utils.h File Reference

#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>
#include <stdint.h>
#include <cjson/cJSON.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <errno.h>
#include <math.h>
#include <log.h>
#include <libpq-fe.h>

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Data Structures
struct	Utils_ReqData_TypeDef
	Holds HTTP response data before converting these data into cJSON objects. More...

Macros
#define	USER_AGENT   "EnvMonitoring/0.1 (NSW Department of Primary Industries)"

Functions
size_t	WriteMemoryCallback (void *contents, size_t size, size_t nmemb, void *userp)
int8_t	MakeDirectory (const char *directory)
	Make directories (with error handling) More...
void	WriteTimeseriesToFile (const char *filename, time_t *dates, double *values, int16_t max_n_values)
	Write timeseries data into a csv file. More...
void	cJSON_Minify_Mod (char *json)
	Modified minify function from cJSON. More...
double	Utils_PointsDistance (double latitude, double longitude, double station_latitude, double station_longitude)
	Distance between two points on earth. More...
void	Utils_PrepareStatement (PGconn *psql_conn, const char *stmt_name, const char *stmt, const int nparams)

Macro Definition Documentation

USER_AGENT

#define USER_AGENT   "EnvMonitoring/0.1 (NSW Department of Primary Industries)"

Function Documentation

cJSON_Minify_Mod()

void cJSON_Minify_Mod

(

char *

json

)

Modified minify function from cJSON.

HTML minify function modified from cJSON library.

The main cJSON_Minify() function gets rid of all white space and '/' characters in a string. This however, causes sentances to appear without the nessessary spaces between words. This modified function keeps only one space between each character (if more than one space occurs) and maintains the spaces between words in a sentance. Additionally '/' characters are maintained as they are used as datetime delimiters.

See also

https://github.com/DaveGamble/cJSON/blob/master/cJSON.c#L2838

Parameters

json	The string to minify (parse).

MakeDirectory()

int8_t MakeDirectory

(

const char *

directory

)

Make directories (with error handling)

Helper function to create directories with error handling.

MakeDirectory("my_directory");
MakeDirectory("my_directory/my_sub_directory");

Parameters

directory

Directory name you want to create.

Returns

Integer representing error status. 0 = OK ... 1 = ERROR

Utils_PointsDistance()

double Utils_PointsDistance	(	double	latitude,
		double	longitude,
		double	station_latitude,
		double	station_longitude
	)

Distance between two points on earth.

Uses haversine formula to calculate the distance in km between two points on earth.

Used to calculate the distance between an POI and the closest Bureau of Meterology station.

Parameters

latitude	Latitude of point of interest.
longitude	Longitude of point of interest.
station_latitude	Latitude of station.
station_longitude	Longitude of station.

Returns

Distance between two points on earth in km.

Utils_PrepareStatement()

void Utils_PrepareStatement	(	PGconn *	psql_conn,
		const char *	stmt_name,
		const char *	stmt,
		const int	nparams
	)

WriteMemoryCallback()

size_t WriteMemoryCallback	(	void *	contents,
		size_t	size,
		size_t	nmemb,
		void *	userp
	)

Helper function to handle a CURL request response which normally gets written to stdout.

Callback function to save HTTP response data to a character array.

CURL defaults to printing to stdout. This function is added to CURL in the setup options (curl_easy_setupopt()). Memory is allocated and then filled with the response string. This character array is then used to create cJSON objects and other items.

MemoryStruct_TypeDef chunk;
chunk.memory = malloc(1);
chunk.size = 0;
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);
free(chunk.memory) // Don't forget to free allocation

See also

https://curl.se/libcurl/c/getinmemory.html

Parameters

contents	The items to add.
size	The size of items to add.
nmemb	The number of members (data size).
userp	The struct to populate with data.

Returns

The size of received data.

WriteTimeseriesToFile()

void WriteTimeseriesToFile	(	const char *	filename,
		time_t *	dates,
		double *	values,
		int16_t	max_n_values
	)

Write timeseries data into a csv file.

Helper function to handle writing timeseries data to a .csv file.

Writes timeseries data to a filename, exiting when the data is un-initialised '\0' or the maxiumum buffer size is reached. This function also converts UNIX time into local (human readable) time in ISO 8601 format.

// Build filename (directory requried)
char filename[100];
sprintf(filename, "%s/low.csv", directory);
WriteTimeseriesToFile(filename,
                      dataset->low_tide_timestamps, // UNIX timestamps
                      dataset->low_tide_values, // Values
                      WW_FORECAST_RESPONSE_BUF); // Max number of values

Parameters

filename	File to write to.
dates	Dates (x values).
values	Data values (y values).
max_n_values	Max buffer size.