I am currently doing a Customers program when a user can add/edit/search/list customers. I decided to use a binary tree as the backbone of this program. My idea was to then save each item in the tree to "customers.dat" right before the program closes, then on start up load everything from the file to the tree. So far so good, however after finally managing to save the binary search tree into a file, I have one bug.
Lets say I add 3 customers the first time. I then close the program, and when I reopen it I will find the same 3 customers in the tree. however, the next time I open the file, it gives me an error from one of my predefined errors, which occurs when a node is not able to identity whether to go left or right, maybe because its empty or uncomparable. here are some code snippets. I aslo tried using other fileopen techniques other than a+b, and I had no such error, but by the way I designed my program, I need the append method or else only one record will save.
Customers are stored in Cstmr in the header:
typedef struct customer
{
char Name[MAXNAME];
char Surname[MAXNAME];
char ID[MAXID];
char Address[MAXADDRESS];
} Cstmr;
else:
void CustomerTreeToFile(Tree*pt)
{
if (TreeIsEmpty(pt))
puts("Nothing to save!");
else
Traverse(pt,saveItem); //Traverses each node, and appliess the function
//saveItem to each node
}
void saveItem(Cstmr C)
{
save = C;
customers = fopen("customers.dat","ab+");
fwrite(&C,sizeof (Cstmr), 1, customers);
fclose(customers);
}
The problem is that you are always appending all the data to the same file ... so everything from the previous run is duplicated.
One solution would be to delete (unlink) the file before saving the data with your current approach.
However, as Freezerburn pointed out earlier, it's more economic to not open and close the file for each item. Just open the file once in overwrite mode (i.e. not append), then write all the data, then close the file. Should be much faster, too.
Another problem is that you save your data in binary format. Try to define an easy to read textual format. That would have made the problem obvious ...
Related
I'm using the FileOutputNode to write the data into the file. I have tried writing the collection messages in the file but every time the file created is of 0 byte and there is no data.
SET OutputRoot.Properties = InputRoot.Properties;
CREATE FIELD OutputRoot.Collection.IN;
DECLARE refCollection REFERENCE TO InputRoot.Collection.IN[1];
WHILE LASTMOVE(refCollection) DO
SET OutputRoot.Collection.IN= refCollection;
SET i = i + 1;
MOVE refCollection NEXTSIBLING REPEAT TYPE NAME;
END WHILE;
RETURN TRUE;
It is very difficult to provide help without knowing what your input message tree looks like.
You should follow the instructions here: https://www.ibm.com/support/knowledgecenter/en/SSMKHH_10.0.0/com.ibm.etools.mft.doc/bc16130_.htm
If you need further help, you should
add Trace nodes into your message flow before and after the Compute node and set the Pattern property on both nodes to ${Root}. This will allow you to see (and share) the structure of InputRoot and OutputRoot.
Enable user trace using the console commands mqsichangetrace, mqsireadlog, mqsiformatlog. This will show you exactly what the message flow is doing. It will also contain the full text of any errors that are being reported.
I have been working on this program for over a week with no breakthrough. The questions states as follows:
A disc file ‘REQUESTS.TXT’ contains airline flight data formatted
(STR6, STR3, STR3, INT).
Example:
AA1011SFxLAx34 (American Airlines 1010, SF to LA, 34 seats)
W0924DNVDFW101 (Western 0924, DNV to DFW, 101 seats)
Another file ‘AVAILABL.TXT’ contains an unspecified number of reservation request records formatted identically as described above except the Seats Available field is a Seats Requested field.
Guidelines:
Read reservation flights and process requests. If the request can be fullfilled (i.e.. it is in AVAILABL and REQUESTS) then print "Reservation Processed", otherwise print "Reservation Denied".
Print out flight data file before and after reservations are processed, ordered by flight ID in a four(4) column format.
