small speedup

diff --git a/bmw_small.c b/bmw_small.c
index 269870014436b46f43e247523808882f81a0e63d..e1ddeffd9b7cb1f36cc1f679652ac77bfc0fd64c 100644 (file)
--- a/bmw_small.c
+++ b/bmw_small.c
@@ -27,8 +27,10 @@
 
 #include <stdint.h>
 #include <string.h>
+#include <avr/pgmspace.h>
 #include "bmw_small.h"
 
+
 #define SHL32(a,n) ((a)<<(n))
 #define SHR32(a,n) ((a)>>(n))
 #define ROTL32(a,n) (((a)<<(n))|((a)>>(32-(n))))
@@ -164,11 +166,18 @@ uint32_t bmw_small_r7(uint32_t x){
        return r;       
 }
 
+#define K 0x05555555L
+uint32_t k_lut[] PROGMEM = {
+       16L*K, 17L*K, 18L*K, 19L*K, 20L*K, 21L*K, 22L*K, 23L*K,
+       24L*K, 25L*K, 26L*K, 27L*K, 28L*K, 29L*K, 30L*K, 31L*K
+};
+
 uint32_t bmw_small_expand1(uint8_t j, const uint32_t* q, const void* m){
        uint32_t(*s[])(uint32_t) = {bmw_small_s1, bmw_small_s2, bmw_small_s3, bmw_small_s0};
        uint32_t r;
        uint8_t i;
-       r = 0x05555555*(j+16);
+       /* r = 0x05555555*(j+16); */
+       r = pgm_read_dword(k_lut+j);
        for(i=0; i<16; ++i){
                r += s[i%4](q[j+i]);
        }
@@ -184,7 +193,8 @@ uint32_t bmw_small_expand2(uint8_t j, const uint32_t* q, const void* m){
                                                             bmw_small_r7};
        uint32_t r;
        uint8_t i;
-       r = 0x05555555*(j+16);
+       /* r = 0x05555555*(j+16); */
+       r = pgm_read_dword(k_lut+j);
        for(i=0; i<14; i+=2){
                r += q[j+i];
        }