libmdbx

https://libmdbx.dqdkfa.ru/
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### MDBX Install API Template Macro

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09.html

Defines a macro for installing API templates.

```cpp
#define MDBX_INSTALL_API_TEMPLATE | ( |  | _API_ATTRIBUTES_ ,   
---|---|---|---  
|  |  | __... )
```

--------------------------------

### mdbx::env::start_write

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Starts a read-write transaction within the environment.

```APIDOC
## mdbx::env::start_write

### Description
Starts a read-write transaction. Can be started independently or as a child of an existing transaction.

### Signature
- `txn_managed mdbx::env::start_write(bool dont_wait=false)`
- `txn_managed mdbx::env::start_write(txn &parent)`
```

--------------------------------

### Transaction Initialization

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Methods to start read-only or read-write transactions.

```cpp
inline txn_managed env::start_read() const {
 ::MDBX_txn *ptr;
 error::success_or_throw(::mdbx_txn_begin(handle_, nullptr, MDBX_TXN_RDONLY, &ptr));
 MDBX_INLINE_API_ASSERT(ptr != nullptr);
 return txn_managed(ptr);
}
```

```cpp
inline txn_managed env::prepare_read() const {
 ::MDBX_txn *ptr;
 error::success_or_throw(::mdbx_txn_begin(handle_, nullptr, MDBX_TXN_RDONLY_PREPARE, &ptr));
 MDBX_INLINE_API_ASSERT(ptr != nullptr);
 return txn_managed(ptr);
}
```

```cpp
inline txn_managed env::start_write(bool dont_wait) {
 ::MDBX_txn *ptr;
 error::success_or_throw(
 ::mdbx_txn_begin(handle_, nullptr, dont_wait ? MDBX_TXN_READWRITE | MDBX_TXN_TRY : MDBX_TXN_READWRITE, &ptr));
 MDBX_INLINE_API_ASSERT(ptr != nullptr || dont_wait);
 return txn_managed(ptr);
}
```

```cpp
inline txn_managed env::start_write(txn &parent) {
 ::MDBX_txn *ptr;
 error::success_or_throw(::mdbx_txn_begin(handle_, parent, MDBX_TXN_READWRITE, &ptr));
 MDBX_INLINE_API_ASSERT(ptr != nullptr);
 return txn_managed(ptr);
}
```

```cpp
inline txn_managed env::try_start_write() { return start_write(true); }
```

--------------------------------

### mdbx::env::start_read

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Starts a read-only transaction within the environment.

```APIDOC
## mdbx::env::start_read

### Description
Starts a read-only transaction for the current environment.

### Signature
- `txn_managed mdbx::env::start_read() const`
```

--------------------------------

### mdbx_txn_begin_ex

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_source.html

Starts a new transaction with an optional user context.

```APIDOC
int mdbx_txn_begin_ex(MDBX_env *env, MDBX_txn *parent, MDBX_txn_flags_t flags, MDBX_txn **txn, void *context);
```

--------------------------------

### Configure Synchronization Settings

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Methods for setting and getting sync thresholds and periods.

```cpp
inline env &env::set_sync_threshold(size_t bytes) {
 error::success_or_throw(::mdbx_env_set_syncbytes(handle_, bytes));
 return *this;
}
```

```cpp
inline size_t env::sync_threshold() const {
 size_t bytes;
 error::success_or_throw(::mdbx_env_get_syncbytes(handle_, &bytes));
 return bytes;
}
```

```cpp
inline env &env::set_sync_period__seconds_16dot16(unsigned seconds_16dot16) {
 error::success_or_throw(::mdbx_env_set_syncperiod(handle_, seconds_16dot16));
 return *this;
}
```

```cpp
inline unsigned env::sync_period__seconds_16dot16() const {
 unsigned seconds_16dot16;
 error::success_or_throw(::mdbx_env_get_syncperiod(handle_, &seconds_16dot16));
 return seconds_16dot16;
}
```

```cpp
inline env &env::set_sync_period__seconds_double(double seconds) {
 return set_sync_period__seconds_16dot16(unsigned(seconds * 65536));
}
```

```cpp
inline double env::sync_period__seconds_double() const { return sync_period__seconds_16dot16() / 65536.0; }
```

```cpp
#if __cplusplus >= 201103L
inline env &env::set_sync_period(const duration &period) { return set_sync_period__seconds_16dot16(period.count()); }

inline duration env::sync_period() const { return duration(sync_period__seconds_16dot16()); }
#endif
```

--------------------------------

### mdbx_preopen_snapinfo

Source: https://libmdbx.dqdkfa.ru/group__c__opening.html

Gets basic information about the database without opening it.

```APIDOC
## int mdbx_preopen_snapinfo (const char *pathname, MDBX_envinfo *info, size_t bytes)

### Description
Gets basic information about the database without opening it.

### Parameters
- **pathname** (const char *) - Required - Path to the database.
- **info** (MDBX_envinfo *) - Required - Pointer to the info structure.
- **bytes** (size_t) - Required - Size of the info structure.
```

--------------------------------

### Transaction Management

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_source.html

Functions for starting and cloning transactions, including extended context support.

```c
3920LIBMDBX_API int mdbx_txn_begin_ex(MDBX_env *env, MDBX_txn *parent, MDBX_txn_flags_t flags, MDBX_txn **txn,
3921 void *context);
3977inline int mdbx_txn_begin(MDBX_env * env, MDBX_txn *parent, MDBX_txn_flags_t flags, MDBX_txn **txn) {
3978 return mdbx_txn_begin_ex(env, parent, flags, txn, NULL);
3979}
4032LIBMDBX_API int mdbx_txn_clone(const MDBX_txn *origin, MDBX_txn **in_out_clone, void *context);
```

