PLUGIN share
lang: "C++"
version: "1.0"
date: "2022-09-21"
author: "Julien BRUGUIER"
maintainer: "Julien BRUGUIER <projet.svm@pappy.tf>"
synopsis: "A simple shared memory handler."
description:
%{
This plugin allows several process within an application to share copiable values through keys acting as addresses. 
.P
The access to the storage is protected by a lock, but the stored values shall be synchronised by their own means.
%}
example: "Simple example"
%{
.nf
#!===SVMBIN===
LOG
PLUGIN "svmcom.so"
PLUGIN "===PLUGINLIB==="
PROCESS "test"
        CODE "main" INLINE
		:memory STR/s
		:share.set "key" "value"
		:share.get "key" -> &s
		:com.message @&s
        END
END
.fi
%}
example: "Several processes"
%{
.nf
#!===SVMBIN===
LOG
PLUGIN "svmcom.so"
PLUGIN "svmrun.so"
PLUGIN "===PLUGINLIB==="
PROCESS "test"
        CODE "main" INLINE
		:share.set "key" "value"
        END
	SCHEDULER run.parallel
END
PROCESS "test"
        CODE "main" INLINE
		:run.sleep HARD 1
		:memory STR/s
		:share.get "key" -> &s
		:com.message @&s
        END
	SCHEDULER run.parallel
END
.fi
%}
seealso:
%{
.BR svm_plugin_mem (7)
for basic memory management.
%}

includes:
%{
#include <map>
%}

code:
%{
	static std::map<std::string, SVM_Value> storage;
	SVM_Lock lock;
%}

initialisation:
%{
	lock = ::svm_lock_new(svm);
	::svm_variable_scope_set_global(svm,lock);
%}

finalisation:
%{
	for(auto& s: storage)
	{
		::svm_variable_scope_set_local(svm,s.second);
	}
	::svm_variable_scope_set_local(svm,lock);
	storage.clear();
%}

DEFINE

WAITING INSTRUCTION share.set STR : key VALUE ? : value
%{
	SVM_LockGuard_Write guard = ::svm_lock_writeguard_new(svm,lock,TRUE);
	::svm_variable_scope_set_local(svm,guard);
	auto raw_key = ARGV_VALUE(0,string);
	std::string key(raw_key.string,raw_key.size);
	auto it = storage.find(key);
	if(argc==1)
	{
		if(it!=storage.end())
		{
			storage.erase(it);
		}
		return nullptr;
	}
	SVM_Value value = ::svm_parameter_value_get(svm,argv[1]);
	::svm_variable_scope_set_global(svm,value);
	if(it==storage.end())
	{
		storage.insert(std::make_pair(key,value));
	}
	else
	{
		::svm_variable_scope_set_local(svm,it->second);
		it->second = value;
	}
%}
help:
%{
This instruction associates a value to a key or overrides a value for a key when a key and a value are specified.
.P
The instruction removes the key and the value when the key only is specified.
%}

WAITING INSTRUCTION share.get STR : key -> VALUE ? : value
%{
	SVM_LockGuard_Read guard = ::svm_lock_readguard_new(svm,lock,TRUE);
	::svm_variable_scope_set_local(svm,guard);
	auto raw_key = ARGV_VALUE(0,string);
	std::string key(raw_key.string,raw_key.size);
	auto it = storage.find(key);
	if(it==storage.end())
	{
		return ::svm_value_automatic_new_null(svm);
	}
	return it->second;
%}
help:
%{
This instruction returns the value associated to a key.
.P
When the key is not associated to a value, a null value is returned.
%}