内存碎片序列化

我们经常有各种字段需要序列化，对于文本，可以使用std::ostringstream,或者snprintf系列函数。

对于二进制流，可以使用ostrstream，不过这个函数似乎被废弃

这里yy一个简单的，注意它不会将所有的内存重新拷贝，而是将它们组织起来，但是对外看起来就像序列化一样

#pragma once #include <vector> class mem { private: class MemoryPtr{ public: MemoryPtr(const char* ptr,size_t size,size_t offset): m_ptr_(ptr), m_size_(size), m_offset_(offset){} inline size_t offset() const{ return m_offset_; } inline size_t size() const{ return m_size_; } inline const char* buf() const{ return m_ptr_; } private: const char* m_ptr_; size_t m_size_; size_t m_offset_; }; typedef std::vector<MemoryPtr*> Vector; typedef Vector::iterator Iter; public: mem(void): m_size_(0), m_last_index_(0){} bool Memcpy(char* buf,size_t offset,size_t size) { if(offset + size <= m_size_) { if( offset < m_container_[m_last_index_]->offset() || offset >= m_container_[m_last_index_]->offset() + m_container_[m_last_index_]->size()) { m_last_index_ = IndexPos(offset); } size_t tmp = offset - m_container_[m_last_index_]->offset(); size_t total = std::min(size,m_container_[m_last_index_]->size() - tmp); size -= total; memcpy(buf,m_container_[m_last_index_]->buf() + tmp,total); size_t index = m_last_index_ + 1; while(size > 0) { tmp = std::min(size,m_container_[index]->size()); memcpy(buf + total,m_container_[index]->buf(),tmp); total += tmp; size -= tmp; index ++; } return true; }else{ return false; } } void Append(const char* ptr,size_t size) { m_container_.push_back(new MemoryPtr(ptr,size,m_size_)); m_size_ += size; } void Clear() { for(Iter iter = m_container_.begin(); iter != m_container_.end(); ++iter) { delete *iter; } m_container_.clear(); } private: size_t IndexPos(size_t pos){ int low = 0; int high = (int)m_container_.size() - 1; int mid; int midVal; while (low <= high) { mid = (low + high) / 2; midVal = (int)(m_container_[mid]->offset()); if (midVal < pos){ low = mid + 1; } else if (midVal > pos){ high = mid - 1; } else{ return (size_t)mid; } } return (size_t)(low-1); } private: Vector m_container_; size_t m_size_; size_t m_last_index_; };

 #include "mem.h" #include <cstdio> int main(int argc,const char** argv) { mem m; char buf1[] = "qiujinwu"; char buf2[] = "lilili"; char buf3[] = "kingqiu"; m.Append(buf1,sizeof(buf1)); m.Append(buf2,sizeof(buf2)); m.Append(buf3,sizeof(buf3)); char buf[11]; m.Memcpy(buf,10,sizeof(buf)); m.Memcpy(buf,10,sizeof(buf)); return 0; }