refactor(pe): share optional header image and alignment facts

src/domain/peOptionalHeader.test.ts

@@ -14,6 +14,10 @@ const header = (
 ): Buffer => {
   const bytes = Buffer.alloc(byteLength);
   bytes.writeUInt16LE(format.magic);
+  if (format.bits === 64) bytes.writeBigUInt64LE(0xfedcba9876540000n, 24);
+  else bytes.writeUInt32LE(0x87650000, 28);
+  bytes.writeUInt32LE(0x1000, 32);
+  bytes.writeUInt32LE(0x200, 36);
   bytes.writeUInt32LE(0x400, 60);
   bytes.writeUInt32LE(directoryCount, format.directoryOffset - 4);
   return bytes;
@@ -32,6 +36,9 @@ it.each(formats)(
     if (!result.ok) throw new Error(result.error.message);
     expect(result.value).toMatchObject({
       ...format,
+      imageBase: format.bits === 64 ? 0xfedcba9876540000n : 0x87650000n,
+      sectionAlignment: 0x1000,
+      fileAlignment: 0x200,
       sizeOfHeaders: 0x400,
       directoryCount: 5,
     });
@@ -54,6 +61,9 @@ it.each(formats)(
       ok: true,
       value: {
         ...format,
+        imageBase: format.bits === 64 ? 0xfedcba9876540000n : 0x87650000n,
+        sectionAlignment: 0x1000,
+        fileAlignment: 0x200,
         sizeOfHeaders: 0xffffffff,
         directoryCount: 0,
         dataDirectories: [],
@@ -157,6 +167,9 @@ it("honors a Uint8Array window and detaches facts from later source changes", ()
   backing.fill(0);
   expect(result.value).toEqual({
     ...formats[1],
+    imageBase: 0xfedcba9876540000n,
+    sectionAlignment: 0x1000,
+    fileAlignment: 0x200,
     sizeOfHeaders: 0x400,
     directoryCount: 1,
     dataDirectories: [{ address: 0x12345678, size: 0x90, offset: 112 }],

src/domain/peOptionalHeader.ts

@@ -13,6 +13,9 @@ export interface PeOptionalHeaderStructure {
   readonly magic: 0x10b | 0x20b;
   readonly bits: 32 | 64;
   readonly format: "pe32" | "pe32-plus";
+  readonly imageBase: bigint;
+  readonly sectionAlignment: number;
+  readonly fileAlignment: number;
   readonly sizeOfHeaders: number;
   readonly directoryOffset: number;
   readonly directoryCount: number;
@@ -74,6 +77,12 @@ export const readPeOptionalHeaderStructure = (
     magic,
     bits,
     format: bits === 64 ? "pe32-plus" : "pe32",
+    imageBase:
+      bits === 64
+        ? view.getBigUint64(24, true)
+        : BigInt(view.getUint32(28, true)),
+    sectionAlignment: view.getUint32(32, true),
+    fileAlignment: view.getUint32(36, true),
     sizeOfHeaders: view.getUint32(60, true),
     directoryOffset,
     directoryCount,

src/native/metadata/PeImage.test.ts

@@ -68,6 +68,27 @@ it.each([32, 64] as const)(
   },
 );
 
+it.each([32, 64] as const)(
+  "retains PE%d declared image base and alignments in native image facts",
+  (bits) => {
+    const { bytes } = createGoBinaryFixture({ format: "pe", bits });
+    const optional = bytes.readUInt32LE(0x3c) + 24;
+    const imageBase = bits === 64 ? 0xfedcba9876540000n : 0x87650000n;
+    if (bits === 64) bytes.writeBigUInt64LE(imageBase, optional + 24);
+    else bytes.writeUInt32LE(Number(imageBase), optional + 28);
+    // These remain declarations; alignment policy belongs to image consumers.
+    bytes.writeUInt32LE(0, optional + 32);
+    bytes.writeUInt32LE(0xffffffff, optional + 36);
+    const container = readPeImage(bytes);
+    expect(container.image_base).toBe(imageBase);
+    expect(container.pe_header_mapping.address).toBe(imageBase);
+    expect(container.mappings[0]?.address).toBe(imageBase + 0x400n);
+    expect(container.pe_section_alignment).toBe(0);
+    expect(container.pe_file_alignment).toBe(0xffffffff);
+    expect(container.sections[0]?.file_alignment).toBe(0xffffffff);
+  },
+);
+
 it("keeps Go fallback candidates when a PE section has no printable name", () => {
   const fixture = createGoBinaryFixture({ format: "pe", bits: 64 });
   const expected = readGoBinaryImage(fixture.bytes).build_info;

src/native/metadata/PeImage.ts

@@ -82,9 +82,14 @@ export const readPeImage = (bytes: Buffer): PeImage => {
   );
   if (!facts.ok)
     throw new BinaryFormatFailure(facts.error.kind, facts.error.message);
-  const { bits, dataDirectories, sizeOfHeaders } = facts.value;
-  const imageBase = reader.word(optional + (bits === 64 ? 24 : 28), bits);
-  const fileAlignment = reader.u32(optional + 36);
+  const {
+    bits,
+    dataDirectories,
+    sizeOfHeaders,
+    imageBase,
+    sectionAlignment,
+    fileAlignment,
+  } = facts.value;
   const headerMapping: FileMapping = {
     address: imageBase,
     offset: 0,
@@ -153,7 +158,7 @@ export const readPeImage = (bytes: Buffer): PeImage => {
     format: "pe",
     image_base: imageBase,
     pe_machine: machine,
-    pe_section_alignment: reader.u32(optional + 32),
+    pe_section_alignment: sectionAlignment,
     pe_file_alignment: fileAlignment,
     pe_data_directories: dataDirectories,
     pe_header_mapping: headerMapping,