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utilities.go
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/
utilities.go
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package files
import (
"bufio"
"context"
"encoding/base64"
"fmt"
"io"
"github.com/xuxiaoshuo/databricks-sdk-go/apierr"
"github.com/xuxiaoshuo/databricks-sdk-go/useragent"
)
// FileMode conveys user intent when opening a file.
type FileMode int
const (
// Exactly one of FileModeRead or FileModeWrite must be specified.
FileModeRead FileMode = 1 << iota
FileModeWrite
FileModeOverwrite
)
// Maximum read or write length for the DBFS API.
const maxDbfsBlockSize = 1024 * 1024
// Internal only state for a read handle.
type fileHandleReader struct {
size int64
offset int64
}
func (f *fileHandleReader) errorf(format string, a ...any) error {
return fmt.Errorf("dbfs read: "+format, a...)
}
func (f *fileHandleReader) error(err error) error {
if err == nil {
return nil
}
return f.errorf("%w", err)
}
// Internal only state for a write handle.
type fileHandleWriter struct {
handle int64
}
func (f *fileHandleWriter) errorf(format string, a ...any) error {
return fmt.Errorf("dbfs write: "+format, a...)
}
func (f *fileHandleWriter) error(err error) error {
if err == nil {
return nil
}
return f.errorf("%w", err)
}
// Internal only state for a DBFS file handle.
type fileHandle struct {
ctx context.Context
api *DbfsAPI
path string
reader *fileHandleReader
writer *fileHandleWriter
}
func (h *fileHandle) checkRead() (*fileHandleReader, error) {
if h.reader != nil {
return h.reader, nil
}
return nil, fmt.Errorf("dbfs: file not open for reading")
}
func (h *fileHandle) checkWrite() (*fileHandleWriter, error) {
if h.writer != nil {
return h.writer, nil
}
return nil, fmt.Errorf("dbfs: file not open for writing")
}
// Handle defines the interface of the object returned by [DbfsAPI.Open].
type Handle interface {
io.ReadWriteCloser
io.WriterTo
io.ReaderFrom
}
// Implement the [io.Reader] interface.
func (h *fileHandle) Read(p []byte) (int, error) {
r, err := h.checkRead()
if err != nil {
return 0, err
}
var ntotal int
for ntotal < len(p) {
if r.offset >= r.size {
return ntotal, io.EOF
}
chunk := p[ntotal:]
if len(chunk) > maxDbfsBlockSize {
chunk = chunk[:maxDbfsBlockSize]
}
res, err := h.api.Read(h.ctx, ReadDbfsRequest{
Path: h.path,
Length: len(chunk),
Offset: int(r.offset), // TODO: make int32/in64 work properly
})
if err != nil {
return ntotal, r.error(err)
}
// The guard against offset >= size happens above, so this can only happen
// if the file is modified or truncated while reading. If this happens,
// the read contents will likely be corrupted, so we return an error.
if res.BytesRead == 0 {
return ntotal, r.errorf("unexpected EOF at offset %d (size %d)", r.offset, r.size)
}
nread, err := base64.StdEncoding.Decode(chunk, []byte(res.Data))
if err != nil {
return ntotal, r.error(err)
}
ntotal += nread
r.offset += int64(nread)
}
return ntotal, nil
}
// Implement the [io.Writer] interface.
func (h *fileHandle) Write(p []byte) (int, error) {
w, err := h.checkWrite()
if err != nil {
return 0, err
}
var ntotal int
for ntotal < len(p) {
chunk := p[ntotal:]
if len(chunk) > maxDbfsBlockSize {
chunk = chunk[:maxDbfsBlockSize]
}
err := h.api.AddBlock(h.ctx, AddBlock{
Data: base64.StdEncoding.EncodeToString(chunk),
Handle: w.handle,
})
if err != nil {
return ntotal, w.error(err)
}
ntotal += len(chunk)
}
return ntotal, nil
}
// Implement the [io.Closer] interface.
func (h *fileHandle) Close() error {
w, err := h.checkWrite()
if err != nil {
return err
}
return w.error(h.api.CloseByHandle(h.ctx, w.handle))
}
// Implement the [io.WriterTo] interface.
func (h *fileHandle) WriteTo(w io.Writer) (int64, error) {
_, err := h.checkRead()
if err != nil {
return 0, err
}
// Limit types to io.Reader and io.Writer to avoid recursion
// into WriteTo or ReadFrom functions on underlying types.
