doos 1.0.0: images, size cap, subuid ids, working apt in host mode

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/util.hpp

@@ -1,8 +1,10 @@
 #pragma once
 #include <cerrno>
+#include <cstdint>
 #include <filesystem>
 #include <stdexcept>
 #include <string>
+#include <vector>
 
 namespace doos {
 
@@ -45,7 +47,31 @@ private:
     Fd fd_;
 };
 
+// Parses "512m", "2g", "1t" (k/m/g/t, optional trailing b) into bytes; throws on garbage.
+std::uint64_t parseSize(const std::string& text);
+std::string formatSize(std::uint64_t bytes);
+
+struct ProcResult {
+    int code = -1;
+    std::string out;  // stdout, only when captured
+};
+// fork+exec without a shell. Captured output is capped; stderr is inherited unless quiet.
+ProcResult runProcess(const std::vector<std::string>& argv, bool capture = false, bool quiet = false);
+
 namespace fsutil {
+struct SeedStats {
+    std::size_t made = 0;
+    std::size_t skipped = 0;  // unreadable or unsupported entries, never silent
+    std::uint64_t bytes = 0;
+};
+// Creates every directory of `lower` in `upper` (owner rwx added) so a unmapped-owner lower stays writable.
+SeedStats mirrorDirs(const std::filesystem::path& lower, const std::filesystem::path& upper);
+// Copies dirs, regular files and symlinks readable by the caller. Capped by spec.hpp limits.
+SeedStats copyTree(const std::filesystem::path& from, const std::filesystem::path& to);
+// Copies only the regular files directly inside `from` (readable ones) into `to`; existing targets stay.
+SeedStats copyFiles(const std::filesystem::path& from, const std::filesystem::path& to);
+// Sum of allocated bytes (st_blocks) below p, lstat only. `skipped` counts unreadable dirs.
+std::uint64_t diskUsage(const std::filesystem::path& p, std::size_t& skipped);
 void mkdirs(const std::filesystem::path& p, mode_t mode = 0755);
 void writeFile(const std::filesystem::path& p, const std::string& content);
 std::string readFile(const std::filesystem::path& p);