Courgette: Add static method QuickDetect() to optimize program detection.

courgette/disassembler_elf_32.cc

Index: courgette/disassembler_elf_32.cc
diff --git a/courgette/disassembler_elf_32.cc b/courgette/disassembler_elf_32.cc
index febcdeabef504e2c540c9d65dde763fbb093b776..3b7d83a887034373e7ed9752e1347476bc2957ae 100644
--- a/courgette/disassembler_elf_32.cc
+++ b/courgette/disassembler_elf_32.cc
@@ -605,4 +605,29 @@ CheckBool DisassemblerElf32::ParseRel32RelocsFromSections() {
   return true;
 }
 
+bool DisassemblerElf32::QuickDetects(const uint8_t* start,
+                                     size_t length,
+                                     e_machine_values elf_em) {
+  if (length < sizeof(Elf32_Ehdr))
+    return false;
+
+  const Elf32_Ehdr* header = reinterpret_cast<const Elf32_Ehdr*>(start);
+
+    // Have magic for ELF header?
+  if (header->e_ident[0] != 0x7f || header->e_ident[1] != 'E' ||
+      header->e_ident[2] != 'L' || header->e_ident[3] != 'F')
+    return false;
+
+  if (header->e_type != ET_EXEC && header->e_type != ET_DYN)
+    return false;
+  if (header->e_machine != elf_em)
+    return false;
+  if (header->e_version != 1)
+    return false;
+  if (header->e_shentsize != sizeof(Elf32_Shdr))
+    return false;
+
+  return true;
+}
+
 }  // namespace courgette