Wissance/StringFormatter

StringFormatter is a high-performance Go library for string (text) formatting. It offers a syntax familiar to C#, Java and Python developers (via template arguments - {0} (positional), {name} (named)), extensive argument formatting options (numbers, lists, code style), and a set of text utilities — all while being significantly fast as the standard fmt package and even more! Typical usage of sf are:

1. Create e-mails, Messages (SMS, Telegram, other Notifications) or other complicated text based on templates
2. Create a complicated log text with specific argument formatting
3. Use for template-based src code generator
4. Other text proccessing

Other important resources:

• Go Report Card A+
• Coverage > 80%

✨ 1 Features

🔤 Flexible Syntax: Supports both indexed / positional ({0}) and named ({user}) placeholders in templates.

🎨 Advanced Formatting: Built-in directives for numbers (HEX, BIN), floats, lists, and code styles (camelCase, SNAKE_CASE).

🚀 Performance: Template formatting and slice conversion are even faster then fmt.

🛠 Utilities: Functions to convert maps and slices into strings with custom separators and formats.

:man_technologist: Safe : StringFormatter aka sf is safe (SAST and tests are running automatically on push)

📦 2 Installation

go get github.com/Wissance/stringFormatter

🚀 3 Usage

3.1 Template Formatting

3.1.1 By Argument Order (Format)

The Format function replaces {n} placeholders with the corresponding argument in the provided order.

package main

import (
    "fmt"
    sf "github.com/Wissance/stringFormatter"
)

func main() {
    template := "Hello, {0}! Your balance is {1} USD."
    result := sf.Format(template, "Alex", 2500)
    fmt.Println(result)
    // Output: Hello, Alex! Your balance is 2500 USD.
}

3.1.2 By Argument Name (FormatComplex)

The FormatComplex function uses a map[string]any to replace named placeholders like {key}.

package main

import (
    "fmt"
    sf "github.com/Wissance/stringFormatter"
)

func main() {
    template := "User {user} (ID: {id}) logged into {app}."
    args := map[string]any{
        "user": "john_doe",
        "id":   12345,
        "app":  "dashboard",
    }
    result := sf.FormatComplex(template, args)
    fmt.Println(result)
    // Output: User john_doe (ID: 12345) logged into dashboard.
}

3.2 Advanced Argument Formatting

You can control how arguments are displayed by adding a colon (:) and a format specifier to the placeholder.

Type	Specifier	Description	Example Template	Example Value	Output
Numbers	:B	Binary (without padding)	"{0:B}"	15	1111
	:B8	Binary with 8-digit padding	"{0:B8}"	15	00001111
	:X	Hexadecimal (lowercase)	"{0:X}"	250	fa
	:X4	Hexadecimal with 4-digit padding	"{0:X4}"	250	00fa
	:o	Octal	"{0:o}"	11	14
Floating Point	:F	Default float format	"{0:F}"	10.4567890	10.456789
	:F2	Float with 2 decimal places	"{0:F2}"	10.4567890	10.46
	:F4	Float with 4 decimal places	"{0:F4}"	10.4567890	10.4568
	:F8	Float with 8 decimal places	"{0:F8}"	10.4567890	10.45678900
	:E2	Scientific notation	"{0:E2}"	191.0478	1.91e+02
Percentage	:P100	Percentage (multiply by 100)	"{0:P100}"	12	12%
Lists (Slices)	:L-	Join with hyphen	"{0:L-}"	[1 2 3]	1-2-3
	:L,	Join with comma and space	"{0:L, }"	[1 2 3]	1, 2, 3
Code Styles	:c:snake	Convert to snake_case	"{0:c:snake}"	myFunc	my_func
	:c:Snake	Convert to Snake_Case (PascalSnake)	"{0:c:Snake}"	myFunc	My_Func
	:c:SNAKE	Convert to SNAKE_CASE (upper)	"{0:c:SNAKE}"	read-timeout	READ_TIMEOUT
	:c:camel	Convert to camelCase	"{0:c:camel}"	my_variable	myVariable
	:c:Camel	Convert to CamelCase (PascalCase)	"{0:c:Camel}"	my_variable	MyVariable
	:c:kebab	Convert to kebab-case	"{0:c:kebab}"	myVariable	my-variable
	:c:Kebab	Convert to Kebab-Case (PascalKebab)	"{0:c:Kebab}"	myVariable	My-Variable
	:c:KEBAB	Convert to KEBAB-CASE (upper)	"{0:c:KEBAB}"	myVariable	MY-VARIABLE

package main

import (
    "fmt"
    sf "github.com/Wissance/stringFormatter"
)

func main() {
    template := "Status 0x{0:X4} (binary: {0:B8}), temp: {1:F1}°C, items: {2:L, }."
    result := sf.Format(template, 475, 23.876, []int{1, 2, 3})
    fmt.Println(result)
    // Output: Status 0x01DB (binary: 00011101), temp: 23.9°C, items: 1, 2, 3.
}

🛠 4 Text Utilities

4.1 Map to String (MapToString)

Converts a map with primitive keys to a formatted string.

options := map[string]any{
    "host": "localhost",
    "port": 8080,
    "ssl":  true,
}

str := sf.MapToString(&options, "{key} = {value}", "\n")
// Possible output (key order is not guaranteed):
// host = localhost
// port = 8080
// ssl = true

4.2 Slice to String (SliceToString, SliceSameTypeToString)

Converts slices to a string using a specified separator.

// For a slice of any type
mixedSlice := []any{100, "text", 3.14}
separator := " | "
result1 := sf.SliceToString(&mixedSlice, &separator)
// result1: "100 | text | 3.14"

// For a typed slice
numSlice := []int{10, 20, 30}
result2 := sf.SliceSameTypeToString(&numSlice, &separator)
// result2: "10 | 20 | 30"

📊 5 Benchmarks

The library is optimized for high-load scenarios. Key benchmarks show significant performance gains (performance could be differ due to 1. different CPU architectures 2. statistics):

Formatting (Format) vs fmt.Sprintf: 3-5x faster for complex templates. Slices (SliceToString) vs manual fmt-based joining: from 2.5 faster up to 20 items.

These benchmarks tests are running with githun ci on push to develop or master, see

Run the benchmarks yourself:

go test -bench=Format -benchmem -cpu 1
go test -bench=Fmt -benchmem -cpu 1
go test -bench=MapToStr -benchmem -cpu 1

Some benchmark screenshots:

1. Format and FormatComplex:

2. MapToStr:

3. SliceToStr:

📄 6 License

This project is licensed under the MIT License - see the LICENSE file for details.

🤝 7 Contributing

Contributions are welcome! If you find a bug or have a feature suggestion, please open an issue or submit a pull request.

Contributors: