From 2e38597a7cc8705414a27bd393a4302670b02108 Mon Sep 17 00:00:00 2001
From: PlexSheep <software@cscherr.de>
Date: Mon, 13 May 2024 14:56:37 +0200
Subject: [PATCH] feat: add a join module to join arrays into larger integers
 #79

---
 members/libpt-bintols/src/join.rs | 44 +++++++++++++++++++++++++++++++
 members/libpt-bintols/src/lib.rs  |  1 +
 2 files changed, 45 insertions(+)
 create mode 100644 members/libpt-bintols/src/join.rs

diff --git a/members/libpt-bintols/src/join.rs b/members/libpt-bintols/src/join.rs
new file mode 100644
index 0000000..35efcd7
--- /dev/null
+++ b/members/libpt-bintols/src/join.rs
@@ -0,0 +1,44 @@
+//! # Join bits and bytes into numbers
+//!
+//! Sometimes you have a `[u8]` that is the representation of a larger unsigned integer, such as
+//! [u128]. This module helps you join them together.
+
+use anyhow::anyhow;
+use libpt_log::trace;
+
+/// Join a [Vec] of [u8]s into an unsigned integer
+///
+/// Say you have the array `[0b00000110, 0b10110101]` and want to use it as a [u32].
+/// This function sets it together to a integer type of your choosing:
+/// 1717 (binary: `00000000 00000000 00000110 10110101`).
+///
+/// If the array is not long enough, the number will be padded with null bytes.
+///
+/// # Examples
+///
+/// ```
+/// # use libpt_bintols::join::*;
+///
+/// let x: [u8; 2] = [0b00000110, 0b10110101];
+///
+/// assert_eq!(array_to_unsigned::<u32>(&x).unwrap(), 1717);
+/// ```
+pub fn array_to_unsigned<T>(parts: &[u8]) -> anyhow::Result<T>
+where
+    u128: std::convert::From<T>,
+    T: std::str::FromStr,
+    <T as std::str::FromStr>::Err: std::fmt::Debug,
+{
+    trace!("amount of parts: {}", parts.len());
+    if parts.len() > (u128::BITS / 8) as usize {
+        return Err(anyhow!(
+            "the list is too long to fit into the specified integer type: {}",
+            std::any::type_name::<T>()
+        ));
+    }
+    let mut ri: u128 = 0;
+    for (i, e) in parts.iter().rev().enumerate() {
+        ri += (*e as u128) * 256u128.pow(i as u32);
+    }
+    Ok(ri.to_string().parse().unwrap())
+}
diff --git a/members/libpt-bintols/src/lib.rs b/members/libpt-bintols/src/lib.rs
index 30dec09..1680664 100644
--- a/members/libpt-bintols/src/lib.rs
+++ b/members/libpt-bintols/src/lib.rs
@@ -26,3 +26,4 @@ pub const YOBI: u128 = 2u128.pow(80);
 pub mod datalayout;
 pub mod display;
 pub mod split;
+pub mod join;