--------------------------------

### int mdbx_cursor_scan_from(MDBX_cursor *cursor, MDBX_predicate_func predicate, void *context, MDBX_cursor_op from_op, MDBX_val *from_key, MDBX_val *from_value, MDBX_cursor_op turn_op, void *arg)

Source: https://libmdbx.dqdkfa.ru/group__c__crud.html

Scans a table using the given predicate, starting with the given key-value pair, and reduces an associated overhead.

```APIDOC
## int mdbx_cursor_scan_from(MDBX_cursor *cursor, MDBX_predicate_func predicate, void *context, MDBX_cursor_op from_op, MDBX_val *from_key, MDBX_val *from_value, MDBX_cursor_op turn_op, void *arg)

### Description
Scans a table using the given predicate, starting with the given key-value pair. The function performs initial cursor positioning, then probes each key-value pair using the predicate function until the end of data is reached, an error occurs, or the predicate returns MDBX_RESULT_TRUE.

### Parameters
- **cursor** (MDBX_cursor *) - In/Out - The cursor for performing the scan operation associated with the active transaction and the table's DBI descriptor.
- **predicate** (MDBX_predicate_func) - In - A predicative function for probing key-value pairs.
- **context** (void *) - In/Out - A pointer to the context with auxiliary information for probing.
- **from_op** (MDBX_cursor_op) - In - The operation of positioning the cursor to the initial position.
- **from_key** (MDBX_val *) - In/Out - A pointer to the key used for initial positioning and subsequent steps.
- **from_value** (MDBX_val *) - In/Out - A pointer to the value used for initial positioning and subsequent steps.
- **turn_op** (MDBX_cursor_op) - In - The operation of positioning the cursor to move to the next element.
- **arg** (void *) - In/Out - An auxiliary argument to the predicative function.

### Returns
- **MDBX_RESULT_TRUE** - If a key-value pair is found for which the predicative function returned MDBX_RESULT_TRUE.
- **MDBX_RESULT_FALSE** - If a suitable key-value pair is NOT found or the end of data has been reached.
- **OTHERWISE** - Any other value is an error code or a user-defined code for stopping the search.
```

--------------------------------

### mdbx_setup_debug

Source: https://libmdbx.dqdkfa.ru/group__c__debug.html

Sets up the global log-level, debug options, and a logger function that accepts format strings and va_list arguments.

```APIDOC
## int mdbx_setup_debug (MDBX_log_level_t log_level, MDBX_debug_flags_t debug_flags, MDBX_debug_func logger)

### Description
Configures the global log-level, debug options, and a logger callback for handling formatted debug messages.

### Parameters
- **log_level** (MDBX_log_level_t) - The desired logging severity level.
- **debug_flags** (MDBX_debug_flags_t) - Flags to configure specific debug behaviors.
- **logger** (MDBX_debug_func) - A callback function for processing log messages.
```

--------------------------------

### mdbx_setup_debug

Source: https://libmdbx.dqdkfa.ru/group__c__debug.html

Configures global log-level, debug options, and the logger callback.

```APIDOC
## mdbx_setup_debug

### Description
Setups global log-level, debug options and logger for format string and va_list.

### Parameters
- **log_level** (MDBX_log_level_t) - New global log-level or MDBX_LOG_DONTCHANGE.
- **debug_flags** (MDBX_debug_flags_t) - New global debug flags or MDBX_DBG_DONTCHANGE.
- **logger** (MDBX_debug_func) - New global logger callback function or MDBX_LOGGER_DONTCHANGE.

### Returns
- A non-negative value on success (previous debug_flags in 0-15 bits, log_level in 16-31 bits).
- A negative value on failure.
```

--------------------------------

### mdbx_cursor_get_userctx

Source: https://libmdbx.dqdkfa.ru/group__c__cursors.html

Get the application information associated with the MDBX_cursor.

```APIDOC
## void * mdbx_cursor_get_userctx(const MDBX_cursor *cursor)

### Description
Get the application information associated with the MDBX_cursor.

### Parameters
- **cursor** (const MDBX_cursor *) - Required - An cursor handle returned by mdbx_cursor_create() or mdbx_cursor_open().

### Returns
- **void*** - The pointer which was passed via the context parameter of mdbx_cursor_create() or set by mdbx_cursor_set_userctx(), or NULL if something wrong.
```

--------------------------------

### mdbx_setup_debug()

Source: https://libmdbx.dqdkfa.ru/group__c__debug.html

Configures the runtime debug flags for the libmdbx library.

```APIDOC
## mdbx_setup_debug()

### Description
Sets the runtime debug flags for libmdbx. These flags control features such as assertions, audits, and jitter, depending on how the library was compiled.

### Parameters
- **flags** (MDBX_debug_flags_t) - The bitwise OR combination of debug flags to apply.

### Debug Flags
- **MDBX_DBG_DONTCHANGE**: Do not change current settings.
- **MDBX_DBG_NONE**: Clear all debug flags.
- **MDBX_DBG_ASSERT**: Enables costly check of debug-like assertions (Requires MDBX_CHECKING >= 2).
- **MDBX_DBG_AUDIT**: Enables extra costly checks and deep verification of page lists (Requires MDBX_CHECKING >= 3).
- **MDBX_DBG_JITTER**: Enables small random delays in critical points (Requires MDBX_DEBUG > 0).
- **MDBX_DBG_DUMP**: Controls including of a database(s) meta-pages in coredump files.
- **MDBX_DBG_LEGACY_MULTIOPEN**: Allow multi-opening environment(s).
- **MDBX_DBG_LEGACY_OVERLAP**: Allow read and write transactions overlapping for the same thread.
- **MDBX_DBG_DONT_UPGRADE**: Disables automatic updating of the database format signature.
- **MDBX_DBG_MAX**: Avoids UBSAN false-positive issues/traps.
```

