Network-Programming Assignment 4 Solution

Part 1
Part 1a
The directory contains a simple database into which you can put records, each consisting of a name and a short message.
demo-db.db
This is the database file. It contains each record one after another. Each record is 40 bytes; the size of this database file is always a multiple of 40.
demo-db-add
This is the program that inserts a record into the demo-db.db database file. It will ask for a name and a short message, and then fills up the following structure with those values:
c struct Record { char name[16]; char msg[24]; };
The program will add each new struct to an in-memory linked list and then write the struct's bytes to the database file. It will then confirm that the record has been added by outputting the new record in a manner identical to demo-db-lookup.
Note that the name and the message will be truncated to 15 and 23 characters, respectively, in order to fit them into the structure.
demo-db-lookup
This is the program you use to see what’s in the database and to search for a particular name or a message. It will prompt for a string to search for. If you simply press ENTER, it will show you all the records in the database. If you type something, it will show you those records that contain what you typed either in the name field or in the msg field.
Only the first 5 letters are used in the search. So searching for "hello" and "helloooooo" will yield the same result. The match is case-sensitive.
The program keeps running, prompting you for another string to search for. You can press Ctrl-D to terminate the program.
Play with demo-db-add and demo-db-lookup, inserting a couple of records into the database:
``` $ touch /tmp/demo-db.db
$ ./demo-db-add /tmp/demo-db.db name please (will truncate to 15 chars): erin msg please (will truncate to 23 chars): hello! 1: {erin} said
{hello!}
$ ./demo-db-add /tmp/demo-db.db name please (will truncate to 15 chars): bob msg please (will truncate to 23 chars): goodbye! 2: {bob} said
{goodbye!}
$ ./demo-db-add /tmp/demo-db.db name please (will truncate to 15 chars): sue msg please (will truncate to 23 chars): good day 3: {sue} said
{good day} ```
$ ./demo-db-lookup /tmp/demo-db.db lookup: erin 1: {erin} said {hello!} lookup: good 2: {bob} said {goodbye}
3: {sue} said {good day} Part 1b
Write both your own db-lookup and db-add programs that behave the same way as mine.
Both db-add and db-lookup should use the load_db function to build a linked list from the bytes in the file. It will return the number of records loaded, or a negative number on error.
Some requirements for your program(s):
1. If the database file does not exist when db-add and db-lookup are run, it should be created.
2. Both programs should attempt to build a linked list (import the one you created in the previous week) from the contents of the database file.
3. You must keep the records in the list in the order in which they appear in the database file, i.e. the first record in your file should be the head of the list.
5. The db-lookup program should truncate the user's input to 5 characters.
6. The db-lookup program must search both record name and message.
You should be able to ascertain more requirements from the provided test suite, e.g. formatting and indentation of expected output.
As usual, don't forget to run the leak detector.