From c2a0a6f1e10d8c51e78cd8b1f8591432fa9b44fc Mon Sep 17 00:00:00 2001
From: Nikita Smith <git.nikita.smith@gmail.com>
Date: Mon, 28 Apr 2025 13:54:51 -0700
Subject: [PATCH] factored out format specific relocation code to COFF layer

---
 src/coff/coff.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)

diff --git a/src/coff/coff.c b/src/coff/coff.c
index 5b65582a..c2ab20a1 100644
--- a/src/coff/coff.c
+++ b/src/coff/coff.c
@@ -179,6 +179,94 @@ coff_apply_size_from_reloc(COFF_MachineType machine, COFF_RelocType x)
   return 0;
 }
 
+internal void
+coff_apply_reloc_x64(String8        data,
+                     COFF_Reloc_X64 type,
+                     U64            apply_off,
+                     U64            reloc_virtual_offset,
+                     U32            symbol_section_number,
+                     U32            symbol_section_offset,
+                     U32            symbol_virtual_offset,
+                     U64            symbol_address)
+{
+  U64 reloc_value_size = 0;
+  S64 reloc_value      = 0;
+  switch (type) {
+  case COFF_Reloc_X64_Abs: {} break;
+  case COFF_Reloc_X64_Addr64: {
+    reloc_value_size = 8;
+    reloc_value      = symbol_address;
+  } break;
+  case COFF_Reloc_X64_Addr32: {
+    reloc_value_size = 4;
+    reloc_value      = safe_cast_u32(symbol_address);
+  } break;
+  case COFF_Reloc_X64_Addr32Nb: {
+    reloc_value_size = 4;
+    reloc_value      = safe_cast_u32(symbol_virtual_offset);
+  } break;
+  case COFF_Reloc_X64_Rel32: {
+    reloc_value_size = 4;
+    reloc_value      = safe_cast_s32(symbol_virtual_offset - reloc_virtual_offset - (4 + 0));
+  } break;
+  case COFF_Reloc_X64_Rel32_1: {
+    reloc_value_size = 4;
+    reloc_value      = safe_cast_s32(symbol_virtual_offset - reloc_virtual_offset - (4 + 1));
+  } break;
+  case COFF_Reloc_X64_Rel32_2: {
+    reloc_value_size = 4;
+    reloc_value      = safe_cast_s32(symbol_virtual_offset - reloc_virtual_offset - (4 + 2));
+  } break;
+  case COFF_Reloc_X64_Rel32_3: {
+    reloc_value_size = 4;
+    reloc_value      = safe_cast_s32(symbol_virtual_offset - reloc_virtual_offset - (4 + 3));
+  } break;
+  case COFF_Reloc_X64_Rel32_4: {
+    reloc_value_size = 4;
+    reloc_value      = safe_cast_s32(symbol_virtual_offset - reloc_virtual_offset - (4 + 4));
+  } break;
+  case COFF_Reloc_X64_Rel32_5: {
+    reloc_value_size = 4;
+    reloc_value = safe_cast_s32(symbol_virtual_offset - reloc_virtual_offset - (4 + 5));
+  } break;
+  case COFF_Reloc_X64_Section: {
+    reloc_value_size = 4;
+    reloc_value      = symbol_section_number;
+  } break;
+  case COFF_Reloc_X64_SecRel: {
+    reloc_value_size = 4;
+    reloc_value      = symbol_section_offset;
+  } break;
+  case COFF_Reloc_X64_SecRel7: {
+    NotImplemented;
+  } break;
+  case COFF_Reloc_X64_Token: {
+    NotImplemented;
+  } break;
+  case COFF_Reloc_X64_SRel32: {
+    NotImplemented;
+  } break;
+  case COFF_Reloc_X64_Pair: {
+    NotImplemented;
+  } break;
+  case COFF_Reloc_X64_SSpan32: {
+    NotImplemented;
+  } break;
+  }
+
+  // read addend
+  Assert(apply_off + reloc_value_size <= data.size);
+  U64 raw_addend = 0;
+  str8_deserial_read(data, apply_off, &raw_addend, reloc_value_size, reloc_value_size);
+
+  // compute new reloc value
+  S64 addend       = extend_sign64(raw_addend, reloc_value_size);
+  U64 reloc_result = reloc_value + addend;
+  
+  // commit new reloc value
+  MemoryCopy(data.str + apply_off, &reloc_result, reloc_value_size);
+}
+
 internal String8
 coff_make_import_lookup(Arena *arena, U16 hint, String8 name)
 {