Look through the file to find the nexe footer.

Rather than hoping we find it on the first read.

When doing macOS signing the signature and entitlements are placed after
the nexe sentinel, so we may not find it immediately.

src/patches/boot-nexe.ts

@@ -1,24 +1,42 @@
 const fs = require('fs'),
  fd = fs.openSync(process.execPath, 'r'),
  stat = fs.fstatSync(fd),
- defaultTailSize = 16000,
- tailSize = Math.min(
- stat.size,
- require('os').platform() === 'darwin' ? defaultTailSize * 100 : defaultTailSize
- ),
- tailWindow = Buffer.from(Array(tailSize))
+ tailSize = Math.min(stat.size, 16000),
+ tailWindow = Buffer.alloc(tailSize),
+ match = '<nexe' + '~~sentinel>',
+ matchLength = match.length,
+ lastBuffer = Buffer.alloc(matchLength + 32)
 
-fs.readSync(fd, tailWindow, 0, tailSize, stat.size - tailSize)
+let offset = stat.size,
+ footerPosition = -1,
+ footerPositionOffset = 0,
+ footer: Buffer
+
+while (true) {
+ const bytesRead = fs.readSync(fd, tailWindow, 0, tailSize, offset - tailSize)
+ if (bytesRead === 0) break
+
+ const combinedBuffers = Buffer.concat([tailWindow, lastBuffer])
+ footerPosition = combinedBuffers.indexOf(match)
+
+ if (footerPosition > -1) {
+ footer = combinedBuffers.slice(footerPosition, footerPosition + 32)
+ break
+ }
+
+ if (offset < 0) break
+
+ tailWindow.copy(lastBuffer)
+ offset = offset - bytesRead
+}
 
-const footerPosition = tailWindow.indexOf('<nexe~~sentinel>')
 if (footerPosition == -1) {
  throw 'Invalid Nexe binary'
 }
 
-const footer = tailWindow.slice(footerPosition, footerPosition + 32),
- contentSize = footer.readDoubleLE(16),
- resourceSize = footer.readDoubleLE(24),
- contentStart = stat.size - tailSize + footerPosition - resourceSize - contentSize,
+const contentSize = footer!.readDoubleLE(16),
+ resourceSize = footer!.readDoubleLE(24),
+ contentStart = offset - tailSize + footerPosition - resourceSize - contentSize,
  resourceStart = contentStart + contentSize
 
 Object.defineProperty(
@@ -52,10 +70,10 @@ Object.defineProperty(
  })()
 )
 
-const contentBuffer = Buffer.from(Array(contentSize)),
+const contentBuffer = Buffer.alloc(contentSize),
  Module = require('module')
 
 fs.readSync(fd, contentBuffer, 0, contentSize, contentStart)
 fs.closeSync(fd)
 
-new Module(process.execPath, null)._compile(contentBuffer.toString(), process.execPath)
+new Module(process.execPath, null)._compile(contentBuffer.slice(1).toString(), process.execPath)