Lightning memory-mapped database library.
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/param.h>
#include <sys/uio.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <errno.h>
#include <limits.h>
#include <stddef.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <netinet/in.h>
#include <resolv.h>
#include <pthread.h>
#include 'lmdb.h'
#include 'midl.h'
struct MDB_rxbody
struct MDB_reader
struct MDB_txbody
struct MDB_txninfo
struct MDB_page
struct MDB_node
struct MDB_db
struct MDB_meta
union MDB_metabuf
struct MDB_dbx
struct MDB_txn
Opaque structure for a transaction handle. struct MDB_cursor
Opaque structure for navigating through a database. struct MDB_xcursor
struct MDB_pgstate
struct MDB_env
Opaque structure for a database environment. struct MDB_ntxn
struct mdb_copy
#define _GNU_SOURCE 1
#define MDB_PID_T pid_t
#define MDB_THR_T pthread_t
#define CACHEFLUSH(addr, bytes, cache)
#define VGMEMP_CREATE(h, r, z)
#define VGMEMP_ALLOC(h, a, s)
#define VGMEMP_FREE(h, a)
#define VGMEMP_DESTROY(h)
#define VGMEMP_DEFINED(a, s)
#define BYTE_ORDER __BYTE_ORDER
#define LITTLE_ENDIAN __LITTLE_ENDIAN
#define BIG_ENDIAN __BIG_ENDIAN
#define ESECT __attribute__ ((section('text_env')))
#define MDB_DEVEL 0
#define mdb_func_ '<mdb_unknown>'
#define THREAD_RET void *
#define THREAD_CREATE(thr, start, arg) pthread_create(&thr,NULL,start,arg)
#define THREAD_FINISH(thr) pthread_join(thr,NULL)
#define Z 'z'
#define MDB_PIDLOCK 1
#define LOCK_MUTEX_R(env) pthread_mutex_lock(&(env)->me_txns->mti_mutex)
#define UNLOCK_MUTEX_R(env) pthread_mutex_unlock(&(env)->me_txns->mti_mutex)
#define LOCK_MUTEX_W(env) pthread_mutex_lock(&(env)->me_txns->mti_wmutex)
#define UNLOCK_MUTEX_W(env) pthread_mutex_unlock(&(env)->me_txns->mti_wmutex)
#define ErrCode() errno
#define HANDLE int
#define INVALID_HANDLE_VALUE (-1)
#define GET_PAGESIZE(x) ((x) = sysconf(_SC_PAGE_SIZE))
#define MNAME_LEN (sizeof(pthread_mutex_t))
#define MDB_DSYNC O_DSYNC
#define MDB_FDATASYNC fdatasync
#define MDB_MSYNC(addr, len, flags) msync(addr,len,flags)
#define MS_SYNC 1
#define MS_ASYNC 0
#define MDB_DEBUG 0
#define DPRINTF(args) ((void) 0)
#define DPUTS(arg) DPRINTF(('%s', arg))
#define DDBI(mc) (((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
#define MAX_PAGESIZE (PAGEBASE ? 0x10000 : 0x8000)
The maximum size of a database page. #define MDB_MINKEYS 2
#define MDB_MAGIC 0xBEEFC0DE
#define MDB_DATA_VERSION ((MDB_DEVEL) ? 999 : 1)
#define MDB_LOCK_VERSION 1
#define MDB_MAXKEYSIZE ((MDB_DEVEL) ? 0 : 511)
The max size of a key we can write, or 0 for dynamic max. #define ENV_MAXKEY(env) (MDB_MAXKEYSIZE)
#define MAXDATASIZE 0xffffffffUL
The maximum size of a data item. #define DKBUF
#define DKEY(x) 0
#define P_INVALID (~(pgno_t)0)
#define F_ISSET(w, f) (((w) & (f)) == (f))
#define EVEN(n) (((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
#define DEFAULT_MAPSIZE 1048576
#define DEFAULT_READERS 126
#define CACHELINE 64
#define mr_txnid mru.mrx.mrb_txnid
#define mr_pid mru.mrx.mrb_pid
#define mr_tid mru.mrx.mrb_tid
#define mti_magic mt1.mtb.mtb_magic
#define mti_format mt1.mtb.mtb_format
#define mti_mutex mt1.mtb.mtb_mutex
