NWEN 241 Assignment 1

NWEN 241 Assignment 1
(Weeks 1–2 Topics)

In this assignment, you will be asked implement C functions, submitted in a file named
editor.c.
You must submit the required file to the Assessment System (https://apps.ecs.vuw.
ac.nz/submit/NWEN241/Assignment_1). Any assignment submitted up to 24 hours
after the deadline will be penalised by 20%, and any assignment submitted between 24
and 48 hours after the deadline will be penalised by 40%. Any assignment submitted 48
hours or more after the deadline will not be marked and will get 0 marks.
Important: The Assessment System is configured not to accept submissions that do not
compile. So please test that your code compiles before submitting it.
Full marks is 100. The following table shows the overall marks distribution:
Criteria Marks Expectations for Full Marks
Compilation 10 Compiles without warnings
Comments 10 Sufficient and appropriate comments
Coding Style 10 Consistent coding style
Correctness 70 Handles all test cases correctly (see
marks distribution below)
Total 100
For the Correctness criteria, the following table shows the marks distribution over the
different task types:
Task Type Marks
Core 45
Completion 15
Challenge 10
Total 70
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NWEN 241 2021-T1 (Weeks 1–2 Topics) Assignment 1
Introduction
This assignment will test your application of the conceptual knowledge of C
fundamentals to solve practical programming tasks. You may only use the Standard C
Library to perform the tasks in this part. You must implement the functions in file
named editor.c.
The programming tasks involve the implementation of several basic text editor
operations: insert, delete, replace, etc. An important component of a text editor is the
editing buffer which can be viewed as one-dimensional array of characters. The functions
you will be implementing in deal with manipulating the contents of the editing buffer:
(i) for Core (Tasks 1 and 2), you will implement editor_insert_char and
editor_delete_char; (ii) for Completion (Task 3), you will implement
editor_replace_str; and (iii) for Challenge (Task 4), you will implement
editor_view.
Sample code showing an example on how you can test your code are provided under
the files directory in the archive that contains this file.
Commenting
You should provide appropriate comments to make your source code readable. If your
code does not work and there are no comments, you may lose all marks.
Coding Style
You should follow a consistent coding style when writing your source code. Coding style
(aka coding standard) refers to the use of appropriate indentation, proper placement of
braces, proper formatting of control constructs, and many others. Following a particular
coding style consistently will make your source code more readable.
There are many coding standards available (search "C coding style"), but we suggest you
consult the lightweight Linux kernel coding style (see https://www.kernel.org/doc/
html/v4.10/process/coding-style.html). The relevant sections are Sections 1, 2,
3, 4, 6, and 8. Note that you do not have to follow every recommendation you can find in
a coding style document, you just have to apply that style consistently.
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NWEN 241 2021-T1 (Weeks 1–2 Topics) Assignment 1
Task 1.
Core [20 Marks]
Implement a function with the prototype
int editor_insert_char(char editing_buffer[], int editing_buflen,
char to_insert, int pos);
which will insert the character to_insert at index pos of editing_buffer. The size
of editing_buffer is editing_buflen. When a character is inserted at index pos,
each of the original characters at index pos until the end of buffer must be moved by one
position to the right. The last character is thrown out. The function should return 1 if the
character insertion occurred, otherwise it should return 0.
For example, if editing_buflen is 16 and the contents of editing_buffer are
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
H e l l o , W o r l d ! \0 \0 \0
after executing
int r = editor_insert_char(editing_buffer, 16, ’s’, 12);
the value of r should be 1 and contents of editing_buffer should be
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
H e l l o , W o r l d s ! \0 \0
You can test your implementation by compiling editor.c together with t1test.c
(provided under the files directory). To do this, just type
gcc editor.c t1test.c -o t1test
in the terminal. Make sure that editor.c and t1test.c are in the same directory. If
everything goes well, this will generate an executable file t1test. To see if your
implementation is correct, run t1test and compare the expected and actual buffer
contents and return values. If they match, it means your implementation passes the test.
You are free to modify t1test.c if you want to add in more test cases.
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NWEN 241 2021-T1 (Weeks 1–2 Topics) Assignment 1
Task 2.
Core [25 Marks]
Implement a function with the prototype
int editor_delete_char(char editing_buffer[], int editing_buflen,
char to_delete, int offset);
which will delete the first occurrence of the character to_delete. The search should
start from index offset of editing_buffer. The size of editing_buffer is
editing_buflen. When a character is deleted at index pos, each of the original
characters at index pos until the end of buffer must be moved by one position to the left.
A null character (’\0’) is inserted at the end of the buffer. The function should return 1
if the character deletion occurred, otherwise it should return 0.
For example, if editing_buflen is 16 and the contents of editing_buffer are
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
H e l l o , W o r l d ! \0 \0 \0
after executing
int r = editor_delete_char(editing_buffer, 16, ’o’, 6);
the value of r should be 1 and the contents of editing_buffer should be
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
H e l l o , W r l d ! \0 \0 \0 \0
You can test your implementation by compiling editor.c together with t2test.c
(provided under the files directory). To do this, just type
gcc editor.c t2test.c -o t2test
in the terminal. Make sure that editor.c and t2test.c are in the same directory. If
everything goes well, this will generate an executable file t2test. To see if your
implementation is correct, run t2test and compare the expected and actual buffer
contents and return values. If they match, it means your implementation passes the test.
