.globl read_matrix

.text
# ==============================================================================
# FUNCTION: Allocates memory and reads in a binary file as a matrix of integers
#
# FILE FORMAT:
#   The first 8 bytes are two 4 byte ints representing the # of rows and columns
#   in the matrix. Every 4 bytes afterwards is an element of the matrix in
#   row-major order.
# Arguments:
#   a0 (char*) is the pointer to string representing the filename
#   a1 (int*)  is a pointer to an integer, we will set it to the number of rows
#   a2 (int*)  is a pointer to an integer, we will set it to the number of columns
# Returns:
#   a0 (int*)  is the pointer to the matrix in memory
# Exceptions:
# - If malloc returns an error,
#   this function terminates the program with error code 88.
# - If you receive an fopen error or eof, 
#   this function terminates the program with error code 90.
# - If you receive an fread error or eof,
#   this function terminates the program with error code 91.
# - If you receive an fclose error or eof,
#   this function terminates the program with error code 92.
# ==============================================================================
read_matrix:

	#open the filename
    
    addi sp,sp,-28
    sw ra, 0(sp)
    sw s0, 4(sp)
    sw s1, 8(sp)
    sw s2, 12(sp)
    sw s3, 16(sp) 
    sw s4, 20(sp)
    sw s5, 24(sp)
    
    
    ##Initialize variables a0,a1,a2
    mv s0,a0
    mv s1,a1
	mv s2,a2
    mv s3,x0 #bytes to store
    mv s4,x0 #file descriptor
    mv s5,x0
    
   
open_file:   
   
    #Give read instructions for fopen
    
    mv a2,x0 #read permission to 0
    mv a1,s0 #filename of the file we are opening
    
    #Opens the file
    jal ra, fopen
    
    #if a0 is -1
    mv t0,x0
    li t1,1
    sub t0,t0,t1
    beq a0,t0,error
    
    
    
    #a0 is now the file descriptor, if -1 account for an error
    mv s4,a0 #set file descriptor
    
read_file:    
    
    #this is for fread
    
    
    #Prepare malloc
    
    
    #Number of bytes to read 4*(2+m*n)
    li t0,1
    lw t1, 0(s1) #rows
    lw t2, 0(s2) #columns
    
    mul t0,t1,t2
    addi t0,t0,2
    li t3,4
    mul t0,t0,t3
    mv s3, t0
 	mv a0, s3 #size of buffer
    
    jal ra, malloc
    
    
    mv a1, s4 #file descriptor
    
    mv a2, a0 #pointer to buffer that we previously malloced
    
    mv a3,s3 #number of bytes to read
    
    jal ra, fread #call fread function
    
    
    #set return value to the address of a2
  
    
    mv s5,a2
    mv a0,s5
 

    lw ra, 0(sp)
    lw s0, 4(sp)
    lw s1, 8(sp)
    lw s2, 12(sp)
    lw s3, 16(sp)
    lw s4, 20(sp)
    lw s5, 24(sp)
    addi sp,sp,28
   
   
   #update stack poitner
   
	ret
    
error:
	li a1, 79
	jal exit2