refactor large parse method

This commit is contained in:
dave 2018-05-10 18:05:46 -07:00
parent c260e0744e
commit a047bbc502
1 changed files with 73 additions and 30 deletions

View File

@ -10,18 +10,80 @@
#include <netdb.h>
#include <limits.h>
// Mostly lifted from https://cs.nyu.edu/~mwalfish/classes/16sp/classnotes/handout01.pdf
// UDP server-related mostly lifted from https://cs.nyu.edu/~mwalfish/classes/16sp/classnotes/handout01.pdf
void panic(const char* s) {
perror(s);
exit(1);
}
struct Message {
int priority;
char application[64];
};
struct Datefields {
char month[9];
int day;
int hour;
int minute;
int second;
};
int parse_priority(char* message, int* priority, int* position) {
/*
Given a string that begins with a message something like: <123>foo
Parse out the number (123) and place it in the passed `priority` int pointer
The position after the final `>` will be placed in the passed `position` int pointer
Returns 0 on success or something else on failure
*/
// Must have >3 chars to form <x> priority
if (strlen(message) < 3) return 1;
// Must start with <
if (message[0] != '<') return 1;
char digits[4];
memset(&digits, '\0', sizeof(digits));
int num_digits = 0;
int pos = 1;
//bool found_priority_end = false; // TODO
while (pos < 4) {
if(!isdigit(message[pos])) return 1; // priority must be numeric
digits[num_digits] = message[pos];
num_digits++;
pos++;
if (message[pos] == '>') {
break;
}
}
// TODO if escape the loop because pos >= 4, we never found '>'
if (num_digits == 0) return 1; // empty priority <> ?
*priority = atoi(digits);
*position = pos;
return 0;
}
int parse_datefield(char* message, struct Datefields* date, int* position) {
/*
Given a message+position pointers, where message + position in a string like:
May 10 03:09:59 filterlog: 5,,,....
Parse out the date and place the fields in the passed datefields struct pointer
Position will be advanced to the character after the parsed data
*/
// char month[8];
// memset(&month, '\0', sizeof(month)); // makes valgrind happy as the above char contains uninitialized memory
int date_length;
if(sscanf(message + *position, "%s %d %d:%d:%d%n",
date->month, &(date->day), &(date->hour), &(date->minute), &(date->second), &date_length) != 5) {
return 1; // Failed to parse all desired fields
}
*position += date_length;
return 0;
}
int parse_message(struct Message* result, char* message) {
/*
parse a message like:
@ -31,38 +93,19 @@ int parse_message(struct Message* result, char* message) {
Assumes null termed string
*/
printf("Got message: %s\n", message);
int priority = 0;
int position = 0;
if(parse_priority(message, &priority, &position) != 0) return 1;
result->priority = priority;
position++; // Now sits on the first character of the ISOTIMESTAMP
// Must have >3 chars to form <x> priority
if (strlen(message) < 3) return 1;
// Must start with <
if (message[0] != '<') return 1;
char digits[] = "\0\0\0";
int num_digits = 0;
int position = 1;
//bool found_priority_end = false; // TODO
while (position < 4) {
if(!isdigit(message[position])) return 1; // priority must be numeric
digits[num_digits] = message[position];
num_digits++;
position++;
if (message[position] == '>') {
position++; // Now sits on the first character of the ISOTIMESTAMP
break;
}
// break;
}
if (num_digits == 0) return 1; // empty priority <> ?
result->priority = atoi(digits);
// Parse date
// May 10 03:09:59 filterlog: 5,,,....
char month[8];
memset(&month, '\0', sizeof(month)); // makes valgrind happy as the above char contains uninitialized memory
int day, hour, minute, second, date_length;
if(sscanf(message + position, "%s %d %d:%d:%d%n", month, &day, &hour, &minute, &second, &date_length) != 5) {
return 1; // Failed to parse all desired fields
struct Datefields date;
if(parse_datefield(message, &date, &position) != 0) {
return 1;
}
position += date_length + 1; // position now at beginning of HOSTNAME field
position++; // position now at beginning of HOSTNAME field
// char msg_remaining[4096];
// memset(&msg_remaining, '\0', sizeof(msg_remaining));
@ -151,7 +194,7 @@ int main(int argc, char** argv) {
//printf("msg[size_recvd] is: %d", msg[size_recvd]);
msg[size_recvd] = '\0'; // We receive 1 full string at a time
if(parse_message(&result, msg) != 1) {
printf("message is valid,\n\tpriority: %d\n\tapplication: %s\n", result.priority, result.application);
printf("message is valid:\n\tpriority: %d\n\tapplication: %s\n", result.priority, result.application);
}
}