SMS Segment Calculator

This repo contains a Go package for an SMS segments calculator. The package replicates Twilio's SMS segmentation logic, telling you how many segments a message will use, which encoding is required (GSM-7 or UCS-2), and how many characters and bits the message consumes.

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Usage

Go

Install the package:

go get github.com/tuanphuong-dev/twilio-segment-calculator

Sample usage:

package main

import (
    "fmt"
    segcalculator "github.com/tuanphuong-dev/twilio-segment-calculator"
)

func main() {
    msg, err := segcalculator.NewSegmentedMessage("Hello World")
    if err != nil {
        panic(err)
    }
    fmt.Println(msg.EncodingName)      // "GSM-7"
    fmt.Println(msg.SegmentsCount())   // 1
}

You can also run the example from the examples/basic folder:

go run ./examples/basic

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Documentation

SegmentedMessage struct

Constructor

NewSegmentedMessage(message string, opts ...Option) (*SegmentedMessage, error)

• message: Body of the SMS
• opts: Optional options, such as encoding or smart encoding

Fields & Methods

• EncodingName — returns the name of the calculated encoding for the message: GSM-7 or UCS-2
• SegmentsCount() — number of segment(s)
• TotalSize() — total size of the message in bits (including User Data Header if present)
• MessageSize() — total size of the message in bits (excluding User Data Header if present)
• GetNonGsmCharacters() — returns a slice of non-GSM-7 characters in the message

Forcing an encoding

By default, NewSegmentedMessage uses segcalculator.Auto to pick the most appropriate encoding. You can force GSM-7 or UCS-2:

msg, err := segcalculator.NewSegmentedMessage(
    body,
    segcalculator.Encoding(segcalculator.GSM7),
)

If you force GSM7 and the message contains non-GSM characters, an error is returned.

Smart encoding

Enable a "smart encoding" mode to replace visually similar characters with GSM-7 equivalents:

msg, err := segcalculator.NewSegmentedMessage(
    body,
    segcalculator.SmartEncoding(true),
)

Inspecting non-GSM characters

Use GetNonGsmCharacters to see which characters forced the message into UCS-2:

nonGsm := msg.GetNonGsmCharacters()
if len(nonGsm) > 0 {
    fmt.Println("Non-GSM characters:", nonGsm)
}

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Try the library

To test the library, run the script in examples/basic:

go run ./examples/basic

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Contributing

This code is open source and welcomes contributions. All contributions are subject to our Code of Conduct.

The source code for the library is in the root directory. Before submitting a PR:

• Run linter using go vet ./... and make sure there are no linter errors
• Run tests using go test ./... and make sure all tests pass

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License

MIT

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Disclaimer

No warranty expressed or implied. Software is as is.