Print an overall outcome report for all processed.(Present totals for the number of requests satisfied and denied)
I have tried a few different approaches.. I tried to split up the first STR6 by isalpha/isdigit and combine them to make the FlightID (AA + 1011). Proceeded to try to then split up the remaining characters between STR3 and STR3 via isalpha + for loop. And lastly, I tried to take the last 3+ digits for the # of seats during each for loop iteration and multiply the first digit by 100(for a 3-digit value) or 10(for a 2-digit value), adding it to a running total for availSeats(INT). This, at least I thought so, would produce a
AA+1011 = AA1011(STR6) // W+0924 = W0924(STR6)
SFx(STR3) // DNV(STR3)
LAx(STR3) // DFW(STR3)
(3*10)+(4*1) = 34(INT) // (1*100)+(0*10)+(1*1) = 101(INT)
All of this stored within a Struct Array.
i.e...
FlightData Flight; ............................................FlightData Flight;
Flight[0].flightID = AA1011; .........................Flight[1].flightID = W0924;
Flight[0].fromCity = SFx; ...............................Flight[1].fromCity = DNV;
Flight[0].toCity = LAx; ..................................Flight[1].toCity = DFW;
Flight[0].seatsAvail = 34; .............................Flight[1].seatsAvail = 101;
I am really at a loss right now and have no other way to progress other than searching up different techniques/methods to use to make this work. I am a beginner clearly and will continue to practice and progress in C, but if anyone could provide me with a push in the right direction on how one would execute this via .txt into a Struct would be amazing. Also, if anyone has another method they used to solve this problem I would love to analyze it. Thanks!
(This is my first post, I spent a lot of time formatting it to be clear on Stackoverflow, so If i messed up in areas some constructive critisism would be useful! This applies to my posting and my coding practices. Thanks again!)
EDIT: The question I am asking here is how to successfully take a string such as AA1011SFxLAx34 and turn it into a Structure like the above diagram. It must also work for the second string W0924DNVDFW101 which has only 1 Char in its ID. (rather than two in AA1011). Im not sure what else I am supposed to edit after reading the guidelines.
I consider this a home work question, so I answer according to
How do I ask and answer homework questions?
Find a tutorial on C, work through it.
Then take a HelloWorld, modify it in small steps to approach your goal in steps from working program to working program. This way you should at least get to being able to read text from a file and print it.
Then learn to store parts of what you print into basic variables.
Then learn about structures.
And so on.
This way you will get quite close to the solution.
If it is not completely what you need show the code you have here at that point and ask a specific question about the first problem explaining what you suspect the problem to be. Show code which has exactly that one problem and makes it visible and has not other warnings (using at least e.g. gcc -Wall mycode).
Fix with the help of commments/answers you receive, repeat.
Trying to put together a file diff route... could someone help? here is what I have ->
CsvDataFormat csv = new CsvDataFormat();
csv.setDelimiter(",");
from("file:inputdir?delete=true&sortBy=ignoreCase:file:name")
.unmarshal(csv)
.pollEnrich("file:backup?fileName=test.csv&sendEmptyMessageWhenIdle=true")
.unmarshal(csv)
// Need to aggregate here!!!!
.log("test");
A csv file gets dropped in the /input directory and then a backup file is consumed from the /backup directory. I would like to compare these two files and output the difference.
This is not a specific Camel problem. In order to solve this problem you may implement a diff functionality on your own, or you may use an existing library such as java-diff-utils.
Pseudocode:
// read file 1 into a list "list1"
// read file 2 into a list "list2"
// use java-diff-utils to calculate the difference
Patch patch = DiffUtils.diff(list1, list2);
I'm using boost log and I want to make basic log principal file: new error log at the beginning of each hour (if error exists), and to name it like "file_%Y%m%d%H.log".
I have 2 problems with this boost library:
1. How to rotate file at the beginning of each hour?
This isn't possible with rotation_at_time_interval parameter because it creates new file regarding first written record in file, and the hour in file name doesn't match that rule. Is it possible to have multiple rotation_at_time_point for one file in sink or is there some other solution?
2. When file exceed some size I want it to start new file and in that case it should append some index to file name. With adding rotation_size parametar and %N to file name it will increment N all the time while application is running. I want that N to be reset at the beginning of each hour, just as my file name changes. Does anybody have any idea how to do that with this boost log library?
