60 lines
2.1 KiB
Go
60 lines
2.1 KiB
Go
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// Package noder provide an interface for defining nodes in a
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// merkletrie, their hashes and their paths (a noders and its
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// ancestors).
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//
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// The hasher interface is easy to implement naively by elements that
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// already have a hash, like git blobs and trees. More sophisticated
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// implementations can implement the Equal function in exotic ways
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// though: for instance, comparing the modification time of directories
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// in a filesystem.
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package noder
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import "fmt"
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// Hasher interface is implemented by types that can tell you
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// their hash.
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type Hasher interface {
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Hash() []byte
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}
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// Equal functions take two hashers and return if they are equal.
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//
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// These functions are expected to be faster than reflect.Equal or
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// reflect.DeepEqual because they can compare just the hash of the
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// objects, instead of their contents, so they are expected to be O(1).
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type Equal func(a, b Hasher) bool
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// The Noder interface is implemented by the elements of a Merkle Trie.
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//
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// There are two types of elements in a Merkle Trie:
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//
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// - file-like nodes: they cannot have children.
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//
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// - directory-like nodes: they can have 0 or more children and their
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// hash is calculated by combining their children hashes.
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type Noder interface {
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Hasher
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fmt.Stringer // for testing purposes
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// Name returns the name of an element (relative, not its full
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// path).
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Name() string
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// IsDir returns true if the element is a directory-like node or
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// false if it is a file-like node.
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IsDir() bool
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// Children returns the children of the element. Note that empty
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// directory-like noders and file-like noders will both return
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// NoChildren.
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Children() ([]Noder, error)
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// NumChildren returns the number of children this element has.
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//
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// This method is an optimization: the number of children is easily
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// calculated as the length of the value returned by the Children
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// method (above); yet, some implementations will be able to
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// implement NumChildren in O(1) while Children is usually more
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// complex.
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NumChildren() (int, error)
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}
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// NoChildren represents the children of a noder without children.
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var NoChildren = []Noder{}
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