1 files changed, 113 insertions, 0 deletions
diff --git a/ref/store/files/packed_parse.go b/ref/store/files/packed_parse.go
new file mode 100644
index 00000000..3662f6ed
--- /dev/null
+++ b/ref/store/files/packed_parse.go
@@ -0,0 +1,113 @@
+package files
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strings"
+
+	objectid "codeberg.org/lindenii/furgit/object/id"
+	"codeberg.org/lindenii/furgit/ref"
+)
+
+func parsePackedRefs(r io.Reader, algo objectid.Algorithm) (map[string]ref.Detached, []ref.Detached, error) {
+	byName := make(map[string]ref.Detached)
+	ordered := make([]ref.Detached, 0, 32)
+
+	br := bufio.NewReader(r)
+	prev := -1
+	lineNum := 0
+	hexsz := algo.Size() * 2
+
+	for {
+		line, err := br.ReadString('\n')
+		if err != nil && err != io.EOF {
+			return nil, nil, err
+		}
+
+		if line == "" && err == io.EOF {
+			break
+		}
+
+		lineNum++
+		hadNewline := strings.HasSuffix(line, "\n")
+		line = strings.TrimSuffix(line, "\n")
+
+		if err == io.EOF && !hadNewline {
+			return nil, nil, fmt.Errorf("refstore/files: line %d: unterminated line", lineNum)
+		}
+
+		if line == "" || strings.HasPrefix(line, "#") {
+			if err == io.EOF {
+				break
+			}
+
+			continue
+		}
+
+		if strings.HasPrefix(line, "^") {
+			if prev < 0 {
+				return nil, nil, fmt.Errorf("refstore/files: line %d: peeled line without preceding ref", lineNum)
+			}
+
+			if len(line) != hexsz+1 {
+				return nil, nil, fmt.Errorf("refstore/files: line %d: malformed peeled line", lineNum)
+			}
+
+			peeled, parseErr := objectid.ParseHex(algo, line[1:])
+			if parseErr != nil {
+				return nil, nil, fmt.Errorf("refstore/files: line %d: invalid peeled oid: %w", lineNum, parseErr)
+			}
+
+			peeledCopy := peeled
+			cur := ordered[prev]
+			cur.Peeled = &peeledCopy
+			ordered[prev] = cur
+			byName[cur.Name()] = cur
+
+			if err == io.EOF {
+				break
+			}
+
+			continue
+		}
+
+		if len(line) < hexsz+2 {
+			return nil, nil, fmt.Errorf("refstore/files: line %d: malformed entry", lineNum)
+		}
+
+		if line[hexsz] != ' ' {
+			return nil, nil, fmt.Errorf("refstore/files: line %d: malformed entry", lineNum)
+		}
+
+		idText := line[:hexsz]
+
+		name := line[hexsz+1:]
+		if name == "" {
+			return nil, nil, fmt.Errorf("refstore/files: line %d: empty ref name", lineNum)
+		}
+
+		id, parseErr := objectid.ParseHex(algo, idText)
+		if parseErr != nil {
+			return nil, nil, fmt.Errorf("refstore/files: line %d: invalid oid: %w", lineNum, parseErr)
+		}
+
+		if _, exists := byName[name]; exists {
+			return nil, nil, fmt.Errorf("refstore/files: line %d: duplicate ref %q", lineNum, name)
+		}
+
+		detached := ref.Detached{
+			RefName: name,
+			ID:      id,
+		}
+		ordered = append(ordered, detached)
+		prev = len(ordered) - 1
+		byName[name] = detached
+
+		if err == io.EOF {
+			break
+		}
+	}
+
+	return byName, ordered, nil
+}