--------------------------------

### mdbx_get_equal_or_great Function

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Get equal or great item from a table.

```c
LIBMDBX_API int mdbx_get_equal_or_great(const MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key, MDBX_val *data)
```

--------------------------------

### Get buffer capacity

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Returns the capacity of the buffer if it is freestanding.

```cpp
MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR size_t capacity() const noexcept {
return is_freestanding() ? silo_.capacity() : 0;
}
```

--------------------------------

### mdbx_env_chk

Source: https://libmdbx.dqdkfa.ru/mdbx_8h.html

Gets basic information about the database without opening it.

```APIDOC
## mdbx_env_chk

### Description
Gets basic information about the database without opening it.

### Signature
int mdbx_env_chk(MDBX_env *env, const MDBX_chk_callbacks_t *cb, MDBX_chk_context_t *ctx, const MDBX_chk_flags_t flags, MDBX_chk_severity_t verbosity, unsigned timeout_seconds_16dot16)
```

--------------------------------

### env::start_write

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Initiates a read-write transaction within the environment.

```APIDOC
## env::start_write

### Description
Starts a new read-write transaction. Can be called with an optional parent transaction or a non-blocking flag.

### Parameters
- **parent** (txn) - Optional - Parent transaction for nested operations.
- **dont_wait** (bool) - Optional - If true, does not block if a write transaction is already active.
```

--------------------------------

### mdbx_env_get_option

Source: https://libmdbx.dqdkfa.ru/group__c__settings.html

Gets the value of an extra runtime option from an environment.

```APIDOC
## int mdbx_env_get_option(const MDBX_env *env, const MDBX_option_t option, uint64_t *pvalue)

### Description
Gets the value of an extra runtime option from an environment.

### Parameters
- **env** (const MDBX_env*) - The environment handle.
- **option** (MDBX_option_t) - The option to retrieve.
- **pvalue** (uint64_t*) - Pointer to store the retrieved value.
```

--------------------------------

### Environment Configuration Options

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_source.html

Enumeration of configurable options for the libmdbx environment.

```c
typedef enum MDBX_option {
	MDBX_opt_max_db,
	MDBX_opt_max_readers,
	MDBX_opt_sync_bytes,
	MDBX_opt_sync_period,
	MDBX_opt_rp_augment_limit,
	MDBX_opt_loose_limit,
	MDBX_opt_dp_reserve_limit,
	MDBX_opt_txn_dp_limit,
	MDBX_opt_txn_dp_initial,
	MDBX_opt_spill_max_denominator,
	MDBX_opt_spill_min_denominator,
	MDBX_opt_spill_parent4child_denominator,
	MDBX_opt_merge_threshold,
	MDBX_opt_writethrough_threshold,
	MDBX_opt_prefault_write_enable,
	MDBX_opt_gc_time_limit,
	MDBX_opt_prefer_waf_insteadof_balance,
	MDBX_opt_subpage_limit,
	MDBX_opt_subpage_room_threshold,
	MDBX_opt_subpage_reserve_prereq,
	MDBX_opt_subpage_reserve_limit,
	MDBX_opt_split_reserve,
	MDBX_opt_presync_threshold
} MDBX_option_t;
```

--------------------------------

### mdbx_env_open()

Source: https://libmdbx.dqdkfa.ru/group__c__opening.html

Opens an environment instance using a previously created handle.

```APIDOC
## int mdbx_env_open(MDBX_env *env, const char *pathname, MDBX_env_flags_t flags, mdbx_mode_t mode)

### Description
Opens an environment instance. The mdbx_env_close() function must be called later to discard the handle and release resources.

### Parameters
- **env** (MDBX_env *) - Required - An environment handle returned by mdbx_env_create().
- **pathname** (const char *) - Required - The pathname for the database or the directory in which the database files reside.
- **flags** (MDBX_env_flags_t) - Required - Specifies options for this environment (e.g., MDBX_RDONLY, MDBX_WRITEMAP).
- **mode** (mdbx_mode_t) - Required - The UNIX permissions to set on created files. Zero value means to open existing, but do not create.

### Returns
- **int** - A non-zero error value on failure and 0 on success. Possible errors include MDBX_VERSION_MISMATCH, MDBX_INVALID, MDBX_ENOENT, MDBX_EACCES, MDBX_BUSY, MDBX_INCOMPATIBLE, MDBX_WANNA_RECOVERY, and MDBX_TOO_LARGE.
```

--------------------------------

### Environment Configuration and Status Methods

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Methods for checking nested transaction availability, retrieving environment limits, and managing context or synchronization thresholds.

```cpp
inline bool is_nested_transactions_available() const { return (get_flags() & (MDBX_WRITEMAP | MDBX_RDONLY)) == 0; }

inline unsigned max_readers() const;

inline unsigned max_maps() const;

inline void *get_context() const noexcept;

inline env &set_context(void *your_context);

inline env &set_sync_threshold(size_t bytes);

inline size_t sync_threshold() const;
```

--------------------------------

### mdbx_env_sync_ex

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_source.html

Synchronizes the environment to disk with configurable options.

```APIDOC
## int mdbx_env_sync_ex(MDBX_env *env, bool force, bool nonblock)

### Description
Flushes the environment data to disk. Allows specifying whether to force the sync and whether to perform it in a non-blocking manner.

### Parameters
- **env** (MDBX_env*) - Required - The environment handle.
- **force** (bool) - Required - Whether to force the synchronization.
- **nonblock** (bool) - Required - Whether to perform the operation without blocking.
```

