make ERC20 more user friendly

- proper handling of token amounts
- code cleanup

helpers/math.c

@@ -0,0 +1,26 @@
+/**
+* @brief 
+* @file math.c
+* @author J.H. 
+* @date 2018-11-07
+*/
+
+/* system includes */
+
+/* local includes */
+#include "math.h"
+
+
+uint64_t ipow(uint64_t base, uint8_t exp)
+{
+    uint64_t result = 1;
+    for (;;)
+    {
+        if (exp & 1) { result *= base; }
+        exp >>= 1;
+        if (!exp) { break; }
+        base *= base;
+    }
+
+    return result;
+}

helpers/math.h

@@ -0,0 +1,18 @@
+#ifndef _MATH_H_
+#define _MATH_H_
+/* system includes */
+#include <stdint.h>
+/* local includes */
+
+
+#ifdef  __cplusplus
+extern "C" {
+#endif
+uint64_t ipow(uint64_t base, uint8_t exp);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _MATH_H_ */
+

helpers/uint256.c

@@ -23,6 +23,7 @@
 #include <string.h>
 
 #include "hextobin.h"
+#include "endian.h"
 
 
 static const char HEXDIGITS[] = "0123456789abcdef";
@@ -56,8 +57,8 @@ void readu256BE(const uint8_t *buffer, uint256_t *target) {
 
 void writeu128BE(const uint128_t *number, uint8_t *buffer)
 {
-    *(uint64_t*)buffer = ENDIAN_SWAP_U64(LOWER_P(number));
-    *(uint64_t*)(buffer + sizeof(uint64_t)) = ENDIAN_SWAP_U64(UPPER_P(number));
+    *(uint64_t*)buffer = ENDIAN_SWAP_U64(UPPER_P(number));
+    *(uint64_t*)(buffer + sizeof(uint64_t)) = ENDIAN_SWAP_U64(LOWER_P(number));
 }
 
 void writeu256BE(const uint256_t *number, uint8_t *buffer)
@@ -587,6 +588,12 @@ void set256_uint64(uint256_t *target, uint64_t val)
     LOWER(LOWER_P(target)) = val;
 }
 
+void set256_uint64BE(uint256_t *target, uint64_t val)
+{
+    clear256(target);
+    LOWER(LOWER_P(target)) = htobe64(val);
+}
+
 // connect hexencoded ASCII to an uint256
 int fromstring256(const char *hexencoded, uint256_t *out)
 {

helpers/uint256.h

@@ -56,6 +56,7 @@ void writeu256BE(const uint256_t *number, uint8_t *buffer);
 void writeu128BE(const uint128_t *number, uint8_t *buffer);
 
 void set256_uint64(uint256_t *target, uint64_t val);
+void set256_uint64BE(uint256_t *target, uint64_t val);
 
 bool zero128(const uint128_t *number);
 bool zero256(const uint256_t *number);

tests/test_helpers.cpp

@@ -16,6 +16,7 @@
 #include "helpers/hextobin.h"
 #include "helpers/fp2str.h"
 #include "helpers/uint256.h"
+#include "helpers/math.h"
 
 #define TEST_BUF_LEN    64
 
@@ -133,3 +134,12 @@ TEST(TEST_HELPERS, TEST_STR2UINT256)
     }
 
 }
+
+TEST(TEST_HELPERS, TEST_IPOW)
+{
+    uint64_t res;
+
+    res = ipow(10, 18);
+
+    ASSERT_EQ(res, 1000000000000000000);
+}