cache I/O implementation and fixes.

Signed-off-by: Gediminas Jakutis <gediminas@varciai.lt>

1 files changed, 89 insertions, 3 deletions

diff --git a/src/cache.c b/src/cache.c
index ebe1047..de182ec 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -6,11 +6,14 @@
 #include <stdlib.h>
 #include "defs.h"
 
+static off_t cache_walker(struct stream * const restrict in, ssize_t idx);
+
 int cache_create(struct stream * const restrict in, const struct settings * const restrict s)
 {
 	int ret;
 	void *cache;
 
+	try(!in->cached, err, EINVAL, "cannot create cache: stream is uncached");
 	try(!(cache = calloc(in->n, s->stride)), err, ENOMEM, "out of memory");
 
 	in->cache = cache;
@@ -21,7 +24,9 @@ err:
 int cache_populate(struct stream * const restrict in)
 {
 	int ret = 0;
-	ssize_t i;
+	size_t i;
+
+	try(!in->cached, err, EINVAL, "cannot populate cache: stream is uncached");
 
 	for (i = 0; i < in->n && !ret; ++i) {
 		ret = in->get_element(in, i, in->cache + i);
@@ -34,7 +39,10 @@ err:
 int cache_flush(struct stream * const in)
 {
 	int ret;
-	ssize_t i;
+	size_t i;
+
+	try(!in->cached, err, EINVAL, "no cache to flush: stream is uncached");
+	try(in->out != 1, err, EINVAL, "cannot flush a non-output cache");
 
 	for (i = 0; i < in->n && !ret; ++i) {
 		ret = in->put_element(in, i, in->cache + i);
@@ -48,9 +56,87 @@ int cache_destroy(struct stream * const in)
 {
 	int ret;
 
-	try(!in->cache, err, EINVAL, "trying to destroy cache of uncached streadm");
+	try(!in->cached, err, EINVAL, "no cache to destroy: stream uncached");
 	free(in->cache);
 	in->cache = NULL;
 err:
 	return ret;
 }
+
+int cache_transfer(struct stream * const from, struct stream * const to)
+{
+	int ret;
+
+	try(!from->cached || !to->cached, err, EINVAL, "cannot transfer caches of uncached streams");
+	try(!from->cache, err, EINVAL, "no cache to transfer");
+	try(!to->cache, err, EINVAL, "cannot transfer cache: recipient cache already exists");
+
+	to->cache = from->cache;
+	from->cache = NULL;
+err:
+	return ret;
+}
+
+int cached_get_array(struct stream * const in, ssize_t idx, struct entry_l * const data)
+{
+	int ret = 0;
+	const struct entry * const cache = in->cache;
+
+	data->val = cache[idx].val;
+
+	return ret;
+}
+
+int cached_get_list(struct stream * const restrict in, ssize_t idx, struct entry_l * const data)
+{
+	int ret = 0;
+	off_t offset;
+
+	offset = cache_walker(in, idx);
+	*data = in->cache[offset];
+
+	return ret;
+}
+
+int cached_put_array(struct stream * const in, ssize_t idx, const struct entry_l * const data)
+{
+	int ret = 0;
+	struct entry * const cache = in->cache;
+
+	cache[idx].val = data->val;
+
+	return ret;
+}
+
+int cached_put_list(struct stream * const restrict in, ssize_t idx, const struct entry_l * const data)
+{
+	int ret = 0;
+	off_t offset;
+
+	offset = cache_walker(in, idx);
+	in->cache[offset] = *data;
+
+	return ret;
+}
+
+static off_t cache_walker(struct stream * const restrict in, ssize_t idx)
+{
+	size_t i;
+	off_t ret = in->prev_off;
+
+	if (in->prev_idx < idx) { /* previous index smaller, walk forward */
+		for (i = labs(idx - in->prev_idx); i; --i) {
+			ret = in->cache[ret].next;
+		}
+
+	} else if (in->prev_idx > idx) { /* previous index larger, walk backwards */
+		for (i = in->prev_idx - idx; i; --i) {
+			ret = in->cache[ret].prev;
+		}
+	} /* ...or we're standing on it already, if neither */
+
+	in->prev_idx = idx;
+	in->prev_off = ret;
+
+	return ret;
+}