package qpack

import (
	
	
	
	

	
)

// A decodingError is something the spec defines as a decoding error.
type decodingError struct {
	err error
}

func ( decodingError) () string {
	return fmt.Sprintf("decoding error: %v", .err)
}

// An invalidIndexError is returned when an encoder references a table
// entry before the static table or after the end of the dynamic table.
type invalidIndexError int

func ( invalidIndexError) () string {
	return fmt.Sprintf("invalid indexed representation index %d", int())
}

var errNoDynamicTable = decodingError{errors.New("no dynamic table")}

// errNeedMore is an internal sentinel error value that means the
// buffer is truncated and we need to read more data before we can
// continue parsing.
var errNeedMore = errors.New("need more data")

// A Decoder is the decoding context for incremental processing of
// header blocks.
type Decoder struct {
	mutex sync.Mutex

	emitFunc func(f HeaderField)

	readRequiredInsertCount bool
	readDeltaBase           bool

	// buf is the unparsed buffer. It's only written to
	// saveBuf if it was truncated in the middle of a header
	// block. Because it's usually not owned, we can only
	// process it under Write.
	buf []byte // not owned; only valid during Write

	// saveBuf is previous data passed to Write which we weren't able
	// to fully parse before. Unlike buf, we own this data.
	saveBuf bytes.Buffer
}

// NewDecoder returns a new decoder
// The emitFunc will be called for each valid field parsed,
// in the same goroutine as calls to Write, before Write returns.
func ( func( HeaderField)) *Decoder {
	return &Decoder{emitFunc: }
}

func ( *Decoder) ( []byte) (int, error) {
	if len() == 0 {
		return 0, nil
	}

	.mutex.Lock()
	,  := .writeLocked()
	.mutex.Unlock()
	return , 
}

func ( *Decoder) ( []byte) (int, error) {
	// Only copy the data if we have to. Optimistically assume
	// that p will contain a complete header block.
	if .saveBuf.Len() == 0 {
		.buf = 
	} else {
		.saveBuf.Write()
		.buf = .saveBuf.Bytes()
		.saveBuf.Reset()
	}

	if  := .decode();  != nil {
		if  != errNeedMore {
			return 0, 
		}
		// TODO: limit the size of the buffer
		.saveBuf.Write(.buf)
	}
	return len(), nil
}

// DecodeFull decodes an entire block.
func ( *Decoder) ( []byte) ([]HeaderField, error) {
	if len() == 0 {
		return []HeaderField{}, nil
	}

	.mutex.Lock()
	defer .mutex.Unlock()

	 := .emitFunc
	defer func() { .emitFunc =  }()

	var  []HeaderField
	.emitFunc = func( HeaderField) {  = append(, ) }
	if ,  := .writeLocked();  != nil {
		return nil, 
	}
	if  := .Close();  != nil {
		return nil, 
	}
	return , nil
}

// Close declares that the decoding is complete and resets the Decoder
// to be reused again for a new header block. If there is any remaining
// data in the decoder's buffer, Close returns an error.
func ( *Decoder) () error {
	if .saveBuf.Len() > 0 {
		.saveBuf.Reset()
		return decodingError{errors.New("truncated headers")}
	}
	.readRequiredInsertCount = false
	.readDeltaBase = false
	return nil
}

func ( *Decoder) () error {
	if !.readRequiredInsertCount {
		, ,  := readVarInt(8, .buf)
		if  != nil {
			return 
		}
		.readRequiredInsertCount = true
		if  != 0 {
			return decodingError{errors.New("expected Required Insert Count to be zero")}
		}
		.buf = 
	}
	if !.readDeltaBase {
		, ,  := readVarInt(7, .buf)
		if  != nil {
			return 
		}
		.readDeltaBase = true
		if  != 0 {
			return decodingError{errors.New("expected Base to be zero")}
		}
		.buf = 
	}
	if len(.buf) == 0 {
		return errNeedMore
	}

	for len(.buf) > 0 {
		 := .buf[0]
		var  error
		switch {
		case &0x80 > 0: // 1xxxxxxx
			 = .parseIndexedHeaderField()
		case &0xc0 == 0x40: // 01xxxxxx
			 = .parseLiteralHeaderField()
		case &0xe0 == 0x20: // 001xxxxx
			 = .parseLiteralHeaderFieldWithoutNameReference()
		default:
			 = fmt.Errorf("unexpected type byte: %#x", )
		}
		if  != nil {
			return 
		}
	}
	return nil
}

func ( *Decoder) () error {
	 := .buf
	if [0]&0x40 == 0 {
		return errNoDynamicTable
	}
	, ,  := readVarInt(6, )
	if  != nil {
		return 
	}
	,  := .at()
	if ! {
		return decodingError{invalidIndexError()}
	}
	.emitFunc()
	.buf = 
	return nil
}

func ( *Decoder) () error {
	 := .buf
	if [0]&0x10 == 0 {
		return errNoDynamicTable
	}
	// We don't need to check the value of the N-bit here.
	// It's only relevant when re-encoding header fields,
	// and determines whether the header field can be added to the dynamic table.
	// Since we don't support the dynamic table, we can ignore it.
	, ,  := readVarInt(4, )
	if  != nil {
		return 
	}
	,  := .at()
	if ! {
		return decodingError{invalidIndexError()}
	}
	if len() == 0 {
		return errNeedMore
	}
	 := [0]&0x80 > 0
	, ,  := .readString(, 7, )
	if  != nil {
		return 
	}
	.Value = 
	.emitFunc()
	.buf = 
	return nil
}

func ( *Decoder) () error {
	 := .buf
	 := [0]&0x8 > 0
	, ,  := .readString(, 3, )
	if  != nil {
		return 
	}
	if len() == 0 {
		return errNeedMore
	}
	 := [0]&0x80 > 0
	, ,  := .readString(, 7, )
	if  != nil {
		return 
	}
	.emitFunc(HeaderField{Name: , Value: })
	.buf = 
	return nil
}

func ( *Decoder) ( []byte,  uint8,  bool) (string, []byte, error) {
	, ,  := readVarInt(, )
	if  != nil {
		return "", nil, 
	}
	if uint64(len()) <  {
		return "", nil, errNeedMore
	}
	var  string
	if  {
		var  error
		,  = hpack.HuffmanDecodeToString([:])
		if  != nil {
			return "", nil, 
		}
	} else {
		 = string([:])
	}
	 = [:]
	return , , nil
}

func ( *Decoder) ( uint64) ( HeaderField,  bool) {
	if  >= uint64(len(staticTableEntries)) {
		return
	}
	return staticTableEntries[], true
}