From c3dd60fcb6e3ac38e4e4048efd939a3b66f777a3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=9B=D0=B5=D0=BE=D0=BD=D0=B8=D0=B4=20=D0=AE=D1=80=D1=8C?=
 =?UTF-8?q?=D0=B5=D0=B2=20=28Leonid=20Yuriev=29?= <leo@yuriev.ru>
Date: Mon, 10 Oct 2022 16:33:51 +0300
Subject: [PATCH] =?UTF-8?q?mdbx:=20=D0=B4=D0=BE=D0=B1=D0=B0=D0=B2=D0=BB?=
 =?UTF-8?q?=D0=B5=D0=BD=D0=B8=D0=B5=20`mdbx=5Fenv=5Fget=5Fpairsize4page=5F?=
 =?UTF-8?q?max()`=20=D0=B8=20`mdbx=5Fenv=5Fget=5Fvalsize4page=5Fmax()`.?=
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---
 mdbx.h     | 26 ++++++++++++++++++++++++++
 src/core.c | 20 ++++++++++++++++++--
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/mdbx.h b/mdbx.h
index 79f444c5..fa72b73d 100644
--- a/mdbx.h
+++ b/mdbx.h
@@ -3307,6 +3307,32 @@ mdbx_env_get_maxvalsize_ex(const MDBX_env *env, MDBX_db_flags_t flags);
 MDBX_DEPRECATED MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int
 mdbx_env_get_maxkeysize(const MDBX_env *env);
 
+/** \brief Returns maximal size of key-value pair to fit in a single page
+ * for specified database flags.
+ * \ingroup c_statinfo
+ *
+ * \param [in] env    An environment handle returned by \ref mdbx_env_create().
+ * \param [in] flags  Database options (\ref MDBX_DUPSORT, \ref MDBX_INTEGERKEY
+ *                    and so on). \see db_flags
+ *
+ * \returns The maximum size of a data can write,
+ *          or -1 if something is wrong. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int
+mdbx_env_get_pairsize4page_max(const MDBX_env *env, MDBX_db_flags_t flags);
+
+/** \brief Returns maximal data size in bytes to fit in a leaf-page or
+ * single overflow/large-page for specified database flags.
+ * \ingroup c_statinfo
+ *
+ * \param [in] env    An environment handle returned by \ref mdbx_env_create().
+ * \param [in] flags  Database options (\ref MDBX_DUPSORT, \ref MDBX_INTEGERKEY
+ *                    and so on). \see db_flags
+ *
+ * \returns The maximum size of a data can write,
+ *          or -1 if something is wrong. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int
+mdbx_env_get_valsize4page_max(const MDBX_env *env, MDBX_db_flags_t flags);
+
 /** \brief Sets application information (a context pointer) associated with
  * the environment.
  * \see mdbx_env_get_userctx()
diff --git a/src/core.c b/src/core.c
index c4ae564e..295d8305 100644
--- a/src/core.c
+++ b/src/core.c
@@ -546,8 +546,16 @@ __cold intptr_t mdbx_limits_pairsize4page_max(intptr_t pagesize,
   return LEAF_NODE_MAX(pagesize) - NODESIZE;
 }
 
-intptr_t mdbx_limits_valsize4page_max(intptr_t pagesize,
-                                      MDBX_db_flags_t flags) {
+__cold int mdbx_env_get_pairsize4page_max(const MDBX_env *env,
+                                          MDBX_db_flags_t flags) {
+  if (unlikely(!env || env->me_signature.weak != MDBX_ME_SIGNATURE))
+    return -1;
+
+  return (int)mdbx_limits_pairsize4page_max((intptr_t)env->me_psize, flags);
+}
+
+__cold intptr_t mdbx_limits_valsize4page_max(intptr_t pagesize,
+                                             MDBX_db_flags_t flags) {
   if (pagesize < 1)
     pagesize = (intptr_t)mdbx_default_pagesize();
   if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
@@ -562,6 +570,14 @@ intptr_t mdbx_limits_valsize4page_max(intptr_t pagesize,
   return PAGEROOM(pagesize);
 }
 
+__cold int mdbx_env_get_valsize4page_max(const MDBX_env *env,
+                                         MDBX_db_flags_t flags) {
+  if (unlikely(!env || env->me_signature.weak != MDBX_ME_SIGNATURE))
+    return -1;
+
+  return (int)mdbx_limits_valsize4page_max((intptr_t)env->me_psize, flags);
+}
+
 /* Calculate the size of a leaf node.
  *
  * The size depends on the environment's page size; if a data item