From 18b8205f3984bff211131f82e4c0a1e33886ea64 Mon Sep 17 00:00:00 2001
From: znone <glyc@sina.com.cn>
Date: Tue, 27 Aug 2019 12:35:52 +0000
Subject: [PATCH] 提供以标准流的方式直接操纵ODBC的BLOB字段
---
include/qtl_common.hpp | 211 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 211 insertions(+), 0 deletions(-)
diff --git a/include/qtl_common.hpp b/include/qtl_common.hpp
index 8bea74d..3b2e8bb 100644
--- a/include/qtl_common.hpp
+++ b/include/qtl_common.hpp
@@ -1116,6 +1116,217 @@
};
};
+class blobbuf : public std::streambuf
+{
+public:
+ blobbuf() = default;
+ blobbuf(const blobbuf&) = default;
+ blobbuf& operator=(const blobbuf&) = default;
+ virtual ~blobbuf()
+ {
+ overflow();
+ }
+
+
+protected:
+ virtual pos_type seekoff(off_type off, std::ios_base::seekdir dir,
+ std::ios_base::openmode which = std::ios_base::in | std::ios_base::out) override
+ {
+ if (which&std::ios_base::in)
+ {
+ pos_type pos = 0;
+ pos = seekoff(m_pos, off, dir);
+ return seekpos(pos, which);
+ }
+ return std::streambuf::seekoff(off, dir, which);
+ }
+
+ virtual pos_type seekpos(pos_type pos,
+ std::ios_base::openmode which = std::ios_base::in | std::ios_base::out) override
+ {
+ if (pos >= m_size)
+ return pos_type(off_type(-1));
+
+ if (which&std::ios_base::out)
+ {
+ if (pos < m_pos || pos >= m_pos + off_type(egptr() - pbase()))
+ {
+ overflow();
+ m_pos = pos;
+ setp(m_buf.data(), m_buf.data() + m_buf.size());
+ }
+ else
+ {
+ pbump(off_type(pos - pabs()));
+ }
+ }
+ else if (which&std::ios_base::in)
+ {
+ if (pos < m_pos || pos >= m_pos + off_type(epptr() - eback()))
+ {
+ m_pos = pos;
+ setg(m_buf.data(), m_buf.data(), m_buf.data());
+ }
+ else
+ {
+ gbump(off_type(pos - gabs()));
+ }
+ }
+ return pos;
+ }
+
+ virtual std::streamsize showmanyc() override
+ {
+ return m_size - pabs();
+ }
+
+ virtual int_type underflow() override
+ {
+ if (pptr() > pbase())
+ overflow();
+
+ off_type count = egptr() - eback();
+ pos_type next_pos = 0;
+ if (count == 0 && eback() == m_buf.data())
+ {
+ setg(m_buf.data(), m_buf.data(), m_buf.data() + m_buf.size());
+ count = m_buf.size();
+ }
+ else
+ {
+ next_pos = m_pos + pos_type(count);
+ }
+ if (next_pos >= m_size)
+ return traits_type::eof();
+
+ count = std::min(count, m_size - next_pos);
+ m_pos = next_pos;
+ if (read_blob(m_buf.data(), count, m_pos))
+ {
+ setg(eback(), eback(), eback() + count);
+ return traits_type::to_int_type(*gptr());
+ }
+ else
+ {
+ return traits_type::eof();
+ }
+ }
+
+ virtual int_type overflow(int_type ch = traits_type::eof()) override
+ {
+ if (pptr() != pbase())
+ {
+ size_t count = pptr() - pbase();
+ write_blob(pbase(), count);
+
+ //auto intersection = interval_intersection(m_pos, egptr() - eback(), m_pos, epptr() - pbase());
+ //if (intersection.first != intersection.second)
+ //{
+ // commit(intersection.first, intersection.second);
+ //}
+
+ m_pos += count;
+ setp(pbase(), epptr());
+ }
+ if (!traits_type::eq_int_type(ch, traits_type::eof()))
+ {
+ char_type c = traits_type::to_char_type(ch);
+ if (m_pos >= m_size)
+ return traits_type::eof();
+ write_blob(&c, 1);
+
+ //auto intersection = interval_intersection(m_pos, egptr() - eback(), m_pos, 1);
+ //if (intersection.first != intersection.second)
+ //{
+ // eback()[intersection.first - m_pos] = c;
+ //}
+ m_pos += 1;
+
+ }
+ return ch;
+ }
+
+ virtual int_type pbackfail(int_type c = traits_type::eof()) override
+ {
+ if (gptr() == 0
+ || gptr() <= eback()
+ || (!traits_type::eq_int_type(traits_type::eof(), c)
+ && !traits_type::eq(traits_type::to_char_type(c), gptr()[-1])))
+ {
+ return (traits_type::eof()); // can't put back, fail
+ }
+ else
+ { // back up one position and store put-back character
+ gbump(-1);
+ if (!traits_type::eq_int_type(traits_type::eof(), c))
+ *gptr() = traits_type::to_char_type(c);
+ return (traits_type::not_eof(c));
+ }
+ }
+
+private:
+
+ off_type seekoff(off_type position, off_type off, std::ios_base::seekdir dir)
+ {
+ off_type result = 0;
+ switch (dir)
+ {
+ case std::ios_base::beg:
+ result = off;
+ break;
+ case std::ios_base::cur:
+ result = position + off;
+ break;
+ case std::ios_base::end:
+ result = m_size - off;
+ }
+ if (result > m_size)
+ result = m_size;
+ return result;
+ }
+
+ pos_type gabs() const // absolute offset of input pointer in blob field
+ {
+ return m_pos + off_type(gptr() - eback());
+ }
+
+ pos_type pabs() const // absolute offset of output pointer in blob field
+ {
+ return m_pos + off_type(pptr() - pbase());
+ }
+
+protected:
+ std::vector<char> m_buf;
+ pos_type m_size;
+ pos_type m_pos; //position in the input sequence
+
+ virtual bool read_blob(char* buffer, off_type& count, pos_type position) = 0;
+ virtual void write_blob(const char* buffer, size_t count) = 0;
+
+ void init_buffer(std::ios_base::openmode mode)
+ {
+ size_t bufsize;
+ if (m_size > 0)
+ bufsize = std::min<size_t>(blob_buffer_size, m_size);
+ else
+ bufsize = blob_buffer_size;
+ if (mode&std::ios_base::in)
+ {
+ m_buf.resize(bufsize);
+ m_pos = 0;
+ setg(m_buf.data(), m_buf.data(), m_buf.data());
+ }
+ else if (mode&std::ios_base::out)
+ {
+ m_buf.resize(bufsize);
+ m_pos = 0;
+ setp(m_buf.data(), m_buf.data() + bufsize);
+ }
+ }
+};
+
+typedef std::function<void(std::ostream&)> blob_writer;
+
template<typename Database>
struct transaction
{
--
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