--------------------------------

### Get buffer modality

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Returns the current memory modality of the buffer.

```cpp
MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR modality asset() const noexcept {
return is_freestanding() ? (is_inplace() ? modality::inplace : modality::allocated) : modality::reference;
}
```

--------------------------------

### mdbx_setup_debug_nofmt

Source: https://libmdbx.dqdkfa.ru/group__c__debug.html

Sets up the global log-level, debug options, and a logger for plain preformatted messages.

```APIDOC
## int mdbx_setup_debug_nofmt (MDBX_log_level_t log_level, MDBX_debug_flags_t debug_flags, MDBX_debug_func_nofmt logger, char *logger_buffer, size_t logger_buffer_size)

### Description
Configures the global log-level, debug options, and a logger for plain messages, including a buffer for message storage.

### Parameters
- **log_level** (MDBX_log_level_t) - The desired logging severity level.
- **debug_flags** (MDBX_debug_flags_t) - Flags to configure specific debug behaviors.
- **logger** (MDBX_debug_func_nofmt) - A callback function for processing preformatted messages.
- **logger_buffer** (char *) - Buffer for storing log messages.
- **logger_buffer_size** (size_t) - Size of the provided logger buffer.
```

--------------------------------

### mdbx_env_get_syncbytes

Source: https://libmdbx.dqdkfa.ru/group__c__statinfo.html

Gets the threshold to force flush data buffers to disk.

```APIDOC
## int mdbx_env_get_syncbytes(const MDBX_env *env, size_t *threshold)

### Description
Get the threshold to force flush the data buffers to disk, even if the MDBX_SAFE_NOSYNC flag is set in the environment.

### Parameters
- **env** (const MDBX_env *) - Required - An environment handle returned by mdbx_env_create().
- **threshold** (size_t *) - Required - Address of a size_t to store the number of bytes of summary changes when a synchronous flush would be made.

### Returns
- **int** - 0 on success, non-zero error value on failure (e.g., MDBX_EINVAL).
```

--------------------------------

### mdbx::slice::starts_with()

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Checks if the data starts with the given prefix.

```APIDOC
## bool mdbx::slice::starts_with(const slice & _prefix_) const

### Description
Checks if the current slice data starts with the specified prefix slice.

### Parameters
- **_prefix_** (const slice &) - The prefix to check against.
```

--------------------------------

### Environment Open Function

Source: https://libmdbx.dqdkfa.ru/group__c__api.html

Opens an environment instance using wide-character path support.

```c
#define mdbx_env_openT(env, pathname, flags, mode) mdbx_env_openW(env, pathname, flags, mode)
```

```c
LIBMDBX_API int mdbx_env_openW(MDBX_env *env, const wchar_t *pathname, MDBX_env_flags_t flags, mdbx_mode_t mode)
```

--------------------------------

### mdbx::env_managed::env_managed(pathname, parameters, accede)

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Constructors for opening an existing database environment using various path types.

```APIDOC
## mdbx::env_managed::env_managed(pathname, parameters, accede)

### Description
Opens an existing database environment.

### Parameters
- **pathname** (const ::mdbx::filesystem::path& / const ::std::wstring& / const wchar_t* / const ::std::string& / const char*) - Required - The path to the database.
- **parameters** (const operate_parameters&) - Required - Operational parameters for the environment.
- **accede** (bool) - Optional - Defaults to true.
```

--------------------------------

### mdbx::env::prepare_read

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Creates a read transaction without starting it.

```APIDOC
## txn_managed mdbx::env::prepare_read()

### Description
Creates but does not start a read transaction.
```

--------------------------------

### mdbx_cache_init Function

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Initializes the cache entry before the first use.

```c
void mdbx_cache_init(MDBX_cache_entry_t *entry)
```

--------------------------------

### Environment Lifecycle and Warmup

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_source.html

Functions for closing the environment, handling forks, and warming up the environment cache.

```c
inline int mdbx_env_close(MDBX_env * env) { return mdbx_env_close_ex(env, false); }
LIBMDBX_API int mdbx_env_resurrect_after_fork(MDBX_env *env);
typedef enum MDBX_warmup_flags {
 MDBX_warmup_default = 0,
 MDBX_warmup_force = 1,
 MDBX_warmup_oomsafe = 2,
 MDBX_warmup_lock = 4,
 MDBX_warmup_touchlimit = 8,
 MDBX_warmup_release = 16,
} MDBX_warmup_flags_t;
LIBMDBX_API int mdbx_env_warmup(const MDBX_env *env, const MDBX_txn *txn, MDBX_warmup_flags_t flags,
 unsigned timeout_seconds_16dot16);
```

--------------------------------

### Get exception error object

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Retrieves the error object associated with the exception.

```cpp
const ::mdbx::error error() const noexcept
```

--------------------------------

### mdbx_env_open

Source: https://libmdbx.dqdkfa.ru/group__c__opening.html

Opens an environment instance with specified flags and mode.

```APIDOC
## int mdbx_env_open (MDBX_env *env, const char *pathname, MDBX_env_flags_t flags, mdbx_mode_t mode)

### Description
Open an environment instance.

### Parameters
- **env** (MDBX_env *) - Required - The environment handle.
- **pathname** (const char *) - Required - Path to the environment directory or file.
- **flags** (MDBX_env_flags_t) - Required - Environment flags.
- **mode** (mdbx_mode_t) - Required - File mode for the environment.
```

--------------------------------

### Canary Operations

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Methods to put and get canary values within a transaction.

```cpp
inline txn &txn::put_canary(const txn::canary &canary) {
 error::success_or_throw(::mdbx_canary_put(handle_, &canary));
 return *this;
}
```

```cpp
inline txn::canary txn::get_canary() const {
 txn::canary r;
 error::success_or_throw(::mdbx_canary_get(handle_, &r));
 return r;
}
```