#define mti_rmname mt1.mtb.mtb_rmname
#define mti_txnid mt1.mtb.mtb_txnid
#define mti_numreaders mt1.mtb.mtb_numreaders
#define mti_wmutex mt2.mt2_wmutex
#define MDB_LOCK_FORMAT
#define mp_pgno mp_p.p_pgno
#define mp_next mp_p.p_next
#define P_BRANCH 0x01
#define P_LEAF 0x02
#define P_OVERFLOW 0x04
#define P_META 0x08
#define P_DIRTY 0x10
#define P_LEAF2 0x20
#define P_SUBP 0x40
#define P_LOOSE 0x4000
#define P_KEEP 0x8000
#define mp_lower mp_pb.pb.pb_lower
#define mp_upper mp_pb.pb.pb_upper
#define mp_pages mp_pb.pb_pages
#define PAGEHDRSZ ((unsigned) offsetof(MDB_page, mp_ptrs))
#define METADATA(p) ((void *)((char *)(p) + PAGEHDRSZ))
#define PAGEBASE ((MDB_DEVEL) ? PAGEHDRSZ : 0)
#define NUMKEYS(p) (((p)->mp_lower - (PAGEHDRSZ-PAGEBASE)) >> 1)
#define SIZELEFT(p) (indx_t)((p)->mp_upper - (p)->mp_lower)
#define PAGEFILL(env, p)
#define FILL_THRESHOLD 250
#define IS_LEAF(p) F_ISSET((p)->mp_flags, P_LEAF)
#define IS_LEAF2(p) F_ISSET((p)->mp_flags, P_LEAF2)
#define IS_BRANCH(p) F_ISSET((p)->mp_flags, P_BRANCH)
#define IS_OVERFLOW(p) F_ISSET((p)->mp_flags, P_OVERFLOW)
#define IS_SUBP(p) F_ISSET((p)->mp_flags, P_SUBP)
#define OVPAGES(size, psize) ((PAGEHDRSZ-1 + (size)) / (psize) + 1)
#define NEXT_LOOSE_PAGE(p) (*(MDB_page **)((p) + 2))
#define F_BIGDATA 0x01
#define F_SUBDATA 0x02
#define F_DUPDATA 0x04
#define NODE_ADD_FLAGS (F_DUPDATA|F_SUBDATA|MDB_RESERVE|MDB_APPEND)
#define NODESIZE offsetof(MDB_node, mn_data)
#define PGNO_TOPWORD ((pgno_t)-1 > 0xffffffffu ? 32 : 0)
#define INDXSIZE(k) (NODESIZE + ((k) == NULL ? 0 : (k)->mv_size))
#define LEAFSIZE(k, d) (NODESIZE + (k)->mv_size + (d)->mv_size)
#define NODEPTR(p, i) ((MDB_node *)((char *)(p) + (p)->mp_ptrs[i] + PAGEBASE))
#define NODEKEY(node) (void *)((node)->mn_data)
#define NODEDATA(node) (void *)((char *)(node)->mn_data + (node)->mn_ksize)
#define NODEPGNO(node)
#define SETPGNO(node, pgno)
#define NODEDSZ(node) ((node)->mn_lo | ((unsigned)(node)->mn_hi << 16))
#define SETDSZ(node, size)
#define NODEKSZ(node) ((node)->mn_ksize)
#define COPY_PGNO(dst, src)
#define LEAF2KEY(p, i, ks) ((char *)(p) + PAGEHDRSZ + ((i)*(ks)))
#define MDB_GET_KEY(node, keyptr)
#define MDB_GET_KEY2(node, key) { key.mv_size = NODEKSZ(node); key.mv_data = NODEKEY(node); }
#define MDB_VALID 0x8000
#define PERSISTENT_FLAGS (0xffff & ~(MDB_VALID))
#define VALID_FLAGS
#define FREE_DBI 0
#define MAIN_DBI 1
#define mm_psize mm_dbs[0].md_pad
#define mm_flags mm_dbs[0].md_flags
#define DB_DIRTY 0x01
#define DB_STALE 0x02
#define DB_NEW 0x04
#define DB_VALID 0x08
#define MDB_TXN_RDONLY 0x01
#define MDB_TXN_ERROR 0x02
#define MDB_TXN_DIRTY 0x04
#define MDB_TXN_SPILLS 0x08
#define CURSOR_STACK 32
#define C_INITIALIZED 0x01
#define C_EOF 0x02
#define C_SUB 0x04
#define C_DEL 0x08
#define C_SPLITTING 0x20
#define C_UNTRACK 0x40
#define MDB_FATAL_ERROR 0x80000000U
#define MDB_ENV_ACTIVE 0x20000000U
#define MDB_ENV_TXKEY 0x10000000U
#define me_pglast me_pgstate.mf_pglast
#define me_pghead me_pgstate.mf_pghead
#define MDB_COMMIT_PAGES 64
#define MAX_WRITE (0x80000000U >> (sizeof(ssize_t) == 4))
#define TXN_DBI_EXIST(txn, dbi) ((txn) && (dbi) < (txn)->mt_numdbs && ((txn)->mt_dbflags[dbi] & DB_VALID))
