77 lines
1.5 KiB
Go
77 lines
1.5 KiB
Go
package model
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import (
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"crypto"
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"encoding/hex"
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"fmt"
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"hash"
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"io"
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"strings"
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)
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func NewHash(s string) (Hash, error) {
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h := Hash{}
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if err := h.parse(s); err != nil {
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return Hash{}, err
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}
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return h, nil
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}
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type Hash struct {
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// Algorithm holds the algorithm used to compute the hash.
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Algorithm string
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// Hex holds the hex portion of the content hash.
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Hex string
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}
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func (h *Hash) parse(unquoted string) error {
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parts := strings.Split(unquoted, ":")
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if len(parts) != 2 {
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return fmt.Errorf("cannot parse hash: %q", unquoted)
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}
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rest := strings.TrimLeft(parts[1], "0123456789abcdef")
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if len(rest) != 0 {
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return fmt.Errorf("found non-hex character in hash: %c", rest[0])
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}
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hasher, err := Hasher(parts[0])
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if err != nil {
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return err
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}
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// Compare the hex to the expected size (2 hex characters per byte)
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if len(parts[1]) != hasher.Size()*2 {
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return fmt.Errorf("wrong number of hex digits for %s: %s", parts[0], parts[1])
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}
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h.Algorithm = parts[0]
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h.Hex = parts[1]
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return nil
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}
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func (h Hash) String() string {
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return fmt.Sprintf("%s:%s", h.Algorithm, h.Hex)
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}
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func Hasher(name string) (hash.Hash, error) {
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switch name {
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case "sha256":
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return crypto.SHA256.New(), nil
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default:
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return nil, fmt.Errorf("unsupported hash: %q", name)
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}
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}
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func SHA256(r io.Reader) (Hash, int64, error) {
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hasher := crypto.SHA256.New()
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n, err := io.Copy(hasher, r)
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if err != nil {
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return Hash{}, 0, err
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}
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return Hash{
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Algorithm: "sha256",
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Hex: hex.EncodeToString(hasher.Sum(make([]byte, 0, hasher.Size()))),
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}, n, nil
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}
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