1 files changed, 120 insertions, 2 deletions
diff --git a/boot/common-boot.s b/boot/common-boot.s
index e5796f1..0cf31f1 100644
--- a/boot/common-boot.s
+++ b/boot/common-boot.s
@@ -1,6 +1,6 @@
 .global _is_alpha, _is_digit, _is_alnum, _is_upper, _is_lower
 .global _write_out, _read_file, _write_error, _put_char, _printi
-.global _get, _memcmp
+.global _get, _memcmp, _memchr, _memmem, _memcpy
 .global _divide_by_zero_error, _exit
 
 .section .rodata
@@ -16,7 +16,8 @@ new_line: .ascii "\n"
 
 .section .text
 
-# Write the current token to stderr.
+# Write the current token to stderr. Ends the output with a newline.
+#
 # a0 - String pointer.
 # a1 - String length.
 .type _write_error, @function
@@ -306,3 +307,120 @@ _put_char:
 _get:
 	lw a0, (a0)
 	ret
+
+# Searches for the occurences of a character in the given memory block.
+#
+# Parameters:
+# a0 - Memory block.
+# a1 - Needle.
+# a2 - Memory size.
+#
+# Sets a0 to the pointer to the found character or to null if the character
+# doesn't occur in the memory block.
+.type _memchr, @function
+_memchr:
+.Lmemchr_loop:
+	beqz a2, .Lmemchr_nil # Exit if the length is 0.
+
+	lbu t0, (a0) # Load the character from the memory block.
+	beq t0, a1, .Lmemchr_end # Exit if the character was found.
+
+	# Otherwise, continue with the next character.
+	addi a0, a0, 1
+	addi a2, a2, -1
+
+	j .Lmemchr_loop
+
+.Lmemchr_nil:
+	li a0, 0
+
+.Lmemchr_end:
+	ret
+
+# Locates a substring.
+#
+# Parameters:
+# a0 - Haystack.
+# a1 - Haystack size.
+# a2 - Needle.
+# a3 - Needle size.
+#
+# Sets a0 to the pointer to the beginning of the substring in memory or to 0
+# if the substring doesn't occur in the block.
+.type _memmem, @function
+_memmem:
+	# Prologue.
+	addi sp, sp, -24
+	sw ra, 20(sp)
+	sw s0, 16(sp)
+	addi s0, sp, 24
+
+	# Save preserved registers. They are used to keep arguments.
+	sw s1, 12(sp)
+	sw s2, 8(sp)
+	sw s3, 4(sp)
+	sw s4, 0(sp)
+
+	mv s1, a0
+	mv s2, a1
+	mv s3, a2
+	mv s4, a3
+
+.Lmemmem_loop:
+	blt s2, s3, .Lmemmem_nil # Exit if the needle length is greater than memory.
+
+	mv a0, s1
+	mv a1, s3
+	mv a2, s4
+	call _memcmp
+
+	mv t0, a0 # memcmp result.
+	mv a0, s1 # Memory pointer for the case the substring was found.
+	beqz t0, .Lmemmem_end
+
+	addi s1, s1, 1
+	add s2, s2, -1
+
+	j .Lmemmem_loop
+
+.Lmemmem_nil:
+	li a0, 0
+
+.Lmemmem_end:
+
+	# Restore the preserved registers.
+	lw s1, 12(sp)
+	lw s2, 8(sp)
+	lw s3, 4(sp)
+	lw s4, 0(sp)
+
+	# Epilogue.
+	lw ra, 20(sp)
+	lw s0, 16(sp)
+	add sp, sp, 24
+	ret
+
+# Copies memory.
+#
+# Parameters:
+# a0 - Destination.
+# a1 - Source.
+# a2 - Size.
+#
+# Preserves a0.
+.type _memcpy, @function
+_memcpy:
+	mv t0, a0
+
+.Lmemcpy_loop:
+	beqz a2, .Lmemcpy_end
+
+	lbu t1, (a1)
+	sb t1, (a0)
+
+	addi a0, a0, 1
+	addi a1, a1, 1
+
+.Lmemcpy_end:
+	mv a0, t0
+	ret