add ItemRT.afs decoder

src/AFSArchive.cc

@@ -0,0 +1,56 @@
+#include "AFSArchive.hh"
+
+#include <stdio.h>
+#include <string.h>
+
+#include <phosg/Encoding.hh>
+#include <phosg/Filesystem.hh>
+#include <phosg/Strings.hh>
+
+using namespace std;
+
+AFSArchive::AFSArchive(std::shared_ptr<const std::string> data)
+    : data(data) {
+  struct FileHeader {
+    be_uint32_t magic;
+    le_uint32_t num_files;
+  } __attribute__((packed));
+
+  struct FileEntry {
+    le_uint32_t offset;
+    le_uint32_t size;
+  } __attribute__((packed));
+
+  StringReader r(*this->data);
+  const auto& header = r.get<FileHeader>();
+  if (header.magic != 0x41465300) {
+    throw runtime_error("file is not an AFS archive");
+  }
+
+  while (this->entries.size() < header.num_files) {
+    const auto& entry = r.get<FileEntry>();
+    this->entries.emplace_back(Entry{.offset = entry.offset, .size = entry.size});
+  }
+}
+
+std::pair<const void*, size_t> AFSArchive::get(size_t index) const {
+  const auto& entry = this->entries.at(index);
+  if (entry.offset > this->data->size()) {
+    throw out_of_range("entry begins beyond end of archive");
+  }
+  if (entry.offset + entry.size > this->data->size()) {
+    throw out_of_range("entry extends beyond end of archive");
+  }
+
+  return make_pair(this->data->data() + entry.offset, entry.size);
+}
+
+std::string AFSArchive::get_copy(size_t index) const {
+  auto ret = this->get(index);
+  return string(reinterpret_cast<const char*>(ret.first), ret.second);
+}
+
+StringReader AFSArchive::get_reader(size_t index) const {
+  auto ret = this->get(index);
+  return StringReader(ret.first, ret.second);
+}