json_query.cpp

//
// json_parser.h
//
// jq wrapper
//

#ifdef __linux__

#include "json_query.h"
#include "sinsp.h"

json_query::json_query(const std::string& json, const std::string& filter, bool dbg) :
	m_jq(jq_init()), m_input{0}, m_result{0}, m_processed(false)
{
	if(!m_jq) { cleanup(); }
	process(json, filter, dbg);
}

json_query::~json_query()
{
	cleanup();
}

bool json_query::process(const std::string& json, const std::string& filter, bool dbg)
{
	cleanup(m_input);
	cleanup(m_result);
	clear();

	if(!m_jq) { cleanup(); }
	if(!jq_compile(m_jq, filter.c_str()))
	{
		m_error = "Filter parsing failed.";
		return false;
	}

	m_input = jv_parse/*_sized*/(json.c_str()/*, json.length()*/);
	if (!jv_is_valid(m_input))
	{
		cleanup(m_input, "JSON parse error.");
		return false;
	}

	jq_start(m_jq, m_input, dbg ? JQ_DEBUG_TRACE : 0);
	m_input = jv_null(); // jq_start() freed it
	m_result = jq_next(m_jq);
	if (!jv_is_valid(m_result))
	{
		cleanup(m_result, "json_query filtering result invalid.");
		return false;
	}
	m_json = json;
	m_filter = filter;
	return m_processed = true;
}

const std::string& json_query::result(int flags)
{
	if(m_processed)
	{
		static const std::string ret;
		if(!m_error.empty()) { return ret; }
		char* buf;
		size_t len;
		FILE* f = open_memstream(&buf, &len);
		if(f == NULL)
		{
			m_error = "Can't open memory stream for writing.";
			return ret;
		}
		jv_dumpf(m_result, f, flags);
		m_result = jv_null();
		clear();
		fclose (f);
		m_filtered_json.assign(buf, len);
		free (buf);
		m_processed = false;
	}
	return m_filtered_json;
}

void json_query::clear()
{
	m_result = jv_null();
	m_input = jv_null();
	m_filtered_json.clear();
	m_error.clear();
	m_processed = false;
}

void json_query::cleanup()
{
	if(m_jq)
	{
		cleanup(m_input);
		cleanup(m_result);
		clear();
		jq_teardown(&m_jq);
		m_jq = 0;
	}
	else
	{
		throw std::runtime_error("json_query handle is null.");
	}
}

void json_query::cleanup(jv& j, const std::string& msg)
{
	if(j.u.ptr)
	{
		jv_free(j);
		j = jv_null();
	}
	m_error = msg;
}

#endif // __linux__