GoSBHPF/SBHPFv1/deserializer.go

package sbhpfv1

import (
	"encoding/binary"
	"errors"
	"io"
)

// Deserialize reads a full binary property file to a usable root node object.
// This includes verifying the start headers to ensure compatibility.
func Deserialize(r io.Reader) (*Node, error) {
	// Read file header (version + feature flag).
	var version, featureFlag uint8
	if err := binary.Read(r, binary.LittleEndian, &version); err != nil {
		return nil, err
	}
	if err := binary.Read(r, binary.LittleEndian, &featureFlag); err != nil {
		return nil, err
	}

	// Validate version.
	if version != FormatVersion {
		return nil, errors.New("unsupported format version")
	}

	// Read root node.
	return DeserializeNode(r)
}

// DeserializeNode deserializes a SBHPF node into a usable node object.
func DeserializeNode(r io.Reader) (*Node, error) {
	// Read node size ("Node Size" node header).
	// TODO: Node size header could possibly be removed entirely in version 2,
	// since properties terminate themselves and the node header already contains
	// info about amount of properties on the node. This would save 16 bytes per node.
	// The size header could potentially contribute to more efficient search algos though.
	var size uint32 // uint32 to align with 4 byte constraint.
	if err := binary.Read(r, binary.LittleEndian, &size); err != nil {
		return nil, err
	}

	// Read property count ("Property Count" node header).
	var propCount uint16 // uint16 to align with 2 byte constraint.
	if err := binary.Read(r, binary.LittleEndian, &propCount); err != nil {
		return nil, err
	}

	// Read child count ("Child Count" node header).
	var childCount uint16
	if err := binary.Read(r, binary.LittleEndian, &childCount); err != nil {
		return nil, err
	}

	// Read node name length ("Name Length" node header).
	var nameLen uint8 // uint8 to align with 1 byte constraint.
	if err := binary.Read(r, binary.LittleEndian, &nameLen); err != nil {
		return nil, err
	}

	// Read node name component.
	nameBytes := make([]byte, nameLen)
	if _, err := io.ReadFull(r, nameBytes); err != nil {
		return nil, err
	}

	// Read properties.
	props := make([]Property, propCount)
	for i := uint16(0); i < propCount; i++ { // uint16 to align with 2 byte constraint of "Property Count"
		prop, err := DeserializeProperty(r)
		if err != nil {
			return nil, err
		}
		props[i] = prop
	}

	// Read child nodes.
	children := make([]*Node, childCount)
	for i := uint16(0); i < childCount; i++ {
		child, err := DeserializeNode(r)
		if err != nil {
			return nil, err
		}
		children[i] = child
	}

	return &Node{Name: string(nameBytes), Properties: props, Children: children}, nil
}

// DeserializeProperty deserializes a SBHPF property into a usable property object.
func DeserializeProperty(r io.Reader) (Property, error) {
	// Read key length
	var keyLen uint8 // uint8 to align with 1 byte constraint
	if err := binary.Read(r, binary.LittleEndian, &keyLen); err != nil {
		return Property{}, err
	}

	// Read type
	var propType PropertyType // PropertyType (byte, uint8) to align with 1 byte and values constraint
	if err := binary.Read(r, binary.LittleEndian, &propType); err != nil {
		return Property{}, err
	}

	// Read key string
	keyBytes := make([]byte, keyLen)
	if _, err := io.ReadFull(r, keyBytes); err != nil {
		return Property{}, err
	}

	// Read value
	var value interface{}
	switch PropertyType(propType) {
	case TypeString:
		var strLen uint16 // uint16 to align with 2 byte length-prefix constraint
		if err := binary.Read(r, binary.LittleEndian, &strLen); err != nil {
			return Property{}, err
		}
		strBytes := make([]byte, strLen)
		if _, err := io.ReadFull(r, strBytes); err != nil {
			return Property{}, err
		}
		value = string(strBytes)
	case TypeBool:
		var val uint8 // uint8 to align with 1 byte constraint
		if err := binary.Read(r, binary.LittleEndian, &val); err != nil {
			return Property{}, err
		}
		value = (val == 1)
	case TypeUint16:
		var val uint16
		if err := binary.Read(r, binary.LittleEndian, &val); err != nil {
			return Property{}, err
		}
		value = val
	case TypeUint32:
		var val uint32
		if err := binary.Read(r, binary.LittleEndian, &val); err != nil {
			return Property{}, err
		}
		value = val
	case TypeUint8:
		var val uint8
		if err := binary.Read(r, binary.LittleEndian, &val); err != nil {
			return Property{}, err
		}
		value = val
	case TypeInt16:
		var val int16
		if err := binary.Read(r, binary.LittleEndian, &val); err != nil {
			return Property{}, err
		}
		value = val
	case TypeInt32:
		var val int32
		if err := binary.Read(r, binary.LittleEndian, &val); err != nil {
			return Property{}, err
		}
		value = val
	case TypeInt8:
		var val int8
		if err := binary.Read(r, binary.LittleEndian, &val); err != nil {
			return Property{}, err
		}
		value = val
	case TypeFloat32:
		var val float32
		if err := binary.Read(r, binary.LittleEndian, &val); err != nil {
			return Property{}, err
		}
		value = val
	case TypeFloat64:
		var val float64
		if err := binary.Read(r, binary.LittleEndian, &val); err != nil {
			return Property{}, err
		}
		value = val
	}

	return Property{
		Key:   string(keyBytes),
		Type:  propType,
		Value: value,
	}, nil
}