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Diffstat (limited to 'vendor/github.com/boltdb/bolt/db.go')
| -rw-r--r-- | vendor/github.com/boltdb/bolt/db.go | 1039 |
1 files changed, 1039 insertions, 0 deletions
diff --git a/vendor/github.com/boltdb/bolt/db.go b/vendor/github.com/boltdb/bolt/db.go new file mode 100644 index 000000000..f352ff14f --- /dev/null +++ b/vendor/github.com/boltdb/bolt/db.go @@ -0,0 +1,1039 @@ +package bolt + +import ( + "errors" + "fmt" + "hash/fnv" + "log" + "os" + "runtime" + "runtime/debug" + "strings" + "sync" + "time" + "unsafe" +) + +// The largest step that can be taken when remapping the mmap. +const maxMmapStep = 1 << 30 // 1GB + +// The data file format version. +const version = 2 + +// Represents a marker value to indicate that a file is a Bolt DB. +const magic uint32 = 0xED0CDAED + +// IgnoreNoSync specifies whether the NoSync field of a DB is ignored when +// syncing changes to a file. This is required as some operating systems, +// such as OpenBSD, do not have a unified buffer cache (UBC) and writes +// must be synchronized using the msync(2) syscall. +const IgnoreNoSync = runtime.GOOS == "openbsd" + +// Default values if not set in a DB instance. +const ( + DefaultMaxBatchSize int = 1000 + DefaultMaxBatchDelay = 10 * time.Millisecond + DefaultAllocSize = 16 * 1024 * 1024 +) + +// default page size for db is set to the OS page size. +var defaultPageSize = os.Getpagesize() + +// DB represents a collection of buckets persisted to a file on disk. +// All data access is performed through transactions which can be obtained through the DB. +// All the functions on DB will return a ErrDatabaseNotOpen if accessed before Open() is called. +type DB struct { + // When enabled, the database will perform a Check() after every commit. + // A panic is issued if the database is in an inconsistent state. This + // flag has a large performance impact so it should only be used for + // debugging purposes. + StrictMode bool + + // Setting the NoSync flag will cause the database to skip fsync() + // calls after each commit. This can be useful when bulk loading data + // into a database and you can restart the bulk load in the event of + // a system failure or database corruption. Do not set this flag for + // normal use. + // + // If the package global IgnoreNoSync constant is true, this value is + // ignored. See the comment on that constant for more details. + // + // THIS IS UNSAFE. PLEASE USE WITH CAUTION. + NoSync bool + + // When true, skips the truncate call when growing the database. + // Setting this to true is only safe on non-ext3/ext4 systems. + // Skipping truncation avoids preallocation of hard drive space and + // bypasses a truncate() and fsync() syscall on remapping. + // + // https://github.com/boltdb/bolt/issues/284 + NoGrowSync bool + + // If you want to read the entire database fast, you can set MmapFlag to + // syscall.MAP_POPULATE on Linux 2.6.23+ for sequential read-ahead. + MmapFlags int + + // MaxBatchSize is the maximum size of a batch. Default value is + // copied from DefaultMaxBatchSize in Open. + // + // If <=0, disables batching. + // + // Do not change concurrently with calls to Batch. + MaxBatchSize int + + // MaxBatchDelay is the maximum delay before a batch starts. + // Default value is copied from DefaultMaxBatchDelay in Open. + // + // If <=0, effectively disables batching. + // + // Do not change concurrently with calls to Batch. + MaxBatchDelay time.Duration + + // AllocSize is the amount of space allocated when the database + // needs to create new pages. This is done to amortize the cost + // of truncate() and fsync() when growing the data file. + AllocSize int + + path string + file *os.File + lockfile *os.File // windows only + dataref []byte // mmap'ed readonly, write throws SEGV + data *[maxMapSize]byte + datasz int + filesz int // current on disk file size + meta0 *meta + meta1 *meta + pageSize int + opened bool + rwtx *Tx + txs []*Tx + freelist *freelist + stats Stats + + pagePool sync.Pool + + batchMu sync.Mutex + batch *batch + + rwlock sync.Mutex // Allows only one writer at a time. + metalock sync.Mutex // Protects meta page access. + mmaplock