October 2006 - Boost-users - lists.preview.boost.org

Re: [Boost-users] Safe way to allocate block of memory
by Nat Goodspeed 31 Oct '06

31 Oct '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Stephen Torri > Sent: Tuesday, October 31, 2006 9:34 AM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] Safe way to allocate block of memory > > On Tue, 2006-10-31 at 06:49 -0500, Nat Goodspeed wrote: > > [Nat] Have you tried using a std::vector<unsigned char>? You can get a > > pointer to the first byte in the vector by &myVector[0]. Then > > std::vector takes care of all the rest for you -- including allocation, > > cleanup and the STL container support. > > // present_pos is an std::vector<boost::uint8_t>::iterator to the > // where the reading will start. > // > // dest_addr_ptr is where to write in memory > // > // length is how many bytes to read. > void read ( boost::uint8_t* dest_addr_ptr, boost::uint32_t const& length ) > { > if ( present_pos + length > data.end() ) > { > // ERROR > } > > memcpy ( dest_addr_ptr, *(*present_pos), length; [Nat] memcpy ( dest_addr_ptr, &(*present_pos), length ); or even // trust STL implementation to optimize appropriately std::copy(present_pos, present_pos + length, dest_addr_ptr); > }

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Re: [Boost-users] Safe way to allocate block of memory
by Nat Goodspeed 31 Oct '06

31 Oct '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Stephen Torri > Sent: Monday, October 30, 2006 11:53 PM > To: boost > Subject: [Boost-users] Safe way to allocate block of memory > > I am trying to create a class which I can use to safely allocate a block > of bytes. > > My present method is create a block via 'new char[size]' and store this > pointer in a class. > > I was wondering if there was a boost method for creating an array of > bytes? [Nat] Have you tried using a std::vector<unsigned char>? You can get a pointer to the first byte in the vector by &myVector[0]. Then std::vector takes care of all the rest for you -- including allocation, cleanup and the STL container support.

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Safe way to allocate block of memory
by Stephen Torri 31 Oct '06