--------------------------------

### int mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower, intptr_t size_now, intptr_t size_upper, intptr_t growth_step, intptr_t shrink_threshold, intptr_t pagesize)

Source: https://libmdbx.dqdkfa.ru/group__c__settings.html

Configures the geometry of the database environment, including size limits and page size. This function should be called after environment creation but before opening the environment.

```APIDOC
## mdbx_env_set_geometry()

### Description
Sets the geometry parameters for the MDBX environment. This function is used to define the database size constraints, growth behavior, and page size.

### Parameters
- **env** (MDBX_env*) - Required - An environment handle returned by mdbx_env_create().
- **size_lower** (intptr_t) - Required - The lower bound of database size in bytes. Zero means minimal acceptable, negative means keep current or default.
- **size_now** (intptr_t) - Required - The size in bytes to set for the database now. Zero means minimal acceptable, negative means keep current or default.
- **size_upper** (intptr_t) - Required - The upper bound of database size in bytes. Zero means minimal acceptable, negative means keep current or default.
- **growth_step** (intptr_t) - Required - The growth step in bytes. Must be greater than zero to allow growth. Negative means keep current or default.
- **shrink_threshold** (intptr_t) - Required - The shrink threshold in bytes. Must be greater than zero to allow shrinking. Negative means keep current or default.
- **pagesize** (intptr_t) - Required - The database page size for new database creation. Must be a power of 2 between MDBX_MIN_PAGESIZE and MDBX_MAX_PAGESIZE. Negative means keep current or default.

### Returns
- **int** - Returns 0 on success, or a non-zero error value on failure.
```

--------------------------------

### MDBX Using C++ Experimental Filesystem Macro

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09.html

Defines whether to use the experimental C++ filesystem library.

```cpp
#define MDBX_USING_CXX_EXPERIMETAL_FILESYSTEM 0
```

--------------------------------

### Manage Environment Context

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Gets or sets the user-defined context pointer for the environment.

```cpp
inline void *env::get_context() const noexcept { return mdbx_env_get_userctx(handle_); }
```

```cpp
inline env &env::set_context(void *ptr) {
 error::success_or_throw(::mdbx_env_set_userctx(handle_, ptr));
 return *this;
}
```

--------------------------------

### Get Environment Limits

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Retrieves maximum reader or map limits for the environment.

```cpp
inline unsigned env::max_readers() const {
 unsigned r;
 error::success_or_throw(::mdbx_env_get_maxreaders(handle_, &r));
 return r;
}
```

```cpp
inline unsigned env::max_maps() const {
 unsigned r;
 error::success_or_throw(::mdbx_env_get_maxdbs(handle_, &r));
 return r;
}
```

--------------------------------

### Database Limits

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Static methods for calculating database and key size limits.

```cpp
static size_t key_min(MDBX_db_flags_t flags) noexcept
```

```cpp
static size_t value_max(intptr_t pagesize, MDBX_db_flags_t flags)
```

```cpp
static size_t dbsize_max(intptr_t pagesize)
```

--------------------------------

### Get Environment Flags

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Retrieves the current environment flags from the MDBX handle.

```cpp
inline MDBX_env_flags_t env::get_flags() const {
 unsigned bits = 0;
 error::success_or_throw(::mdbx_env_get_flags(handle_, &bits));
 return MDBX_env_flags_t(bits);
}
```

--------------------------------

### Get Environment File Descriptor

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_source.html

Retrieves the file descriptor associated with the environment.

```c
3395LIBMDBX_API int mdbx_env_get_fd(const MDBX_env *env, mdbx_filehandle_t *fd);
```

--------------------------------

### Version and Build Information Structures

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_source.html

Structures defining the versioning and build-time metadata for libmdbx.

```c
663 uint16_t tweak; 
664 const char *semver_prerelease; 
665 struct {
666 const char *datetime; 
667 const char *tree; 
668 const char *commit; 
669 const char *describe; 
670 } git; 
665 struct  {…};
671 const char *sourcery; 
672} mdbx_version;
659extern LIBMDBX_VERINFO_API const struct MDBX_version_info {…};
```

```c
677extern LIBMDBX_VERINFO_API const struct MDBX_build_info {
678 const char *datetime; 
679 const char *target; 
680 const char *options; 
681 const char *compiler; 
682 const char *flags; 
683 const char *metadata; 
686} mdbx_build;
677extern LIBMDBX_VERINFO_API const struct MDBX_build_info {…};
```

--------------------------------

### Get buffer capacity

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Returns the number of bytes that can be held in currently allocated storage.

```cpp
constexpr size_t capacity() const noexcept
```

--------------------------------

### mdbx::env::copy

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Methods to create a backup copy of an existing environment.

```APIDOC
## mdbx::env::copy

### Description
Creates a backup copy of an existing environment to a specified destination path.

### Signature
`env & copy(const path_type &destination, bool compactify, bool force_dynamic_size = false)`

### Parameters
- **destination** (path/string): The target path for the backup.
- **compactify** (bool): Whether to compact the database during the copy process.
- **force_dynamic_size** (bool): Optional flag to force dynamic sizing, defaults to false.
```

--------------------------------

### Cursor Context Management

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Methods for getting and setting user-defined context pointers on the cursor.

```cpp
inline void *cursor::get_context() const noexcept { return mdbx_cursor_get_userctx(handle_); }
```

```cpp
inline cursor &cursor::set_context(void *ptr) {
 error::success_or_throw(::mdbx_cursor_set_userctx(handle_, ptr));
 return *this;
}
```