sync.RWMutex // Protects mmap access during remapping. + statlock sync.RWMutex // Protects stats access. + + ops struct { + writeAt func(b []byte, off int64) (n int, err error) + } + + // Read only mode. + // When true, Update() and Begin(true) return ErrDatabaseReadOnly immediately. + readOnly bool +} + +// Path returns the path to currently open database file. +func (db *DB) Path() string { + return db.path +} + +// GoString returns the Go string representation of the database. +func (db *DB) GoString() string { + return fmt.Sprintf("bolt.DB{path:%q}", db.path) +} + +// String returns the string representation of the database. +func (db *DB) String() string { + return fmt.Sprintf("DB<%q>", db.path) +} + +// Open creates and opens a database at the given path. +// If the file does not exist then it will be created automatically. +// Passing in nil options will cause Bolt to open the database with the default options. +func Open(path string, mode os.FileMode, options *Options) (*DB, error) { + var db = &DB{opened: true} + + // Set default options if no options are provided. + if options == nil { + options = DefaultOptions + } + db.NoGrowSync = options.NoGrowSync + db.MmapFlags = options.MmapFlags + + // Set default values for later DB operations. + db.MaxBatchSize = DefaultMaxBatchSize + db.MaxBatchDelay = DefaultMaxBatchDelay + db.AllocSize = DefaultAllocSize + + flag := os.O_RDWR + if options.ReadOnly { + flag = os.O_RDONLY + db.readOnly = true + } + + // Open data file and separate sync handler for metadata writes. + db.path = path + var err error + if db.file, err = os.OpenFile(db.path, flag|os.O_CREATE, mode); err != nil { + _ = db.close() + return nil, err + } + + // Lock file so that other processes using Bolt in read-write mode cannot + // use the database at the same time. This would cause corruption since + // the two processes would write meta pages and free pages separately. + // The database file is locked exclusively (only one process can grab the lock) + // if !options.ReadOnly. + // The database file is locked using the shared lock (more than one process may + // hold a lock at the same time) otherwise (options.ReadOnly is set). + if err := flock(db, mode, !db.readOnly, options.Timeout); err != nil { + _ = db.close() + return nil, err + } + + // Default values for test hooks + db.ops.writeAt = db.file.WriteAt + + // Initialize the database if it doesn't exist. + if info, err := db.file.Stat(); err != nil { + return nil, err + } else if info.Size() == 0 { + // Initialize new files with meta pages. + if err := db.init(); err != nil { + return nil, err + } + } else { + // Read the first meta page to determine the page size. + var buf [0x1000]byte + if _, err := db.file.ReadAt(buf[:], 0); err == nil { + m := db.pageInBuffer(buf[:], 0).meta() + if err := m.validate(); err != nil { + // If we can't read the page size, we can assume it's the same + // as the OS -- since that's how the page size was chosen in the + // first place. + // + // If the first page is invalid and this OS uses a different + // page size than what the database was created with then we + // are out of luck and cannot access the database. + db.pageSize = os.Getpagesize() + } else { + db.pageSize = int(m.pageSize) + } + } + } + + // Initialize page pool. + db.pagePool = sync.Pool{ + New: func() interface{} { + return make([]byte, db.pageSize) + }, + } + + // Memory map the data file. + if err := db.mmap(options.InitialMmapSize); err != nil { + _ = db.close() + return nil, err + } + + // Read in the freelist. + db.freelist = newFreelist() + db.freelist.read(db.page(db.meta().freelist)) + + // Mark the database as opened and return. + return db, nil +} + +// mmap opens the underlying memory-mapped file and initializes the meta references. +// minsz is the minimum size that the new mmap can be. +func (db *DB) mmap(minsz int) error { + db.mmaplock.Lock() + defer db.mmaplock.Unlock() + + info, err := db.file.Stat() + if err != nil { + return fmt.Errorf("mmap stat error: %s", err) + } else if int(info.Size()) < db.pageSize*2 { + return fmt.Errorf("file size too small") + } + + // Ensure the size is at least the minimum size. + var size = int(info.Size()) + if size < minsz { + size = minsz + } + size, err = db.mmapSize(size) + if err != nil { + return err + } + + // Dereference all mmap references before unmapping. + if db.rwtx != nil { + db.rwtx.root.dereference() + } + + // Unmap existing data before continuing. + if err := db.munmap(); err != nil { + return err + } + + // Memory-map the data file as a byte slice. + if err := mmap(db, size); err != nil { + return err + } + + // Save references to the meta pages. + db.meta0 = db.page(0).meta() + db.meta1 = db.page(1).meta() + + // Validate the meta pages. We only return an error if both meta pages fail + // validation, since meta0 failing validation means that it wasn't saved + // properly -- but we can recover using meta1. And vice-versa. + err0 := db.meta0.validate() + err1 := db.meta1.validate() + if err0 != nil && err1 != nil { + return err0 + } + + return nil +} + +// munmap unmaps the data file from memory. +func (db *DB) munmap() error { + if err := munmap(db); err != nil { + return fmt.Errorf("unmap error: " + err.Error()) + } + return nil +} + +// mmapSize determines the appropriate size for the mmap given the current size +// of the database. The minimum size is 32KB and doubles until it reaches 1GB. +// Returns an error if the new mmap size is greater than the max allowed. +func (db *DB) mmapSize(size int) (int, error) { + // Double the size from 32KB until 1GB. + for i := uint(15); i <= 30; i++ { + if size <= 1<<i { + return 1 << i, nil + } + } + + // Verify the requested size is not above the maximum allowed. + if size > maxMapSize { + return 0, fmt.Errorf("mmap too large") + } + + // If larger than 1GB then grow by 1GB at a time. + sz := int64(size) + if remainder := sz % int64(maxMmapStep); remainder > 0 { + sz += int64(maxMmapStep) - remainder + } + + // Ensure that the mmap size is a multiple of the page size. + // This should always be true since we're incrementing in MBs. + pageSize := int64(db.pageSize) + if (sz % pageSize) != 0 { + sz = ((sz / pageSize) + 1) * pageSize + } + + // If we've exceeded the max size then only grow up to the max size. + if sz > maxMapSize { + sz = maxMapSize + } + + return int(sz), nil +} + +// init creates a new database file and initializes its meta pages. +func (db *DB) init() error { + // Set the page size to the OS page size. + db.pageSize = os.Getpagesize() + + // Create two meta pages on a buffer. + buf := make([]byte, db.pageSize*4) + for i := 0; i < 2; i++ { + p := db.pageInBuffer(buf[:], pgid(i)) + p.id = pgid(i) + p.flags = metaPageFlag + + // Initialize the meta page. + m := p.meta() + m.magic = magic + m.version = version + m.pageSize = uint32(db.pageSize) + m.freelist = 2 + m.root = bucket{root: 3} + m.pgid = 4 + m.txid = txid(i) + m.checksum = m.sum64() + } + + // Write an empty freelist at page 3. + p := db.pageInBuffer(buf[:], pgid(2)) + p.id = pgid(2) + p.flags = freelistPageFlag + p.count = 0 + + // Write an empty leaf page at page 4. + p = db.pageInBuffer(buf[:], pgid(3)) + p.id = pgid(3) + p.flags = leafPageFlag + p.count = 0 + + // Write the buffer to our data file. + if _, err := db.ops.writeAt(buf, 0); err != nil { + return err + } + if err := fdatasync(db); err != nil { + return err + } + + return nil +} + +// Close releases all database resources. +// All transactions must be closed before closing the database. +func (db *DB) Close() error { + db.rwlock.Lock() + defer db.rwlock.Unlock() + + db.metalock.Lock() + defer db.metalock.Unlock() + + db.mmaplock.RLock() + defer db.mmaplock.RUnlock() + + return db.close() +} + +func (db *DB) close() error { + if !db.opened { + return nil + } + + db.opened = false + + db.freelist = nil + + // Clear ops. + db.ops.writeAt = nil + + // Close the mmap. + if err := db.munmap(); err != nil { + return err + } + + // Close file handles. + if db.file != nil { + // No need to unlock read-only file. + if !db.readOnly { + // Unlock the file. + if err := funlock(db); err != nil { + log.Printf("bolt.Close(): funlock error: %s", err) + } + } + + // Close the file descriptor. + if err := db.file.Close(); err != nil { + return fmt.Errorf("db file close: %s", err) + } + db.file = nil + } + + db.path = "" + return