From 349eb14a9c7cc4fa678a751681920c739a1ba48b Mon Sep 17 00:00:00 2001
From: John <j@soft.fish>
Date: Sun, 7 Jul 2024 04:34:32 -0500
Subject: [PATCH] Add (untested!!!) support for IPS32

---
 src/ips.rs | 40 ++++++++++++++++++++++++----------------
 src/lib.rs | 17 +----------------
 2 files changed, 25 insertions(+), 32 deletions(-)

diff --git a/src/ips.rs b/src/ips.rs
index 3cd2cdf..2ac18e8 100644
--- a/src/ips.rs
+++ b/src/ips.rs
@@ -21,7 +21,7 @@
 //!             | { _:   u16 == 0, len: u16, byte: u8 }     // Run-length-encoded data
 //! ```
 
-use crate::{parse_utils::*, Apply};
+use crate::{parse_helpers::*, Apply};
 use std::io::{self, Read, Seek, SeekFrom, Write};
 
 pub struct IPS {
@@ -29,13 +29,11 @@ pub struct IPS {
     pub patches: Vec<Patch>,
 }
 
-// A single IPS patch
 pub struct Patch {
     pub offset: u32,
     pub data: Data,
 }
 
-/// The data
 pub enum Data {
     /// Run-length-encoded (repeated) data
     RLEnc(u16, u8),
@@ -74,20 +72,23 @@ impl Apply for Data {
 }
 
 impl IPS {
-    /// The expected magic number
-    pub const MAGIC: &[u8] = b"PATCH";
+    const MAGIC24: &[u8] = b"PATCH";
+    const MAGIC32: &[u8] = b"IPS32";
 
     /// Reads an IPS file out of the provided reader.
     ///
     /// Consumes 5 bytes and returns Ok(None) if the reader doesn't yield an IPS file.
     pub fn parse(reader: &mut impl Read) -> io::Result<Option<Self>> {
         let magic = read_bytes(reader)?;
-        if Self::MAGIC != magic {
-            return Ok(None);
-        }
+
+        let parse = match magic.as_slice() {
+            Self::MAGIC24 => Patch::parse::<3>,
+            Self::MAGIC32 => Patch::parse::<4>,
+            _ => return Ok(None),
+        };
 
         let mut patches = vec![];
-        while let Some(patch) = Patch::parse(reader)? {
+        while let Some(patch) = parse(reader)? {
             patches.push(patch)
         }
 
@@ -96,14 +97,21 @@ impl IPS {
 }
 
 impl Patch {
-    pub fn parse(reader: &mut impl Read) -> io::Result<Option<Self>> {
-        match offset(reader)? {
-            None => Ok(None),
-            Some(offset) => {
-                let data = Data::parse(reader)?;
-                Ok(Some(Self { offset, data }))
-            }
+    pub fn parse<const WIDTH: usize>(reader: &mut impl Read) -> io::Result<Option<Self>> {
+        const EOF: [&[u8]; 2] = [b"EOF", b"EEOF"];
+
+        let buf: [u8; WIDTH] = read_bytes(reader)?;
+        if const {EOF[WIDTH - 3]} == buf {
+            return Ok(None);
         }
+
+        let mut offset = 0;
+        for byte in buf {
+            offset = offset << 8 | byte as u32;
+        }
+
+        let data = Data::parse(reader)?;
+        Ok(Some(Self { offset, data }))
     }
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index e3f3427..752a3f1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -24,7 +24,7 @@ pub trait Apply {
     fn apply<W: Write + Seek>(&self, writer: &mut W) -> IoResult<()>;
 }
 
-mod parse_utils {
+mod parse_helpers {
     use std::io;
 
     pub fn read_bytes<const N: usize>(reader: &mut impl io::Read) -> io::Result<[u8; N]> {
@@ -32,21 +32,6 @@ mod parse_utils {
         reader.read_exact(&mut buf).map(|_| buf)
     }
 
-    /// Parses a 24-bit big-endian "offset" and ensures it isn't `0x454f46` (`b"EOF"`)
-    pub fn offset(reader: &mut impl io::Read) -> io::Result<Option<u32>> {
-        let buf = read_bytes(reader)?;
-
-        if buf == *b"EOF" {
-            return Ok(None);
-        }
-
-        let mut offset = 0;
-        for byte in buf {
-            offset = offset << 8 | byte as u32;
-        }
-        Ok(Some(offset))
-    }
-
     pub fn read16(reader: &mut impl io::Read) -> io::Result<u16> {
         Ok(u16::from_be_bytes(read_bytes(reader)?))
     }