forked from TrueCloudLab/distribution
70 lines
2 KiB
Go
70 lines
2 KiB
Go
package digest
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import (
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"fmt"
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"regexp"
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)
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// TarsumRegexp defines a regular expression to match tarsum identifiers.
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var TarsumRegexp = regexp.MustCompile("tarsum(?:.[a-z0-9]+)?\\+[a-zA-Z0-9]+:[A-Fa-f0-9]+")
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// TarsumRegexpCapturing defines a regular expression to match tarsum identifiers with
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// capture groups corresponding to each component.
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var TarsumRegexpCapturing = regexp.MustCompile("(tarsum)(.([a-z0-9]+))?\\+([a-zA-Z0-9]+):([A-Fa-f0-9]+)")
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// TarSumInfo contains information about a parsed tarsum.
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type TarSumInfo struct {
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// Version contains the version of the tarsum.
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Version string
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// Algorithm contains the algorithm for the final digest
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Algorithm string
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// Digest contains the hex-encoded digest.
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Digest string
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}
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// InvalidTarSumError provides informations about a TarSum that cannot be parsed
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// by ParseTarSum.
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type InvalidTarSumError string
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func (e InvalidTarSumError) Error() string {
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return fmt.Sprintf("invalid tarsum: %q", string(e))
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}
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// ParseTarSum parses a tarsum string into its components of interest. For
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// example, this method may receive the tarsum in the following format:
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//
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// tarsum.v1+sha256:220a60ecd4a3c32c282622a625a54db9ba0ff55b5ba9c29c7064a2bc358b6a3e
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//
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// The function will return the following:
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//
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// TarSumInfo{
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// Version: "v1",
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// Algorithm: "sha256",
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// Digest: "220a60ecd4a3c32c282622a625a54db9ba0ff55b5ba9c29c7064a2bc358b6a3e",
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// }
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//
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func ParseTarSum(tarSum string) (tsi TarSumInfo, err error) {
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components := TarsumRegexpCapturing.FindStringSubmatch(tarSum)
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if len(components) != 1+TarsumRegexpCapturing.NumSubexp() {
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return TarSumInfo{}, InvalidTarSumError(tarSum)
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}
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return TarSumInfo{
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Version: components[3],
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Algorithm: components[4],
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Digest: components[5],
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}, nil
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}
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// String returns the valid, string representation of the tarsum info.
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func (tsi TarSumInfo) String() string {
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if tsi.Version == "" {
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return fmt.Sprintf("tarsum+%s:%s", tsi.Algorithm, tsi.Digest)
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}
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return fmt.Sprintf("tarsum.%s+%s:%s", tsi.Version, tsi.Algorithm, tsi.Digest)
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}
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