From 3e884f5f3d42cbc4874a04da31dde10314b0cfad Mon Sep 17 00:00:00 2001
From: Runxi Yu
Date: Thu, 26 Mar 2026 09:17:14 +0000
Subject: format: Move commitgraph and packfile here

---
 format/commitgraph/read/position.go | 38 +++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 format/commitgraph/read/position.go

(limited to 'format/commitgraph/read/position.go')

diff --git a/format/commitgraph/read/position.go b/format/commitgraph/read/position.go
new file mode 100644
index 00000000..b2e1138b
--- /dev/null
+++ b/format/commitgraph/read/position.go
@@ -0,0 +1,38 @@
+package read
+
+import (
+	"fmt"
+
+	"codeberg.org/lindenii/furgit/internal/intconv"
+)
+
+// Position identifies one commit record by layer and row index.
+type Position struct {
+	Graph uint32
+	Index uint32
+}
+
+func (reader *Reader) globalToPosition(global uint32) (Position, error) {
+	for i := range reader.layers {
+		layer := &reader.layers[i]
+		from := layer.globalFrom
+
+		to := from + layer.numCommits
+		if global >= from && global < to {
+			graph, err := intconv.IntToUint32(i)
+			if err != nil {
+				return Position{}, err
+			}
+
+			return Position{
+				Graph: graph,
+				Index: global - from,
+			}, nil
+		}
+	}
+
+	return Position{}, &MalformedError{
+		Path:   "commit-graph",
+		Reason: fmt.Sprintf("parent global position out of range: %d", global),
+	}
+}
-- 
cgit v1.3.1-10-gc9f91