1. .globl read_matrix
2.  
3. .text
4. # ==============================================================================
5. # FUNCTION: Allocates memory and reads in a binary file as a matrix of integers
6. #
7. # FILE FORMAT:
8. #   The first 8 bytes are two 4 byte ints representing the # of rows and columns
9. #   in the matrix. Every 4 bytes afterwards is an element of the matrix in
10. #   row-major order.
11. # Arguments:
12. #   a0 (char*) is the pointer to string representing the filename
13. #   a1 (int*)  is a pointer to an integer, we will set it to the number of rows
14. #   a2 (int*)  is a pointer to an integer, we will set it to the number of columns
15. # Returns:
16. #   a0 (int*)  is the pointer to the matrix in memory
17. # Exceptions:
18. # - If malloc returns an error,
19. #   this function terminates the program with error code 88.
20. # - If you receive an fopen error or eof,
21. #   this function terminates the program with error code 90.
22. # - If you receive an fread error or eof,
23. #   this function terminates the program with error code 91.
24. # - If you receive an fclose error or eof,
25. #   this function terminates the program with error code 92.
26. # ==============================================================================
27. read_matrix:
28.  
29.         #open the filename
30.    
31.     addi sp,sp,-28
32.     sw ra, 0(sp)
33.     sw s0, 4(sp)
34.     sw s1, 8(sp)
35.     sw s2, 12(sp)
36.     sw s3, 16(sp)
37.     sw s4, 20(sp)
38.     sw s5, 24(sp)
39.    
40.    
41.     ##Initialize variables a0,a1,a2
42.     mv s0,a0
43.     mv s1,a1
44.         mv s2,a2
45.     mv s3,x0 #bytes to store
46.     mv s4,x0 #file descriptor
47.     mv s5,x0
48.    
49.    
50. open_file:  
51.    
52.     #Give read instructions for fopen
53.    
54.     mv a2,x0 #read permission to 0
55.     mv a1,s0 #filename of the file we are opening
56.    
57.     #Opens the file
58.     jal ra, fopen
59.    
60.     #if a0 is -1
61.     mv t0,x0
62.     li t1,1
63.     sub t0,t0,t1
64.     beq a0,t0,error
65.    
66.    
67.    
68.     #a0 is now the file descriptor, if -1 account for an error
69.     mv s4,a0 #set file descriptor
70.    
71. read_file:    
72.    
73.     #this is for fread
74.    
75.    
76.     #Prepare malloc
77.    
78.    
79.     #Number of bytes to read 4*(2+m*n)
80.     li t0,1
81.     lw t1, 0(s1) #rows
82.     lw t2, 0(s2) #columns
83.    
84.     mul t0,t1,t2
85.     addi t0,t0,2
86.     li t3,4
87.     mul t0,t0,t3
88.     mv s3, t0
89.         mv a0, s3 #size of buffer
90.    
91.     jal ra, malloc
92.    
93.    
94.     mv a1, s4 #file descriptor
95.    
96.     mv a2, a0 #pointer to buffer that we previously malloced
97.    
98.     mv a3,s3 #number of bytes to read
99.    
100.     jal ra, fread #call fread function
101.    
102.    
103.     #set return value to the address of a2
104.  
105.    
106.     mv s5,a2
107.     mv a0,s5
108.  
109.  
110.     lw ra, 0(sp)
111.     lw s0, 4(sp)
112.     lw s1, 8(sp)
113.     lw s2, 12(sp)
114.     lw s3, 16(sp)
115.     lw s4, 20(sp)
116.     lw s5, 24(sp)
117.     addi sp,sp,28
118.    
119.    
120.    #update stack poitner
121.    
122.         ret
123.    
124. error:
125.         li a1, 79
126.         jal exit2
127.  
128.  
129.