day 5, pretty blinkenlights mem, awful performance

lib.h

@@ -34,6 +34,7 @@ void exit_group(uint64_t code) {
 #define str(s) #s
 
 typedef uint64_t bcdint;
+typedef uint64_t num;
 
 static
 void printns(size_t len, unsigned char chars[len]) {
@@ -81,6 +82,23 @@ void printd(unsigned long v) {
     write(STDOUT_FILENO, p, count);
 }
 
+static
+void snprintd(unsigned long v, size_t n, unsigned char d[n]) {
+    memset(d, 0, n);
+    if (!v) {
+        d[n-1] = '0';
+        return;
+    }
+    unsigned char *p = d+n;
+    unsigned count = 0;
+    while (v) {
+        p--;
+        *p = '0' + (v % 10);
+        v /= 10;
+        if (p == d) return;
+    }
+}
+
 static
 void printh(unsigned long v) {
     if (!v) {
@@ -103,6 +121,28 @@ void printh(unsigned long v) {
     write(STDOUT_FILENO, p, count);
 }
 
+static
+void snprinth(unsigned long v, size_t n, unsigned char d[n]) {
+    memset(d, 0, n);
+    if (!v) {
+        d[n-1] = '0';
+        return;
+    }
+    unsigned char *p = d+n;
+    unsigned count = 0;
+    while (v) {
+        p--;
+        if ((v & 0x0F) < 0xA) {
+            *p = '0' + (v & 0x0F);
+        } else {
+            *p = 'A' - 0xA + (v & 0x0F);
+        }
+        v >>= 4;
+        if (p == d) return;
+    }
+    while (p >= d) *p-- = 0;
+}
+
 static
 void print_hex_char(unsigned char v) {
     char buf[2];
@@ -169,3 +209,48 @@ static bcdint bcdadd(bcdint a, bcdint b) {
     t2 = (t2 >> 2) | (t2 >> 3);
     return t1 - t2;
 }
+
+// https://homepage.cs.uiowa.edu/~jones/bcd/bcd.html
+static bcdint bcdcomp(bcdint a) {
+    bcdint t1, t2, t3, t4, t5, t6;
+    t1 = 0xFFFFFFFFFFFFFFFF - a;
+    t2 = - a;
+    t3 = t1 ^ 0x0000000000000001;
+    t4 = t2 ^ t3;
+    t5 = ~t4 & 0x1111111111111110;
+    t6 = (t5 >> 2) | (t5 >> 3);
+    return t2 - t6;
+}
+
+static bcdint bcdsub(bcdint a, bcdint b) {
+    return bcdadd(a, bcdcomp(b));
+}
+
+static num bcdtonum(bcdint a) {
+    return 0
+        + ((a >>  0) & 0xF) * 1
+        + ((a >>  4) & 0xF) * 10
+        + ((a >>  8) & 0xF) * 100
+        + ((a >> 12) & 0xF) * 1000
+        + ((a >> 16) & 0xF) * 10000
+        + ((a >> 24) & 0xF) * 100000
+        + ((a >> 28) & 0xF) * 1000000
+        + ((a >> 32) & 0xF) * 10000000
+        + ((a >> 36) & 0xF) * 100000000
+        + ((a >> 40) & 0xF) * 1000000000
+        + ((a >> 44) & 0xF) * 10000000000
+        + ((a >> 48) & 0xF) * 100000000000
+        + ((a >> 52) & 0xF) * 1000000000000
+        + ((a >> 56) & 0xF) * 10000000000000
+        + ((a >> 60) & 0xF) * 100000000000000;
+}
+
+static bcdint numtobcd(num a) {
+    bcdint r = 0;
+    while (a) {
+        r <<= 4;
+        r |= (a % 10);
+        a /= 10;
+    }
+    return r;
+}