This is basic principal in creating log files in industry. I really don't understand how this can't be done with library which is dedicated for creating log files.
Library itself doesn't provide a way to rotate file at the begging of every hour, but i had same problem so i used a function wrapper, which return true on begging of every hour.
I find this way better for me, because i can controll efficency of code.
from boost.org:
bool is_it_time_to_rotate();
void init_logging(){
boost::shared_ptr< sinks::text_file_backend > backend =
boost::make_shared< sinks::text_file_backend >(
keywords::file_name = "file_%5N.log",
keywords::time_based_rotation = &is_it_time_to_rotate
);
}
For a second question i really dont undrestand it well.
can anyone in this forum give an example in C how two threads process data from one textfile.
As an example, I have one textfile that contains a paragraph. I have two threads that will process the data in the said file. One thread will count the number of lines in the paragraph. The second thread will count the numeric characters.
thanks
If you asked in C++ I could give you a code example, but I havent done ANSI C in a very long time so I will give you the design and pseudo code.
Please keep in mind this is really bad pseudo code that is meant to give an example. I'm not questioning WHY you would want to do this. For all I know it could be an excercise with threads or because you "feel like it".
Example 1
int integerCount = 0;
int lineCount = 0;
numericThread()
{
// By flagging the file as readonly you should
// be able to open it as many times as you wish
handle h = openfile ("textfile.txt". readonly);
while (!eof(h)) {
String word = readWord (h);
int outInteger
if (stringToInteger(word, outInteger)) {
++integerCount;
}
}
}
lineThread()
{
// By flagging the file as readonly you should
// be able to open it as many times as you wish
handle h = openfile ("textfile.txt". readonly);
while (!eof(h)) {
String word = readWord (h);
if (word.equals("\n") {
++lineCount ;
}
}
}
If for some reason you aren't able to open the file twice in readonly you will need to maintain a queue for each thread, having the main thread put words into each threads queue. The threads will then pull from the queue.
Example 2
int integerCount = 0;
int lineCount = 0;
queue numericQueue;
queue lineQueue;
numericThread()
{
while (!numericQueue.closed()) {
String word = numericQueue.pop();
int outInteger
if (stringToInteger(word, outInteger)) {
++integerCount;
}
}
}
lineThread()
{
while (!lineQueue.closed()) {
String word = lineQueue.pop();
if (word.equals("\n") {
++lineCount ;
}
}
}
mainThread()
{
handle h = openfile ("textfile.txt". readonly);
while (!eof(h)) {
String word = readWord(h);
numericQueue.push(word);
lineQueue.push(word);
}
numericQueue.close();
lineQueue.close();
}
There are lots of ways to do this. You can make different design decisions depending on how fast or simple or elegant or overengineered you want this to be. One way, as posted by Andrew Finnell is to have each thread open the file and read it completely independently. In theory this isn't great because you are doing expensive IO twice but in practice it's probably fine because the OS has likely cached the contents of whichever read executes first. Double IO is still more expensive than average because it involves a lot of needless system calls, but again in practice it will be irrelevant unless you have a very large file.
Another model of how to do this would be for each thread to have an input queue, or a shared global queue. The main thread reads the file and places each line in turn on the queue(s), and perhaps main doubles as one of your worker threads. This is more complicated because access to the queue(s) must be synchronized, or some lockless queue implementation must be used. In the case of a shared global queue, there is less duplication of data but now the lifecycle of that data is more complicated.
Just to point out how many ways such a simple thing can be done, you could go the overengineering route and make each thread generic. Instead of placing data on the queue(s) you place both data (or pointers to data) and function pointers and let each thread execute the callback. This kind of model might might sense if you plan on adding lots more kind of things to compute but want to limit the number of threads you will use.
I don't think you will see much performance difference in using 2 threads over one. Either way, you don't want both threads to read the file. Read the file first, then pass a COPY of the stream to the methods you want and process both. The threads will not have access to the same stream of data at the same time so you'll need to use 2 copies of the textfile.
P.S. It's possible that depending on the size of the file, you will actually loose performance using 2 threads.