You are free to modify t2test.c if you want to add in more test cases.
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NWEN 241 2021-T1 (Weeks 1–2 Topics) Assignment 1
Task 3.
Completion [15 Marks]
Implement a function with the prototype
int editor_replace_str(char editing_buffer[], int editing_buflen,
const char *str, const char *replacement,
int offset);
which will replace the first occurrence of the string str with replacement. The search
for the first occurrence should start from index offset of editing_buffer. The size
of editing_buffer is editing_buflen.
The replacement should not overwrite other contents in the buffer. This means that if
replacement is longer than str, there is a need move the characters after str to the
right. Likewise, if replacement is shorter than str, there is a need move the characters
after str to the left. When moving characters to the right, throw out characters that will
not fit in the buffer and when moving characters to the left, insert null characters in the
vacated positions.
If str is empty (regardless of the value of replacement), no string replacement should
occur. If replacement is empty, then this is tantamount to deleting the string str.
If the replacement text will go beyond the limits of editing_buffer, then replacement
should only occur until the end of editing_buffer.
If the string replacement occurred, the function should return the index corresponding
the last letter of replacement in editing_buffer, otherwise, it should return -1. If
the replacement text will go beyond the limits of editing_buffer, the function should
return editing_buflen-1.
For example, if editing_buflen is 16 and the contents of editing_buffer are
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
H e l l o , W o r l d ! \0 \0 \0
After executing
int r = editor_replace_str(editing_buffer, 16, "World!", "there", 0);
the value of r should be 11 (which is the index of the last ‘e’ in “there”) and the contents
of editing_buffer should be
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
H e l l o , t h e r e \0 \0 \0 \0
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NWEN 241 2021-T1 (Weeks 1–2 Topics) Assignment 1
You can test your implementation by compiling editor.c together with t3test.c
(provided under the files directory). To do this, just type
gcc editor.c t3test.c -o t3test
in the terminal. Make sure that editor.c and t3test.c are in the same directory. If
everything goes well, this will generate an executable file t3test. To see if your
implementation is correct, run t3test and compare the expected and actual buffer
contents and return values. If they match, it means your implementation passes the test.
You are free to modify t3test.c if you want to add in more test cases.
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NWEN 241 2021-T1 (Weeks 1–2 Topics) Assignment 1
Task 4.
Challenge [10 Marks]
Implement a function with the prototype
void editor_view(int rows, int cols,
char viewing_buffer[rows][cols],
const char editing_buffer[],
int editing_buflen, int wrap);
which will copy the contents of the editing_buffer to the viewing_buffer for
display to the user. Note that the viewing_buffer is a two-dimensional array, with
dimensions cols columns and rows rows. Prior to the copying, the function must set
every character in the viewing_buffer to the null character.
The argument wrap controls the behaviour of the copying process from
editing_buffer to viewing_buffer as follows:
• Regardless of the value of wrap, whenever a newline character is encountered in
editing_buffer, the text after the newline character is copied to the next row in
viewing_buffer. Note that the newline character is not copied to
viewing_buffer.
• When wrap is 0, the text is not wrapped. This means that when the newline
character is not encountered before the end of the current row (at column cols-1),
the rest of the text in the editing_buffer are discarded until a newline is
encountered which will cause the rest of the text to be copied to the next row. Note
that column cols-1 in viewing_buffer is never filled and will retain the null
character.
• When wrap is non-zero, the text must be wrapped. This means that when the
newline character is not encountered before the end of the current row (at column
cols-1 in viewing_buffer), the text after is copied to the next row. Note that
column cols-1 in viewing_buffer is never filled and will retain the null
character.
The copying process should terminate when a null character in the editing_buffer is
encountered.
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NWEN 241 2021-T1 (Weeks 1–2 Topics) Assignment 1
For example, if editing_buflen is 48 and the contents of editing_buffer are
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
T h e q u i c k b r o w n \n ...
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
f o x j u m p s o v e r \n \n ...
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
t h e l a z y d o g \0 \0 \0 \0
and cols and rows are 11 and 8, respectively. After executing
editor_view(8, 11, viewing_buffer, editing_buffer, 48, 0);
the resulting contents of viewing_buffer should be
0 1 2 3 4 5 6 7 8 9 10
0 T h e q u i c k \0
1 f o x j u m p s \0
2 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
3 t h e l a z y d \0
4 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
5 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
6 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
7 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
Alternatively, after executing
editor_view(8, 11, viewing_buffer, editing_buffer, 48, 1);
the resulting contents of viewing_buffer should be
0 1 2 3 4 5 6 7 8 9 10
0 T h e q u i c k \0
1 b r o w n \0 \0 \0 \0 \0 \0
2 f o x j u m p s \0
3 o v e r \0 \0 \0 \0 \0 \0 \0
4 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
5 t h e l a z y d \0
6 o g \0 \0 \0 \0 \0 \0 \0 \0 \0
7 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
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NWEN 241 2021-T1 (Weeks 1–2 Topics) Assignment 1
You can test your implementation by compiling editor.c together with t4test.c
(provided under the files directory). To do this, just type
gcc editor.c t4test.c -o t4test
in the terminal. Make sure that editor.c and t4test.c are in the same directory. If
everything goes well, this will generate an executable file t4test. To see if your
implementation is correct, run t4test and compare the expected and actual buffer
contents and return values. If they match, it means your implementation passes the test.
You are free to modify t4test.c if you want to add in more test cases.
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