#define TXN_DBI_CHANGED(txn, dbi) ((txn)->mt_dbiseqs[dbi] != (txn)->mt_env->me_dbiseqs[dbi])
#define MDB_PS_MODIFY 1
#define MDB_PS_ROOTONLY 2
#define MDB_PS_FIRST 4
#define MDB_PS_LAST 8
#define MDB_SPLIT_REPLACE MDB_APPENDDUP
#define mdb_env_close0(env, excl) mdb_env_close1(env)
#define mdb_cassert(mc, expr) mdb_assert0((mc)->mc_txn->mt_env, expr, #expr)
#define mdb_tassert(mc, expr) mdb_assert0((txn)->mt_env, expr, #expr)
#define mdb_eassert(env, expr) mdb_assert0(env, expr, #expr)
#define mdb_assert0(env, expr, expr_txt)
#define mdb_txn_reset0(txn, act) mdb_txn_reset0(txn)
#define DO_PWRITE(rc, fd, ptr, size, len, pos)
#define MDB_ERRCODE_ROFS EROFS
#define MDB_CLOEXEC 0
#define LOCKNAME '/lock.mdb'
#define DATANAME '/data.mdb'
#define LOCKSUFF '-lock'
#define CHANGEABLE (MDB_NOSYNC|MDB_NOMETASYNC|MDB_MAPASYNC|MDB_NOMEMINIT)
#define CHANGELESS
#define mdb_cmp_clong mdb_cmp_cint
#define MDB_NOSPILL 0x8000
#define MDB_WBUF (1024*1024)
#define DO_WRITE(rc, fd, ptr, w2, len) len = write(fd, ptr, w2); rc = (len >= 0)
#define DO_WRITE(rc, fd, ptr, w2, len) len = write(fd, ptr, w2); rc = (len >= 0)
typedef MDB_ID pgno_t
typedef MDB_ID txnid_t
typedef uint16_t indx_t
enum Pidlock_op { Pidset = F_SETLK, Pidcheck = F_GETLK }
static int mdb_page_alloc (MDB_cursor *mc, int num, MDB_page **mp)
static int mdb_page_new (MDB_cursor *mc, uint32_t flags, int num, MDB_page **mp)
static int mdb_page_touch (MDB_cursor *mc)
static int mdb_page_get (MDB_txn *txn, pgno_t pgno, MDB_page **mp, int *lvl)
static int mdb_page_search_root (MDB_cursor *mc, MDB_val *key, int modify)
static int mdb_page_search (MDB_cursor *mc, MDB_val *key, int flags)
static int mdb_page_merge (MDB_cursor *csrc, MDB_cursor *cdst)
static int mdb_page_split (MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata, pgno_t newpgno, unsigned int nflags)
static int mdb_env_read_header (MDB_env *env, MDB_meta *meta)
static int mdb_env_pick_meta (const MDB_env *env)
static int mdb_env_write_meta (MDB_txn *txn)
static void mdb_env_close0 (MDB_env *env, int excl)
static MDB_node * mdb_node_search (MDB_cursor *mc, MDB_val *key, int *exactp)
static int mdb_node_add (MDB_cursor *mc, indx_t indx, MDB_val *key, MDB_val *data, pgno_t pgno, unsigned int flags)
static void mdb_node_del (MDB_cursor *mc, int ksize)
static void mdb_node_shrink (MDB_page *mp, indx_t indx)
static int mdb_node_move (MDB_cursor *csrc, MDB_cursor *cdst)
static int mdb_node_read (MDB_txn *txn, MDB_node *leaf, MDB_val *data)
static size_t mdb_leaf_size (MDB_env *env, MDB_val *key, MDB_val *data)
static size_t mdb_branch_size (MDB_env *env, MDB_val *key)
static int mdb_rebalance (MDB_cursor *mc)
static int mdb_update_key (MDB_cursor *mc, MDB_val *key)
static void mdb_cursor_pop (MDB_cursor *mc)
static int mdb_cursor_push (MDB_cursor *mc, MDB_page *mp)
static int mdb_cursor_del0 (MDB_cursor *mc)
static int mdb_del0 (MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data, unsigned flags)
static int mdb_cursor_sibling (MDB_cursor *mc, int move_right)
static int mdb_cursor_next (MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op)
