hdr := r.opts.HeaderSize // remaining header bytes
	var tokens int           // number of tokens to request

	if hdr > 0 { // available tokens go towards header first
		if hdr < b { // all of header can be accommodated
			r.opts.HeaderSize = 0
			need = int(math.Min(float64(b-hdr), float64(need))) // use remaining tokens towards payload
			tokens = need + hdr

		} else { // part of header can be accommodated
			r.opts.HeaderSize -= b - 1

	ErrHeader = errors.New("zlib: invalid header")
)

type reader struct {
	r            flate.Reader
	decompressor io.ReadCloser
	digest       hash.Hash32
	err          error
	scratch      [4]byte
}

// Resetter resets a ReadCloser returned by [NewReader] or [NewReaderDict]
// to switch to a new underlying Reader. This permits reusing a ReadCloser

)

// A Reader wraps an io.Reader and computes the MD5 checksum
// of the read content as ETag. Optionally, it also computes
// the SHA256 checksum of the content.
//
// If the reference values for the ETag and content SHA26
// are not empty then it will check whether the computed
// match the reference values.
type Reader struct {
	src         io.Reader
	bytesRead   int64
	expectedMin int64

}

// NewReader creates a new trace reader.
func NewReader(r io.Reader) (*Reader, error) {
	br := bufio.NewReader(r)
	v, err := version.ReadHeader(br)
	if err != nil {
		return nil, err
	}
	switch v {
	case version.Go111, version.Go119, version.Go121:
		tr, err := oldtrace.Parse(br, v)
		if err != nil {
			return nil, err
		}
		return &Reader{
			go121Events: convertOldFormat(tr),
		}, nil

	errTooMuch   = errors.New("gif: too much image data")
	errBadPixel  = errors.New("gif: invalid pixel value")
)

// If the io.Reader does not also have ReadByte, then decode will introduce its own buffering.
type reader interface {
	io.Reader
	io.ByteReader
}

// Masks etc.
const (
	// Fields.
	fColorTable         = 1 << 7
	fInterlace          = 1 << 6
	fColorTableBitsMask = 7

package strings

import (
	"errors"
	"io"
	"unicode/utf8"
)

// A Reader implements the [io.Reader], [io.ReaderAt], [io.ByteReader], [io.ByteScanner],
// [io.RuneReader], [io.RuneScanner], [io.Seeker], and [io.WriterTo] interfaces by reading
// from a string.
// The zero value for Reader operates like a Reader of an empty string.
type Reader struct {
	s        string
	i        int64 // current reading index

//
//	// Now, we need an io.Reader that can access
//	// the ETag computed over the content.
//	reader := etag.Wrap(encryptedContent, content)
func Wrap(wrapped, content io.Reader) io.Reader {
	if t, ok := content.(Tagger); ok {
		return wrapReader{
			Reader: wrapped,
			Tagger: t,
		}
	}
	return wrapReader{
		Reader: wrapped,
	}
}

// A Reader wraps an io.Reader and computes the

	"strconv"
	"strings"
	"time"
)

// Reader provides sequential access to the contents of a tar archive.
// Reader.Next advances to the next file in the archive (including the first),
// and then Reader can be treated as an io.Reader to access the file's data.
type Reader struct {
	r    io.Reader
	pad  int64      // Amount of padding (ignored) after current file entry
	curr fileReader // Reader for current file entry

func HalfReader(r io.Reader) io.Reader { return &halfReader{r} }

type halfReader struct {
	r io.Reader
}

func (r *halfReader) Read(p []byte) (int, error) {
	return r.r.Read(p[0 : (len(p)+1)/2])
}

// DataErrReader changes the way errors are handled by a Reader. Normally, a
// Reader returns an error (typically EOF) from the first Read call after the
// last piece of data is read. DataErrReader wraps a Reader and changes its

var SSECopy = ssecCopy{}

type ssecCopy struct{}

// IsRequested returns true if the HTTP headers contains
// at least one SSE-C copy header. Regular SSE-C headers
// are ignored.
func (ssecCopy) IsRequested(h http.Header) bool {
	if _, ok := h[xhttp.AmzServerSideEncryptionCopyCustomerAlgorithm]; ok {
		return true
	}
	if _, ok := h[xhttp.AmzServerSideEncryptionCopyCustomerKey]; ok {
		return true