// Copyright 2021 The Gitea Authors. All rights reserved. // SPDX-License-Identifier: MIT package lfs import ( "crypto/sha256" "encoding/hex" "errors" "fmt" "io" "path" "regexp" "strconv" "strings" ) 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 }