Method read

src/io/file_memory_source.cpp:37–49

    const std::string& name() const override { return name_; }

    std::size_t read(u64 offset, void* out, std::size_t len) const override {
        if (offset >= size_) return 0;
        // Overflow-safe clamp (offset < size_ guaranteed above, so the
        // subtraction can't underflow); `offset + len` could wrap for huge len.
        if (len > size_ - offset) len = static_cast<std::size_t>(size_ - offset);
        std::lock_guard<std::mutex> lk(mu_);
        if (LMPFS_FSEEK64(fp_, static_cast<i64>(offset), SEEK_SET) != 0)
            throw_error("seek({}) failed in {}", offset, name_);
        std::size_t got = std::fread(out, 1, len, fp_);
        if (got != len && std::ferror(fp_))
            throw_error("read({},{}) failed in {}", offset, len, name_);
        return got;
    }

private:
    std::FILE*  fp_   = nullptr;