Support global variables and constants

boot/common-boot.s

@@ -1,4 +1,4 @@
-.global is_alpha, is_digit, is_alnum, write_out, read_file, exit
+.global is_alpha, is_digit, is_alnum, is_upper, is_lower, write_out, read_file, exit, memcmp, write_error
 
 .section .rodata
 
@@ -9,30 +9,112 @@
 .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:
-	li t0, 'A' - 1
-	sltu t1, t0, a0 # t1 = a0 >= 'A'
+	# Prologue.
+	addi sp, sp, -16
+	sw ra, 12(sp)
+	sw s0, 8(sp)
+	addi s0, sp, 16
 
-	sltiu t2, a0, 'Z' + 1 # t2 = a0 <= 'Z'
-	and t1, t1, t2 # t1 = a0 >= 'A' & a0 <= 'Z'
+	sw a0, 4(sp)
 
-	li t0, 'a' - 1
-	sltu t2, t0, a0 # t2 = a0 >= 'a'
+	call is_upper
+	sw a0, 0(sp)
 
-	sltiu t3, a0, 'z' + 1 # t3 = a0 <= 'z'
-	and t2, t2, t3 # t2 = a0 >= 'a' & a0 <= 'z'
+	lw a0, 4(sp)
+	call is_lower
 
-	xori t3, a0, '_'
-	seqz t3, t3
+	lw t0, 4(sp)
+	xori t1, t0, '_'
+	seqz t1, t1
 
-	or a0, t1, t2
-	or a0, a0, t3
+	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