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- // Copyright 2021 The Gitea Authors. All rights reserved.
- // SPDX-License-Identifier: MIT
-
- package lfs
-
- import (
- "encoding/hex"
- "errors"
- "fmt"
- "io"
- "path"
- "regexp"
- "strconv"
- "strings"
-
- "github.com/minio/sha256-simd"
- )
-
- const (
- blobSizeCutoff = 1024
-
- // MetaFileIdentifier is the string appearing at the first line of LFS pointer files.
- // https://github.com/git-lfs/git-lfs/blob/master/docs/spec.md
- MetaFileIdentifier = "version https://git-lfs.github.com/spec/v1"
-
- // MetaFileOidPrefix appears in LFS pointer files on a line before the sha256 hash.
- MetaFileOidPrefix = "oid sha256:"
- )
-
- var (
- // ErrMissingPrefix occurs if the content lacks the LFS prefix
- ErrMissingPrefix = errors.New("content lacks the LFS prefix")
-
- // ErrInvalidStructure occurs if the content has an invalid structure
- ErrInvalidStructure = errors.New("content has an invalid structure")
-
- // ErrInvalidOIDFormat occurs if the oid has an invalid format
- ErrInvalidOIDFormat = errors.New("OID has an invalid format")
- )
-
- // ReadPointer tries to read LFS pointer data from the reader
- func ReadPointer(reader io.Reader) (Pointer, error) {
- buf := make([]byte, blobSizeCutoff)
- n, err := io.ReadFull(reader, buf)
- if err != nil && err != io.ErrUnexpectedEOF {
- return Pointer{}, err
- }
- buf = buf[:n]
-
- return ReadPointerFromBuffer(buf)
- }
-
- var oidPattern = regexp.MustCompile(`^[a-f\d]{64}$`)
-
- // ReadPointerFromBuffer will return a pointer if the provided byte slice is a pointer file or an error otherwise.
- func ReadPointerFromBuffer(buf []byte) (Pointer, error) {
- var p Pointer
-
- headString := string(buf)
- if !strings.HasPrefix(headString, MetaFileIdentifier) {
- return p, ErrMissingPrefix
- }
-
- splitLines := strings.Split(headString, "\n")
- if len(splitLines) < 3 {
- return p, ErrInvalidStructure
- }
-
- oid := strings.TrimPrefix(splitLines[1], MetaFileOidPrefix)
- if len(oid) != 64 || !oidPattern.MatchString(oid) {
- return p, ErrInvalidOIDFormat
- }
- size, err := strconv.ParseInt(strings.TrimPrefix(splitLines[2], "size "), 10, 64)
- if err != nil {
- return p, err
- }
-
- p.Oid = oid
- p.Size = size
-
- return p, nil
- }
-
- // IsValid checks if the pointer has a valid structure.
- // It doesn't check if the pointed-to-content exists.
- func (p Pointer) IsValid() bool {
- if len(p.Oid) != 64 {
- return false
- }
- if !oidPattern.MatchString(p.Oid) {
- return false
- }
- if p.Size < 0 {
- return false
- }
- return true
- }
-
- // StringContent returns the string representation of the pointer
- // https://github.com/git-lfs/git-lfs/blob/main/docs/spec.md#the-pointer
- func (p Pointer) StringContent() string {
- return fmt.Sprintf("%s\n%s%s\nsize %d\n", MetaFileIdentifier, MetaFileOidPrefix, p.Oid, p.Size)
- }
-
- // RelativePath returns the relative storage path of the pointer
- func (p Pointer) RelativePath() string {
- if len(p.Oid) < 5 {
- return p.Oid
- }
-
- return path.Join(p.Oid[0:2], p.Oid[2:4], p.Oid[4:])
- }
-
- func (p Pointer) LogString() string {
- if p.Oid == "" && p.Size == 0 {
- return "<LFSPointer empty>"
- }
- return fmt.Sprintf("<LFSPointer %s:%d>", p.Oid, p.Size)
- }
-
- // GeneratePointer generates a pointer for arbitrary content
- func GeneratePointer(content io.Reader) (Pointer, error) {
- h := sha256.New()
- c, err := io.Copy(h, content)
- if err != nil {
- return Pointer{}, err
- }
- sum := h.Sum(nil)
- return Pointer{Oid: hex.EncodeToString(sum), Size: c}, nil
- }
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