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forgejo/modules/git/object_format.go

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// Copyright 2023 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package git
import (
"crypto/sha1"
"regexp"
"strconv"
)
// sha1Pattern can be used to determine if a string is an valid sha
var sha1Pattern = regexp.MustCompile(`^[0-9a-f]{4,40}$`)
type ObjectFormat interface {
// Name returns the name of the object format
Name() string
// EmptyObjectID creates a new empty ObjectID from an object format hash name
EmptyObjectID() ObjectID
// EmptyTree is the hash of an empty tree
EmptyTree() ObjectID
// FullLength is the length of the hash's hex string
FullLength() int
// IsValid returns true if the input is a valid hash
IsValid(input string) bool
// MustID creates a new ObjectID from a byte slice
MustID(b []byte) ObjectID
// ComputeHash compute the hash for a given ObjectType and content
ComputeHash(t ObjectType, content []byte) ObjectID
}
type Sha1ObjectFormatImpl struct{}
var (
emptyObjectID = &Sha1Hash{}
emptyTree = &Sha1Hash{
0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60,
0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04,
}
)
func (Sha1ObjectFormatImpl) Name() string { return "sha1" }
func (Sha1ObjectFormatImpl) EmptyObjectID() ObjectID {
return emptyObjectID
}
func (Sha1ObjectFormatImpl) EmptyTree() ObjectID {
return emptyTree
}
func (Sha1ObjectFormatImpl) FullLength() int { return 40 }
func (Sha1ObjectFormatImpl) IsValid(input string) bool {
return sha1Pattern.MatchString(input)
}
func (Sha1ObjectFormatImpl) MustID(b []byte) ObjectID {
var id Sha1Hash
copy(id[0:20], b)
return &id
}
// ComputeHash compute the hash for a given ObjectType and content
func (h Sha1ObjectFormatImpl) ComputeHash(t ObjectType, content []byte) ObjectID {
hasher := sha1.New()
_, _ = hasher.Write(t.Bytes())
_, _ = hasher.Write([]byte(" "))
_, _ = hasher.Write([]byte(strconv.FormatInt(int64(len(content)), 10)))
_, _ = hasher.Write([]byte{0})
// HashSum generates a SHA1 for the provided hash
var sha1 Sha1Hash
copy(sha1[:], hasher.Sum(nil))
return &sha1
}
var Sha1ObjectFormat ObjectFormat = Sha1ObjectFormatImpl{}
var SupportedObjectFormats = []ObjectFormat{
Sha1ObjectFormat,
// TODO: add sha256
}
func ObjectFormatFromName(name string) ObjectFormat {
for _, objectFormat := range SupportedObjectFormats {
if name == objectFormat.Name() {
return objectFormat
}
}
return nil
}
func IsValidObjectFormat(name string) bool {
return ObjectFormatFromName(name) != nil
}