/*
?*?File:?atu_shm_buffer.cpp
?*?Description:?A?shared?memory?buffer.?Read/write?a?shared?memory?just?like?a?normal?buffer.
?*?Use?a?semaphore?with?the?same?name?to?synchronize?the?shared?memory?buffer?in?multi-process.
?*?Created?on:?2012-9-18
?*?Author:?PArt
?*?Any?questions?please?mail?me:）?atu8292991@gmail.com
?*/

#include?
#include?
#include?
#include?
#include?
#include?
#include?
#include?“atu_shm_buffer.h“

namespace?atu_libs?{

namespace?atu_shm_buffer?{
/*
?*??Constructor?of?atu_shm_buffer.
?*??@name:?????the?name?of?the?shared?memory.
?*??@len:??????if?first?created?specify?the?length?of?the?shared?memroy.
?*??@create:???true?create?a?new?shared?memory?false?link?to?an?exist?shared?memory.
?*/
atu_shm_buffer::atu_shm_buffer（const?char?*name?size_t?len?bool?create）
:?m_buf（NULL）
?m_len（len）
?m_name（name）
{
	assert（NULL?!=?name）;

	int?ret（0）;

	//link?to?the?shared?memory.
	if?（create）
	{
		m_fd?=?shm_open（name?O_RDWR?|?O_CREAT?0644）;

		//create?a?semaphore?for?w/r?operation.
		m_sem?=?sem_open（name?O_CREAT?0644?1）;
		if?（SEM_FAILED?==?m_sem）
		{
			fprintf（stderr?“Failed?to?create?semaphore?%s!\n“?name）;
			return;
		}
		//set?the?size?of?the?shared?memory.
		ret?=?ftruncate（m_fd?len）;
		if?（-1?==?ret）
		{
			fprintf（stderr?“Failed?to?re-size?shared?memory?buffer?%s!\n“?name）;
			return;
		}
	}
	else
	{
		m_fd?=?shm_open（name?O_RDWR?0644）;
		//set?a?sem?for?w/r?operation.
		m_sem?=?sem_open（name?O_RDWR）;
		if?（SEM_FAILED?==?m_sem）
		{
			fprintf（stderr?“Failed?to?create?semaphore?%s!\n“?name）;
			return;
		}
	}
	if?（-1?==?m_fd）
	{
		fprintf（stderr?“Failed?to?create?shared?memory?buffer?%s!\n“?name）;
		return;
	}

	//get?shared?memory?status.
	ret?=?fstat（m_fd?&m_stat）;
	if?（-1?==?ret）
	{
		fprintf（stderr?“Failed?to?get?status?of?shared?memory!\n“）;
		return;
	}
	m_len?=?m_stat.st_size;

	//map?the?shared?memory?to?buffer.
	m_buf?=?mmap（NULL?len?PROT_READ?|?PROT_WRITE?MAP_SHARED?m_fd?0）;
	if?（MAP_FAILED?==?m_buf）
	{
		perror（“Failed?to?map?shared?memory?to?process!“）;
		return;
	}

	//If?the?shared?memory?is?created?for?the?first?time?initialize?it.
	if?（create）
	{
		memset（m_buf?0?len）;
	}
}

atu_shm_buffer::~atu_shm_buffer（）?{
	if?（-1?!=?m_fd）
	{
		munmap（m_buf?m_len）;
	}

	//!!!If?you?want?to?unlink?semaphore?and?shared?memory?please?use?function?unlink（）.
}

/*
?*??Unlink?the?shared?memory?and?semaphore?from?linux?kernel.
?*/
void?atu_shm_buffer::unlink（void）
{
	if?（MAP_FAILED?!=?m_buf）
	{
		sem_unlink（m_name.c_str（））;
		shm_unlink（m_name.c_str（））;
	}
}

/*
?*??Read?from?shared?memory.?Use?a?semaphore?with?the?same?name?to?synchronize.
?*??@buf:????the?point?to?a?buffer?the?buffer?must?be?allocated.
?*??@len:????the?length?of?bytes?read?from?shared?memory.
?*/
void?atu_shm_buffer::read（char?*buffer?size_t?len）
{
	if?（len?>?m_len）
	{
		fprintf（stderr?“[read]?Buffer?is?truncated!?From?%d?to?%d?bytes.\n“
				（int）len?（int

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2012-09-19?11:57??atu_shm_buffer\
?????文件???????12243??2012-09-18?16:45??atu_shm_buffer\.cproject
?????目錄???????????0??2012-09-19?16:27??__MACOSX\
?????目錄???????????0??2012-09-19?16:27??__MACOSX\atu_shm_buffer\
?????文件??????????82??2012-09-18?16:45??__MACOSX\atu_shm_buffer\._.cproject
?????文件????????6148??2012-09-19?11:57??atu_shm_buffer\.DS_Store
?????文件??????????82??2012-09-19?11:57??__MACOSX\atu_shm_buffer\._.DS_Store
?????文件?????????815??2012-09-18?16:21??atu_shm_buffer\.project
?????文件??????????82??2012-09-18?16:21??__MACOSX\atu_shm_buffer\._.project
?????文件????????3609??2012-09-19?11:56??atu_shm_buffer\atu_shm_buffer.cpp
?????文件????????2017??2012-09-19?11:55??atu_shm_buffer\atu_shm_buffer.h
?????文件????????1229??2012-09-19?11:52??atu_shm_buffer\atu_shm_buffer_example.cpp