littlebigcomputer/programs/parva_0.2/hashmap.parva

# hashmap

.extern malloc
.export hashmap__new

# structure:
# <entry count>
# <capacity magnitude> (capacity = 2 ^ capacity magnitude)
# {
#   <hash>
#   <value>
# } * 2^capacity


# Uses open addressing


# a0 = initial capacity magnitude
# returns: pointer to hashmap
hashmap__new:
	push ra
	push s0
	mv s0, a0
	li a0, 1
	sll a0, a0, s0
	addi a0, s0, 2
	li a1, 0
	call malloc
	li t0, 0
zero_fill_loop:
	addi t0, t0, 1
	sw zero, [a0 + t0 + 2]
	bne t0, s0 zero_fill_loop

	sw zero, [a0 + s0 + 0]
	sw s0, [a0 + s0 + 1]
	pop s0
	pop ra
	ret

index_from_hash:
	beqz a1, error
	li t2, 1
	lw a3, [a0 + 1]
	sll t2, t2, a3
	addi t2, t2, -1
	and t1, a1, t2
	add t1, t1, t1
	jr t0

# a0 = pointer to hashmap
# a1 = 24-bit hash of key
# returns: value
hashmap__get:
	jal t0, index_from_hash
get_loop:
	lw t2, [a0 + t1 + 2] # t2 = hash of entry key
	beq t2, a1, entry_found
	beqz t2, entry_not_found
	addi t1, t1, 2
	b get_loop
entry_found:
	lw a0, [a0 + t0 + 3]
	ret
entry_not_found:
	li a0, 0
	ret

# a0 = pointer to hashmap
# a1 = 24-bit hash of key
# a2 = 24-bit value
# returns: pointer to value
hashmap__insert:
	lw a3, [a0] # entry count
	lw a4, [a0 + 1] # capacity magnitude
	li t0, 1
	addi a5, a4, -1
	sll a5, t0, a5 # capacity / 2
	ble a3, a5, insert_no_resize
	slli a4, a4, 2 # capacity * 2
	jal s0, resize
insert_no_resize:
	jal t0, index_from_hash
	add a3, a3, a3
insert_loop:
	lw t2, [a0 + t1 + 2] # t2 = hash of entry key
	addi t1, t1, 2
	bnez t2 slot_found


	beq t2, a1, entry_found
	beqz t2, entry_not_found
	addi t1, t1, 1
	b insert_loop

# a4 = new capacity
resize:
	push a0, a1, a2, a3, a4
	mv a0, a4
	mv s0, t0
	call hashmap__new
	pop t0, a1, a2, a3, a4
	addi a4, a4, 1
	sw a4, [a0]