Encode and Decode Message Length Indicators for TCP/IP socket based protocols

Related tags

Network golang iso8583
Overview

SimpleMLI

A Message Length Indicator Encoder/Decoder

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Message Length Indicators (MLI) are commonly used in communications over raw TCP/IP sockets. This method of denoting message length is especially popular with users of ISO 8583 messages, a common communication protocol for financial transactions.

This package provides an easy-to-use Encoder and Decoder for Message Length Indicators.

Usage:

import (
	"github.com/americanexpress/simplemli"
)

func main() {
	msg := []byte("This is a message")
	
	// Encoding Example
	mli, err := simplemli.Encode(simplemli.2I, len(msg))
	if err != nil {
		// Do something
	}
	
	// Append the MLI to the message
	msg := append(mli, msg)
	
	// Write to TCP Connection
	_, err = conn.Write(msg)
	
	
	// Reading MLI from TCP Connection
	b := make([]byte, simplemli.Size2I)
	_, err = conn.Read(&b) // only read the MLI from buffer
	if err != nil {
		// Do something
	}
	
	// Decoding Example
	length, err := simplemli.Decode(simplemli.2I, &b)
	if err != nil {
		// Do something
	}
	
	// Reading Message from TCP Connection
	msg := make([]byte, length)
	_, err = conn.Read(&msg)
}

Message Length Types

There are many common ways to encode message lengths and this library attempts to provide the most common MLI types.

Valid Options are listed in the table below.

Name Description
2I 2-byte network byte order with MLI included
2E 2-byte network byte order with MLI excluded
4I 4-byte network byte order with MLI included
4E 4-byte network byte order with MLI excluded
2EE 2-byte network byte order with MLI excluded, additional 2-byte header is included with message
2BCD2 2-byte Header with a 2-byte binary-coded decimal with MLI excluded
A4E 4-byte ASCII string with MLI excluded

Inclusive vs. Exclusive MLI

An inclusive MLI is an MLI type where the length of the Message Length Indicator itself is included in the MLI value.

For example, if a message is 1500 bytes and 2I encoded, the resulting MLI will have a value of 1502. The reverse is true for Exclusive MLI types, a 1500-byte message with a 2E encoded MLI will have a value of 1500.

When calling the Decoder, the MLI inclusive/exclusive nature is already taken care of. If you pass an MLI with a value of 1502 and decode it with 2I encoding. The resulting integer will be 1500.

Contributing

We welcome Your interest in the American Express Open Source Community on Github. Any Contributor to any Open Source Project managed by the American Express Open Source Community must accept and sign an Agreement indicating agreement to the terms below. Except for the rights granted in this Agreement to American Express and to recipients of software distributed by American Express, You reserve all right, title, and interest, if any, in and to Your Contributions. Please fill out the Agreement.

License

Any contributions made under this project will be governed by the Apache License 2.0.

Code of Conduct

This project adheres to the American Express Community Guidelines. By participating, you are expected to honor these guidelines.

Issues
  • Decode: use unsafe []byte->string conversion for discarded value

    Decode: use unsafe []byte->string conversion for discarded value

    For Decode's MLI4I, we invoke strconv.Atoi after string(*b) which incurs a []byte->string allocation. The converted []byte->string is discarded so anyways it is okay to use unsafe, as the string is never used again. You can see the results at https://dashboard.github.orijtech.com/benchmark/dbb0fca65f644d95bcf8d0c8caafc601

    Results:

    • time/op (ns/op) Encoding/Decoding_2I-8 7.5ns ± 1% 6.7ns ± 0% -10.36% (p=0.000 n=10+9) Encoding/Decoding_4E-8 8.8ns ± 0% 7.9ns ± 0% -10.35% (p=0.000 n=10+10) Encoding/Decoding_A4E-8 38ns ± 1% 17ns ± 0% -54.84% (p=0.000 n=10+10)

    • allocs/op (B/op) Encoding/Decoding_A4E-8 4.0B ± 0% 0 -100.00% (p=0.000 n=10+10)

    • allocs/op (N/op) Encoding/Decoding_A4E-8 1.0 ± 0% 0 -100.00% (p=0.000 n=10+10)

    Or visually Screen Shot 2021-09-25 at 12 58 38 AM

    Problem Statement

    What is the current behavior? Why and how does it need to change?

    string(*b) incurs a []byte->string allocation yet the value will be discarded.

    Description of Change

    Please include a summary of the change and, if applicable, tag related issues, add code snippets or logs.

    This change removes a []byte->string allocation

    Breaking Change

    Is this a breaking change?

    No.

    Caveats

    Please list any caveats or special considerations for this change.

    It uses unsafe, but the usage is isolated as we directly insert the converted string into strconv.Atoi, so this isn't a caveat really. /cc @kirbyquerby @cuonglm @madflojo

    opened by odeke-em 3
  • Improve performance by reducing conversions and allocation

    Improve performance by reducing conversions and allocation

    Avoid a hex.EncodeToString conversion just to compare against "00000000" and then later "0000", just by using bytes.Count(... '0')

    While here, also added (*testing.B).ReportAllocs to each benchmark to report allocations.

    Problem Statement

    What is the current behavior? Why and how does it need to change?

    Having examined this library's code and benchmarked it, we can reduce allocations by noticing that instead of invoking hex.EncodetoString "00000000" and then skip the if s == "0000" check and use string(*b) inside strconv.Atoi

    Description of Change

    Please include a summary of the change and, if applicable, tag related issues, add code snippets or logs.

    The benchmarking results https://dashboard.github.orijtech.com/benchmark/3319ffe57baa4553b37c704be8984aea show huge improvements in ~78% improvement in CPU time and also a huge reduction in allocations Screen Shot 2021-09-02 at 11 05 55 PM

    /cc @cuonglm @kirbyquerby

    Breaking Change

    Is this a breaking change?

    No

    Caveats

    Please list any caveats or special considerations for this change.

    None

    opened by odeke-em 3
  • Adding GitHub Actions for Lint and Tests

    Adding GitHub Actions for Lint and Tests

    Problem Statement

    What is the current behavior? Why and how does it need to change?

    Currently this repository is using Travis CI and due to some of the ways Travis CI has changed their support for Open Source projects it seems like it may be a challenge to use the Open Source tier in the future.

    Description of Change

    Please include a summary of the change and, if applicable, tag related issues, add code snippets or logs.

    This change adds two GitHub actions that will run on Pull Requests as well as the main/release branches. One will run make tests and the other will run the golangci-lint workflow.

    At this time, I'm not removing the Travis configuration, as these can run in conjunction.

    Breaking Change

    Is this a breaking change?

    No

    Caveats

    Please list any caveats or special considerations for this change.

    opened by madflojo 0
  • Adding Badges for Travis, Coveralls, and Docs

    Adding Badges for Travis, Coveralls, and Docs

    Problem Statement

    What is the current behavior? Why and how does it need to change?

    Currently the Repository has no links to documentation, build status, coverage, or code quality.

    Description of Change

    Please include a summary of the change and, if applicable, tag related issues, add code snippets or logs.

    This change adds badges for all of the items above. It also has a gofmt change recommended by GoReportCard.

    Breaking Change

    Is this a breaking change?

    No

    Caveats

    Please list any caveats or special considerations for this change.

    opened by madflojo 0
  • use constant name not value in documentation.

    use constant name not value in documentation.

    Problem Statement

    Documentation is out of sync with code. Uses constant value and not constant name.

    Description of Change

    Changes all instances in documentation from value to constant name.

    Breaking Change

    not

    Closes #5

    opened by wadearnold 1
Releases(v1.0.1)
Owner
American Express
American Express
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