fast_string

High-performance Ruby String extensions implemented in C.

Optimized string methods for high-throughput workloads: log processing, CSV parsing, HTTP parsing, text analytics, streaming pipelines.

Installation

gem 'fast_string'

Usage

require 'fast_string'

"hello".fs_count("l")                     #=> 2
"line1\nline2\nline3".fs_lines            #=> 2
"   \t\n  ".fs_blank?                     #=> true
"  hello  ".fs_trim                       #=> "hello"
"hello\nworld".fs_byte_replace("\n", " ") #=> "hello world"
"hello\r\nworld".fs_byte_delete("\r")     #=> "hello\nworld"

data.fs_each_line { |line| puts line }

API

Method	Ruby equivalent	What it does
`fs_count(char)`	`str.count(char)`	Count occurrences of a single byte
`fs_lines`	`str.count("\n")`	Count newline characters
`fs_blank?`	`str.strip.empty?`	Check if string is whitespace-only
`fs_trim`	`str.strip`	Strip whitespace (zero-copy)
`fs_byte_replace(from, to)`	`str.tr(from, to)`	Replace one byte with another
`fs_byte_delete(char)`	`str.delete(char)`	Delete all occurrences of a byte
`fs_each_line { }`	`str.each_line { }`	Iterate lines via memchr

All methods operate at byte level using memchr and direct memory access. Single-character arguments only.

fs_trim returns a zero-copy shared substring — no memcpy unlike Ruby's strip.

fs_byte_replace and fs_byte_delete return new strings; originals are not mutated.

Benchmark

Apple Silicon (M1), Ruby 2.7. Numbers are times faster than Ruby stdlib equivalent:

Method	42KB	10MB	9.6MB CSV	38MB Log	5.8MB Unicode
`fs_count`	1.8x	7.9x	6.2x	9.0x	9.2x
`fs_lines`	1.9x	7.9x	6.2x	9.0x	9.1x
`fs_blank?`	4.1x	4.0x	4.0x	4.0x	4.1x
`fs_trim`	3.8x	4.0x	4.0x	3.9x	4.0x
`fs_byte_replace`	5.7x	15.0x	13.0x	16.1x	67.9x
`fs_byte_delete`	3.8x	13.5x	12.2x	15.1x	33.2x
`fs_each_line`	1.1x	1.1x	1.0x	1.1x	1.0x

fs_byte_replace and fs_byte_delete show the largest gains because Ruby's tr and delete go through the encoding layer per character, while fast_string uses memchr to skip non-matching regions in bulk.

ruby benchmark/benchmark.rb

Requirements

Ruby >= 2.7.0
C compiler (GCC, Clang)

Platforms

Linux, macOS, BSD, ARM (Apple Silicon), x86_64

Development

bundle install
rake compile
ruby test_basic.rb
ruby benchmark/benchmark.rb

License

MIT