From 4909c2f98b0d361cdee3f9e5002bd47f400adeab Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Wilhelm=20=C3=85gren?=
 <36638274+wilhelmagren@users.noreply.github.com>
Date: Thu, 14 Dec 2023 12:41:55 +0100
Subject: [PATCH] [feat] padding, testing, and benchmarking (#3)

* [bench] criterion benchmarking format! vs pad

* [feat] implement efficient padding

* [build] crate metadata, deps, and criterion bench conf

* [feat] cargo fmt and clippy lint changes
---
 Cargo.toml                                    |  36 ++++
 benches/bench_main.rs                         |   7 +
 .../benchmarks/format_whitespace_leftalign.rs |  42 ++++
 benches/benchmarks/mod.rs                     |   2 +
 .../benchmarks/pad_whitespace_leftalign.rs    |  51 +++++
 src/lib.rs                                    | 197 ++++++++++++++++++
 6 files changed, 335 insertions(+)
 create mode 100644 Cargo.toml
 create mode 100644 benches/bench_main.rs
 create mode 100644 benches/benchmarks/format_whitespace_leftalign.rs
 create mode 100644 benches/benchmarks/mod.rs
 create mode 100644 benches/benchmarks/pad_whitespace_leftalign.rs
 create mode 100644 src/lib.rs

diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..75061aa
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,36 @@
+[package]
+name = "padder"
+version = "0.1.0"
+edition = "2021"
+description = "String formatting done right."
+authors = [
+    "Wilhelm Ågren <wilhelmagren98@gmail.com>",
+]
+
+readme = "README.md"
+license-file = "LICENSE"
+homepage = "https://github.com/firelink-data/padder"
+repository = "https://github.com/firelink-data/padder"
+
+include = [
+    "**/*.rs",
+    "Cargo.toml",
+    "LICENSE",
+    "README.md",
+]
+
+[lib]
+name = "padder"
+path = "src/lib.rs"
+test = true
+bench = true
+crate-type = [ "lib" ]
+
+[dependencies]
+
+[dev-dependencies]
+criterion = "0.5.1"
+
+[[bench]]
+name = "bench_main"
+harness = false
diff --git a/benches/bench_main.rs b/benches/bench_main.rs
new file mode 100644
index 0000000..ddf6759
--- /dev/null
+++ b/benches/bench_main.rs
@@ -0,0 +1,7 @@
+use criterion::criterion_main;
+mod benchmarks;
+
+criterion_main! {
+    benchmarks::format_whitespace_leftalign::formats,
+    benchmarks::pad_whitespace_leftalign::pads,
+}
diff --git a/benches/benchmarks/format_whitespace_leftalign.rs b/benches/benchmarks/format_whitespace_leftalign.rs
new file mode 100644
index 0000000..13170ff
--- /dev/null
+++ b/benches/benchmarks/format_whitespace_leftalign.rs
@@ -0,0 +1,42 @@
+use criterion::{black_box, criterion_group, Criterion};
+
+pub fn format_whitespace_10_leftalign(c: &mut Criterion) {
+    let width: usize = 10;
+    c.bench_function("format! ws 10 la", |b| {
+        b.iter(|| black_box(format!("{:<width$}", "hej")))
+    });
+}
+
+pub fn format_whitespace_100_leftalign(c: &mut Criterion) {
+    let width: usize = 100;
+    c.bench_function("format! ws 100 la", |b| {
+        b.iter(|| black_box(format!("{:<width$}", "bingbong")))
+    });
+}
+
+pub fn format_whitespace_1000_leftalign(c: &mut Criterion) {
+    let width: usize = 1000;
+    c.bench_function("format! ws 1000 la", |b| {
+        b.iter(|| black_box(format!("{:<width$}", "Undercity is a cool capital...")))
+    });
+}
+
+pub fn format_whitespace_10000_leftalign(c: &mut Criterion) {
+    let width: usize = 10000;
+    c.bench_function("format! ws 10000 la", |b| {
+        b.iter(|| {
+            black_box(format!(
+                "{:<width$}",
+                "¤)(åäöåa this is a very long string... xd"
+            ))
+        })
+    });
+}
+
+criterion_group!(
+    formats,
+    format_whitespace_10_leftalign,
+    format_whitespace_100_leftalign,
+    format_whitespace_1000_leftalign,
+    format_whitespace_10000_leftalign,
+);
diff --git a/benches/benchmarks/mod.rs b/benches/benchmarks/mod.rs
new file mode 100644
index 0000000..08693d1
--- /dev/null
+++ b/benches/benchmarks/mod.rs
@@ -0,0 +1,2 @@
+pub mod format_whitespace_leftalign;
+pub mod pad_whitespace_leftalign;
diff --git a/benches/benchmarks/pad_whitespace_leftalign.rs b/benches/benchmarks/pad_whitespace_leftalign.rs
new file mode 100644
index 0000000..25091cb
--- /dev/null
+++ b/benches/benchmarks/pad_whitespace_leftalign.rs
@@ -0,0 +1,51 @@
+use criterion::{black_box, criterion_group, Criterion};
+use padder::whitespace;
+use padder::Alignment;
+
+pub fn pad_whitespace_10_leftalign(c: &mut Criterion) {
+    let width: usize = 10;
+    c.bench_function("pad ws 10 la", |b| {
+        b.iter(|| black_box(whitespace("hej", width, Alignment::Left)))
+    });
+}
+
+pub fn pad_whitespace_100_leftalign(c: &mut Criterion) {
+    let width: usize = 100;
+    c.bench_function("pad ws 100 la", |b| {
+        b.iter(|| black_box(whitespace("bingbong", width, Alignment::Left)))
+    });
+}
+
+pub fn pad_whitespace_1000_leftalign(c: &mut Criterion) {
+    let width: usize = 1000;
+    c.bench_function("pad ws 1000 la", |b| {
+        b.iter(|| {
+            black_box(whitespace(
+                "Undercity is a cool capital...",
+                width,
+                Alignment::Left,
+            ))
+        })
+    });
+}
+
+pub fn pad_whitespace_10000_leftalign(c: &mut Criterion) {
+    let width: usize = 10000;
+    c.bench_function("pad ws 10000 la", |b| {
+        b.iter(|| {
+            black_box(whitespace(
+                "¤)(åäöåa this is a very long string... xd",
+                width,
+                Alignment::Left,
+            ))
+        })
+    });
+}
+
+criterion_group!(
+    pads,
+    pad_whitespace_10_leftalign,
+    pad_whitespace_100_leftalign,
+    pad_whitespace_1000_leftalign,
+    pad_whitespace_10000_leftalign,
+);
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..ae22d90
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,197 @@
+/*
+* MIT License
+*
+* Copyright (c) 2023 Firelink Data
+*
+* Permission is hereby granted, free of charge, to any person obtaining a copy
+* of this software and associated documentation files (the "Software"), to deal
