1 files changed, 46 insertions, 0 deletions
diff --git a/format/packfile/ingest/record_inflate.go b/format/packfile/ingest/record_inflate.go
new file mode 100644
index 00000000..b8eca25b
--- /dev/null
+++ b/format/packfile/ingest/record_inflate.go
@@ -0,0 +1,46 @@
+package ingest
+
+import (
+	"compress/zlib"
+	"fmt"
+	"io"
+
+	"codeberg.org/lindenii/furgit/internal/intconv"
+)
+
+// inflateRecordPayload inflates one record's zlib payload from pack file.
+func inflateRecordPayload(state *ingestState, idx int) ([]byte, error) {
+	record := state.records[idx]
+	if record.packedLen < uint64(record.headerLen) {
+		return nil, &MalformedPackEntryError{Offset: record.offset, Reason: "entry packed span underflow"}
+	}
+
+	compressedOffset := record.offset + uint64(record.headerLen)
+	compressedLen := record.packedLen - uint64(record.headerLen)
+
+	compressedOffsetInt64, err := intconv.Uint64ToInt64(compressedOffset)
+	if err != nil {
+		return nil, err
+	}
+
+	compressedLenInt64, err := intconv.Uint64ToInt64(compressedLen)
+	if err != nil {
+		return nil, err
+	}
+
+	section := io.NewSectionReader(state.packFile, compressedOffsetInt64, compressedLenInt64)
+
+	reader, err := zlib.NewReader(section)
+	if err != nil {
+		return nil, &MalformedPackEntryError{Offset: record.offset, Reason: fmt.Sprintf("open payload zlib: %v", err)}
+	}
+
+	defer func() { _ = reader.Close() }()
+
+	out, err := io.ReadAll(reader)
+	if err != nil {
+		return nil, &MalformedPackEntryError{Offset: record.offset, Reason: fmt.Sprintf("inflate payload: %v", err)}
+	}
+
+	return out, nil
+}