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-rw-r--r--libraries/liblmdb/mdb.c77
1 files changed, 65 insertions, 12 deletions
diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 59e3d93..4a364f7 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -480,12 +480,6 @@ typedef pthread_mutex_t *mdb_mutexref_t;
#define MUTEXNAME_PREFIX "/MDB"
#endif
-#ifdef MDB_USE_SYSV_SEM
-#define SYSV_SEM_FLAG 1 /**< SysV sems in lockfile format */
-#else
-#define SYSV_SEM_FLAG 0
-#endif
-
/** @} */
#ifdef MDB_ROBUST_SUPPORTED
@@ -628,6 +622,10 @@ static txnid_t mdb_debug_start;
#define MDB_DATA_VERSION ((MDB_DEVEL) ? 999 : 1)
/** The version number for a database's lockfile format. */
#define MDB_LOCK_VERSION ((MDB_DEVEL) ? 999 : 2)
+ /** Number of bits representing #MDB_LOCK_VERSION in #MDB_LOCK_FORMAT.
+ * The remaining bits must leave room for #MDB_lock_desc.
+ */
+#define MDB_LOCK_VERSION_BITS 12
/** @brief The max size of a key we can write, or 0 for computed max.
*
@@ -693,6 +691,19 @@ static txnid_t mdb_debug_start;
/** Round \b n up to an even number. */
#define EVEN(n) (((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
+ /** Least significant 1-bit of \b n. n must be of an unsigned type. */
+#define LOW_BIT(n) ((n) & (-(n)))
+
+ /** (log2(\b p2) % \b n), for p2 = power of 2 and 0 < n < 8. */
+#define LOG2_MOD(p2, n) (7 - 86 / ((p2) % ((1U<<(n))-1) + 11))
+ /* Explanation: Let p2 = 2**(n*y + x), x<n and M = (1U<<n)-1. Now p2 =
+ * (M+1)**y * 2**x = 2**x (mod M). Finally "/" "happens" to return 7-x.
+ */
+
+ /** Should be alignment of \b type. Ensure it is a power of 2. */
+#define ALIGNOF2(type) \
+ LOW_BIT(offsetof(struct { char ch_; type align_; }, align_))
+
/** Used for offsets within a single page.
* Since memory pages are typically 4 or 8KB in size, 12-13 bits,
* this is plenty.
@@ -849,7 +860,6 @@ typedef struct MDB_txninfo {
#define mti_magic mt1.mtb.mtb_magic
#define mti_format mt1.mtb.mtb_format
#define mti_rmutex mt1.mtb.mtb_rmutex
-#define mti_rmname mt1.mtb.mtb_rmname
#define mti_txnid mt1.mtb.mtb_txnid
#define mti_numreaders mt1.mtb.mtb_numreaders
#define mti_mutexid mt1.mtb.mtb_mutexid
@@ -876,11 +886,54 @@ typedef struct MDB_txninfo {
/** Lockfile format signature: version, features and field layout */
#define MDB_LOCK_FORMAT \
- ((uint32_t) \
- ((MDB_LOCK_VERSION) \
- /* Flags which describe functionality */ \
- + (SYSV_SEM_FLAG << 18) \
- + (((MDB_PIDLOCK) != 0) << 16)))
+ ((uint32_t) \
+ (((MDB_LOCK_VERSION) % (1U << MDB_LOCK_VERSION_BITS)) \
+ + MDB_lock_desc * (1U << MDB_LOCK_VERSION_BITS)))
+
+ /** Lock type and layout. Values 0-119. _WIN32 implies #MDB_PIDLOCK.
+ * Some low values are reserved for future tweaks.
+ */
+#ifdef _WIN32
+# define MDB_LOCK_TYPE (0 + ALIGNOF2(mdb_hash_t)/8 % 2)
+#elif defined MDB_USE_POSIX_SEM
+# define MDB_LOCK_TYPE (4 + ALIGNOF2(mdb_hash_t)/8 % 2)
+#elif defined MDB_USE_SYSV_SEM
+# define MDB_LOCK_TYPE (8)
+#elif defined MDB_USE_POSIX_MUTEX
+/* We do not know the inside of a POSIX mutex and how to check if mutexes
+ * used by two executables are compatible. Just check alignment and size.
+ */
+# define MDB_LOCK_TYPE (10 + \
+ LOG2_MOD(ALIGNOF2(pthread_mutex_t), 5) + \
+ sizeof(pthread_mutex_t) / 4U % 22 * 5)
+#endif
+
+enum {
+ /** Magic number for lockfile layout and features.
+ *
+ * This *attempts* to stop liblmdb variants compiled with conflicting
+ * options from using the lockfile at the same time and thus breaking
+ * it. It describes locking types, and sizes and sometimes alignment
+ * of the various lockfile items.
+ *
+ * The detected ranges are mostly guesswork, or based simply on how
+ * big they could be without using more bits. So we can tweak them
+ * in good conscience when updating #MDB_LOCK_VERSION.
+ */
+ MDB_lock_desc =
+ /* Default CACHELINE=64 vs. other values (have seen mention of 32-256) */
+ (CACHELINE==64 ? 0 : 1 + LOG2_MOD(CACHELINE >> (CACHELINE>64), 5))
+ + 6 * (sizeof(MDB_PID_T)/4 % 3) /* legacy(2) to word(4/8)? */
+ + 18 * (sizeof(pthread_t)/4 % 5) /* can be struct{id, active data} */
+ + 90 * (sizeof(MDB_txbody) / CACHELINE % 3)
+ + 270 * (MDB_LOCK_TYPE % 120)
+ /* The above is < 270*120 < 2**15 */
+ + ((sizeof(txnid_t) == 8) << 15) /* 32bit/64bit */
+ + ((sizeof(MDB_reader) > CACHELINE) << 16)
+ /* Not really needed - implied by MDB_LOCK_TYPE != (_WIN32 locking) */
+ + (((MDB_PIDLOCK) != 0) << 17)
+ /* 18 bits total: Must be <= (32 - MDB_LOCK_VERSION_BITS). */
+};
/** @} */
/** Common header for all page types. The page type depends on #mp_flags.