nil +} + +// Begin starts a new transaction. +// Multiple read-only transactions can be used concurrently but only one +// write transaction can be used at a time. Starting multiple write transactions +// will cause the calls to block and be serialized until the current write +// transaction finishes. +// +// Transactions should not be dependent on one another. Opening a read +// transaction and a write transaction in the same goroutine can cause the +// writer to deadlock because the database periodically needs to re-mmap itself +// as it grows and it cannot do that while a read transaction is open. +// +// If a long running read transaction (for example, a snapshot transaction) is +// needed, you might want to set DB.InitialMmapSize to a large enough value +// to avoid potential blocking of write transaction. +// +// IMPORTANT: You must close read-only transactions after you are finished or +// else the database will not reclaim old pages. +func (db *DB) Begin(writable bool) (*Tx, error) { + if writable { + return db.beginRWTx() + } + return db.beginTx() +} + +func (db *DB) beginTx() (*Tx, error) { + // Lock the meta pages while we initialize the transaction. We obtain + // the meta lock before the mmap lock because that's the order that the + // write transaction will obtain them. + db.metalock.Lock() + + // Obtain a read-only lock on the mmap. When the mmap is remapped it will + // obtain a write lock so all transactions must finish before it can be + // remapped. + db.mmaplock.RLock() + + // Exit if the database is not open yet. + if !db.opened { + db.mmaplock.RUnlock() + db.metalock.Unlock() + return nil, ErrDatabaseNotOpen + } + + // Create a transaction associated with the database. + t := &Tx{} + t.init(db) + + // Keep track of transaction until it closes. + db.txs = append(db.txs, t) + n := len(db.txs) + + // Unlock the meta pages. + db.metalock.Unlock() + + // Update the transaction stats. + db.statlock.Lock() + db.stats.TxN++ + db.stats.OpenTxN = n + db.statlock.Unlock() + + return t, nil +} + +func (db *DB) beginRWTx() (*Tx, error) { + // If the database was opened with Options.ReadOnly, return an error. + if db.readOnly { + return nil, ErrDatabaseReadOnly + } + + // Obtain writer lock. This is released by the transaction when it closes. + // This enforces only one writer transaction at a time. + db.rwlock.Lock() + + // Once we have the writer lock then we can lock the meta pages so that + // we can set up the transaction. + db.metalock.Lock() + defer db.metalock.Unlock() + + // Exit if the database is not open yet. + if !db.opened { + db.rwlock.Unlock() + return nil, ErrDatabaseNotOpen + } + + // Create a transaction associated with the database. + t := &Tx{writable: true} + t.init(db) + db.rwtx = t + + // Free any pages associated with closed read-only transactions. + var minid txid = 0xFFFFFFFFFFFFFFFF + for _, t := range db.txs { + if t.meta.txid < minid { + minid = t.meta.txid + } + } + if minid > 0 { + db.freelist.release(minid - 1) + } + + return t, nil +} + +// removeTx removes a transaction from the database. +func (db *DB) removeTx(tx *Tx) { + // Release the read lock on the mmap. + db.mmaplock.RUnlock() + + // Use the meta lock to restrict access to the DB object. + db.metalock.Lock() + + // Remove the transaction. + for i, t := range db.txs { + if t == tx { + last := len(db.txs) - 1 + db.txs[i] = db.txs[last] + db.txs[last] = nil + db.txs = db.txs[:last] + break + } + } + n := len(db.txs) + + // Unlock the meta pages. + db.metalock.Unlock() + + // Merge statistics. + db.statlock.Lock() + db.stats.OpenTxN = n + db.stats.TxStats.add(&tx.stats) + db.statlock.Unlock() +} + +// Update executes a function within the context of a read-write managed transaction. +// If no error is returned from the function then the transaction is committed. +// If an error is returned then the entire transaction is rolled back. +// Any error that is returned from the function or returned from the commit is +// returned from the Update() method. +// +// Attempting to manually commit or rollback within the function will cause a panic. +func (db *DB) Update(fn func(*Tx) error) error { + t, err := db.Begin(true) + if