From c7ab4da1a7c0ecb9508d585075b88c173948642c Mon Sep 17 00:00:00 2001
From: angie <angheloalf95@gmail.com>
Date: Thu, 11 Jan 2024 15:40:18 -0300
Subject: [PATCH] CICKind.get_entrypoint

---
 CHANGELOG.md                               |  5 +++++
 bindings/c/include/ipl3checksum/cickinds.h |  2 ++
 src/ipl3checksum/cickinds.pyi              |  8 +++++++
 src/rs/checksum.rs                         |  6 +-----
 src/rs/cickinds.rs                         | 25 ++++++++++++++++++++++
 5 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0078400..a9e94e5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `CICKind.get_entrypoint`: Returns the entrypoint address that would be used
+  on runtime.
+
 ### Changed
 
 - Rewrite the checksum algorithm for readability and simplicity.
diff --git a/bindings/c/include/ipl3checksum/cickinds.h b/bindings/c/include/ipl3checksum/cickinds.h
index bed923c..6f4d7f7 100644
--- a/bindings/c/include/ipl3checksum/cickinds.h
+++ b/bindings/c/include/ipl3checksum/cickinds.h
@@ -29,6 +29,8 @@ uint32_t ipl3checksum_cickind_get_seed(Ipl3Checksum_CICKind self);
 
 uint32_t ipl3checksum_cickind_get_magic(Ipl3Checksum_CICKind self);
 
+uint32_t ipl3checksum_cickind_get_entrypoint(Ipl3Checksum_CICKind self, uint32_t header_entrypoint);
+
 /**
  * Returns the md5 hash for the specified CIC kind.
  *
diff --git a/src/ipl3checksum/cickinds.pyi b/src/ipl3checksum/cickinds.pyi
index 1a86808..8d309a2 100644
--- a/src/ipl3checksum/cickinds.pyi
+++ b/src/ipl3checksum/cickinds.pyi
@@ -20,6 +20,7 @@ class CICKind():
     def getSeed(self) -> int:
         """
         Seed value set by the PIF ROM before the CPU (and the IPL3) is executed.
+
         https://n64brew.dev/wiki/PIF-NUS#IPL3_checksum_algorithm
         """
 
@@ -28,6 +29,13 @@ class CICKind():
         Magic value hardcoded inside the IPL3 itself
         """
 
+    def getEntrypoint(self, header_entrypoint: int) -> int:
+        """
+        Calculates the actual entrypoint address based on the entrypoint specified on the header.
+
+        CIC 7102 is a notable case since its IPL3 hardcodes it, ignoring the entrypoint from the header.
+        """
+
     def getHashMd5(self) -> str:
         """
         Expected md5 hash of the IPL3 blob
diff --git a/src/rs/checksum.rs b/src/rs/checksum.rs
index 2cca1ab..e0cbf56 100644
--- a/src/rs/checksum.rs
+++ b/src/rs/checksum.rs
@@ -7,11 +7,7 @@ use crate::{detect, error::Ipl3ChecksumError, utils};
 fn get_entrypoint_addr(rom_bytes: &[u8], kind: CICKind) -> Result<u32, Ipl3ChecksumError> {
     let entrypoint_addr: u32 = utils::read_u32(rom_bytes, 8)?;
 
-    match kind {
-        CICKind::CIC_X103 | CICKind::CIC_5101 => Ok(entrypoint_addr.wrapping_sub(0x100000)),
-        CICKind::CIC_X106 => Ok(entrypoint_addr.wrapping_sub(0x200000)),
-        _ => Ok(entrypoint_addr),
-    }
+    Ok(kind.get_entrypoint(entrypoint_addr))
 }
 
 const HEADER_IPL3_SIZE: usize = 0x1000;
diff --git a/src/rs/cickinds.rs b/src/rs/cickinds.rs
index 998aa0c..d0b3661 100644
--- a/src/rs/cickinds.rs
+++ b/src/rs/cickinds.rs
@@ -27,6 +27,9 @@ pub enum CICKind {
 }
 
 impl CICKind {
+    /// Seed value set by the PIF ROM before the CPU (and the IPL3) is executed.
+    ///
+    /// https://n64brew.dev/wiki/PIF-NUS#IPL3_checksum_algorithm
     pub fn get_seed(&self) -> u32 {
         match self {
             Self::CIC_6101 | Self::CIC_6102_7101 | Self::CIC_7102 => 0x3F,
@@ -37,6 +40,7 @@ impl CICKind {
         }
     }
 
+    /// Magic value hardcoded inside the IPL3 itself
     pub fn get_magic(&self) -> u32 {
         match self {
             Self::CIC_6101 | Self::CIC_6102_7101 | Self::CIC_7102 | Self::CIC_X105 => 0x5D588B65,
@@ -44,6 +48,18 @@ impl CICKind {
         }
     }
 
+    /// Calculates the actual entrypoint address based on the entrypoint specified on the header.
+    ///
+    /// CIC 7102 is a notable case since its IPL3 hardcodes it, ignoring the entrypoint from the header.
+    pub fn get_entrypoint(&self, header_entrypoint: u32) -> u32 {
+        match self {
+            CICKind::CIC_7102 => 0x80000480,
+            CICKind::CIC_X103 | CICKind::CIC_5101 => header_entrypoint.wrapping_sub(0x100000),
+            CICKind::CIC_X106 => header_entrypoint.wrapping_sub(0x200000),
+            _ => header_entrypoint,
+        }
+    }
+
     pub fn get_hash_md5(&self) -> &'static str {
         match self {
             Self::CIC_6101 => "900b4a5b68edb71f4c7ed52acd814fc5",
@@ -163,6 +179,10 @@ mod python_bindings {
             self.get_magic()
         }
 
+        pub fn getEntrypoint(&self, header_entrypoint: u32) -> u32 {
+            self.get_entrypoint(header_entrypoint)
+        }
+
         pub fn getHashMd5(&self) -> &str {
             self.get_hash_md5()
         }
@@ -226,6 +246,11 @@ mod c_bindings {
         kind.get_magic()
     }
 
+    #[no_mangle]
+    pub extern "C" fn ipl3checksum_cickind_get_entrypoint(kind: CICKind, header_entrypoint: u32) -> u32 {
+        kind.get_entrypoint(header_entrypoint)
+    }
+
     #[no_mangle]
     pub extern "C" fn ipl3checksum_cickind_get_hash_md5(
         kind: CICKind,