Question

我正在尝试使用mips指令对文件进行一些访问我想逐行读取文件，而不是一次读取所有文件，因此这段代码（1）不起作用。

此外，我想写入文件而不是覆盖！
任何人都可以帮助我吗？

代码：

打开文件进行编写

li   $v0, 13       # system call for open file
la   $a0, file      # board file name
li   $a1, 0        # Open for reading
li   $a2, 0
syscall            # open a file (file descriptor returned in $v0)
move $s6, $v0      # save the file descriptor

从文件中读取

li   $v0, 14       # system call for read from file  
move $a0, $s6      # file descriptor   
la   $a1, buffer   # address of buffer to which to read  
li   $a2, 40     # hardcoded buffer length  
syscall            # read from file

关闭文件

li   $v0, 16       # system call for close file  
move $a0, $s6      # file descriptor to close  
syscall            # close file

Answer 1

我想逐行读取文件，而不是一次读取所有文件，因此此代码（1）不起作用。

将数据块读入缓冲区（例如几千字节）。然后逐行处理缓冲区（通过查找换行符），并在到达缓冲区末尾时从文件中读取更多数据。

此外，我想写入文件而不是覆盖！

打开文件时将标志（$a1）设置为9（系统调用13）。这对应于“只写与创建和附加”（参见this MARS syscall reference）。

Answer 2

它的工作很多很多：）

.data  
fin: .asciiz "file.txt"      # filename for input
buffer: .space 128
buffer1: .asciiz "\n"
val : .space 128
.text

################################################ fileRead:

# Open file for reading

li   $v0, 13       # system call for open file
la   $a0, fin      # input file name
li   $a1, 0        # flag for reading
li   $a2, 0        # mode is ignored
syscall            # open a file 
move $s0, $v0      # save the file descriptor 

# reading from file just opened

li   $v0, 14       # system call for reading from file
move $a0, $s0      # file descriptor 
la   $a1, buffer   # address of buffer from which to read
li   $a2,  6  # hardcoded buffer length
syscall            # read from file

li  $v0, 4          # 
la  $a0, buffer     # buffer contains the values
syscall             # print int

lb $t1 , buffer

# reading from file just opened

li   $v0, 14       # system call for reading from file
move $a0, $s0      # file descriptor 
la   $a1, buffer   # address of buffer from which to read
li   $a2,  6  # hardcoded buffer length
syscall            # read from file

li  $v0, 4          # 
la  $a0, buffer     # buffer contains the values
syscall             # print int

## sh  $t5 , val($0)    #sw    $t5, theArray($t0)

# Close the file 

li   $v0, 16       # system call for close file
move $a0, $s6      # file descriptor to close
syscall            # close file

使用mars工具以mips访问文件

2 个答案: