cleanup and optimizations.algos-ld1-1.0

· No longer rewinding a stream being split, just to skip half through it
again, which was not only stupid, but inneficient.
· No longer using "index" anywhere when working with lists, lest we get
accused of not actually doing lists.

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

1 files changed, 25 insertions, 26 deletions

diff --git a/src/stream.c b/src/stream.c
index 13df929..48f7e4c 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -125,15 +125,19 @@ struct entry_l *file_get_list(struct stream * const in, struct entry_l * const s
 	struct entry_l *ret = NULL;
 	ssize_t bytes_read;
 
-	if (in->index < in->n) {
-		in->cnode = in->cnode ? in->cnode : &in->cnode_f;
+	if (in->cnode) {
 		do {
 			try(0 > (bytes_read = pread(in->fd, &ent, sizeof(ent), in->cnode->file_offset)), err, NULL, "Writing to stream failed with %i", errno);
 		} while (bytes_read != sizeof(ent));
 
-		in->cnode->file_offset = ent.file_offset;
-		++in->index;
 		store->val = ent.val;
+
+		if (ent.file_offset) {
+			in->cnode->file_offset = ent.file_offset;
+		} else { /* reached end of list; unhook */
+			in->cnode = NULL;
+		}
+
 		ret = store;
 	}
 
@@ -161,29 +165,27 @@ int file_put_list(struct stream * const in, const struct entry_l * const node)
 {
 	int ret = 0;
 	ssize_t bytes_written;
-	struct entry_l tmp = {0};
-
-	try(in->index >= in->n, err, EINVAL, "can't add element: out of cache bounds");
+	struct entry_l tmp = {0}; /* we use a temp var for next offest to be zero */
+	off_t offset = 0;
 
 	if (!in->cnode) { /* if this is the very first one */
 		in->cnode = &in->cnode_f;
 	} else {
-		in->cnode->file_offset += sizeof(*node);
+		offset = in->cnode->file_offset;
+		offset += sizeof(*node); /* advance by one */
 		/* writing the offset of the node being added to the current node's offset field */
 		do {
-			try(0 > (bytes_written = pwrite(in->fd, &in->cnode->file_offset, sizeof(in->cnode->file_offset), in->cnode->file_offset - sizeof(*node) + sizeof(node->val))), err, errno, "Writing to stream failed with %i", ret);
+			try(0 > (bytes_written = pwrite(in->fd, &offset, sizeof(offset), offset - sizeof(in->cnode->file_offset))), err, errno, "Writing to stream failed with %i", ret);
 		} while (bytes_written != sizeof(in->cnode->file_offset));
 	}
 
 	tmp.val = node->val;
 
-	if (in->index < in->n) {
-		do {
-			try(0 > (bytes_written = pwrite(in->fd, &tmp, sizeof(tmp), in->cnode->file_offset)), err, errno, "Writing to stream failed with %i", ret);
-		} while (bytes_written != sizeof(tmp));
-	}
+	do {
+		try(0 > (bytes_written = pwrite(in->fd, &tmp, sizeof(tmp), offset)), err, errno, "Writing to stream failed with %i", ret);
+	} while (bytes_written != sizeof(tmp));
 
-	++in->index;
+	in->cnode->file_offset = offset; /* store the new "current" offset */
 err:
 	return ret;
 }
@@ -206,23 +208,16 @@ int file_transfer(struct stream * const src, struct stream * const dest)
 int stream_copy_range(struct stream * const restrict src, struct stream * const restrict dest)
 {
 	int ret = 0;
-	size_t ss;
+	struct entry_l *tmp;
 	struct entry_l tmp_store;
+	size_t i = 0;
 
 	try(src->n < dest->settings->to, err, EINVAL, "invalid copy size");
 
-	ss = dest->settings->ss;
-
-	/* skip over to start position */
-	while (ss--) {
-		src->get(src, &tmp_store);
+	while (i++ < (dest->n) && (tmp = src->get(src, &tmp_store))) {
+		dest->put(dest, tmp);
 	}
 
-	do {
-		dest->put(dest, src->get(src, &tmp_store));
-	} while (dest->index < (dest->n));
-
-	stream_rewind(src);
 	stream_rewind(dest);
 
 err:
@@ -320,6 +315,10 @@ static int stream_open_in(struct stream * const in)
 	in->fd = open(in->name, O_RDONLY | O_NOATIME);
 	try(in->fd < 0, err, errno, "failed opening input file: %s", strerror(ret));
 
+	if (in->settings->access == direct) {
+		in->cnode = &in->cnode_f;
+	}
+
 err:
 	return ret;
 }