From 5693fad51d8e0ca7c63059a66c59d6c00706c17d Mon Sep 17 00:00:00 2001
From: Leonid Yuriev <leo@yuriev.ru>
Date: Tue, 1 Oct 2019 13:53:52 +0300
Subject: [PATCH] mdbx: add mdbx_osal_monotime_to_16dot16().

Change-Id: Ia65057def67cebf67252a77665efde4223b14d10
---
 src/elements/core.c | 14 ++++++++++++++
 src/elements/osal.c | 35 ++++++++++++++++++++++++++++++-----
 src/elements/osal.h |  1 +
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/src/elements/core.c b/src/elements/core.c
index 98bd9249..67ed37aa 100644
--- a/src/elements/core.c
+++ b/src/elements/core.c
@@ -505,6 +505,20 @@ __cold void mdbx_rthc_global_init(void) {
   mdbx_trace("pid %d, &mdbx_rthc_key = %p, value 0x%x", mdbx_getpid(),
              &rthc_key, (unsigned)rthc_key);
 #endif
+  /* checking time conversion, this also avoids racing on 32-bit architectures
+   * during writing calculated 64-bit ratio(s) into memory. */
+  uint32_t proba = UINT32_MAX;
+  while (true) {
+    unsigned time_conversion_checkup =
+        mdbx_osal_monotime_to_16dot16(mdbx_osal_16dot16_to_monotime(proba));
+    unsigned one_more = (proba < UINT32_MAX) ? proba + 1 : proba;
+    unsigned one_less = (proba > 0) ? proba - 1 : proba;
+    mdbx_ensure(nullptr, time_conversion_checkup >= one_less &&
+                             time_conversion_checkup <= one_more);
+    if (proba == 0)
+      break;
+    proba >>= 1;
+  }
 }
 
 /* dtor called for thread, i.e. for all mdbx's environment objects */
diff --git a/src/elements/osal.c b/src/elements/osal.c
index 70357da0..3cd139c4 100644
--- a/src/elements/osal.c
+++ b/src/elements/osal.c
@@ -1344,26 +1344,51 @@ static __cold clockid_t choice_monoclock() {
 }
 #endif
 
+/*----------------------------------------------------------------------------*/
+
+#if defined(_WIN32) || defined(_WIN64)
+static LARGE_INTEGER performance_frequency;
+#elif defined(__APPLE__) || defined(__MACH__)
+static uint64_t ratio_16dot16_to_monotine;
+#endif
+
 MDBX_INTERNAL_FUNC uint64_t
 mdbx_osal_16dot16_to_monotime(uint32_t seconds_16dot16) {
 #if defined(_WIN32) || defined(_WIN64)
-  static LARGE_INTEGER performance_frequency;
-  if (performance_frequency.QuadPart == 0)
+  if (unlikely(performance_frequency.QuadPart == 0))
     QueryPerformanceFrequency(&performance_frequency);
   const uint64_t ratio = performance_frequency.QuadPart;
 #elif defined(__APPLE__) || defined(__MACH__)
-  static uint64_t ratio;
-  if (!ratio) {
+  if (unlikely(ratio_16dot16_to_monotine == 0)) {
     mach_timebase_info_data_t ti;
     mach_timebase_info(&ti);
-    ratio = UINT64_C(1000000000) * ti.denom / ti.numer;
+    ratio_16dot16_to_monotine = UINT64_C(1000000000) * ti.denom / ti.numer;
   }
+  const uint64_t ratio = ratio_16dot16_to_monotine;
 #else
   const uint64_t ratio = UINT64_C(1000000000);
 #endif
   return (ratio * seconds_16dot16 + 32768) >> 16;
 }
 
+MDBX_INTERNAL_FUNC uint32_t mdbx_osal_monotime_to_16dot16(uint64_t monotime) {
+  static uint64_t limit;
+  if (unlikely(monotime > limit)) {
+    if (limit != 0)
+      return UINT32_MAX;
+    limit = mdbx_osal_16dot16_to_monotime(UINT32_MAX - 1);
+    if (monotime > limit)
+      return UINT32_MAX;
+  }
+#if defined(_WIN32) || defined(_WIN64)
+  return (uint32_t)((monotime << 16) / performance_frequency.QuadPart);
+#elif defined(__APPLE__) || defined(__MACH__)
+  return (uint32_t)((monotime << 16) / ratio_16dot16_to_monotine);
+#else
+  return (uint32_t)(monotime * 128 / 1953125);
+#endif
+}
+
 MDBX_INTERNAL_FUNC uint64_t mdbx_osal_monotime(void) {
 #if defined(_WIN32) || defined(_WIN64)
   LARGE_INTEGER counter;
diff --git a/src/elements/osal.h b/src/elements/osal.h
index 5e089745..8c17047d 100644
--- a/src/elements/osal.h
+++ b/src/elements/osal.h
@@ -646,6 +646,7 @@ MDBX_INTERNAL_FUNC void __maybe_unused mdbx_osal_jitter(bool tiny);
 MDBX_INTERNAL_FUNC uint64_t mdbx_osal_monotime(void);
 MDBX_INTERNAL_FUNC uint64_t
 mdbx_osal_16dot16_to_monotime(uint32_t seconds_16dot16);
+MDBX_INTERNAL_FUNC uint32_t mdbx_osal_monotime_to_16dot16(uint64_t monotime);
 
 /*----------------------------------------------------------------------------*/
 /* lck stuff */