--------------------------------

### Query Database Size Limits

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Calculates minimum and maximum database sizes based on page size, throwing an exception on invalid input.

```cpp
inline size_t env::limits::dbsize_min(intptr_t pagesize) {
 const intptr_t result = mdbx_limits_dbsize_min(pagesize);
 if (result < 0)
 MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_EINVAL);
 return static_cast<size_t>(result);
}
```

```cpp
inline size_t env::limits::dbsize_max(intptr_t pagesize) {
 const intptr_t result = mdbx_limits_dbsize_max(pagesize);
 if (result < 0)
 MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_EINVAL);
 return static_cast<size_t>(result);
}
```

--------------------------------

### Get buffer headroom and tailroom

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Calculates available space before or after the current data pointer.

```cpp
MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR size_t headroom() const noexcept {
return is_freestanding() ? inherited::byte_ptr() - silo_begin() : 0;
}
```

```cpp
MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR size_t tailroom() const noexcept {
return is_freestanding() ? silo_end() - inherited::end_byte_ptr() : 0;
}
```

--------------------------------

### Environment Lifecycle Management

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Constructors, assignment operators, and destructor for the environment handle.

```cpp
MDBX_CXX11_CONSTEXPR env::env(MDBX_env *ptr) noexcept : handle_(ptr) {}
```

```cpp
inline env &env::operator=(env &&other) noexcept {
 if (this != &other) {
 handle_ = other.handle_;
 other.handle_ = nullptr;
 }
 return *this;
}
```

```cpp
inline env::env(env &&other) noexcept : handle_(other.handle_) { other.handle_ = nullptr; }
```

```cpp
inline env::~env() noexcept {
#if (defined(MDBX_CHECKING) && MDBX_CHECKING > 0) || (defined(MDBX_DEBUG) && MDBX_DEBUG > 0)
 handle_ = reinterpret_cast<MDBX_env *>(uintptr_t(0xDeadBeef));
#endif
}
```

--------------------------------

### checkpoint_get_latency()

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Commits all operations of the transaction and immediately starts the next, returning latency information.

```APIDOC
## checkpoint_get_latency()

### Description
Commits all the operations of the transaction and immediately starts next without releasing any locks.

### Returns
- **std::pair<bool, finalization_latency>** - Latency information of commit stages.
```

--------------------------------

### Library API Visibility and Versioning

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_source.html

Macros for managing DLL export/import visibility and defining the library version structure.

```c
#ifndef LIBMDBX_API
#if defined(LIBMDBX_EXPORTS) || defined(DOXYGEN)
#define LIBMDBX_API __dll_export
#elif defined(LIBMDBX_IMPORTS)
#define LIBMDBX_API __dll_import
#else
#define LIBMDBX_API
#endif
#endif /* LIBMDBX_API */

extern LIBMDBX_VERINFO_API const struct MDBX_version_info {
 uint16_t major; 
 uint16_t minor; 
 uint16_t patch; 
```

--------------------------------

### checkpoint()

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Commits all operations of the transaction and immediately starts the next without releasing locks.

```APIDOC
## checkpoint()

### Description
Commits all the operations of the transaction and immediately starts next without releasing any locks.

### Overloads
1. checkpoint()
2. checkpoint(finalization_latency & _latency_)
3. checkpoint(finalization_latency * _latency_)

### Returns
- **bool** - Status of the checkpoint operation.
```

--------------------------------

### amend()

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Starts a writing transaction to amend data in the MVCC-snapshot used by the read-only transaction.

```APIDOC
## amend()

### Description
Starts a writing transaction to amending data in the MVCC-snapshot used by the read-only transaction.

### Parameters
- **_dont_wait_** (bool) - Optional - Default: false

### Returns
- **bool** - True if writing transaction successfully started, false if read-only one still continues.
```

--------------------------------

### mdbx_env_openW

Source: https://libmdbx.dqdkfa.ru/group__c__api.html

Opens an MDBX environment instance.

```APIDOC
## int mdbx_env_openW(MDBX_env *env, const wchar_t *pathname, MDBX_env_flags_t flags, mdbx_mode_t mode)

### Description
Open an environment instance.

### Parameters
- **env** (MDBX_env*) - Required - The environment handle.
- **pathname** (const wchar_t*) - Required - The path to the environment.
- **flags** (MDBX_env_flags_t) - Required - Environment flags.
- **mode** (mdbx_mode_t) - Required - File mode.
```

--------------------------------

### Transaction Management

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Methods for starting and preparing read and write transactions within the environment.

```APIDOC
## env::start_read
### Description
Starts a read-only transaction.
### Signature
txn_managed start_read() const

## env::start_write
### Description
Starts a read-write transaction.
### Signature
txn_managed start_write(txn &parent)
txn_managed start_write(bool dont_wait=false)
```

--------------------------------

### Environment Accessor Methods

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Methods for retrieving environment configuration and status.

```cpp
inline env::operate_parameters get_operation_parameters() const;
inline env::mode get_mode() const;
inline env::durability get_durability() const;
inline env::reclaiming_options get_reclaiming() const;
inline env::operate_options get_options() const;

bool is_pristine() const;
bool is_empty() const;

static size_t default_pagesize() noexcept { return ::mdbx_default_pagesize(); }

struct limits {
limits() = delete;
```

--------------------------------

### mdbx_env_warmup

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_source.html

Warms up the database by loading pages into memory.

```APIDOC
int mdbx_env_warmup(const MDBX_env *env, const MDBX_txn *txn, MDBX_warmup_flags_t flags, unsigned timeout_seconds_16dot16)
```