err != nil { + return err + } + + // Make sure the transaction rolls back in the event of a panic. + defer func() { + if t.db != nil { + t.rollback() + } + }() + + // Mark as a managed tx so that the inner function cannot manually commit. + t.managed = true + + // If an error is returned from the function then rollback and return error. + err = fn(t) + t.managed = false + if err != nil { + _ = t.Rollback() + return err + } + + return t.Commit() +} + +// View executes a function within the context of a managed read-only transaction. +// Any error that is returned from the function is returned from the View() method. +// +// Attempting to manually rollback within the function will cause a panic. +func (db *DB) View(fn func(*Tx) error) error { + t, err := db.Begin(false) + if err != nil { + return err + } + + // Make sure the transaction rolls back in the event of a panic. + defer func() { + if t.db != nil { + t.rollback() + } + }() + + // Mark as a managed tx so that the inner function cannot manually rollback. + t.managed = true + + // If an error is returned from the function then pass it through. + err = fn(t) + t.managed = false + if err != nil { + _ = t.Rollback() + return err + } + + if err := t.Rollback(); err != nil { + return err + } + + return nil +} + +// Batch calls fn as part of a batch. It behaves similar to Update, +// except: +// +// 1. concurrent Batch calls can be combined into a single Bolt +// transaction. +// +// 2. the function passed to Batch may be called multiple times, +// regardless of whether it returns error or not. +// +// This means that Batch function side effects must be idempotent and +// take permanent effect only after a successful return is seen in +// caller. +// +// The maximum batch size and delay can be adjusted with DB.MaxBatchSize +// and DB.MaxBatchDelay, respectively. +// +// Batch is only useful when there are multiple goroutines calling it. +func (db *DB) Batch(fn func(*Tx) error) error { + errCh := make(chan error, 1) + + db.batchMu.Lock() + if (db.batch == nil) || (db.batch != nil && len(db.batch.calls) >= db.MaxBatchSize) { + // There is no existing batch, or the existing batch is full; start a new one. + db.batch = &batch{ + db: db, + } + db.batch.timer = time.AfterFunc(db.MaxBatchDelay, db.batch.trigger) + } + db.batch.calls = append(db.batch.calls, call{fn: fn, err: errCh}) + if len(db.batch.calls) >= db.MaxBatchSize { + // wake up batch, it's ready to run + go db.batch.trigger() + } + db.batchMu.Unlock() + + err := <-errCh + if err == trySolo { + err = db.Update(fn) + } + return err +} + +type call struct { + fn func(*Tx) error + err chan<- error +} + +type batch struct { + db *DB + timer *time.Timer + start sync.Once + calls []call +} + +// trigger runs the batch if it hasn't already been run. +func (b *batch) trigger() { + b.start.Do(b.run) +} + +// run performs the transactions in the batch and communicates results +// back to DB.Batch. +func (b *batch) run() { + b.db.batchMu.Lock() + b.timer.Stop() + // Make sure no new work is added to this batch, but don't break + // other batches. + if b.db.batch == b { + b.db.batch = nil + } + b.db.batchMu.Unlock() + +retry: + for len(b.calls) > 0 { + var failIdx = -1 + err := b.db.Update(func(tx *Tx) error { + for i, c := range b.calls { + if err := safelyCall(c.fn, tx); err != nil { + failIdx = i + return err + } + } + return nil + }) + + if failIdx >= 0 { + // take the failing transaction out of the batch. it's + // safe to shorten b.calls here because db.batch no longer + // points to us, and we hold the mutex anyway. + c := b.calls[failIdx] + b.calls[failIdx], b.calls = b.calls[len(b.calls)-1], b.calls[:len(b.calls)-1] + // tell the submitter re-run it solo, continue with the rest of the batch + c.err <- trySolo + continue retry + } + + // pass success, or bolt internal errors, to all callers + for _, c := range b.calls { + if c.err != nil { + c.err <- err + } + } + break retry + } +} + +// trySolo is a special sentinel error value used for signaling that a +// transaction function should be re-run. It should never be seen by +// callers. +var trySolo = errors.New("batch function returned an error and should be re-run solo") + +type panicked struct { + reason interface{} +} + +func (p panicked) Error() string { + if err, ok := p.reason.