ddl_ar tool to work with ddls

tools/ddl_ar_class.cpp

@@ -0,0 +1,51 @@
+#include "ddl_ar_class.h"
+
+
+bool DDLArchive::open(std::filesystem::path ar_file) {
+    _directory.clear();
+    _ar_file = std::move(ar_file);
+
+    std::ifstream f = begin_read();
+    if (!f) return false;
+    f.seekg(4,std::ios::beg);
+    uint32_t dir_offset;
+    f.read(reinterpret_cast<char *>(&dir_offset), sizeof(dir_offset));
+    if (f.gcount() != sizeof(dir_offset)) return false;
+    uint32_t smallest_offset = std::numeric_limits<uint32_t>::max();
+    f.seekg(dir_offset, std::ios::beg);
+    while (f.tellg() < smallest_offset) {
+        char name[13];
+        f.read(name, 12);
+        if (f.gcount() != 12) return false;
+        name[12] = 0;
+        uint32_t offset;
+        f.read(reinterpret_cast<char *>(&offset), 4);
+        if (f.gcount() != 4) return false;
+        _directory.emplace(name, FileRec{offset, {}});
+        smallest_offset = std::min(offset, smallest_offset);
+    }
+    return true;
+}
+
+std::ifstream DDLArchive::begin_read() {
+    return std::ifstream(_ar_file, std::ios::in|std::ios::binary);
+}
+
+DDLArchive::Extracted DDLArchive::extract_file(std::ifstream &s,
+        std::string_view fname) {
+
+    auto iter = _directory.find(fname);
+    if (iter == _directory.end()) {
+        return {fname, false, {}};
+    }
+    s.seekg(iter->second.offset, std::ios::beg);
+    uint32_t sz;
+    s.read(reinterpret_cast<char *>(&sz),4);
+    if (s.gcount() != 4) return {fname, false, {}};
+    std::vector<char> data;
+    data.resize(sz);
+    s.read(data.data(), sz);
+    if (s.gcount() != sz) return {fname, false, {}};
+    return {fname, true, std::move(data)};
+
+}