static int mdb_cursor_prev (MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op)
static int mdb_cursor_set (MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op, int *exactp)
static int mdb_cursor_first (MDB_cursor *mc, MDB_val *key, MDB_val *data)
static int mdb_cursor_last (MDB_cursor *mc, MDB_val *key, MDB_val *data)
static void mdb_cursor_init (MDB_cursor *mc, MDB_txn *txn, MDB_dbi dbi, MDB_xcursor *mx)
static void mdb_xcursor_init0 (MDB_cursor *mc)
static void mdb_xcursor_init1 (MDB_cursor *mc, MDB_node *node)
static int mdb_drop0 (MDB_cursor *mc, int subs)
static void mdb_default_cmp (MDB_txn *txn, MDB_dbi dbi)
char * mdb_version (int *major, int *minor, int *patch)
Return the LMDB library version information. char * mdb_strerror (int err)
Return a string describing a given error code. static void mdb_assert_fail (MDB_env *env, const char *expr_txt, const char *func, const char *file, int line)
int mdb_cmp (MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b)
Compare two data items according to a particular database. int mdb_dcmp (MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b)
Compare two data items according to a particular database. static MDB_page * mdb_page_malloc (MDB_txn *txn, unsigned num)
static void mdb_page_free (MDB_env *env, MDB_page *mp)
static void mdb_dpage_free (MDB_env *env, MDB_page *dp)
static void mdb_dlist_free (MDB_txn *txn)
static int mdb_page_loose (MDB_cursor *mc, MDB_page *mp)
static int mdb_pages_xkeep (MDB_cursor *mc, unsigned pflags, int all)
static int mdb_page_flush (MDB_txn *txn, int keep)
static int mdb_page_spill (MDB_cursor *m0, MDB_val *key, MDB_val *data)
static txnid_t mdb_find_oldest (MDB_txn *txn)
static void mdb_page_dirty (MDB_txn *txn, MDB_page *mp)
static void mdb_page_copy (MDB_page *dst, MDB_page *src, unsigned int psize)
static int mdb_page_unspill (MDB_txn *txn, MDB_page *mp, MDB_page **ret)
int mdb_env_sync (MDB_env *env, int force)
Flush the data buffers to disk. static int mdb_cursor_shadow (MDB_txn *src, MDB_txn *dst)
static void mdb_cursors_close (MDB_txn *txn, unsigned merge)
static void mdb_txn_reset0 (MDB_txn *txn, const char *act)
static int mdb_reader_pid (MDB_env *env, enum Pidlock_op op, MDB_PID_T pid)
static int mdb_txn_renew0 (MDB_txn *txn)
int mdb_txn_renew (MDB_txn *txn)
Renew a read-only transaction. int mdb_txn_begin (MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
Create a transaction for use with the environment. MDB_env * mdb_txn_env (MDB_txn *txn)
Returns the transaction's MDB_env. static void mdb_dbis_update (MDB_txn *txn, int keep)
void mdb_txn_reset (MDB_txn *txn)
Reset a read-only transaction. void mdb_txn_abort (MDB_txn *txn)
Abandon all the operations of the transaction instead of saving them. static int mdb_freelist_save (MDB_txn *txn)
int mdb_txn_commit (MDB_txn *txn)
Commit all the operations of a transaction into the database. static void ESECT mdb_env_init_meta0 (MDB_env *env, MDB_meta *meta)
static int ESECT mdb_env_init_meta (MDB_env *env, MDB_meta *meta)
int ESECT mdb_env_create (MDB_env **env)
Create an LMDB environment handle. static int ESECT mdb_env_map (MDB_env *env, void *addr)
