Unmarshal() (type)

Converts a structured file format into structured memory

Description

This is a function you would write when programming a Murex data-type. The unmarshal function takes in a byte slice and returns a Go (golang) type or struct or an error.

This unmarshaller is then registered to Murex inside an init() function and Murex builtins can use that unmarshaller via the UnmarshalData() API.

Usage

Registering Unmarshal() (for writing builtin data-types)

// To avoid data races, this should only happen inside func init()
lang.Unmarshallers[ /* your type name */ ] = /* your readIndex func */

Using an existing unmarshaller (eg inside a builtin command)

// See documentation on lang.UnmarshalData for more details
v, err := lang.UnmarshalData(p *lang.Process, dataType string)

Examples

Defining a marshaller for a murex data-type

package example

import (
	"encoding/json"

	"github.com/lmorg/murex/lang"
)

func init() {
	// Register data-type
	lang.Unmarshallers["example"] = unmarshal
}

// Describe unmarshaller
func unmarshal(p *lang.Process) (interface{}, error) {
	// Read data from STDIN. Because JSON expects closing tokens, we should
	// read the entire stream before unmarshalling it. For formats like CSV or
	// jsonlines which are more line based, we might want to read STDIN line by
	// line. However given there is just one data return, you still effectively
	// head to read the entire file before returning the structure. There are
	// other APIs for iterative returns for streaming data - more akin to the
	// traditional way UNIX pipes would work.
	b, err := p.Stdin.ReadAll()
	if err != nil {
		return nil, err
	}

	var v interface{}
	err = json.Unmarshal(b, &v)

	// Return the Go data structure or error
	return v, err
}

Parameters

1. *lang.Process: Process's runtime state. Typically expressed as the variable p

See Also

• apis/Marshal() (type): Converts structured memory into a structured file format (eg for stdio)
• apis/lang.MarshalData() (system API): Converts structured memory into a Murex data-type (eg for stdio)
• apis/lang.UnmarshalData() (system API): Converts a Murex data-type into structured memory

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This document was generated from lang/define_unmarshal_doc.yaml.