Add DefaultOptions variable.

This commit adds an explicit DefaultOptions variable for additional documentation.
Open() can still be passed a nil options which will cause options to be change to
the DefaultOptions variable. This change also allows options to be set globally for
an application if more than one database is being opened in a process.

This commit also moves all errors to errors.go so that the godoc groups them together.

bucket.go

@@ -2,7 +2,6 @@ package bolt
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"unsafe"
 )
@@ -15,32 +14,6 @@ const (
 	MaxValueSize = 4294967295
 )
 
-var (
-	// ErrBucketNotFound is returned when trying to access a bucket that has
-	// not been created yet.
-	ErrBucketNotFound = errors.New("bucket not found")
-
-	// ErrBucketExists is returned when creating a bucket that already exists.
-	ErrBucketExists = errors.New("bucket already exists")
-
-	// ErrBucketNameRequired is returned when creating a bucket with a blank name.
-	ErrBucketNameRequired = errors.New("bucket name required")
-
-	// ErrKeyRequired is returned when inserting a zero-length key.
-	ErrKeyRequired = errors.New("key required")
-
-	// ErrKeyTooLarge is returned when inserting a key that is larger than MaxKeySize.
-	ErrKeyTooLarge = errors.New("key too large")
-
-	// ErrValueTooLarge is returned when inserting a value that is larger than MaxValueSize.
-	ErrValueTooLarge = errors.New("value too large")
-
-	// ErrIncompatibleValue is returned when trying create or delete a bucket
-	// on an existing non-bucket key or when trying to create or delete a
-	// non-bucket key on an existing bucket key.
-	ErrIncompatibleValue = errors.New("incompatible value")
-)
-
 const (
 	maxUint = ^uint(0)
 	minUint = 0

db.go

@@ -1,7 +1,6 @@
 package bolt
 
 import (
-	"errors"
 	"fmt"
 	"hash/fnv"
 	"os"
@@ -33,30 +32,6 @@ const (
 // This value can be changed by setting DB.FillPercent.
 const DefaultFillPercent = 0.5
 
-var (
-	// ErrDatabaseNotOpen is returned when a DB instance is accessed before it
-	// is opened or after it is closed.
-	ErrDatabaseNotOpen = errors.New("database not open")
-
-	// ErrDatabaseOpen is returned when opening a database that is
-	// already open.
-	ErrDatabaseOpen = errors.New("database already open")
-
-	// ErrInvalid is returned when a data file is not a Bolt-formatted database.
-	ErrInvalid = errors.New("invalid database")
-
-	// ErrVersionMismatch is returned when the data file was created with a
-	// different version of Bolt.
-	ErrVersionMismatch = errors.New("version mismatch")
-
-	// ErrChecksum is returned when either meta page checksum does not match.
-	ErrChecksum = errors.New("checksum error")
-
-	// ErrTimeout is returned when a database cannot obtain an exclusive lock
-	// on the data file after the timeout passed to Open().
-	ErrTimeout = errors.New("timeout")
-)
-
 // 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.
@@ -117,9 +92,9 @@ func (db *DB) String() string {
 func Open(path string, mode os.FileMode, options *Options) (*DB, error) {
 	var db = &DB{opened: true, FillPercent: DefaultFillPercent}
 
-	// Set default options.
+	// Set default options if no options are provided.
 	if options == nil {
-		options = &Options{}
+		options = DefaultOptions
 	}
 
 	// Open data file and separate sync handler for metadata writes.
@@ -575,6 +550,12 @@ type Options struct {
 	Timeout time.Duration
 }
 
+// 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,
+}
+
 // Stats represents statistics about the database.
 type Stats struct {
 	// Freelist stats

errors.go

@@ -0,0 +1,70 @@
+package bolt
+
+import "errors"
+
+// These errors can be returned when opening or calling methods on a DB.
+var (
+	// ErrDatabaseNotOpen is returned when a DB instance is accessed before it
+	// is opened or after it is closed.
+	ErrDatabaseNotOpen = errors.New("database not open")
+
+	// ErrDatabaseOpen is returned when opening a database that is
+	// already open.
+	ErrDatabaseOpen = errors.New("database already open")
+
+	// ErrInvalid is returned when a data file is not a Bolt-formatted database.
+	ErrInvalid = errors.New("invalid database")
+
+	// ErrVersionMismatch is returned when the data file was created with a
+	// different version of Bolt.
+	ErrVersionMismatch = errors.New("version mismatch")
+
+	// ErrChecksum is returned when either meta page checksum does not match.
+	ErrChecksum = errors.New("checksum error")
+
+	// ErrTimeout is returned when a database cannot obtain an exclusive lock
+	// on the data file after the timeout passed to Open().
+	ErrTimeout = errors.New("timeout")
+)
+
+// These errors can occur when beginning or committing a Tx.
+var (
+	// ErrTxNotWritable is returned when performing a write operation on a
+	// read-only transaction.
+	ErrTxNotWritable = errors.New("tx not writable")
+
+	// ErrTxClosed is returned when committing or rolling back a transaction
+	// that has already been committed or rolled back.
+	ErrTxClosed = errors.New("tx closed")
+
+	// ErrFreelistOverflow is returned when the total number of free pages
+	// exceeds 65,536 and the freelist cannot hold any more.
+	ErrFreelistOverflow = errors.New("freelist overflow")
+)
+
+// These errors can occur when putting or deleting a value or a bucket.
+var (
+	// ErrBucketNotFound is returned when trying to access a bucket that has
+	// not been created yet.
+	ErrBucketNotFound = errors.New("bucket not found")
+
+	// ErrBucketExists is returned when creating a bucket that already exists.
+	ErrBucketExists = errors.New("bucket already exists")
+
+	// ErrBucketNameRequired is returned when creating a bucket with a blank name.
+	ErrBucketNameRequired = errors.New("bucket name required")
+
+	// ErrKeyRequired is returned when inserting a zero-length key.
+	ErrKeyRequired = errors.New("key required")
+
+	// ErrKeyTooLarge is returned when inserting a key that is larger than MaxKeySize.
+	ErrKeyTooLarge = errors.New("key too large")
+
+	// ErrValueTooLarge is returned when inserting a value that is larger than MaxValueSize.
+	ErrValueTooLarge = errors.New("value too large")
+
+	// ErrIncompatibleValue is returned when trying create or delete a bucket
+	// on an existing non-bucket key or when trying to create or delete a
+	// non-bucket key on an existing bucket key.
+	ErrIncompatibleValue = errors.New("incompatible value")
+)

freelist.go

@@ -1,18 +1,11 @@
 package bolt
 
 import (
-	"errors"
 	"fmt"
 	"sort"
 	"unsafe"
 )
 
-var (
-	// ErrFreelistOverflow is returned when the total number of free pages
-	// exceeds 65,536 and the freelist cannot hold any more.
-	ErrFreelistOverflow = errors.New("freelist overflow")
-)
-
 // freelist represents a list of all pages that are available for allocation.
 // It also tracks pages that have been freed but are still in use by open transactions.
 type freelist struct {

tx.go

@@ -1,7 +1,6 @@
 package bolt
 
 import (
-	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -10,16 +9,6 @@ import (
 	"unsafe"
 )
 
-var (
-	// ErrTxNotWritable is returned when performing a write operation on a
-	// read-only transaction.
-	ErrTxNotWritable = errors.New("tx not writable")
-
-	// ErrTxClosed is returned when committing or rolling back a transaction
-	// that has already been committed or rolled back.
-	ErrTxClosed = errors.New("tx closed")
-)
-
 // txid represents the internal transaction identifier.
 type txid uint64