archive-file.h

#pragma once

#include "mold.h"
#include "filetype.h"

namespace mold {

struct ArHdr {
  char ar_name[16];
  char ar_date[12];
  char ar_uid[6];
  char ar_gid[6];
  char ar_mode[8];
  char ar_size[10];
  char ar_fmag[2];

  bool starts_with(std::string_view s) const {
    return std::string_view(ar_name, s.size()) == s;
  }

  bool is_strtab() const {
    return starts_with("// ");
  }

  bool is_symtab() const {
    return starts_with("/ ") || starts_with("/SYM64/ ");
  }

  std::string read_name(std::string_view strtab, u8 *&ptr) const {
    // BSD-style long filename
    if (starts_with("#1/")) {
      int namelen = atoi(ar_name + 3);
      std::string name{(char *)ptr, (size_t)namelen};
      ptr += namelen;

      if (size_t pos = name.find('\0'))
        name = name.substr(0, pos);
      return name;
    }

    // SysV-style long filename
    if (starts_with("/")) {
      const char *start = strtab.data() + atoi(ar_name + 1);
      return {start, (const char *)strstr(start, "/\n")};
    }

    // Short fileanme
    if (const char *end = (char *)memchr(ar_name, '/', sizeof(ar_name)))
      return {ar_name, end};
    return {ar_name, sizeof(ar_name)};
  }
};

template <typename C>
std::vector<MappedFile<C> *>
read_thin_archive_members(C &ctx, MappedFile<C> *mf) {
  u8 *begin = mf->data;
  u8 *data = begin + 8;
  std::vector<MappedFile<C> *> vec;
  std::string_view strtab;

  while (data < begin + mf->size) {
    // Each header is aligned to a 2 byte boundary.
    if ((begin - data) % 2)
      data++;

    ArHdr &hdr = *(ArHdr *)data;
    u8 *body = data + sizeof(hdr);
    u64 size = atol(hdr.ar_size);

    // Read a string table.
    if (hdr.is_strtab()) {
      strtab = {(char *)body, (size_t)size};
      data = body + size;
      continue;
    }

    // Skip a symbol table.
    if (hdr.is_symtab()) {
      data = body + size;
      continue;
    }

    if (!hdr.starts_with("#1/") && !hdr.starts_with("/"))
      Fatal(ctx) << mf->name << ": filename is not stored as a long filename";

    std::string name = hdr.read_name(strtab, body);

    // Skip if symbol table
    if (name == "__.SYMDEF" || name == "__.SYMDEF SORTED")
      continue;

    std::string path = name.starts_with('/') ?
      name : (filepath(mf->name).parent_path() / name).string();
    vec.push_back(MappedFile<C>::must_open(ctx, path));
    data = body;
  }
  return vec;
}

template <typename C>
std::vector<MappedFile<C> *>
read_fat_archive_members(C &ctx, MappedFile<C> *mf) {
  u8 *begin = mf->data;
  u8 *data = begin + 8;
  std::vector<MappedFile<C> *> vec;
  std::string_view strtab;

  while (begin + mf->size - data >= 2) {
    if ((begin - data) % 2)
      data++;

    ArHdr &hdr = *(ArHdr *)data;
    u8 *body = data + sizeof(hdr);
    u64 size = atol(hdr.ar_size);
    data = body + size;

    // Read if string table
    if (hdr.is_strtab()) {
      strtab = {(char *)body, (size_t)size};
      continue;
    }

    // Skip if symbol table
    if (hdr.is_symtab())
      continue;

    // Read the name field
    std::string name = hdr.read_name(strtab, body);

    // Skip if symbol table
    if (name == "__.SYMDEF" || name == "__.SYMDEF SORTED")
      continue;

    vec.push_back(mf->slice(ctx, name, body - begin, data - body));
  }
  return vec;
}

template <typename C>
std::vector<MappedFile<C> *>
read_archive_members(C &ctx, MappedFile<C> *mf) {
  switch (get_file_type(mf)) {
  case FileType::AR:
    return read_fat_archive_members(ctx, mf);
  case FileType::THIN_AR:
    return read_thin_archive_members(ctx, mf);
  default:
    unreachable();
  }
}

} // namespace mold