31 Oct '06

I am trying to create a class which I can use to safely allocate a block of bytes. One purpose is to allow me to easily fill in a variable with N bytes from the block. For example the code below would attempt to fill a variable (e.g. boost::uint32_t val ). template <typename Value_Type> void read (Value_Type* value) { m_file_img->read (reinterpret_cast<char*>(value), sizeof(Value_Type)); } The second purpose is to create a block of bytes which I can write bytes to at particular offsets from the beginning. For example if I created a block of 50 bytes I may want to fill in bytes 5 through 8 with 4 bytes of data. My present method is create a block via 'new char[size]' and store this pointer in a class. This works for reading by when later in my program when I create a instance to write data to it I get a segfault. I was wondering if there was a boost method for creating an array of bytes? My code is below. I would greatly appreciate comments on how to utilize more of boost's functionality. Stephen ----------------------- #ifndef MEMORY_MAP_H_ #define MEMORY_MAP_H_ #include <boost/cstdint.hpp> #include <boost/scoped_ptr.hpp> #include <boost/shared_ptr.hpp> #include <boost/format.hpp> #include <iostream> #include <iomanip> #include "io/exceptions/IO_Exception.hpp" namespace libreverse { namespace data_types { class Memory_Map { public: typedef char data_type; typedef char const* const_iterator; typedef data_type* iterator; typedef boost::shared_ptr<Memory_Map> ptr; Memory_Map ( boost::uint32_t const& size ); Memory_Map ( boost::uint64_t const& size ); Memory_Map ( Memory_Map const& rhs ); virtual ~Memory_Map(); template <typename Offset_Type> void seek ( Offset_Type offset ) { if (offset > m_size) { std::cerr << "The offset given, " << offset << " is invalid. Its pointing to a " << std::endl << "memory location outside of space " << "allocated to" << std::endl << "this Memory Map. (" << m_size << ")" << std::endl; throw errors::IO_Exception ( errors::IO_Exception::OUT_OF_RANGE ); } m_present_pos = m_base_addr + offset; std::cout << boost::format ("Memory_Map::seek - new present pos = %1p") % *m_present_pos << std::endl; } void read ( iterator dest_addr_ptr, boost::uint32_t const& len); void copy ( const_iterator src_addr_ptr, boost::uint32_t const& len ); iterator begin(); const_iterator begin() const; const_iterator end() const; iterator get_Present_Position (void); const_iterator get_Present_Position (void) const; boost::uint32_t const& size (void) const; private: char* m_base_addr; boost::uint32_t m_size; // Size of memory iterator m_present_pos; iterator m_end_addr; }; #endif /* MEMORY_MAP_H_ */ ---------------- #include "Memory_Map.hpp" namespace libreverse { namespace data_types { Memory_Map::Memory_Map ( boost::uint32_t const& size ) : m_size ( size ) { m_base_addr = new char[size]; m_present_pos = m_base_addr; /* std::cout << boost::format ("Memory_Map::constructor - start present pos = %1%") % boost::io::group ( std::hex, m_present_pos ) << std::endl; */ m_end_addr = m_base_addr + size; } Memory_Map::Memory_Map ( boost::uint64_t const& size ) : m_size ( size ) { m_base_addr = new char[size]; m_present_pos = m_base_addr; m_end_addr = m_base_addr + size; } Memory_Map::Memory_Map ( Memory_Map const& rhs ) : m_base_addr (rhs.m_base_addr), m_size (rhs.m_size), m_present_pos ( rhs.m_present_pos ), m_end_addr ( rhs.m_end_addr ) { /* std::cout << "Memory_Map::copy_constructor - start present pos = " << m_present_pos << std::endl; */ #warning We do not deep copy the data here } Memory_Map::~Memory_Map () { delete[] m_base_addr; } void Memory_Map::read ( iterator dest_addr_ptr, boost::uint32_t const& length ) { if ( m_present_pos > m_end_addr ) { std::cerr << "The present position pointer is invalid. " << "Its pointing" << std::endl << "to a memory location out side of space " << "allocated to" << std::endl << "this Memory Map." << std::endl; throw errors::IO_Exception ( errors::IO_Exception::INVALID_INDEX ); } memcpy ( dest_addr_ptr, m_present_pos, length ); m_present_pos += length; } Memory_Map::iterator Memory_Map::begin() { return m_base_addr; } Memory_Map::const_iterator Memory_Map::begin() const { return m_base_addr; } Memory_Map::const_iterator Memory_Map::end() const { return m_end_addr; } Memory_Map::iterator Memory_Map::get_Present_Position (void) { return m_present_pos; } Memory_Map::const_iterator Memory_Map::get_Present_Position (void) const { return m_present_pos; } boost::uint32_t const& Memory_Map::size (void) const { return m_size; } void Memory_Map::copy ( const_iterator src_addr_ptr, boost::uint32_t const& length ) { // If m_present_pos + length > m_end_addr ERROR if ( m_present_pos + length > m_end_addr ) { std::cerr << "The present position pointer will be" << " invalid if we write from the present" << std::endl << "position with the given length. It will" << " cause an segfault. Recheck the value" << std::endl << "given for length (" << length << ") or check" << " the setting of the present position." << std::endl; throw errors::IO_Exception ( errors::IO_Exception::OUT_OF_RANGE ); } memcpy ( m_present_pos, src_addr_ptr, length ); m_present_pos += length; }

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Re: [Boost-users] boost filesystem
by Nat Goodspeed 31 Oct '06

31 Oct '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Peng Yu > Sent: Monday, October 30, 2006 11:53 AM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] boost filesystem > > > > I have the following program and files .test.seg and test.seg. I try > > > to run the main program. It seems that boost filesystem doesn't > > > recognize file name starting with a dot. > > > > > > Is it a bug in boost filesystem. Or I didn't use it properly? > > > http://boost.org/libs/filesystem/doc/portability_guide.htm#name_check-_f un > ctions > > > > If you use the default constructor for path, then it uses a name > > checker that doesn't allow filenames starting with dots. This was > > intended to promote portability, but has been found to be a bad idea > > and will not be in boost 1.34 (nor is it in the tr2 proposal). > > There is only version 1.33 online. How can I get 1.34? [Nat] You don't need to use 1.34 to suppress the name check. Pass (e.g.) boost::filesystem::no_check as the second parameter to the boost::filesystem::path constructor.