--------------------------------

### mdbx_txn_commit_embark_read()

Source: https://libmdbx.dqdkfa.ru/group__c__transactions.html

Commits all operations of a transaction and immediately starts a read transaction before releasing locks.

```APIDOC
## mdbx_txn_commit_embark_read()

### Description
Commits all the operations of the transaction and immediately starts a read transaction before releasing locks. This ensures that no other changes occur between the commit and the start of the new read transaction.

### Signature
`int mdbx_txn_commit_embark_read(MDBX_txn **ptxn, MDBX_commit_latency *latency)`

### Parameters
- **ptxn** (MDBX_txn **) - In/Out - A pointer to the transaction handle returned by mdbx_txn_begin().
- **latency** (MDBX_commit_latency *) - Out - An optional pointer for getting information of latencies during the commit stages.

### Returns
- **0** - Success.
- **Non-zero** - Error value on failure (e.g., MDBX_RESULT_TRUE, MDBX_PANIC, MDBX_BAD_TXN, MDBX_EBADSIGN, MDBX_THREAD_MISMATCH, MDBX_EINVAL).
```

--------------------------------

### mdbx_dbi_open()

Source: https://libmdbx.dqdkfa.ru/group__c__dbi.html

Opens or creates a named table in the environment. Returns a handle that identifies the table and its parameters.

```APIDOC
## int mdbx_dbi_open(MDBX_txn *txn, const char *name, MDBX_db_flags_t flags, MDBX_dbi *dbi)

### Description
Open or create a named table in the environment. A table handle denotes the name and parameters of a table, independently of whether such a table exists.

### Parameters
- **txn** (MDBX_txn*) - Required - Transaction handle returned by mdbx_txn_begin().
- **name** (const char*) - Required - The name of the table to open. If only a single table is needed, this may be NULL.
- **flags** (MDBX_db_flags_t) - Required - Special options for this table (e.g., MDBX_REVERSEKEY, MDBX_DUPSORT, MDBX_CREATE).
- **dbi** (MDBX_dbi*) - Required - Address where the new MDBX_dbi handle will be stored.

### Returns
- **int** - A non-zero error value on failure and 0 on success.

### Error Values
- **MDBX_NOTFOUND**: The specified table doesn't exist and MDBX_CREATE was not specified.
- **MDBX_DBS_FULL**: Too many tables have been opened.
- **MDBX_INCOMPATIBLE**: Table is incompatible with given flags.
- **MDBX_THREAD_MISMATCH**: Given transaction is not owned by current thread.
```

--------------------------------

### Open and Create Database Maps

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Methods for opening or creating database maps with specified key and value modes.

```cpp
inline map_handle txn::open_map(const ::std::string &name, const ::mdbx::key_mode key_mode,
 const ::mdbx::value_mode value_mode) const {
 return open_map(slice(name), key_mode, value_mode);
}
```

```cpp
inline map_handle txn::open_map_accede(const ::std::string &name) const { return open_map_accede(slice(name)); }
```

```cpp
inline map_handle txn::create_map(const ::std::string &name, const ::mdbx::key_mode key_mode,
 const ::mdbx::value_mode value_mode) {
 return create_map(slice(name), key_mode, value_mode);
}
```

--------------------------------

### mdbx_txn_amend()

Source: https://libmdbx.dqdkfa.ru/group__c__transactions.html

Starts a writing transaction to amend data in the MVCC-snapshot used by a read-only transaction.

```APIDOC
## mdbx_txn_amend()

### Description
Starts a writing transaction to amend data in the MVCC-snapshot used by the read-only transaction. If successful, the handle of the new writing transaction is returned, and the previous reading transaction is finished.

### Parameters
- **read_txn** (MDBX_txn *) - A read-only transaction handle returned by mdbx_txn_begin().
- **ptr_write_txn** (MDBX_txn **) - A pointer for returning the MDBX_txn handle of newly started writing transaction.
- **flags** (MDBX_txn_flags_t) - Special options for new write transaction (e.g., MDBX_TXN_RDONLY_PREPARE, MDBX_TXN_TRY).
- **context** (void *) - A pointer to application context to be associated with created transaction.

### Returns
- **0** - Success.
- **MDBX_RESULT_TRUE** - A more recent MVCC-snapshot has been committed; no actions performed.
- **MDBX_TXN_OVERLAPPING** - Current thread is already executing a write transaction.
- **MDBX_PANIC** - Fatal error occurred.
- **MDBX_BAD_TXN** - Unexpected or wrong transaction state.
- **MDBX_EBADSIGN** - Transaction object has invalid signature.
- **MDBX_THREAD_MISMATCH** - Transaction not owned by current thread.
- **MDBX_EINVAL** - Transaction handle is NULL.
```

--------------------------------

### mdbx_get_ex Function

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Get items from a table and optionally number of data items for a given key.

```c
LIBMDBX_API int mdbx_get_ex(const MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key, MDBX_val *data, size_t *values_count)
```

--------------------------------

### Key Conversion Utilities

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_source.html

Helper functions to convert various data types into MDBX-compatible keys.

```c
MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API uint64_t mdbx_key_from_jsonInteger(const int64_t json_integer);
```

```c
MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API uint64_t mdbx_key_from_double(const double ieee754_64bit);
```

```c
MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API uint64_t mdbx_key_from_ptrdouble(const double *const ieee754_64bit);
```

--------------------------------

### Handle Slow Readers Configuration

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Sets or gets the callback function for handling slow readers.

```cpp
inline env &env::set_HandleSlowReaders(MDBX_hsr_func cb) {
 error::success_or_throw(::mdbx_env_set_hsr(handle_, cb));
 return *this;
}
```

```cpp
inline MDBX_hsr_func env::get_HandleSlowReaders() const noexcept { return ::mdbx_env_get_hsr(handle_); }
```

