From 2f5a00f0a55f29833e12b935f1a03ebebc166732 Mon Sep 17 00:00:00 2001
From: Holger Vogt <holger.vogt@uni-due.de>
Date: Mon, 12 Jul 2021 22:52:17 +0200
Subject: [PATCH] hash functions for cpl garbage collector

---
 src/spicelib/devices/cpl/cplhash.c | 139 +++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)
 create mode 100644 src/spicelib/devices/cpl/cplhash.c

diff --git a/src/spicelib/devices/cpl/cplhash.c b/src/spicelib/devices/cpl/cplhash.c
new file mode 100644
index 000000000..7809fced3
--- /dev/null
+++ b/src/spicelib/devices/cpl/cplhash.c
@@ -0,0 +1,139 @@
+/* This is a test file including a local garbage collector and removal.
+It might be especially useful, if the ngspice shared library (.dll or .so)
+is loaded and unloaded several times by a master program.
+At ngspice initialization mem_init() is called setting up a hash table
+to store memory addresses.
+Each time calloc() is called, the resulting address is stored.
+Each time free() is called, the address is removed.
+For realloc(), the old address is deleted, the new one is stored,
+if there is a change in the address.
+Upon exiting the program, mem_delete() is called, deleting all memory
+at addresses still in the hash table, then the hash table itself is removed.
+The Windows dll uses DllMain() to call mem_delete() exit, the LINUX .so
+will use void __attribute__((destructor)) mem_delete(void) or atexit()
+(both are not tested so far).
+
+The master program has to make copies of all the data that have to be kept
+for further use before detaching the shared lib! */
+
+// #define DB_FULL /* uncomment for debugging output, all addresses to files */
+#ifdef DB_FULL
+#define DB
+#else
+#define DB /* uncomment for printing some debugging output */
+#endif
+
+void mem_init(void);
+void mem_delete(void);
+
+int memsaved(void *ptr);
+void memdeleted(const void *ptr);
+
+int gc_is_on = 0;
+
+/* add some debugging printout */
+#ifdef DB
+static int mem_in = 0, mem_out = 0, mem_freed = 0;
+#endif
+#ifdef DB_FULL
+static FILE *alloclog, *freelog, *finallog;
+#endif
+
+NGHASHPTR memory_table;
+
+/* initialize hash table to store allocated mem addresses */
+void mem_init(void) {
+    gc_is_on = 0;
+    memory_table = nghash_init_pointer(1024);
+    gc_is_on = 1;
+#ifdef DB_FULL
+    alloclog = fopen("alloc_log.txt", "wt");
+    freelog = fopen("free_log.txt", "wt");
+    finallog = fopen("final_log.txt", "wt");
+#endif
+}
+
+/* add to counter and hash table if memory is allocated */
+static int memsaved(void *ptr) {
+    if (gc_is_on) {
+        gc_is_on = 0;
+
+        if (nghash_insert(memory_table, ptr, NULL) == NULL) {
+#ifdef DB
+            mem_in++;
+#ifdef DB_FULL
+            fprintf(alloclog, "0x%p\n", ptr);
+#endif
+#endif
+        } else
+            fprintf(stderr, "Could not insert item into hashtable at 0x%p\n", ptr);
+        gc_is_on = 1;
+    }
+    return OK;
+}
+
+/* add to counter and remove from hash table if memory is deleted */
+static void memdeleted(const void *ptr) {
+    if (gc_is_on) {
+        gc_is_on = 0;
+        if (nghash_delete_special(memory_table, (void*)ptr) == NULL) {
+#ifdef DB
+            mem_out++;
+#ifdef DB_FULL
+            fprintf(freelog, "0x%p\n", ptr);
+#endif
+        }
+        else
+            fprintf(stderr, "Could not delete item from hashtable at 0x%p\n", ptr);
+#else
+        }
+#endif
+        gc_is_on = 1;
+    }
+}
+
+/* helper functions */
+void my_free_func(void *data)
+{
+    if (data)
+        free(data);
+}
+
+void my_key_free(void * key)
+{
+    if (key) {
+        free(key);
+        key = NULL;
+#ifdef DB
+        mem_freed++;
+#endif
+    }
+}
+
+/* free hash table, all entries and then the table itself */
+void mem_delete(void) {
+#ifdef DB
+    char buf[128];
+    printf("memory allocated %d times, freed %d times\n", mem_in, mem_out);
+    printf("Size of hash table to be freed: %d entries.\n", nghash_get_size(memory_table));
+#ifdef DB_FULL
+    void *data, *key;
+    data = nghash_enumeratek(memory_table, &key, TRUE);
+    for (void *hkey = key; hkey;) {
+        fprintf(finallog, "0x%p\n", hkey);
+        data = nghash_enumeratek(memory_table, &hkey, FALSE);
+    }
+    fclose(alloclog);
+    fclose(freelog);
+    fclose(finallog);
+#endif
+#endif
+    gc_is_on = 0;
+    nghash_free(memory_table, NULL, my_key_free);
+#ifdef DB
+    /* printf via sh_printf will need some info from variables that have
+    been deleted already, therefore we use fputs */
+    sprintf(buf, "Number of addresses freed: %d entries.\n", mem_freed);
+    fputs(buf, stdout);
+#endif
+}