int ESECT mdb_env_set_mapsize (MDB_env *env, size_t size)
Set the size of the memory map to use for this environment. int ESECT mdb_env_set_maxdbs (MDB_env *env, MDB_dbi dbs)
Set the maximum number of named databases for the environment. int ESECT mdb_env_set_maxreaders (MDB_env *env, unsigned int readers)
Set the maximum number of threads/reader slots for the environment. int ESECT mdb_env_get_maxreaders (MDB_env *env, unsigned int *readers)
Get the maximum number of threads/reader slots for the environment. static int ESECT mdb_env_open2 (MDB_env *env)
static void mdb_env_reader_dest (void *ptr)
static int ESECT mdb_env_share_locks (MDB_env *env, int *excl)
static int ESECT mdb_env_excl_lock (MDB_env *env, int *excl)
static int ESECT mdb_env_setup_locks (MDB_env *env, char *lpath, int mode, int *excl)
int ESECT mdb_env_open (MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode)
Open an environment handle. void ESECT mdb_env_close (MDB_env *env)
Close the environment and release the memory map. static int mdb_cmp_long (const MDB_val *a, const MDB_val *b)
static int mdb_cmp_int (const MDB_val *a, const MDB_val *b)
static int mdb_cmp_cint (const MDB_val *a, const MDB_val *b)
static int mdb_cmp_memn (const MDB_val *a, const MDB_val *b)
static int mdb_cmp_memnr (const MDB_val *a, const MDB_val *b)
static int mdb_page_search_lowest (MDB_cursor *mc)
static int mdb_ovpage_free (MDB_cursor *mc, MDB_page *mp)
int mdb_get (MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data)
Get items from a database. int mdb_cursor_get (MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op)
Retrieve by cursor. static int mdb_cursor_touch (MDB_cursor *mc)
int mdb_cursor_put (MDB_cursor *mc, MDB_val *key, MDB_val *data, unsigned int flags)
Store by cursor. int mdb_cursor_del (MDB_cursor *mc, unsigned int flags)
Delete current key/data pair. int mdb_cursor_open (MDB_txn *txn, MDB_dbi dbi, MDB_cursor **ret)
Create a cursor handle. int mdb_cursor_renew (MDB_txn *txn, MDB_cursor *mc)
Renew a cursor handle. int mdb_cursor_count (MDB_cursor *mc, size_t *countp)
Return count of duplicates for current key. void mdb_cursor_close (MDB_cursor *mc)
Close a cursor handle. MDB_txn * mdb_cursor_txn (MDB_cursor *mc)
Return the cursor's transaction handle. MDB_dbi mdb_cursor_dbi (MDB_cursor *mc)
Return the cursor's database handle. static void mdb_cursor_copy (const MDB_cursor *csrc, MDB_cursor *cdst)
int mdb_del (MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data)
Delete items from a database. int mdb_put (MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data, unsigned int flags)
Store items into a database. static THREAD_RET ESECT mdb_env_copythr (void *arg)
static int ESECT mdb_env_cthr_toggle (mdb_copy *my, int st)
static int ESECT mdb_env_cwalk (mdb_copy *my, pgno_t *pg, int flags)
static int ESECT mdb_env_copyfd1 (MDB_env *env, HANDLE fd)
static int ESECT mdb_env_copyfd0 (MDB_env *env, HANDLE fd)
int ESECT mdb_env_copyfd2 (MDB_env *env, HANDLE fd, unsigned int flags)
int ESECT mdb_env_copyfd (MDB_env *env, HANDLE fd)
int ESECT mdb_env_copy2 (MDB_env *env, const char *path, unsigned int flags)