--------------------------------

### mdbx_dbi_open_ex()

Source: https://libmdbx.dqdkfa.ru/group__c__dbi.html

Opens or creates a named table in the environment using custom comparison functions. This function takes a null-terminated string for the table name.

```APIDOC
## int mdbx_dbi_open_ex(MDBX_txn *txn, const char *name, MDBX_db_flags_t flags, MDBX_dbi *dbi, MDBX_cmp_func keycmp, MDBX_cmp_func datacmp)

### Description
Open or Create a named table in the environment with using custom comparison functions. Please avoid using custom comparators and use mdbx_dbi_open() instead.

### Parameters
- **txn** (MDBX_txn*) - [in] A transaction handle returned by mdbx_txn_begin().
- **name** (const char*) - [in] The name of the table to open (null terminated).
- **flags** (MDBX_db_flags_t) - [in] Special options for this table.
- **dbi** (MDBX_dbi*) - [out] Address where the new MDBX_dbi handle will be stored.
- **keycmp** (MDBX_cmp_func) - [in] Optional custom key comparison function.
- **datacmp** (MDBX_cmp_func) - [in] Optional custom data comparison function.

### Returns
A non-zero error value on failure and 0 on success.
```

--------------------------------

### Get Bin Address

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Retrieves the memory address of the bin, selecting between inplace or allocated storage.

```cpp
constexpr const byte *address() const noexcept {
	return is_inplace() ? inplace_.buffer_ : static_cast<const byte *>(to_address(allocated_ptr_));
}
```

```cpp
MDBX_CXX17_CONSTEXPR byte *address() noexcept {
	return is_inplace() ? inplace_.buffer_ : static_cast<byte *>(to_address(allocated_ptr_));
}
```

--------------------------------

### env::sync_to_disk()

Source: https://libmdbx.dqdkfa.ru/mdbx_8h_09_09_source.html

Synchronizes the environment to disk.

```APIDOC
## bool env::sync_to_disk(bool force, bool nonblock)

### Description
Flushes the environment data to disk.

### Parameters
- **force** (bool) - Required - Whether to force the sync.
- **nonblock** (bool) - Required - Whether to perform the sync in non-blocking mode.

### Returns
- **bool** - Returns true if the flush was successful or no data is pending, false if the environment is busy.
```

--------------------------------

### mdbx::env::sync_period__seconds_16dot16()

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Gets the relative period for forcing data buffer flushes to disk.

```APIDOC
## unsigned mdbx::env::sync_period__seconds_16dot16() const

### Description
Gets the relative period since the last unsteady commit used to force flush data buffers to disk for non-sync durability modes.
```

--------------------------------

### mdbx::slice::safe_middle

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Returns the middle n bytes of the slice starting from a specific offset.

```APIDOC
## slice mdbx::slice::safe_middle(size_t from, size_t n) const

### Description
Returns the middle n bytes of the slice.

### Exceptions
- std::out_of_range: if from + n >= size()
```

--------------------------------

### mdbx_env_warmup

Source: https://libmdbx.dqdkfa.ru/group__c__settings.html

Warms up the database by loading pages into memory, optionally locking them.

```APIDOC
## int mdbx_env_warmup(const MDBX_env *env, const MDBX_txn *txn, MDBX_warmup_flags_t flags, unsigned timeout_seconds_16dot16)

### Description
Warms up the database by loading pages into memory, optionally locking them.

### Parameters
- **env** (const MDBX_env*) - The environment handle.
- **txn** (const MDBX_txn*) - The transaction handle.
- **flags** (MDBX_warmup_flags_t) - Warming up options.
- **timeout_seconds_16dot16** (unsigned) - Timeout for the operation.
```

--------------------------------

### mdbx_env_warmup

Source: https://libmdbx.dqdkfa.ru/group__c__settings.html

Warms up the database by loading pages into memory, optionally locking them.

```APIDOC
## mdbx_env_warmup

### Description
Notifies the OS kernel about upcoming access and forces loading of database pages into memory. At least one of env or txn must be non-null.

### Signature
int mdbx_env_warmup(const MDBX_env *env, const MDBX_txn *txn, MDBX_warmup_flags_t flags, unsigned timeout_seconds_16dot16)

### Parameters
- **env** (const MDBX_env*) - Optional - An environment handle returned by mdbx_env_create().
- **txn** (const MDBX_txn*) - Optional - A transaction handle returned by mdbx_txn_begin().
- **flags** (MDBX_warmup_flags_t) - Required - The warmup_flags, bitwise OR'ed together.
- **timeout_seconds_16dot16** (unsigned) - Required - Optional timeout checked during page loading if MDBX_warmup_force is specified.

### Returns
- **int** - Returns 0 on success, or a non-zero error value on failure (e.g., MDBX_ENOSYS, MDBX_RESULT_TRUE).
```

--------------------------------

### mdbx::cursor::scan_until_from

Source: https://libmdbx.dqdkfa.ru/group__cxx__api.html

Scans the database starting from a specific key or pair until a predicate is satisfied.

```APIDOC
## template<typename CALLABLE_PREDICATE> bool mdbx::cursor::scan_until_from(CALLABLE_PREDICATE _predicate_, pair & _from_, move_operation _start_ = pair_greater_or_equal, move_operation _turn_ = next)
## template<typename CALLABLE_PREDICATE> bool mdbx::cursor::scan_until_from(CALLABLE_PREDICATE _predicate_, slice & _from_, move_operation _start_ = key_greater_or_equal, move_operation _turn_ = next)

### Description
Scans the database starting from a given key or pair until the predicate returns true.
```
Tokens:
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