(error); ok { + return err.Error() + } + return fmt.Sprintf("panic: %v", p.reason) +} + +func safelyCall(fn func(*Tx) error, tx *Tx) (err error) { + defer func() { + if p := recover(); p != nil { + err = panicked{p} + } + }() + return fn(tx) +} + +// Sync executes fdatasync() against the database file handle. +// +// This is not necessary under normal operation, however, if you use NoSync +// then it allows you to force the database file to sync against the disk. +func (db *DB) Sync() error { return fdatasync(db) } + +// Stats retrieves ongoing performance stats for the database. +// This is only updated when a transaction closes. +func (db *DB) Stats() Stats { + db.statlock.RLock() + defer db.statlock.RUnlock() + return db.stats +} + +// This is for internal access to the raw data bytes from the C cursor, use +// carefully, or not at all. +func (db *DB) Info() *Info { + return &Info{uintptr(unsafe.Pointer(&db.data[0])), db.pageSize} +} + +// page retrieves a page reference from the mmap based on the current page size. +func (db *DB) page(id pgid) *page { + pos := id * pgid(db.pageSize) + return (*page)(unsafe.Pointer(&db.data[pos])) +} + +// pageInBuffer retrieves a page reference from a given byte array based on the current page size. +func (db *DB) pageInBuffer(b []byte, id pgid) *page { + return (*page)(unsafe.Pointer(&b[id*pgid(db.pageSize)])) +} + +// meta retrieves the current meta page reference. +func (db *DB) meta() *meta { + // We have to return the meta with the highest txid which doesn't fail + // validation. Otherwise, we can cause errors when in fact the database is + // in a consistent state. metaA is the one with the higher txid. + metaA := db.meta0 + metaB := db.meta1 + if db.meta1.txid > db.meta0.txid { + metaA = db.meta1 + metaB = db.meta0 + } + + // Use higher meta page if valid. Otherwise fallback to previous, if valid. + if err := metaA.validate(); err == nil { + return metaA + } else if err := metaB.validate(); err == nil { + return metaB + } + + // This should never be reached, because both meta1 and meta0 were validated + // on mmap() and we do fsync() on every write. + panic("bolt.DB.meta(): invalid meta pages") +} + +// allocate returns a contiguous block of memory starting at a given page. +func (db *DB) allocate(count int) (*page, error) { + // Allocate a temporary buffer for the page. + var buf []byte + if count == 1 { + buf = db.pagePool.Get().([]byte) + } else { + buf = make([]byte, count*db.pageSize) + } + p := (*page)(unsafe.Pointer(&buf[0])) + p.overflow = uint32(count - 1) + + // Use pages from the freelist if they are available. + if p.id = db.freelist.allocate(count); p.id != 0 { + return p, nil + } + + // Resize mmap() if we're at the end. + p.id = db.rwtx.meta.pgid + var minsz = int((p.id+pgid(count))+1) * db.pageSize + if minsz >= db.datasz { + if err := db.mmap(minsz); err != nil { + return nil, fmt.Errorf("mmap allocate error: %s", err) + } + } + + // Move the page id high water mark. + db.rwtx.meta.pgid += pgid(count) + + return p, nil +} + +// grow grows the size of the database to the given sz. +func (db *DB) grow(sz int) error { + // Ignore if the new size is less than available file size. + if sz <= db.filesz { + return nil + } + + // If the data is smaller than the alloc size then only allocate what's needed. + // Once it goes over the allocation size then allocate in chunks. + if db.datasz < db.AllocSize { + sz = db.datasz + } else { + sz += db.AllocSize + } + + // Truncate and fsync to ensure file size metadata is flushed. + // https://github.com/boltdb/bolt/issues/284 + if !db.NoGrowSync && !db.readOnly { + if runtime.GOOS != "windows" { + if err := db.file.Truncate(int64(sz)); err != nil { + return fmt.Errorf("file resize error: %s", err) + } + } + if err := db.file.Sync(); err != nil { + return fmt.Errorf("file sync error: %s", err) + } + } + + db.filesz = sz + return nil +} + +func (db *DB) IsReadOnly() bool { + return db.readOnly +} + +// Options represents the options that can be set when opening a database. +type Options struct { + // Timeout is