Announcements

Please read the entire file before you ask any question.
You should write your own Makefile to test the code.
You will use your own Connect() and Close() functions from HW04 in this assignment. Those functions are not provided. Please define these two functions in pa06.c
Do not print anything other than the required output (i.e., no debugging output, etc.). ifndef is used for grading. Please do not change it.
This assignment takes time. You should start earlier.
In this assignment, you will implement a SQL-like statement. SQL is a standard
language for storing, manipulating and retrieving data in databases.
For example, if we want to select cerntain fields from a table in database
following certain conditions, we will type this query
SELECT field1, filed2, … FROM table_name WHERE field1=.., field2=..;
—|—
Here, field1, field2, … are the names of the fields in table you want to
select data from. The WHERE clause is used to filter records and extract data
that fulfill a specified condition.
For example, if we want to get the name of students who are in sophemore year
and have enrolled this semester. We will type the following SQL query (Assume
we have a table named db).
SELECT name FROM db WHERE year=”Sophemore” AND enrollment=”Yes”;
—|—
After running this query, we will get the name of students who meet the
specified condidtions.

Learning Goals

You will learn to

Allocate and release memory.
Write text file.
Use argc and argv correctly in main.

Our SQL-like query.

In this assignment, you will implement our version of SELECT statement and
WEHRE clause. Before that, you have to understand the SQL syntax we define in
this assignment. You should follow this syntax.
SELECT field1 field2 … WHERE field3 = val1 AND field5 < val2
—|—

The field1 field2 between SELECT and WHERE are the selected fields. You will use a SelectedField object to keep the information of which fields are selected.
We define field3 = val1 , field5 < val2 as Condition . In this example, you will need to use two Condition ojects to store the informations.
The AND is defined as logic. In this homeowrk, we only have one type of logic in each query. We will not have the case that has AND and OR in the same query. For example, we only have the cases like
SELECT field1 field2 … WHERE condition1 AND condition2 AND condition3 …
SELECT field1 field2 … WHERE condition1 OR condition2 OR condition3 …
—|—
Each word is seperated by a space.
You don’t have to specify table name in the query.
You will pass the query in command line. For exapmle,
SELECT name age WHERE id “<” 100```.
—|—
Note that you have yo use double quotation marks for < and > when you
type the query in bash.
You will use < , > , = , <= , >= operators when doing comparisons in id and age fields. For example,
SELECT name WHERE age <= 20 AND id > 10
—|—
You will use “=” operator when doing comparisions in name, enrollment, year, and major fields. For example,
SELECT name WHERE name = BLABLABLA OR major = ECE
—|—
We will not have the cases like
SELECT name WHERE name <= BLABLABLA OR major != ECE
SELECT age WHERE enrollment <= YES AND name >= BLABLABLA
—|—

Steps to complete this homework

Complete ParseQuery(int num, char ** query) function.
1. Know what fields are selected and store it in SelectedField object.
2. Know what are the conditions and store it in Condition objects.
3. Know what logic is used in the query (AND or OR).
4. Store the information above to ParseResult object.
Complete ExecuteQuery(StudentDatabase * db, ParseResult * res) function.
1. Use info in ParseResult object to find the students who meet the specified conditions.
2. Get the array of matched student’s index and store it in ExecuteResult object.
Complete WriteDb(StudentDatabase * db, SelectedField * info, ExecuteResult * execute_res, char * filename) function.
1. Use SelectedField object to know what fields should be written into the output file.
2. Use ExecuteResult object to know the index of students who meet the specified conditions.
3. Create a output file with all those students’ who meet the specified conditions and only write the selectedfield to the file.
Complete all functions that free memory.

Functions you need to complete

In this assignment, you have to complete seven functions - ConstructField() , ParseQuery() , ExecuteQuery() , FreeParseResult() , FreeExecuteResult() , and WriteDb() in pa06.c , and main() in main.c .