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Re: [Boost-users] boost filesystem
by Wu Yinghui, Freddie 31 Oct '06

31 Oct '06

> > There is only version 1.33 online. How can I get 1.34? > 1.34 is not yet officially released. Check out page http://sourceforge.net/cvs/?group_id=7586 for CVS checkout instructions. Cheers, Freddie -- Wu Yinghui, Freddie Research & Development Senior Software Engineer Volume Interactions Pte Ltd 1 Kim Seng Promenade, #12-01 Great World City East Tower Singapore 237994 Tel: +65 62226962 (Ext 216) Fax: +65 62226215 Email: yhwu(a)volumeinteractions.com URL: http://www.volumeinteractions.com Important: This message is intended for the recipient(s) addressed above. It contains privileged and confidential information. If you are not the intended recipient, please notify the sender immediately by replying to this message and then delete it from your system. You must not read, copy, use, or disseminate this communication in any form. Thank you.

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[boost::shared_ptr] lightweight_mutex question
by Ovanes Markarian 30 Oct '06

30 Oct '06

Hi! I saw that shared_ptr used lightweight_mutext to enable locking/unlocking in MT environments. Is it an official class which I could also use in my project, or should I really bind to the boost threading library? With Kind Regards, Ovanes Markarian

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[asio] reported memory leaks when using MFC
by Christian Henning 30 Oct '06

30 Oct '06

Hi there, I have been spending some hour now on trackign down memory issues that are reported from MFC. In my client program I'm calling io_service::post( ... ) quite often and is seems to me that it allocates memory that is never been deallocated afterwards. Every call of post( ... ) will result in one memory leak. The allocation takes place in the file handler_alloc_helpers.hpp in line 39. Setting a breakpoint here shows that every post(...) call allocates some memory. The deallocation which is right below in the file is never called. Is this an known issue? Regards, Christian

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[Date_Time] Posix Time Zone offset question
by Jacob L. Anawalt 30 Oct '06

30 Oct '06

Hi, I've started experimenting with Boost.Date_Time's Local Time stuff. While using a posix_time_zone object the results were not what I expected. I used the POSIX.1 (IEEE Std 1003.1) timezone string suitable for use in the TZ environment variable describing my timezone for the year 2006: MST7MDT,M4.1.0,M10.5.0 Date_Time's posix_time_zone object told me that it was already the 26th but my wall clock disagrees. :) The online documentation says "A posix_time_zone is unique in that the object is created from a Posix time zone string (IEEE Std 1003.1)." and "'offset' is the offset from UTC." In the sources I've come across the offset part of a POSIX.1 timezone string is defined as "the value added to the local time to arrive at Coordinated Universal Time" with a not that "[i]f preceded by a '-', the timezone shall be east of the Prime Meridian; otherwise, it shall be west (which may be indicated by an optional preceding '+' )." * http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap08.html * man pages of tzset Why do I need a negative (-) offset to make posix_time_zone work when the time zone is west of the Prime Meridian? I couldn't find anyone else raising this issue on the list or bug tracker, so maybe I'm just up in the night. Thank-you for the library. I really like some of the concepts in Date_Time Posix Time and Gregorian and have high hopes for Local Time stuff. -- Jacob

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Compiling for 32 bits on x86_64
by Björn Regnström 30 Oct '06

30 Oct '06

I compiled boost on a SuSE 9.2 x86_64 machine (AMD Athlon), it built everything but compiled and linked for 64 bits. The libraries ended up in /usr/local/lib instead of lib64 though. How do I tell the build system to build 32 bit libraries (and put the 64 bit libraries in lib64)? Best regards, (and apologies if this is not the right forum...) Bjorn Regnstrom

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boost filesystem
by Peng Yu 30 Oct '06

30 Oct '06

Hi, I have the following program and files .test.seg and test.seg. I try to run the main program. It seems that boost filesystem doesn't recognize file name starting with a dot. Is it a bug in boost filesystem. Or I didn't use it properly? Thanks, Peng $ ls -a . .dep main-g.exe main.o main-o.o .test.seg .. main.cc main-g.o main-o.exe Makefile test.seg $ cat main.cc #include <iostream> #include <boost/filesystem/operations.hpp> // includes boost/filesystem/path.hpp #include <boost/filesystem/fstream.hpp> int main() { if(boost::filesystem::exists("test.seg")) std::cout << "good" << std::endl; if(boost::filesystem::exists(".test.seg")) std::cout << "good1" << std::endl; } $ ./main-g.exe good terminate called after throwing an instance of 'boost::filesystem::filesystem_error' what(): boost::filesystem::path: invalid name ".test.seg" in path: ".test.seg" Aborted

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