initial part of bigint-library; some bugs left

[avr-crypto-lib.git] / bigint / bigint_add_u.S

diff --git a/bigint/bigint_add_u.S b/bigint/bigint_add_u.S
new file mode 100644 (file)
index 0000000..7c34f1a
--- /dev/null
+++ b/bigint/bigint_add_u.S
@@ -0,0 +1,137 @@
+/* bigint_add_u.S */
+/*
+    This file is part of the AVR-Crypto-Lib.
+    Copyright (C) 2010 Daniel Otte (daniel.otte@rub.de)
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/**
+ * \file     bigint_add_u.S
+ * \email    daniel.otte@rub.de
+ * \author   Daniel Otte
+ * \date     2010-03-01
+ * \license  GPLv3 or later
+ *
+ */
+
+#include "avr-asm-macros.S"
+
+/*
+ param dest: r24:r25
+ param a:    r22:r23
+ param b:    r20:r21
+*/
+LEN_A_0 = 22
+LEN_A_1 = 23
+LEN_B_0 = 20
+LEN_B_1 = 21
+
+
+.global bigint_add_u
+bigint_add_u:
+       push_range 28, 29
+       push_range 24, 25
+       movw r26, r24 ; X is our destination pointer
+       movw r30, r22 ; Z = a
+       movw r28, r20 ; Y = b
+       ldd LEN_A_0, Z+0
+       ldd LEN_A_1, Z+1
+       ldd LEN_B_0, Y+0
+       ldd LEN_B_1, Y+1
+       cp LEN_A_0, LEN_B_0
+       cpc LEN_A_1, LEN_B_1
+       brsh 3f
+       movw r18, LEN_A_0    ; swap length values
+       movw LEN_A_0, LEN_B_0
+       movw LEN_B_0, r18
+       movw r18, r30        ; swap pointers
+       movw r30, r28
+       movw r28, r18
+3:     ; now a is the longer integer
+    movw r24, LEN_A_0
+    adiw r24, 0
+    brne 4f
+    st X+, r1 ; store length
+    st X+, r1
+    st X+, r1 ; store 0 in info field
+    rjmp 9f
+4:
+    adiw r24, 1
+    st X+, r24 ; store length
+    st X+, r25
+    st X+, r1 ; store 0 in info field
+    ld r18, X+
+    ld r19, X+
+    movw r26, r18
+    adiw r30, 3 ; adjust pointers to point at wordv
+    ld r18, Z+
+    ld r19, Z+
+    movw r30, r18
+    adiw r28, 3
+    ld r18, Y+
+    ld r19, Y+
+    movw r28, r18
+
+    sub LEN_A_0, LEN_B_0
+    sbc LEN_A_1, LEN_B_1
+    movw r24, LEN_B_0
+    clr r0
+    adiw r24, 0
+    breq 6f
+    clc
+5:
+    ld r0, Z+
+    ld r1, Y+
+    adc r0, r1
+    st X+, r0
+    dec r24
+       brne 5b
+       rol r0 ; store carry bit
+       tst r25
+       breq 6f
+       dec r25
+       dec r24
+       ror r0 ; write carry back
+       rjmp 5b
+6: /* the main part is done */
+       movw r24, LEN_A_0
+       clr r1
+       adiw r24, 0
+       breq 8f
+62:
+       ror r0 ; write carry back
+7:
+    ld r0, Z+
+    adc r0, r1
+    st X+, r0
+    dec r24
+       brne 7b
+       rol r0 ; store carry bit
+       tst r25
+       breq 8f
+       dec r25
+       dec r24
+       rjmp 62b
+8:
+       ror r0
+       clr r0
+       rol r0
+       st X+, r0
+9:
+       pop_range 24, 25
+       pop_range 28, 29
+       jmp bigint_adjust
+
+