    // range [0, 2^31)
+    return rand_iter48_xsubi(xsubi) >> 17;
+}
+#endif
+
+#ifndef HAVE_JRAND48
+long jrand48(unsigned short xsubi[3]) {
+    // range [-2^31, 2^31)
+    union {
+        uint32_t u;
+        int32_t i;
+    } v;
+    v.u = rand_iter48_xsubi(xsubi) >> 16;
+    return v.i;
+}
+#endif
+
+#endif
diff --git a/app/src/compat.h b/app/src/compat.h
index 8265dbc8..857623e6 100644
--- a/app/src/compat.h
+++ b/app/src/compat.h
@@ -59,4 +59,12 @@ int asprintf(char **strp, const char *fmt, ...);
 int vasprintf(char **strp, const char *fmt, va_list ap);
 #endif
 
+#ifndef HAVE_NRAND48
+long nrand48(unsigned short xsubi[3]);
+#endif
+
+#ifndef HAVE_JRAND48
+long jrand48(unsigned short xsubi[3]);
+#endif
+
 #endif