zeroshade commented on code in PR #216:
URL: https://github.com/apache/arrow-go/pull/216#discussion_r1887304246
##########
arrow/ipc/file_reader.go:
##########
@@ -33,16 +33,166 @@ import (
"github.com/apache/arrow-go/v18/arrow/memory"
)
-// FileReader is an Arrow file reader.
-type FileReader struct {
+type readerImpl interface {
+ getFooterEnd() (int64, error)
+ readFooter(*footerBlock) error
+ dict(memory.Allocator, *footerBlock, int) (dataBlock, error)
+ block(memory.Allocator, *footerBlock, int) (dataBlock, error)
+}
+
+type footerBlock struct {
+ offset int64
+ buffer *memory.Buffer
+ data *flatbuf.Footer
+}
+
+type dataBlock interface {
+ Offset() int64
+ Meta() int32
+ Body() int64
+ NewMessage() (*Message, error)
+}
+
+type basicReaderImpl struct {
r ReadAtSeeker
+}
- footer struct {
- offset int64
- buffer *memory.Buffer
- data *flatbuf.Footer
+func (r *basicReaderImpl) getFooterEnd() (int64, error) {
+ return r.r.Seek(0, io.SeekEnd)
+}
+
+func (r *basicReaderImpl) readFooter(f *footerBlock) error {
+ var err error
+
+ if f.offset <= int64(len(Magic)*2+4) {
+ return fmt.Errorf("arrow/ipc: file too small (size=%d)",
f.offset)
+ }
+
+ eof := int64(len(Magic) + 4)
+ buf := make([]byte, eof)
+ n, err := r.r.ReadAt(buf, f.offset-eof)
+ if err != nil {
+ return fmt.Errorf("arrow/ipc: could not read footer: %w", err)
+ }
+ if n != len(buf) {
+ return fmt.Errorf("arrow/ipc: could not read %d bytes from end
of file", len(buf))
+ }
+
+ if !bytes.Equal(buf[4:], Magic) {
+ return errNotArrowFile
+ }
+
+ size := int64(binary.LittleEndian.Uint32(buf[:4]))
Review Comment:
@lidavidm is correct, only the unsigned versions are available and you are
expected to convert to signed integer yourself if you need.
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