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.global is_alpha, is_digit, is_alnum, is_upper, is_lower, write_out, read_file, exit, memcmp, write_error
.section .rodata
.equ SYS_READ, 63
.equ SYS_WRITE, 64
.equ SYS_EXIT, 93
.equ STDIN, 0
.equ STDOUT, 1
.equ STDERR, 2
new_line: .ascii "\n"
.section .text
# Write the current token to stderr.
# a0 - String pointer.
# a1 - String length.
.type write_error, @function
write_error:
mv t0, a0
mv t1, a1
li a0, STDERR
mv a1, t0
mv a2, t1
li a7, SYS_WRITE
ecall
li a0, STDERR
la a1, new_line
li a2, 1
li a7, SYS_WRITE
ecall
ret
# a0 - First pointer.
# a1 - Second pointer.
# a2 - The length to compare.
#
# Returns 0 in a0 if memory regions are equal.
.type memcmp, @function
memcmp:
mv t0, a0
li a0, 0
.Lmemcmp_loop:
beqz a2, .Lmemcmp_end
lbu t1, (t0)
lbu t2, (a1)
sub a0, t1, t2
bnez a0, .Lmemcmp_end
addi t0, t0, 1
addi a1, a1, 1
addi a2, a2, -1
j .Lmemcmp_loop
.Lmemcmp_end:
ret
# Detects if a0 is an uppercase character. Sets a0 to 1 if so, otherwise to 0.
is_upper:
li t0, 'A' - 1
sltu t1, t0, a0 # t1 = a0 >= 'A'
sltiu t2, a0, 'Z' + 1 # t2 = a0 <= 'Z'
and a0, t1, t2 # t1 = a0 >= 'A' & a0 <= 'Z'
ret
# Detects if a0 is an lowercase character. Sets a0 to 1 if so, otherwise to 0.
.type is_lower, @function
is_lower:
li t0, 'a' - 1
sltu t2, t0, a0 # t2 = a0 >= 'a'
sltiu t3, a0, 'z' + 1 # t3 = a0 <= 'z'
and a0, t2, t3 # t2 = a0 >= 'a' & a0 <= 'z'
ret
# Detects if the passed character is a 7-bit alpha character or an underscore.
# The character is passed in a0.
# Sets a0 to 1 if the character is an alpha character or underscore, sets it to 0 otherwise.
.type is_alpha, @function
is_alpha:
# Prologue.
addi sp, sp, -16
sw ra, 12(sp)
sw s0, 8(sp)
addi s0, sp, 16
sw a0, 4(sp)
call is_upper
sw a0, 0(sp)
lw a0, 4(sp)
call is_lower
lw t0, 4(sp)
xori t1, t0, '_'
seqz t1, t1
lw t0, 0(sp)
or a0, a0, t0
or a0, a0, t1
# Epilogue.
lw ra, 12(sp)
lw s0, 8(sp)
addi sp, sp, 16
ret
.type is_digit, @function
is_digit:
li t0, '0' - 1
sltu t1, t0, a0 # t1 = a0 >= '0'
sltiu t2, a0, '9' + 1 # t2 = a0 <= '9'
and a0, t1, t2
ret
.type is_alnum, @function
is_alnum:
# Prologue.
addi sp, sp, -16
sw ra, 12(sp)
sw s0, 8(sp)
addi s0, sp, 16
sw a0, 4(sp)
call is_alpha
sw a0, 0(sp)
lw a0, 4(sp)
call is_digit
lw a1, 0(sp)
or a0, a0, a1
# Epilogue.
lw ra, 12(sp)
lw s0, 8(sp)
addi sp, sp, 16
ret
.type write, @function
write_out:
# Prologue.
addi sp, sp, -8
sw ra, 4(sp)
sw s0, 0(sp)
addi s0, sp, 8
mv a2, a1
mv a1, a0
li a0, STDOUT
li a7, SYS_WRITE
ecall
# Epilogue.
lw ra, 4(sp)
lw s0, 0(sp)
addi sp, sp, 8
ret
# Reads standard input into a buffer.
# a0 - Buffer pointer.
# a1 - Buffer size.
#
# Returns the result in a0.
.type read_file, @function
read_file:
# Prologue.
addi sp, sp, -8
sw ra, 4(sp)
sw s0, 0(sp)
addi s0, sp, 8
mv a2, a1
mv a1, a0
li a0, STDIN
li a7, SYS_READ
ecall
# Epilogue.
lw ra, 4(sp)
lw s0, 0(sp)
addi sp, sp, 8
ret
# Terminates the program. a0 contains the return code.
exit:
li a7, SYS_EXIT
ecall
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