#file name:linux.s
# system call numbers(按数字大小排列，方便查看).equ SYS_READ, 0.equ SYS_WRITE, 1.equ SYS_OPEN, 2.equ SYS_CLOSE, 3.equ SYS_EXIT, 60
# standard file descriptors.equ STDIN, 0.equ STDOUT, 1.equ STDERR, 2
# common status codes.equ END_OF_FILE, 0

#file name: record-def.s
.equ RECORD_FIRSTNAME, 0.equ RECORD_LASTNAME, 40.equ RECORD_ADDRESS, 80.equ RECORD_AGE, 320.equ RECORD_SIZE, 328

#file name: read-record.s
.include "record-def.s".include "linux.s"
# stack local variables.equ ST_READ_BUFFER, 16.equ ST_FILEDES, 24
.section .text
.global read_record.type read_record, @functionread_record:    push %rbp    mov %rsp, %rbp
    push %rbx    mov ST_FILEDES(%rbp), %rdi    mov ST_READ_BUFFER(%rbp), %rsi    mov $RECORD_SIZE, %rdx    mov $SYS_READ, %rax    syscall    pop %rbx        mov %rbp, %rsp    pop %rbp    ret

#file name: read-records.s
.include "linux.s".include "record-def.s"
.section .data
filename:    .ascii "ch6/test.dat\0"
newline:    .ascii "\n\0"
.section .bss
.lcomm RECORD_BUFFER, RECORD_SIZE
.section .text
.global _start
_start:    .equ INPUT_DESCRIPTOR, -8    .equ OUTPUT_DESCRIPTOR, -16
    mov %rsp, %rbp
    # open ch6/test.dat    mov $SYS_OPEN, %rax    mov $filename, %rdi    mov $0, %rsi    mov $0666, %rdx    syscall
    push %rax       # push input file descriptor onto stack    push $STDOUT    # push output file descriptor onto stack
record_read_loop:    # invoke read_record function    push INPUT_DESCRIPTOR(%rbp)    push $RECORD_BUFFER    call read_record    add $16, %rsp       # pop function args off of stack
    cmp $RECORD_SIZE, %rax    jne finished_reading
    push $RECORD_FIRSTNAME + RECORD_BUFFER    call count_chars    add $8, %rsp        
    mov %rax, %rdx                      # count of chars to print    mov $RECORD_BUFFER, %rsi    mov OUTPUT_DESCRIPTOR(%rbp), %rdi    mov $SYS_WRITE, %rax    syscall
    mov $1, %rdx                      # count of chars to print    mov $newline, %rsi    mov OUTPUT_DESCRIPTOR(%rbp), %rdi    mov $SYS_WRITE, %rax    syscall
    jmp record_read_loop
finished_reading:    mov $SYS_EXIT, %rax    mov $0, %rdi    syscall

#filename:write-record.s
.include "linux.s".include "record-def.s"
#PURPOSE:   This function writes a record to#           the given file descriptor##INPUT:     The file descriptor(%rdi) and a buffer(%rsi)##OUTPUT:    This function produces a status code#.section .text    .globl write_record    .type write_record, @function  write_record:    #将 system call number 1存入rax寄存器，执行syscall的时候表示执行write操作    movq  $SYS_WRITE, %rax    #执行syscall时，RECORD_SIZE(值为324)用作write(unsigned int fd,const char *buf,size_t count)的第三个参数。    movq  $RECORD_SIZE, %rdx                                     syscall
    ret

#file name: write-record.s.include "linux.s".include "record-def.s" 
.section .datarecord1:    .ascii "Fredrick\0"    .rept 31    .byte 0    .endr    .ascii "Bartlett\0"    .rept 31    .byte 0    .endr    .ascii "4242 S Prairie\nTulsa, OK 55555\0"    .rept 209    .byte 0    .endr    .long 45    record2:    .ascii "Marilyn\0"    .rept 32    .byte 0    .endr    .ascii "Taylor\0"    .rept 33    .byte 0    .endr    .ascii "2224 S Johannan St\nChicago, IL 12345\0"    .rept 203    .byte 0    .endr    .long 29    record3:    .ascii "Derrick\0"    .rept 32    .byte 0    .endr    .ascii "McIntire\0"    .rept 31    .byte 0    .endr    .ascii "500 W Oakland\nSan Diego, CA 54321\0"    .rept 206    .byte 0    .endr    .long 36
file_name:    .ascii "test.dat\0"    .section .text.globl _start_start:    subq  $8, %rsp                 # Allocate space for the file descriptor on the stack        movq  $SYS_OPEN, %rax          # Open the file    movq  $file_name, %rdi         # Filename    movq  $0101, %rsi              # Flags: O_WRONLY | O_CREAT    movq  $0666, %rdx              # Permissions: 0666    syscall
    movq  %rax, (%rsp)             # Store the file descriptor on the stack
    # Write the first record    movq (%rsp), %rdi              # Load the file descriptor    movq $record1, %rsi            # Load the address of the first record    call  write_record
    # Write the second record    movq (%rsp), %rdi              # Load the file descriptor    movq $record2, %rsi            # Load the address of the second record    call  write_record
    # Write the third record    movq (%rsp), %rdi              # Load the file descriptor    movq $record3, %rsi            # Load the address of the third record    call  write_record
    # Close the file descriptor    movq  $SYS_CLOSE, %rax    movq  (%rsp), %rdi    syscall
    # Exit the program    movq $SYS_EXIT, %rax    movq  $0, %rdi    syscall