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forked from charmbracelet/soft-serve
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import ( "crypto/sha256" "encoding/hex" "errors" "fmt" "io" "path" "regexp" "strconv" "strings")
const ( blobSizeCutoff = 1024
// HashAlgorithmSHA256 is the hash algorithm used for Git LFS. HashAlgorithmSHA256 = "sha256"
// 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 " + HashAlgorithmSHA256 + ":")
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 readerfunc 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}
// String returns the string representation of the pointer// https://github.com/git-lfs/git-lfs/blob/main/docs/spec.md#the-pointerfunc (p Pointer) String() 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// https://github.com/git-lfs/git-lfs/blob/main/docs/spec.md#intercepting-gitfunc (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)}
// GeneratePointer generates a pointer for arbitrary contentfunc 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}