# --------------------------------------------
# FUNCTION: make_array_from_file
# PURPOSE : Take a file descriptor, and convert it to the array data structure
# INPUTS  : rdi = File descriptor
# OUTPUTS : rax = Pointer to start of array in memory 
#           rdx = Length of array in 8 byte chunks (the number of elements)
# CLOBBERS: rax, rsi
# --------------------------------------------
.globl make_array_from_file
.type make_array_from_file, @function
 make_array_from_file:

    push %r15
    push %r14
    push %r13
    push %r12

    # The file descriptor is in rdi
    call create_file_buffer
    movq %rax, %rdi         # Select pointer to file data
    movq %rdx, %rsi         # Select length of file data

    call make_pairwise_data # Make the pairwise data
    movq %rax, %r15         # Save pointer to pariwise data in r15
    movq %rdx, %r14         # Save the number of pairs in r14
    
    # Allocate space for the array
    movq %r14, %rdi         # Select the number of coordinates 
    imulq $8, %rdi          # 8 byte elements in array. Space for pointers
    call allocate           
    movq %rax, %r13         # Save array pointer in r13

    # Add pointers in array that point to pairwise array. Pointer 0
    # points to pair 0 and so on.
    movq $0, %r12           # Counter for displacing pointers in array
loop:
    cmp %r14, %r12          # Compare number of pairs with the counter
    je end

    movq %r15, (%r13, %r12, 8) # Save pointer to pair_i in position_i in array
    
    addq $1, %r12           # Go to next spot in array
    addq $16, %r15          # Go to next pair

    jmp loop
end:
    movq %r13, %rax         # Return pointer to array
    movq %r14, %rdx         # Return the number of elements in the array
    
    pop %r12
    pop %r13
    pop %r14
    pop %r15

    ret

# --------------------------------------------
# FUNCTION: make_pairwise_data
# PURPOSE : Take the raw data from the file, and convert it to an array of x,y
#           coordinates side by side: [x_1,y_1,x_2,y_2,...]
# INPUTS  : rdi = Pointer to start of file data in memory
#           rsi = Size of file
# OUTPUTS : rax = Pointer to start of pairwise data in memory 
#           rdx = The number of pairs 
# CLOBBERS: rdi, rsi, rdx, rax
# --------------------------------------------
.globl make_pairwise_data
.type make_pairwise_data, @function
 make_pairwise_data:
    push %r15
    push %r14
    push %r13
    push %r12

    movq %rdi, %r15     # Save file pointer in r15
    movq %rsi, %r14     # Save file size in r14

    # Count number of lines
    movq %r15, %rdi     # Select the file pointer
    movq %r14, %rsi     # Select the file size
    call getLineCount
    movq %rax, %r13     # Save number of lines (coordinates) in r13

    # Allocate space for the pairwise coordinates after parseData
    # The space allocated should be 2*(#coordinates)*8 bytes
    imulq $16, %r13     # Multiply number of coordinates with 2*8
    movq %r13, %rdi     # Select the number of coordinates
    call allocate
    movq %rax, %r12     # Save pointer to where pairwise data will be placed

    # Parse the data from the file into the pairwise data, and place it into the
    # allocated space
    movq %r15, %rdi     # Select the pointer to the file data
    movq %r14, %rsi     # Select size of file
    movq %r12, %rdx     # Select memory location for where to put data
    call parseData

    # Divide r13 with 16, this is to go from total length of array to the number 
    # of coordinates
    movq %r13, %rax     # Use r13 as dividend
    movq $16, %rdi      # Use 16 as divisor
    cqo                 # Sign extend rax into rdx
    idivq %rdi          # r13/16 -> quotient in rax

    movq %rax, %rdx     # Return number of pairs (the quotient of division)
    movq %r12, %rax     # Return pointer to pairwise data

    pop %r12
    pop %r13
    pop %r14
    pop %r15

    ret

# --------------------------------------------
# FUNCTION: create_file_buffer
# PURPOSE : Take a file descriptor and create a memory location and put the
#           data of the file in that location.
# INPUTS  : rdi = File descriptor
# OUTPUTS : rax = Pointer to start of file in memory 
#           rdx = Length of file in bytes
# CLOBBERS: rax, rsi, rdi, rdx
# --------------------------------------------
.globl create_file_buffer
.type create_file_buffer, @function
 create_file_buffer:
    
    push %r15
    push %r14
    push %r13

    movq %rdi, %r15     # Save file descriptor in r15
    movq %r15, %rdi     # Select file descriptor
    call getFileSize    # Get the file size
    movq %rax, %r14     # Save file size in r14

    movq %r14, %rdi     # Select file size
    call allocate       # Allocate memory for file contents
    movq %rax, %r13     # Save file buffer in r13

    movq %r15, %rdi     # Select the file discriptor
    movq %r13, %rsi     # Select the buffer to store input
    movq %r14, %rdx     # Size to read from file
    movq $0, %rax       # Select read syscall
    syscall             # Read from the file

    movq %r13, %rax     # Return pointer to start of file
    movq %r14, %rdx     # Return length of file

    pop %r13
    pop %r14
    pop %r15

    ret