log.h

// 2013 - Ryan Leonard <ryan.leonard71@gmail.com>
/* 
Log.c provides an implementation of a logging method to files. Typical
usage for this program would be to log behaviour of a process. This supports
logging messages of the following form.
YYYY/MM/DD HH:MM:SS <prefix>: <message>
*/
#ifndef __LOG_H__
#define __LOG_H__
#define MAX_STRLEN_LOGMSG 1024
#define MAX_STRLEN_TIME 32
#define MAX_STRLEN_PREFIX 32      
#define MAX_STRLEN_LOGMESSAGE 320 // Allows 255 bytes for log messages
#define MAX_STRLEN_FILENAME 256

struct Log{
   char prefix[MAX_STRLEN_PREFIX];    // Information about this log which will print in every
                                      // message logged.
   char fileName[MAX_STRLEN_FILENAME];// Name of the file that the log is writing to.
   int log_fd;      // File descriptor that we are writing to.
};



/*
Description: This will fill the fields of the log structure provided, and will
open the file indicated by the fileName parameter.

fileName: The name of the file which will be opened for logging.
prefixMessage: A message that will be printed with every line of the log.
log: The struct Log which will be initialized.

Return: 0 if success, 
-2 if any parameter passed is incorrectly NULL,
-4 if ioError (could not open fileName).
*/
int initLog(char *fileName, char *prefixMessage, struct Log *log);



/*
Description: Close all system resources affiliated with this Log struct, 
consisting only of the opened file referenced by log->log_fd

log: The struct Log to be closed up.

Return: 0 if success, 
-2 if any parameter passed is incorrectly NULL, 
-4 if ioError (could not close file).
*/
int closeLog(struct Log *log);



/*
Description: Write the provided message to the log using the format indicated at
the top of this file, and restated here:
YYYY/MM/DD HH:MM:SS <prefix>: <message>

message: String to be printed to the log.
log: A struct Log which has already been initialized.

Return: 0 if success, 
-1 if general memory Error, 
-2 if any parameter passed is incorrectly NULL, 
-4 if ioError (could not write to log_fd).
*/
int writeMessage(char *message, struct Log *log);

#endif//__LOG_H__