refactor: replace Azure Blob SDK with a REST client (#39315)

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/util/io.go

@@ -17,17 +17,18 @@ func (NopCloser) Close() error { return nil }
 
 // ReadAtMost reads at most len(buf) bytes from r into buf.
 // It returns the number of bytes copied. n is only less than len(buf) if r provides fewer bytes.
-// If EOF or ErrUnexpectedEOF occurs while reading, err will be nil.
+// If EOF occurs while reading, err will be nil.
 func ReadAtMost(r io.Reader, buf []byte) (n int, err error) {
-	n, err = io.ReadFull(r, buf)
-	if err == io.EOF || err == io.ErrUnexpectedEOF {
-		err = nil
+	for n < len(buf) && err == nil {
+		var read int
+		read, err = r.Read(buf[n:])
+		n += read
 	}
-	return n, err
+	return n, Iif(err == io.EOF, nil, err)
 }
 
 // ReadWithLimit reads at most "limit" bytes from r into buf.
-// If EOF or ErrUnexpectedEOF occurs while reading, err will be nil.
+// If EOF occurs while reading, err will be nil.
 func ReadWithLimit(r io.Reader, n int) (buf []byte, err error) {
 	return readWithLimit(r, 4*1024, n)
 }
@@ -49,12 +50,11 @@ func readWithLimit(r io.Reader, batch, limit int) ([]byte, error) {
 		if res.Len()+batch > limit {
 			bufTmp = bufFix[:limit-res.Len()]
 		}
-		n, err := io.ReadFull(r, bufTmp)
-		if err == io.EOF || err == io.ErrUnexpectedEOF {
-			eof = true
-		} else if err != nil {
+		n, err := ReadAtMost(r, bufTmp)
+		if err != nil {
 			return nil, err
 		}
+		eof = n != len(bufTmp)
 		if _, err = res.Write(bufTmp[:n]); err != nil {
 			return nil, err
 		}
@@ -82,24 +82,3 @@ func IsEmptyReader(r io.Reader) (err error) {
 		}
 	}
 }
-
-type CountingReader struct {
-	io.Reader
-	n int
-}
-
-var _ io.Reader = &CountingReader{}
-
-func (w *CountingReader) Count() int {
-	return w.n
-}
-
-func (w *CountingReader) Read(p []byte) (int, error) {
-	n, err := w.Reader.Read(p)
-	w.n += n
-	return n, err
-}
-
-func NewCountingReader(rd io.Reader) *CountingReader {
-	return &CountingReader{Reader: rd}
-}