1 files changed, 64 insertions, 0 deletions
diff --git a/object/store/packed/internal/reading/entry_inflate.go b/object/store/packed/internal/reading/entry_inflate.go
new file mode 100644
index 00000000..82b2a7a8
--- /dev/null
+++ b/object/store/packed/internal/reading/entry_inflate.go
@@ -0,0 +1,64 @@
+package reading
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"math"
+
+	"codeberg.org/lindenii/furgit/internal/compress/zlib"
+	"codeberg.org/lindenii/furgit/internal/iolimit"
+)
+
+// zlibReaderAt opens a zlib reader starting at data offset within pack.
+func zlibReaderAt(pack *packFile, offset int) (io.ReadCloser, error) {
+	if offset < 0 || offset > len(pack.data) {
+		return nil, fmt.Errorf("objectstore/packed: pack %q zlib offset out of bounds", pack.name)
+	}
+
+	return zlib.NewReader(bytes.NewReader(pack.data[offset:]))
+}
+
+// inflateAt inflates one entry payload from data offset.
+func inflateAt(pack *packFile, offset int, expectedSize int64) ([]byte, error) {
+	reader, err := zlibReaderAt(pack, offset)
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() { _ = reader.Close() }()
+
+	if expectedSize >= 0 {
+		if expectedSize > int64(math.MaxInt) {
+			return nil, fmt.Errorf(
+				"objectstore/packed: pack %q expected inflated size overflows int: %d",
+				pack.name,
+				expectedSize,
+			)
+		}
+
+		reader := iolimit.ExpectLengthReader(reader, expectedSize)
+		body := make([]byte, int(expectedSize))
+
+		_, err := io.ReadFull(reader, body)
+		if err != nil {
+			return nil, err
+		}
+
+		var probe [1]byte
+
+		_, err = reader.Read(probe[:])
+		if err != nil && err != io.EOF {
+			return nil, err
+		}
+
+		return body, nil
+	}
+
+	body, err := io.ReadAll(reader)
+	if err != nil {
+		return nil, err
+	}
+
+	return body, nil
+}