From 8add210a380df6219baebdbb2475acfeec54d2cd Mon Sep 17 00:00:00 2001
From: Harald Wolff <haraldwolff@pc-harald.waldrennach.l--n.de>
Date: Mon, 22 Mar 2021 23:41:08 +0100
Subject: [PATCH] Fix big_cmp, big_divmod

---
 big.impl/Makefile |  6 ++---
 big.impl/bigint.c | 64 ++++++++++++++++++++++++++++++++---------------
 2 files changed, 46 insertions(+), 24 deletions(-)

diff --git a/big.impl/Makefile b/big.impl/Makefile
index 68685d3..ebe1a3d 100644
--- a/big.impl/Makefile
+++ b/big.impl/Makefile
@@ -10,12 +10,10 @@ all: linux Darwin
 clean:
 	rm -f ../ln.biginteger/libbigint.so ../ln.biginteger/libbigint.dylib ../ln.biginteger/libbigint.dll
 
-distribute: ../ln.biginteger/libbigint.so
-
 linux: ../ln.biginteger/libbigint.so
 ../ln.biginteger/libbigint.so: $(SRC)
-	gcc -shared -o ../ln.biginteger/libbigint.so $(SRC)
+	gcc -shared -o ../ln.biginteger/libbigint.so $(SRC) -fPIC
 
 Darwin: ../ln.biginteger/libbigint.dylib
 ../ln.biginteger/libbigint.dylib: $(SRC)
-	gcc -shared -o ../ln.biginteger/libbigint.dylib $(SRC)
+	gcc -shared -o ../ln.biginteger/libbigint.dylib $(SRC) -fPIC
diff --git a/big.impl/bigint.c b/big.impl/bigint.c
index 2dbe046..a0d29fa 100644
--- a/big.impl/bigint.c
+++ b/big.impl/bigint.c
@@ -9,7 +9,15 @@ int32_t max(int32_t a,int32_t b)
     return a>b ? a : b;
 }
 
-#define DUMP(op,l) for (int ___p = 0; ___p < l; ___p++) printf("0x%08x", op[___p]); printf("\n");
+int32_t big_is_zero( uint32_t* op, int32_t length)
+{
+    for (int n=0;n<length;n++)
+        if (op[n])
+            return 0;
+    return -1;
+}
+
+#define DUMP(op,l) for (int ___p = l-1; ___p >= 0; ___p--) printf("%08x", op[___p]); printf("\n");
 
 int32_t big_get_bitlength(uint32_t *op, int32_t length)
 {
@@ -62,24 +70,6 @@ int32_t big_sign(uint32_t *op, int32_t length)
 //     }
 // }
 
-int32_t big_cmp(uint32_t* op_a, int32_t length_a, uint32_t* op_b, int32_t length_b)
-{
-    int l = max(length_a, length_b);
-    for (int n=l-1; n >= 0; n--)
-    {
-        int a = n < length_a ? op_a[n] : 0;
-        int b = n < length_b ? op_b[n] : 0;
-
-        int d = a - b;
-
-        if (d > 0)
-            return 1;
-        else if (d < 0)
-            return -1;
-    }
-    return 0;
-}
-
 void big_shl(uint32_t *op, int32_t length, int32_t n)
 {
     if (n > 0)
@@ -151,7 +141,7 @@ void big_add(uint32_t* op_a, int32_t length_a, uint32_t* op_b, int32_t length_b)
 }
 void big_sub(uint32_t* op_a, int32_t length_a, uint32_t* op_b, int32_t length_b)
 {
-    uint64_t c = 0;
+    int64_t c = 0;
     for (int n=0;n<length_a;n++)
     {
         c += (int64_t)op_a[n] - ((n < length_b) ? op_b[n] : 0);
@@ -163,6 +153,21 @@ void big_sub(uint32_t* op_a, int32_t length_a, uint32_t* op_b, int32_t length_b)
     }
 }
 
+int32_t big_cmp(uint32_t* op_a, int32_t length_a, uint32_t* op_b, int32_t length_b)
+{
+    int32_t l = max(length_a, length_b);
+    uint32_t temp[l];
+    memcpy(temp, op_a, length_a << 2);
+    big_sub( temp, l, op_b, length_b );
+
+    if (temp[l-1] & 0x80000000)
+        return -1;
+    if (big_is_zero( temp, l ))
+        return 0;
+    return 1;
+}
+
+
 void big_twos(uint32_t *op, int32_t length)
 {
     for (int n=0;n<length;n++)
@@ -221,11 +226,26 @@ void big_divmod(uint32_t* op_a, int32_t length_a, uint32_t* op_b, int32_t length
     lg2b = big_get_bitlength(divisor, l);
     shift = lg2a - lg2b;
 
+    // printf("big_divmod():\n");
+    // printf(" dividend           = ");
+    // DUMP(dividend, l);
+    // printf(" divisor            = ");
+    // DUMP(divisor, l);
+
     if (shift > 0)
         big_shl(divisor, l, shift);
 
+    // printf(" divisor (SHIFTED)  = ");
+    // DUMP(divisor, l);
+
     for (int n = 0; n <= (shift); n++)
     {
+        // printf("+++\n");
+        // printf(" dividend           = ");
+        // DUMP(dividend, l);
+        // printf(" divisor            = ");
+        // DUMP(divisor, l);
+
         big_shl(op_a, length_a, 1);
 
         if (big_cmp( divisor, l, dividend, l ) <= 0)
@@ -234,6 +254,9 @@ void big_divmod(uint32_t* op_a, int32_t length_a, uint32_t* op_b, int32_t length
             big_sub( dividend, l, divisor, l );
         }
 
+        // printf(" result             = ");
+        // DUMP(op_a, length_a);
+
         big_shr( divisor, l, 1);
     }
 
@@ -243,6 +266,7 @@ void big_divmod(uint32_t* op_a, int32_t length_a, uint32_t* op_b, int32_t length
         big_twos(dividend, l);
 
     memcpy( op_b, dividend, length_b << 2);
+    // printf("----------------------------------------\n");
 }
 
 int32_t big_parse(uint32_t* op, int32_t length, char *source, int32_t radix)