ior := struct{ io.Reader }{h}
iow := struct{ io.Writer }{w}
return bufio.NewReaderSize(ior, maxDbfsBlockSize).WriteTo(iow)
}
// Implement the [io.ReaderFrom] interface.
func (h *fileHandle) ReadFrom(r io.Reader) (int64, error) {
_, err := h.checkWrite()
if err != nil {
return 0, err
}
// Limit types to io.Reader and io.Writer to avoid recursion
// into WriteTo or ReadFrom functions on underlying types.
ior := struct{ io.Reader }{r}
iow := struct{ io.Writer }{h}
bw := bufio.NewWriterSize(iow, maxDbfsBlockSize)
n, err := bw.ReadFrom(ior)
if err != nil {
return n, err
}
return n, bw.Flush()
}
func (h *fileHandle) openForRead(mode FileMode) error {
res, err := h.api.GetStatusByPath(h.ctx, h.path)
if err != nil {
return err
}
if res.IsDir {
return fmt.Errorf("cannot open directory for reading")
}
h.reader = &fileHandleReader{
size: res.FileSize,
}
return nil
}
func (h *fileHandle) openForWrite(mode FileMode) error {
res, err := h.api.Create(h.ctx, Create{
Path: h.path,
Overwrite: (mode & FileModeOverwrite) != 0,
})
if err != nil {
return err
}
h.writer = &fileHandleWriter{
handle: res.Handle,
}
return nil
}
// Open opens a remote DBFS file for reading or writing.
// The returned object implements relevant [io] interfaces for convenient
// integration with other code that reads or writes bytes.
//
// The [io.WriterTo] interface is provided and maximizes throughput for
// bulk reads by reading data with the DBFS maximum read chunk size of 1MB.
// Similarly, the [io.ReaderFrom] interface is provided for bulk writing.
//
// A file opened for writing must always be closed.
func (a *DbfsAPI) Open(ctx context.Context, path string, mode FileMode) (Handle, error) {
h := &fileHandle{
ctx: useragent.InContext(ctx, "sdk-feature", "dbfs-handle"),
api: a,
path: path,
}
isRead := (mode & FileModeRead) != 0
isWrite := (mode & FileModeWrite) != 0
if (isRead && isWrite) || (!isRead && !isWrite) {
return nil, fmt.Errorf("dbfs open: must specify files.FileModeRead or files.FileModeWrite")
}
var err error
if isRead {
err = h.openForRead(mode)
}
if isWrite {
err = h.openForWrite(mode)
}
if err != nil {
return nil, fmt.Errorf("dbfs open: %w", err)
}
return h, nil
}
// ReadFile is identical to [os.ReadFile] but for DBFS.
func (a *DbfsAPI) ReadFile(ctx context.Context, name string) ([]byte, error) {
h, err := a.Open(ctx, name, FileModeRead)
if err != nil {
return nil, err
}
h_ := h.(*fileHandle)
buf := make([]byte, h_.reader.size)
_, err = h.Read(buf)
if err != nil && err != io.EOF {
return nil, err
}
return buf, nil
}
// WriteFile is identical to [os.WriteFile] but for DBFS.
func (a *DbfsAPI) WriteFile(ctx context.Context, name string, data []byte) error {
h, err := a.Open(ctx, name, FileModeWrite|FileModeOverwrite)
if err != nil {
return err
}
_, err = h.Write(data)
cerr := h.Close()
if err == nil && cerr != nil {
err = cerr
}
return err
}
// RecursiveList traverses the DBFS tree and returns all non-directory
// objects under the path
func (a DbfsAPI) RecursiveList(ctx context.Context, path string) ([]FileInfo, error) {
ctx = useragent.InContext(ctx, "sdk-feature", "recursive-list")
var results []FileInfo
queue := []string{path}
for len(queue) > 0 {
path := queue[0]
queue = queue[1:]
batch, err := a.ListAll(ctx, ListDbfsRequest{
Path: path,
})
if apierr.IsMissing(err) {
// skip on path deleted during iteration
continue
}
if err != nil {
return nil, fmt.Errorf("list %s: %w", path, err)
}
for _, v := range batch {
if v.IsDir {
queue = append(queue, v.Path)
continue
}
results = append(results, v)
}
}
return results, nil
}