Copy an LMDB environment to the specified path, with options. int ESECT mdb_env_copy (MDB_env *env, const char *path)
Copy an LMDB environment to the specified path. int ESECT mdb_env_set_flags (MDB_env *env, unsigned int flag, int onoff)
Set environment flags. int ESECT mdb_env_get_flags (MDB_env *env, unsigned int *arg)
Get environment flags. int ESECT mdb_env_set_userctx (MDB_env *env, void *ctx)
Set application information associated with the MDB_env. void *ESECT mdb_env_get_userctx (MDB_env *env)
Get the application information associated with the MDB_env. int ESECT mdb_env_set_assert (MDB_env *env, MDB_assert_func *func)
int ESECT mdb_env_get_path (MDB_env *env, const char **arg)
Return the path that was used in mdb_env_open(). int ESECT mdb_env_get_fd (MDB_env *env, mdb_filehandle_t *arg)
Return the filedescriptor for the given environment. static int ESECT mdb_stat0 (MDB_env *env, MDB_db *db, MDB_stat *arg)
int ESECT mdb_env_stat (MDB_env *env, MDB_stat *arg)
Return statistics about the LMDB environment. int ESECT mdb_env_info (MDB_env *env, MDB_envinfo *arg)
Return information about the LMDB environment. int mdb_dbi_open (MDB_txn *txn, const char *name, unsigned int flags, MDB_dbi *dbi)
Open a database in the environment. int mdb_stat (MDB_txn *txn, MDB_dbi dbi, MDB_stat *arg)
Retrieve statistics for a database. void mdb_dbi_close (MDB_env *env, MDB_dbi dbi)
Close a database handle. Normally unnecessary. Use with care: int mdb_dbi_flags (MDB_txn *txn, MDB_dbi dbi, unsigned int *flags)
Retrieve the DB flags for a database handle. int mdb_drop (MDB_txn *txn, MDB_dbi dbi, int del)
Empty or delete+close a database. int mdb_set_compare (MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp)
Set a custom key comparison function for a database. int mdb_set_dupsort (MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp)
Set a custom data comparison function for a MDB_DUPSORT database. int mdb_set_relfunc (MDB_txn *txn, MDB_dbi dbi, MDB_rel_func *rel)
Set a relocation function for a MDB_FIXEDMAP database. int mdb_set_relctx (MDB_txn *txn, MDB_dbi dbi, void *ctx)
Set a context pointer for a MDB_FIXEDMAP database's relocation function. int ESECT mdb_env_get_maxkeysize (MDB_env *env)
Get the maximum size of keys and MDB_DUPSORT data we can write. int ESECT mdb_reader_list (MDB_env *env, MDB_msg_func *func, void *ctx)
Dump the entries in the reader lock table. static int ESECT mdb_pid_insert (MDB_PID_T *ids, MDB_PID_T pid)
int ESECT mdb_reader_check (MDB_env *env, int *dead)
Check for stale entries in the reader lock table.
static char *const mdb_errstr []
Lightning memory-mapped database library.
A Btree-based database management library modeled loosely on the BerkeleyDB API, but much simplified.
Put infrequently used env functions in separate section
shorthand for mrb_txnid
The size of pages used in this DB
Any persistent environment flags. Environment Flags
Failed to update the meta page. Probably an I/O error.
Some fields are initialized.
me_txkey is set
Value:
do { len = pwrite(fd, ptr, size, pos); rc = (len >= 0); } while(0)
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