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Issue #297 - Implemented BasicMemoryStreamBuf::seekoff

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This change adds support for `tellp`, `tellg` and seeking.

**Additional notes:**

+ `tellg` calls `rdbuf->pubseekoff(0, cur, out)` [lib.ostream.seeks] so need to
  provide an override of `seekoff`.
+ Requirements for `seekoff` are in 27.7.1.3.
+ 27.7.1.3 - Standard has a roundabout way of saying `cur` is valid if only one
  of `in` or `out` is specified (Condition 3).
+ `xend` is `egptr`/`epptr` (get area/put area).
+ `xbeg` is `eback`/`pbase` (get area/put area).
+ `xnext` is `gptr`/`pptr` (get area/put area).
+ `newoff` is a bit of a misnomer, the new offset into the stream is given by
  `newoff + off`.  `newoff` is really the start point.
+ You can set `gnext` with `setg`, but you can't do that with `setp` you have
  to `pbump` by the new offset minus the current offset.
This commit is contained in:
martin-osborne
2015-01-24 18:39:06 +00:00
parent f79ab5b77a
commit 5e104addd3
3 changed files with 202 additions and 12 deletions
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82
Foundation/include/Poco/MemoryStream.h
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@@ -32,8 +32,8 @@
namespace Poco {
template <typename ch, typename tr>
class BasicMemoryStreamBuf: public std::basic_streambuf<ch, tr>
template <typename charT, typename traits>
class BasicMemoryStreamBuf: public std::basic_streambuf<charT, traits>
/// BasicMemoryStreamBuf is a simple implementation of a
/// stream buffer for reading and writing from a memory area.
///
@@ -43,13 +43,11 @@ class BasicMemoryStreamBuf: public std::basic_streambuf<ch, tr>
/// ostream, but not for an iostream.
{
protected:
typedef std::basic_streambuf<ch, tr> Base;
typedef std::basic_ios<ch, tr> IOS;
typedef ch char_type;
typedef tr char_traits;
typedef typename Base::int_type int_type;
typedef typename Base::pos_type pos_type;
typedef typename Base::off_type off_type;
typedef charT char_type;
typedef typename traits::int_type int_type;
typedef typename traits::pos_type pos_type;
typedef typename traits::off_type off_type;
typedef traits traits_type;
public:
BasicMemoryStreamBuf(char_type* pBuffer, std::streamsize bufferSize):
@@ -66,12 +64,74 @@ public:
virtual int_type overflow(int_type /*c*/)
{
return char_traits::eof();
return traits_type::eof();
}
virtual int_type underflow()
{
return char_traits::eof();
return traits_type::eof();
}
virtual pos_type seekoff(off_type off, std::ios_base::seekdir way, std::ios_base::openmode which = std::ios_base::in | std::ios_base::out)
{
const pos_type fail = off_type(-1);
off_type newoff = off_type(-1);
if ((which & std::ios_base::in) != 0)
{
// Position the input sequence
if (gptr() == 0)
return fail;
switch (way)
{
case std::ios_base::beg:
newoff = 0;
break;
case std::ios_base::cur:
// cur is not valid if both in and out are specified (Condition 3)
if ((which & std::ios_base::out) != 0)
return fail;
newoff = gptr() - eback();
break;
case std::ios_base::end:
newoff = egptr() - eback();
break;
}
if ((newoff + off) < 0 || (egptr() - eback()) < (newoff + off))
return fail;
this->setg(eback(), eback() + newoff + off, egptr());
}
if ((which & std::ios_base::out) != 0)
{
if (pptr() == 0)
return fail;
switch (way)
{
case std::ios_base::beg:
newoff = 0;
break;
case std::ios_base::cur:
// cur is not valid if both in and out are specified (Condition 3)
if ((which & std::ios_base::in) != 0)
return fail;
newoff = pptr() - pbase();
break;
case std::ios_base::end:
newoff = epptr() - pbase();
break;
}
if (newoff + off < 0 || (epptr() - pbase()) < newoff + off)
return fail;
this->pbump((int)(newoff + off - (pptr() - pbase())));
}
return newoff;
}
virtual int sync()