SelectedField * ConstructField() :
1. This function returns a pointer to SelectedField object.
2. Allocate memory for SelectedField object.
3. Initialize all the fields in this object to “false”.
4. return NULL and print “Fail to allocate memory\n” to screen if you fail to allocate memory for SelectedField object.
ParseResult * ParseQuery(int num, char ** query) :
Parse the query and store the information into ParseResult object.
1. You should pass argc and argv into this fuction.
2. This function returns a pointer to ParseResult object.
3. In this function, you should parse the qeury and store the information to ParseResult object. Similar to Connect() function in HW04, you should allocate memory for the required objects and then update the fields in the objects.
ExecuteResult * ExecuteQuery(StudentDatabase * db, ParseResult * res) :
1. This function takes two arguments: First, a pointer to StudentDatabase object. Second, a pointer to ParseResult object.
2. This function returns a pointer to ExecuteResult object.
3. The ExecuteResult object has two fields: First, an array of matched Student’s index. Second, length of the array.
void FreeParseResult(ParseResult * res) : Free the allocated memory in ParseResult object.
void FreeExecuteResult(ExecuteResult * res) : Free the allocated memory in ExecuteResult object.
void WriteDb(StudentDatabase * db, SelectedField * info, ExecuteResult * execute_res, char * filename) :
1. Only write selected fields of students who meet specified conditions to output file.
2. Print error message “Failed to open file\n” to monitor if the fopen fail. You should not have output file generated if fopen fail.
3. Follow this format “field:%s “, or “field:%d “. Add “\n” when you finish writing the selected fileds of a student. Please look at the files in expected folder to make sure you understand the format. We will use diff to test. Make sure your output format is correct.
4. You should write the info of each student in the following order if that fields are selected. id -> name -> major -> year -> enrollment -> age.
5. The order in selected fields does not affect the order you write to the file. e.g., SELECT id name WHERE ... and SELECT name id WHERE ... should have the same output file.
main(int argc, char ** argv) :
1. Use Connect() function to connect to database.txt. You should hard code database.txt in Connect() function.
2. Pass argc , argv to ParseQuery() and get the parse results.
3. Call ExecuteQuery() function to get the result of students who meet the condition we specify in the query.
4. Use WriteDb() to write to file named output.txt . You should hard code this name.
5. Free memory.

Testing your code

Following are the files we provide:

pa06.c - Define your functions in this assignment.
pa06.h - Header file, which has definition for the functions and structures you need in this assignment.
main.c - main file of this assignment.
database.txt - This is the database file which stores all student’s info.
expected/ - This folder has the expected output of the following commands.
1. test1.txt - ./pa06 SELECT name age WHERE age ">" 10 AND id = 1
2. test2.txt - ./pa06 SELECT age name WHERE age ">" 10 AND id = 1
3. test3.txt - ./pa06 SELECT enrollment age major WHERE age "<" 22 OR id = 100
1. test4.txt - ./pa06 SELECT major enrollment WHERE major = CS AND enrollment = No AND year = Sophomore
  1. test5.txt - ./pa06 SELECT id WHERE enrollment = Yes
  2. test6.txt - ./pa06 SELECT id WHERE enrollment = Yes AND name = aa
  3. test7.txt - ./pa06 SELECT age enrollment year major name id WHERE enrollment = No
    To test your code. You have to first compile it and then run the following
    command.
    ./pa06 SELECT field1 field2 … WHERE condition1 condition2 ….
    —|—
pa06 - This is binary that should get generated
field1, field2, … should only be the fields defined in Student structure. We will not use fields that are not is Student structue when testing your code.
condition shoud consist of field , optr , and val .
You will have a “output.txt” file generated. The file should only have the selected fields of the students who meet the specified conditions. You will have an empty file if no studdents meet the specified conditions.

Checking for memory errors

You should also run./pa06 with arguments under valgrind. To do that, you have
to use, for example, the following command:
valgrind –tool=memcheck –leak-check=full –verbose –log-file=memcheck.log ./pa06 YOUR QUERY
—|—
Note that you should use other input arguments to extensively test your
function. If you follow the instructions and keep the malloc and free
functions in the right place, you should not have memory problems in this
assignment.

Submitting Your code

This is a programming assignment, so you would have to submit the code on
Blackboard.
Follow this submission instructions:

Type
zip pa06.zip pa06.c main.c
—|—
Submit pa06.zip to blackboard.
Your assignment will not be graded if you do not follow this instructions.
The only way to submit homework is through Blackboard.
The instructor will never accept any requestion for exception “my
submission is only one minute late”. It is your responsibility to meet the
deadline. You are strongly encouraged to submit at least ten minutes before
the deadline because submission may take time.
If there is a campus-wide problem (such as network outage or the Blackboard
server is down), the deadline will be extended for the entire class. If the
problem is specific to yourself (for example, your computer crashes), the
deadline will not be extended for you.
DO NOT send your code by email. Your code will not be graded if it is sent
by email.
The teaching staff is strictly prohibited to look at files on your computer
(or your Purdue account) for grading. Thus, NEVER say “I finished before
the deadline but I forgot to submit”. NEVER say “I have not made any
change after the submission deadline.” because the teaching staff is not
allowed to look at your files that have not been submitted through Blackboard.

Grading

If your program has any compilation error or warning (remember to use gcc -std=c99 -g -Wall -Wshadow --pedantic -Wvla -Werror ), you will receive zero
in this assignment.
In absolutely no circumstance can the teaching staff modify your program for
grading. You cannot say, “If you change this, my program works.” If your
program misses a semicolon and cannot compile, you will receive zero. Your
score depends on what is submitted, nothing else.
This exercise will be graded as folows:

ParseQuery() : This function should parse the query and return a pointer to ParseResult object with correct information.
ExecuteQuery() : This function should return a pinter ExeucuteResult object with correct information.
WriteDb() function: This function should write the output of given database to a file.
The correctness of your program: We will use 10 different queries to test the correctness of your program. The score will be proportional to the number of passed test cases
Code that contains memory problems reportable by Valgrind will be subject to a penalty of 40% of the total possible points.