the amount of time to wait to obtain a file lock. + // When set to zero it will wait indefinitely. This option is only + // available on Darwin and Linux. + Timeout time.Duration + + // Sets the DB.NoGrowSync flag before memory mapping the file. + NoGrowSync bool + + // Open database in read-only mode. Uses flock(..., LOCK_SH |LOCK_NB) to + // grab a shared lock (UNIX). + ReadOnly bool + + // Sets the DB.MmapFlags flag before memory mapping the file. + MmapFlags int + + // InitialMmapSize is the initial mmap size of the database + // in bytes. Read transactions won't block write transaction + // if the InitialMmapSize is large enough to hold database mmap + // size. (See DB.Begin for more information) + // + // If <=0, the initial map size is 0. + // If initialMmapSize is smaller than the previous database size, + // it takes no effect. + InitialMmapSize int +} + +// DefaultOptions represent the options used if nil options are passed into Open(). +// No timeout is used which will cause Bolt to wait indefinitely for a lock. +var DefaultOptions = &Options{ + Timeout: 0, + NoGrowSync: false, +} + +// Stats represents statistics about the database. +type Stats struct { + // Freelist stats + FreePageN int // total number of free pages on the freelist + PendingPageN int // total number of pending pages on the freelist + FreeAlloc int // total bytes allocated in free pages + FreelistInuse int // total bytes used by the freelist + + // Transaction stats + TxN int // total number of started read transactions + OpenTxN int // number of currently open read transactions + + TxStats TxStats // global, ongoing stats. +} + +// Sub calculates and returns the difference between two sets of database stats. +// This is useful when obtaining stats at two different points and time and +// you need the performance counters that occurred within that time span. +func (s *Stats) Sub(other *Stats) Stats { + if other == nil { + return *s + } + var diff Stats + diff.FreePageN = s.FreePageN + diff.PendingPageN = s.PendingPageN + diff.FreeAlloc = s.FreeAlloc + diff.FreelistInuse = s.FreelistInuse + diff.TxN = s.TxN - other.TxN + diff.TxStats = s.TxStats.Sub(&other.TxStats) + return diff +} + +func (s *Stats) add(other *Stats) { + s.TxStats.add(&other.TxStats) +} + +type Info struct { + Data uintptr + PageSize int +} + +type meta struct { + magic uint32 + version uint32 + pageSize uint32 + flags uint32 + root bucket + freelist pgid + pgid pgid + txid txid + checksum uint64 +} + +// validate checks the marker bytes and version of the meta page to ensure it matches this binary. +func (m *meta) validate() error { + if m.magic != magic { + return ErrInvalid + } else if m.version != version { + return ErrVersionMismatch + } else if m.checksum != 0 && m.checksum != m.sum64() { + return ErrChecksum + } + return nil +} + +// copy copies one meta object to another. +func (m *meta) copy(dest *meta) { + *dest = *m +} + +// write writes the meta onto a page. +func (m *meta) write(p *page) { + if m.root.root >= m.pgid { + panic(fmt.Sprintf("root bucket pgid (%d) above high water mark (%d)", m.root.root, m.pgid)) + } else if m.freelist >= m.pgid { + panic(fmt.Sprintf("freelist pgid (%d) above high water mark (%d)", m.freelist, m.pgid)) + } + + // Page id is either going to be 0 or 1 which we can determine by the transaction ID. + p.id = pgid(m.txid % 2) + p.flags |= metaPageFlag + + // Calculate the checksum. + m.checksum = m.sum64() + + m.copy(p.meta()) +} + +// generates the checksum for the meta. +func (m *meta) sum64() uint64 { + var h = fnv.New64a() + _, _ = h.Write((*[unsafe.Offsetof(meta{}.checksum)]byte)(unsafe.Pointer(m))[:]) + return h.Sum64() +} + +// _assert will panic with a given formatted message if the given condition is false. +func _assert(condition bool, msg string, v ...interface{}) { + if !condition { + panic(fmt.Sprintf("assertion failed: "+msg, v...)) + } +} + +func warn(v ...interface{}) { fmt.Fprintln(os.Stderr, v...) } +func warnf(msg string, v ...interface{}) { fmt.Fprintf(os.Stderr, msg+"\n", v...) } + +func printstack() { + stack := strings.Join(strings.Split(string(debug.Stack()), "\n")[2:], "\n") + fmt.Fprintln(os.Stderr, stack) +} |