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# Read records previously written in file.dat, by write-records software
.include "linux.s"
.include "record-def.s"
.section .data
filename:
.ascii "test.dat\0"
.section .bss
.lcomm record_buffer, RECORD_SIZE
.section .text
.globl _start
_start:
# Stack locations for INPUT and OUTPUT FDs
.equ ST_INPUT_DESCRIPTOR, -8
.equ ST_OUTPUT_DESCRIPTOR, -16
movq %rsp, %rbp
subq $16, %rsp # Save space in the stack for FDs
# Open data file
movq $SYS_OPEN, %rax
movq $filename, %rdi
movq $0, %rsi # Open for read only
movq $0666, %rdx
syscall
# Save FD
movq %rax, ST_INPUT_DESCRIPTOR(%rbp)
# Yes, STDOUT is always 1, but if I want to change the output location
# later, I don't need to change everywhere...
movq $STDOUT, ST_OUTPUT_DESCRIPTOR(%rbp)
record_read_loop:
pushq ST_INPUT_DESCRIPTOR(%rbp)
pushq $record_buffer
call read_record
addq $16, %rsp # Cleanup stack
# All records are RECORD_SIZE size, if we didn't get this amount of
# bytes from read function, we either are at EOF or we hit an error.
cmpq $RECORD_SIZE, %rax
jne finished_reading
# We are ok, so print the first name in the record
pushq $RECORD_FIRSTNAME + record_buffer # Location of firstname
# record in the buffer
# we just read
call count_chars
addq $8, %rsp # Cleanup stack
# Write name to OUTPUT
movq %rax, %rdx # Returned record size, used as argument to
# write()
movq $RECORD_FIRSTNAME + record_buffer, %rsi
movq ST_OUTPUT_DESCRIPTOR(%rbp), %rdi
movq $SYS_WRITE, %rax
syscall
pushq ST_OUTPUT_DESCRIPTOR(%rbp)
call write_newline
addq $8, %rsp
jmp record_read_loop
finished_reading:
movq $SYS_EXIT, %rax
movq $0, %rdi
syscall
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