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134 lines
3.5 KiB
134 lines
3.5 KiB
package db
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// DBs are goroutine safe.
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type DB interface {
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// Get returns nil iff key doesn't exist.
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// A nil key is interpreted as an empty byteslice.
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// CONTRACT: key, value readonly []byte
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Get([]byte) []byte
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// Has checks if a key exists.
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// A nil key is interpreted as an empty byteslice.
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// CONTRACT: key, value readonly []byte
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Has(key []byte) bool
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// Set sets the key.
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// A nil key is interpreted as an empty byteslice.
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// CONTRACT: key, value readonly []byte
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Set([]byte, []byte)
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SetSync([]byte, []byte)
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// Delete deletes the key.
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// A nil key is interpreted as an empty byteslice.
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// CONTRACT: key readonly []byte
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Delete([]byte)
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DeleteSync([]byte)
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// Iterate over a domain of keys in ascending order. End is exclusive.
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// Start must be less than end, or the Iterator is invalid.
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// A nil start is interpreted as an empty byteslice.
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// If end is nil, iterates up to the last item (inclusive).
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// CONTRACT: No writes may happen within a domain while an iterator exists over it.
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// CONTRACT: start, end readonly []byte
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Iterator(start, end []byte) Iterator
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// Iterate over a domain of keys in descending order. End is exclusive.
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// Start must be greater than end, or the Iterator is invalid.
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// If start is nil, iterates from the last/greatest item (inclusive).
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// If end is nil, iterates up to the first/least item (inclusive).
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// CONTRACT: No writes may happen within a domain while an iterator exists over it.
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// CONTRACT: start, end readonly []byte
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ReverseIterator(start, end []byte) Iterator
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// Closes the connection.
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Close()
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// Creates a batch for atomic updates.
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NewBatch() Batch
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// For debugging
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Print()
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// Stats returns a map of property values for all keys and the size of the cache.
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Stats() map[string]string
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}
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//----------------------------------------
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// Batch
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type Batch interface {
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SetDeleter
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Write()
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WriteSync()
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}
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type SetDeleter interface {
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Set(key, value []byte) // CONTRACT: key, value readonly []byte
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Delete(key []byte) // CONTRACT: key readonly []byte
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}
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//----------------------------------------
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// Iterator
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/*
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Usage:
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var itr Iterator = ...
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defer itr.Close()
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for ; itr.Valid(); itr.Next() {
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k, v := itr.Key(); itr.Value()
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// ...
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}
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*/
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type Iterator interface {
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// The start & end (exclusive) limits to iterate over.
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// If end < start, then the Iterator goes in reverse order.
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//
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// A domain of ([]byte{12, 13}, []byte{12, 14}) will iterate
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// over anything with the prefix []byte{12, 13}.
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//
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// The smallest key is the empty byte array []byte{} - see BeginningKey().
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// The largest key is the nil byte array []byte(nil) - see EndingKey().
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// CONTRACT: start, end readonly []byte
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Domain() (start []byte, end []byte)
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// Valid returns whether the current position is valid.
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// Once invalid, an Iterator is forever invalid.
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Valid() bool
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// Next moves the iterator to the next sequential key in the database, as
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// defined by order of iteration.
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//
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// If Valid returns false, this method will panic.
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Next()
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// Key returns the key of the cursor.
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// If Valid returns false, this method will panic.
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// CONTRACT: key readonly []byte
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Key() (key []byte)
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// Value returns the value of the cursor.
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// If Valid returns false, this method will panic.
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// CONTRACT: value readonly []byte
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Value() (value []byte)
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// Close releases the Iterator.
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Close()
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}
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// For testing convenience.
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func bz(s string) []byte {
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return []byte(s)
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}
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// We defensively turn nil keys or values into []byte{} for
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// most operations.
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func nonNilBytes(bz []byte) []byte {
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if bz == nil {
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return []byte{}
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}
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return bz
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}
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