Added patchelf.h

Added a header file to make things easier to navigate.

Renamed findSection3 -> getSectionIndex since thats more sensible to
read.

Renamed findSection -> findSectionHeader to better distinguish sections
from headers.

src/patchelf.h

@@ -0,0 +1,180 @@
+using FileContents = std::shared_ptr<std::vector<unsigned char>>;
+
+#define ElfFileParams class Elf_Ehdr, class Elf_Phdr, class Elf_Shdr, class Elf_Addr, class Elf_Off, class Elf_Dyn, class Elf_Sym, class Elf_Verneed, class Elf_Versym
+#define ElfFileParamNames Elf_Ehdr, Elf_Phdr, Elf_Shdr, Elf_Addr, Elf_Off, Elf_Dyn, Elf_Sym, Elf_Verneed, Elf_Versym
+
+template<ElfFileParams>
+class ElfFile
+{
+    
+    /**
+     * @brief The ELF section header
+     * 
+     */
+    class Section {
+        public:
+            const std::string & getName() {
+                return name;
+            }
+            const Elf_Shdr * toStruct() {
+                return (Elf_Shdr *) this->data.data();
+            }
+            void resize(unsigned int size) {
+                data.resize(size, '\0');
+            }
+        private:
+            std::string name;
+            std::vector<unsigned char> data;
+    };
+
+public:
+
+    const FileContents fileContents;
+
+private:
+
+    std::vector<Elf_Phdr> phdrs;
+    std::vector<Elf_Shdr> shdrs;
+
+    bool littleEndian;
+
+    bool changed = false;
+
+    bool isExecutable = false;
+
+    using SectionName = std::string;
+    using ReplacedSections = std::map<SectionName, std::string>;
+
+    ReplacedSections replacedSections;
+
+    std::string sectionNames; /* content of the .shstrtab section */
+
+    /* Align on 4 or 8 bytes boundaries on 32- or 64-bit platforms
+       respectively. */
+    size_t sectionAlignment = sizeof(Elf_Off);
+
+    std::vector<SectionName> sectionsByOldIndex;
+
+public:
+    explicit ElfFile(FileContents fileContents);
+
+    bool isChanged()
+    {
+        return changed;
+    }
+
+private:
+
+    struct CompPhdr
+    {
+        ElfFile * elfFile;
+        bool operator ()(const Elf_Phdr & x, const Elf_Phdr & y)
+        {
+            // A PHDR comes before everything else.
+            if (elfFile->rdi(y.p_type) == PT_PHDR) return false;
+            if (elfFile->rdi(x.p_type) == PT_PHDR) return true;
+
+            // Sort non-PHDRs by address.
+            return elfFile->rdi(x.p_paddr) < elfFile->rdi(y.p_paddr);
+        }
+    };
+
+    friend struct CompPhdr;
+
+    void sortPhdrs();
+
+    struct CompShdr
+    {
+        ElfFile * elfFile;
+        bool operator ()(const Elf_Shdr & x, const Elf_Shdr & y)
+        {
+            return elfFile->rdi(x.sh_offset) < elfFile->rdi(y.sh_offset);
+        }
+    };
+
+    friend struct CompShdr;
+
+    unsigned int getPageSize() const;
+
+    void sortShdrs();
+
+    void shiftFile(unsigned int extraPages, Elf_Addr startPage);
+
+    std::string getSectionName(const Elf_Shdr & shdr) const;
+
+    Elf_Shdr & findSectionHeader(const SectionName & sectionName);
+
+    std::optional<std::reference_wrapper<Elf_Shdr>> findSection2(const SectionName & sectionName);
+
+    unsigned int getSectionIndex(const SectionName & sectionName);
+
+    std::string & replaceSection(const SectionName & sectionName,
+        unsigned int size);
+
+    bool haveReplacedSection(const SectionName & sectionName) const;
+
+    void writeReplacedSections(Elf_Off & curOff,
+        Elf_Addr startAddr, Elf_Off startOffset);
+
+    void rewriteHeaders(Elf_Addr phdrAddress);
+
+    void rewriteSectionsLibrary();
+
+    void rewriteSectionsExecutable();
+
+    void normalizeNoteSegments();
+
+public:
+
+    void rewriteSections();
+
+    std::string getInterpreter();
+
+    typedef enum { printSoname, replaceSoname } sonameMode;
+
+    void modifySoname(sonameMode op, const std::string & newSoname);
+
+    void setInterpreter(const std::string & newInterpreter);
+
+    typedef enum { rpPrint, rpShrink, rpSet, rpAdd, rpRemove } RPathOp;
+
+    void modifyRPath(RPathOp op, const std::vector<std::string> & allowedRpathPrefixes, std::string newRPath);
+    std::string shrinkRPath(char* rpath, std::vector<std::string> &neededLibs, const std::vector<std::string> & allowedRpathPrefixes);
+    void removeRPath(Elf_Shdr & shdrDynamic);
+
+    void addNeeded(const std::set<std::string> & libs);
+
+    void removeNeeded(const std::set<std::string> & libs);
+
+    void replaceNeeded(const std::map<std::string, std::string> & libs);
+
+    void printNeededLibs() /* should be const */;
+
+    void noDefaultLib();
+
+    void clearSymbolVersions(const std::set<std::string> & syms);
+
+private:
+
+    /* Convert an integer in big or little endian representation (as
+       specified by the ELF header) to this platform's integer
+       representation. */
+    template<class I>
+    I rdi(I i) const;
+
+    /* Convert back to the ELF representation. */
+    template<class I>
+    I wri(I & t, unsigned long long i) const
+    {
+        t = rdi((I) i);
+        return i;
+    }
+
+    Elf_Ehdr *hdr() {
+      return (Elf_Ehdr *)fileContents->data();
+    }
+
+    const Elf_Ehdr *hdr() const {
+      return (const Elf_Ehdr *)fileContents->data();
+    }
+};