Programming-From-The-Ground-Up/Chapter-5/to-upper-new-buffer.s at main · Sivnerof/Programming-From-The-Ground-Up · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
# The only difference between this program and the to-upper program is that
# this program has changed the line ".equ BUFFER_SIZE, 500" to
# .equ BUFFER_SIZE, 250

.section .data

.equ SYS_OPEN, 5
.equ SYS_WRITE, 4
.equ SYS_READ, 3
.equ SYS_CLOSE, 6
.equ SYS_EXIT, 1


.equ O_RDONLY, 0
.equ O_CREAT_WRONLY_TRUNC, 03101


.equ STDIN, 0
.equ STDOUT, 1
.equ STDERR, 2


.equ LINUX_SYSCALL, 0x80

.equ END_OF_FILE, 0

.equ NUMBER_ARGUMENTS, 2

.section .bss

.equ BUFFER_SIZE, 250
.lcomm BUFFER_DATA, BUFFER_SIZE

.section .text


.equ ST_SIZE_RESERVE, 8
.equ ST_FD_IN, -4
.equ ST_FD_OUT, -8
.equ ST_ARGC, 0
.equ ST_ARGV_0, 4
.equ ST_ARGV_1, 8
.equ ST_ARGV_2, 12

.globl _start
_start:
    movl %esp, %ebp
    subl $ST_SIZE_RESERVE, %esp

open_files:
open_fd_in:
    movl $SYS_OPEN, %eax
    movl ST_ARGV_1(%ebp), %ebx
    movl $O_RDONLY, %ecx
    movl $0666, %edx
    int $LINUX_SYSCALL

store_fd_in:
    movl %eax, ST_FD_IN(%ebp)

open_fd_out:
    movl $SYS_OPEN, %eax
    movl ST_ARGV_2(%ebp), %ebx
    movl $O_CREAT_WRONLY_TRUNC, %ecx
    movl $0666, %edx
    int $LINUX_SYSCALL

store_fd_out:
    movl %eax, ST_FD_OUT(%ebp)


read_loop_begin:
    movl $SYS_READ, %eax
    movl ST_FD_IN(%ebp), %ebx
    movl $BUFFER_DATA, %ecx
    movl $BUFFER_SIZE, %edx
    int $LINUX_SYSCALL

    cmpl $END_OF_FILE, %eax
    jle end_loop

continue_read_loop:
    pushl $BUFFER_DATA
    pushl %eax
    call convert_to_upper
    popl %eax
    addl $4, %esp

    movl %eax, %edx
    movl $SYS_WRITE, %eax
    movl ST_FD_OUT(%ebp), %ebx
    movl $BUFFER_DATA, %ecx
    int $LINUX_SYSCALL

    jmp read_loop_begin

end_loop:
    movl $SYS_CLOSE, %eax
    movl ST_FD_OUT(%ebp), %ebx
    int $LINUX_SYSCALL

    movl $SYS_CLOSE, %eax
    movl ST_FD_IN(%ebp), %ebx
    int $LINUX_SYSCALL

    movl $SYS_EXIT, %eax
    movl $0, %ebx
    int $LINUX_SYSCALL


.equ LOWERCASE_A, 'a'
.equ LOWERCASE_Z, 'z'
.equ UPPER_CONVERSION, 'A' - 'a'


.equ ST_BUFFER_LEN, 8
.equ ST_BUFFER, 12
convert_to_upper:
pushl %ebp
movl %esp, %ebp


movl ST_BUFFER(%ebp), %eax
movl ST_BUFFER_LEN(%ebp), %ebx
movl $0, %edi
cmpl $0, %ebx
je end_convert_loop

convert_loop:
    movb (%eax,%edi,1), %cl

    cmpb $LOWERCASE_A, %cl
    jl next_byte
    cmpb $LOWERCASE_Z, %cl
    jg next_byte

    addb $UPPER_CONVERSION, %cl
    movb %cl, (%eax,%edi,1)

next_byte:
    incl %edi
    cmpl %edi, %ebx
    jne convert_loop

end_convert_loop:
    movl %ebp, %esp
    popl %ebp
    ret