decode.go

/*
 * Atree - Scalable Arrays and Ordered Maps
 *
 * Copyright Flow Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package atree

import "github.com/fxamacker/cbor/v2"

type StorableDecoder func(
	decoder *cbor.StreamDecoder,
	storableSlabID SlabID,
	inlinedExtraData []ExtraData,
) (
	Storable,
	error,
)

func DecodeSlab(
	id SlabID,
	data []byte,
	decMode cbor.DecMode,
	decodeStorable StorableDecoder,
	decodeTypeInfo TypeInfoDecoder,
) (
	Slab,
	error,
) {
	if len(data) < versionAndFlagSize {
		return nil, NewDecodingErrorf("data is too short")
	}

	h, err := newHeadFromData(data[:versionAndFlagSize])
	if err != nil {
		return nil, NewDecodingError(err)
	}

	switch h.getSlabType() {

	case slabArray:

		arrayDataType := h.getSlabArrayType()

		switch arrayDataType {
		case slabArrayData:
			return newArrayDataSlabFromData(id, data, decMode, decodeStorable, decodeTypeInfo)
		case slabArrayMeta:
			return newArrayMetaDataSlabFromData(id, data, decMode, decodeTypeInfo)
		default:
			return nil, NewDecodingErrorf("data has invalid head 0x%x", h[:])
		}

	case slabMap:

		mapDataType := h.getSlabMapType()

		switch mapDataType {
		case slabMapData:
			return newMapDataSlabFromData(id, data, decMode, decodeStorable, decodeTypeInfo)
		case slabMapMeta:
			return newMapMetaDataSlabFromData(id, data, decMode, decodeTypeInfo)
		case slabMapCollisionGroup:
			return newMapDataSlabFromData(id, data, decMode, decodeStorable, decodeTypeInfo)
		default:
			return nil, NewDecodingErrorf("data has invalid head 0x%x", h[:])
		}

	case slabStorable:
		cborDec := decMode.NewByteStreamDecoder(data[versionAndFlagSize:])
		storable, err := decodeStorable(cborDec, id, nil)
		if err != nil {
			// Wrap err as external error (if needed) because err is returned by StorableDecoder callback.
			return nil, wrapErrorfAsExternalErrorIfNeeded(err, "failed to decode slab storable")
		}
		return &StorableSlab{
			slabID:   id,
			storable: storable,
		}, nil

	default:
		return nil, NewDecodingErrorf("data has invalid head 0x%x", h[:])
	}
}