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package asm
import (
"bytes"
"fmt"
"io"
"github.com/vbatts/tar-split/archive/tar"
"github.com/vbatts/tar-split/tar/storage"
)
// IterateHeaders calls handler for each tar header provided by Unpacker
func IterateHeaders(unpacker storage.Unpacker, handler func(hdr *tar.Header) error) error {
// We assume about NewInputTarStream:
// - There is a separate SegmentType entry for every tar header, but only one SegmentType entry for the full header incl. any extensions
// - (There is a FileType entry for every tar header, we ignore it)
// - Trailing padding of a file, if any, is included in the next SegmentType entry
// - At the end, there may be SegmentType entries just for the terminating zero blocks.
var pendingPadding int64 = 0
for {
tsEntry, err := unpacker.Next()
if err != nil {
if err == io.EOF {
return nil
}
return fmt.Errorf("reading tar-split entries: %w", err)
}
switch tsEntry.Type {
case storage.SegmentType:
payload := tsEntry.Payload
if int64(len(payload)) < pendingPadding {
return fmt.Errorf("expected %d bytes of padding after previous file, but next SegmentType only has %d bytes", pendingPadding, len(payload))
}
payload = payload[pendingPadding:]
pendingPadding = 0
tr := tar.NewReader(bytes.NewReader(payload))
hdr, err := tr.Next()
if err != nil {
if err == io.EOF { // Probably the last entry, but let’s let the unpacker drive that.
break
}
return fmt.Errorf("decoding a tar header from a tar-split entry: %w", err)
}
if err := handler(hdr); err != nil {
return err
}
pendingPadding = tr.ExpectedPadding()
case storage.FileType:
// Nothing
default:
return fmt.Errorf("unexpected tar-split entry type %q", tsEntry.Type)
}
}
}
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