+* in the Software without restriction, including without limitation the rights
+* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+* copies of the Software, and to permit persons to whom the Software is
+* furnished to do so, subject to the following conditions:
+*
+* The above copyright notice and this permission notice shall be included in all
+* copies or substantial portions of the Software.
+*
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+* SOFTWARE.
+*
+* File created: 2023-12-14
+* Last updated: 2023-12-14
+*/
+
+use std::fmt;
+
+///
+#[derive(Debug, Clone)]
+pub struct WidthError;
+
+///
+impl fmt::Display for WidthError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "Invalid target pad width for the provided string length."
+        )
+    }
+}
+
+///
+pub enum Alignment {
+    Left,
+    Right,
+    Center,
+}
+
+///
+pub fn whitespace(string: &str, width: usize, mode: Alignment) -> String {
+    pad(string, width, mode, ' ')
+}
+
+///
+pub fn zeros(string: &str, width: usize, mode: Alignment) -> String {
+    pad(string, width, mode, '0')
+}
+
+///
+pub fn pad_into_bytes(string: &str, width: usize, mode: Alignment, pad_char: char) -> Vec<u8> {
+    pad(string, width, mode, pad_char).into_bytes()
+}
+
+///
+pub fn pad_and_push_to_buffer(
+    string: &str,
+    width: usize,
+    mode: Alignment,
+    pad_char: char,
+    buffer: &mut Vec<u8>,
+) {
+    buffer.extend_from_slice(pad(string, width, mode, pad_char).as_bytes());
+}
+
+///
+/// Panics
+/// Iff the target pad width is less than the provided string length.
+fn pad(string: &str, width: usize, mode: Alignment, pad_char: char) -> String {
+    if width < string.len() {
+        panic!("Invalid target pad width for the provide string length.")
+    }
+
+    let mut output = String::with_capacity(width);
+    let diff: usize = width - string.len();
+
+    if diff == 0 {
+        return string.to_string();
+    }
+
+    let (lpad, rpad) = match mode {
+        Alignment::Left => (0, diff),
+        Alignment::Right => (diff, 0),
+        Alignment::Center => (diff / 2, diff - diff / 2),
+    };
+
+    (0..lpad).for_each(|_| output.push(pad_char));
+    output.push_str(string);
+    (0..rpad).for_each(|_| output.push(pad_char));
+
+    output
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    #[should_panic]
+    fn pad_should_panic() {
+        let _ = whitespace("lol hahahah xd test", 15, Alignment::Center);
+    }
+
+    #[test]
+    fn pad_whitespace_right_align_into_bytes() {
+        let width: usize = 30;
+        let bytes = pad_into_bytes("this is cool", width, Alignment::Right, ' ');
+
+        assert_eq!(format!("{:>width$}", "this is cool").into_bytes(), bytes,);
+    }
+
+    #[test]
+    fn pad_zeros_left_align_push_to_buffer() {
+        let width: usize = 128;
+        let expected: Vec<u8> =
+            format!("{:0<width$}", "testing buffer reuse smart memory").into_bytes();
+
+        let mut buffer: Vec<u8> = Vec::with_capacity(1024 * 1024);
+        pad_and_push_to_buffer(
+            "testing buffer reuse smart memory",
+            width,
+            Alignment::Left,
+            '0',
+            &mut buffer,
+        );
+
+        assert_eq!(expected.len(), buffer.len());
+        assert_eq!(expected, buffer);
+    }
+
+    #[test]
+    fn pad_whitespace_left_align() {
+        let width: usize = 30;
+        let pad = whitespace("this is cool", width, Alignment::Left);
+
+        assert_eq!(format!("{:<width$}", "this is cool"), pad);
+    }
+
+    #[test]
+    fn pad_whitespace_right_align() {
+        let width: usize = 30;
+        let pad = whitespace("this is cool", width, Alignment::Right);
+
+        assert_eq!(format!("{:>width$}", "this is cool"), pad);
+    }
+
+    #[test]
+    fn pad_whitespace_center_align() {
+        let width: usize = 30;
+        let pad = whitespace("this is cool", width, Alignment::Center);
+
+        assert_eq!(format!("{:^width$}", "this is cool"), pad);
+    }
+
+    #[test]
+    fn pad_zeros_left_align() {
+        let width: usize = 30;
+        let pad = zeros("this is cool", width, Alignment::Left);
+
+        assert_eq!(format!("{:0<width$}", "this is cool"), pad);
+    }
+
+    #[test]
+    fn pad_zeros_right_align() {
+        let width: usize = 30;
+        let pad = zeros("this is cool", width, Alignment::Right);
+
+        assert_eq!(format!("{:0>width$}", "this is cool"), pad);
+    }
+
+    #[test]
+    fn pad_zeros_center_align() {
+        let width: usize = 30;
+        let pad = zeros("this is cool", width, Alignment::Center);
+
+        assert_eq!(format!("{:0^width$}", "this is cool"), pad);
+    }
+
+    #[test]
+    fn pad_1000000_zeros_center() {
+        let width: usize = 100_000_000;
+        let pad = zeros("this is cool", width, Alignment::Center);
+
+        assert_eq!(format!("{:0^width$}", "this is cool"), pad);
+    }
+}