From 511df339b55f8f8d6fa743b5c5f052a9d6d412ec Mon Sep 17 00:00:00 2001
From: Valentin Gehrke <madmaurice@zom.bi>
Date: Sun, 22 Nov 2015 18:19:21 +0100
Subject: [PATCH] Added nand simulator for dldtg

---
 nandsimulator.c | 221 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 221 insertions(+)
 create mode 100644 nandsimulator.c

diff --git a/nandsimulator.c b/nandsimulator.c
new file mode 100644
index 0000000..50bdfd2
--- /dev/null
+++ b/nandsimulator.c
@@ -0,0 +1,221 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <assert.h>
+#include <stdlib.h>
+
+enum element_type { INPUT, NAND };
+
+struct element {
+    enum element_type type;
+    int a;
+    int b;
+};
+
+struct element_stack {
+    struct element** data;
+    int top;
+    int size;
+};
+
+struct element_stack* sCreate(int size) {
+    struct element_stack* e = malloc(sizeof(struct element_stack));
+    e->data = malloc(sizeof(struct element*)*size);
+    e->size = size;
+    e->top = 0;
+}
+
+int sPush(struct element_stack* stack,struct element* e) {
+    //printf("Pushed %d %d %d\n", e->a, e->b, stack->top);
+    if(stack->top == stack->size) return 1;
+    stack->data[stack->top] = e;
+    stack->top++;
+}
+
+struct element* sPop(struct element_stack* stack) {
+    if(stack->top == 0) return NULL;
+    stack->top--;
+    struct element* e = stack->data[stack->top];
+    //printf("Popped %d %d %d\n", e->a, e->b, stack->top);
+    return e;
+}
+
+struct element* sGet(struct element_stack* stack, int index) {
+    if(index < 0 || index >= stack->top) return NULL;
+    return stack->data[index];
+}
+
+void sFree(struct element_stack* stack) {
+    free(stack->data);
+    free(stack);
+}
+
+void sPrint(struct element_stack* stack) {
+    for(int i = 0; i < stack->top; i++) {
+        struct element* e = sGet(stack,i);
+        if(e->type == INPUT) {
+            printf("%d: INPUT %d\n",i,e->a);
+        } else {
+            printf("%d: NAND %d %d\n",i,e->a,e->b);
+        }
+    }
+}
+
+struct element* sFind(struct element_stack* stack, struct element* pattern) {
+    for(int i = 0; i<stack->top; i++) {
+        struct element* e = stack->data[i];
+        if(e->type == pattern->type && e->a == pattern->a && e->b == pattern->b) {
+            return e;
+        }
+    }
+    return NULL;
+}
+
+struct truth_table {
+    int z;
+    int* in;
+};
+
+int test_truth_table( struct element_stack* stack, const struct truth_table te) {
+    int* netvalues = malloc(sizeof(int)*stack->top);
+    int inputs = 0;
+    for(int i = 0; i < stack->top; i++) {
+        struct element* e = sGet(stack,i);
+        if(e->type == INPUT) {
+            netvalues[i] = te.in[e->a];
+            if(inputs <= e->a) inputs = e->a+1;
+        } else if(e->type == NAND) {
+            if(netvalues[e->a] == 1 && netvalues[e->b] == 1) {
+                netvalues[i] = 0;
+            } else {
+                netvalues[i] = 1;
+            }
+        }
+    }
+    int result = netvalues[stack->top-1];
+
+    free(netvalues);
+    if(result == te.z) {
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+int buildnet( struct element_stack* stack, int inputs, int nands, const struct truth_table* tt ) {
+    if(stack->top == inputs+nands) {
+        //sPrint(stack);
+        for(int i = 0; i < (1 << inputs); i++) {
+            if(!test_truth_table(stack, tt[i] )) {
+                return 0;
+            }
+        }
+        return 1;
+    } else {
+        struct element* e = malloc(sizeof(struct element));
+        e->type = NAND;
+        sPush(stack,e);
+        for(int a = 0; a < stack->top-1; a++) {
+            e->a = a;
+            for(int b = a; b < stack->top-1; b++) {
+                e->b = b;
+                struct element* f = sFind(stack,e);
+                if(f != NULL && f != e) continue;
+                if(buildnet(stack, inputs, nands, tt)) {
+                    return 1;
+                }
+            }
+        }
+        assert(sPop(stack) == e);
+        free(e);
+        return 0;
+    }
+}
+
+struct element_stack* findnet( int inputs, int nands, const struct truth_table* tt ) {
+    struct element_stack* stack = sCreate(inputs+nands);
+    // Add inputs to stack
+    for(int i = 0; i < inputs; i++) {
+        struct element* e = malloc(sizeof(struct element));
+        e->type = INPUT;
+        e->a = i;
+        e->b = 0;
+        sPush(stack,e);
+    }
+
+    if(buildnet(stack, inputs, nands, tt)) {
+        return stack;
+    } else {
+        while(stack->top > 0) {
+            free(sPop(stack));
+        }
+        sFree(stack);
+        return NULL;
+    }
+}
+
+
+int main( int argc, char *argv[] ) {
+    /*const struct truth_table tt[16] = {
+        { .in = {0,0,0,0}, .z = 0 },
+        { .in = {0,0,0,1}, .z = 0 },
+        { .in = {0,0,1,0}, .z = 0 },
+        { .in = {0,0,1,1}, .z = 0 },
+        { .in = {0,1,0,0}, .z = 1 },
+        { .in = {0,1,0,1}, .z = 1 },
+        { .in = {0,1,1,0}, .z = 1 },
+        { .in = {0,1,1,1}, .z = 0 },
+        { .in = {1,0,0,0}, .z = 1 },
+        { .in = {1,0,0,1}, .z = 0 },
+        { .in = {1,0,1,0}, .z = 1 },
+        { .in = {1,0,1,1}, .z = 1 },
+        { .in = {1,1,0,0}, .z = 1 },
+        { .in = {1,1,0,1}, .z = 1 },
+        { .in = {1,1,1,0}, .z = 1 },
+        { .in = {1,1,1,1}, .z = 1 }
+    };*/
+
+    /*const struct truth_table tt[4] = {
+        { .in = {0,0}, .z = 0 },
+        { .in = {0,1}, .z = 1 },
+        { .in = {1,0}, .z = 1 },
+        { .in = {1,1}, .z = 0 }
+    };*/
+
+    int inputs, z;
+    printf("number of inputs: ");
+    scanf("%d",&inputs);
+    struct truth_table* tt = malloc( sizeof(struct truth_table) * (1<<inputs) );
+
+    for(int v = 0; v < (1<<inputs); v++) {
+        tt[v].in = malloc(sizeof(int)*inputs);
+        for(int n = inputs-1; n >= 0; n--) {
+            tt[v].in[inputs-n-1] = ((v>>n)&1);
+            printf("%d ",tt[v].in[inputs-n-1]);
+        }
+        printf(" => ");
+        scanf("%d",&z);
+        if(z != 0) z = 1;
+        tt[v].z = z;
+    }
+
+    struct element_stack* result;
+    for(int nands = 1; nands <= 20; nands++) {
+        printf("-- Trying to find solution for %d NANDS\n",nands);
+        result = findnet(inputs,nands,tt);
+        if(result != NULL) break;
+        printf("No solution\n");
+    }
+
+    if(result != NULL) {
+        sPrint(result);
+    } else {
+        printf("No result.\n");
+    }
+
+    for(int v = 0; v < (1<<inputs); v++) {
+        free(tt[v].in);
+    }
+    free(tt);
+
+	return 0;
+}