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>

5 files changed, 49 insertions, 35 deletions

diff --git a/src/cache.c b/src/cache.c
index 2b24dd0..3a169b8 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -122,10 +122,9 @@ struct entry_l *cached_get_list(struct stream * const in, struct entry_l * const
 {
 	struct entry_l *ret = NULL;
 
-	if (in->index < in->n) {
+	if (in->cnode) {
 		ret = in->cnode;
-		in->cnode = ret->next ? ret->next : in->cnode;
-		++in->index;
+		in->cnode = ret->next;
 		*store = *ret;
 		ret = store;
 	}
@@ -163,17 +162,14 @@ int cached_put_list(struct stream * const restrict in, const struct entry_l * co
 
 	if (!in->cnode) { /* if this is the very first one */
 		in->cnode = in->cache_l;
-		in->cnode->val = node->val;
-		in->cnode->next = NULL;
-		in->index = 1;
 	} else {
 		in->cnode->next = in->cnode + 1; /* lol says librin, lmao */
 		in->cnode = in->cnode->next;
-		in->cnode->val = node->val;
-		in->cnode->next = NULL;
-		++in->index;
 	}
 
+	in->cnode->val = node->val;
+	in->cnode->next = NULL;
+
 err:
 	return ret;
 }
diff --git a/src/main.c b/src/main.c
index f4990ac..905da11 100644
--- a/src/main.c
+++ b/src/main.c
@@ -72,6 +72,7 @@ int main(int argc, char **argv)
 
 		switch (settings.opmode) {
 		case mode_fetch:
+			stream_skip(&file_in);
 			stream_shallow_copy(&file_in, &file_tmp);
 			if (settings.format == array) {
 				try_s((ret = cache_block_copy(&file_in, &file_tmp)), out);
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;
 }
diff --git a/src/util.c b/src/util.c
index c14a848..2b32a94 100644
--- a/src/util.c
+++ b/src/util.c
@@ -22,6 +22,21 @@ int stream_rewind(struct stream * const restrict in)
 	return ret;
 }
 
+int stream_skip(struct stream * const restrict in)
+{
+	int ret = 0;
+	size_t ss;
+	struct entry_l discard;
+
+	ss = in->settings->ss;
+
+	while (ss--) {
+		in->get(in, &discard);
+	}
+
+	return ret;
+}
+
 int split(struct stream * const src, struct stream * const A, struct stream * const B)
 {
 	int ret = 0;
@@ -57,6 +72,7 @@ int split(struct stream * const src, struct stream * const A, struct stream * co
 		try_s((ret = src->copy(src, A)), err);
 		try_s((ret = cache_create(B)), err);
 		try_s((ret = src->copy(src, B)), err);
+		stream_rewind(src);
 	} else {
 		A->name = B->name = src->name;
 		A->type = B->type = stream_lite;
@@ -64,6 +80,7 @@ int split(struct stream * const src, struct stream * const A, struct stream * co
 		try_s((ret = src->copy(src, A)), err);
 		try_s((ret = stream_open(B)), err);
 		try_s((ret = src->copy(src, B)), err);
+		stream_rewind(src);
 	}
 
 	A->settings = B->settings = src->settings;
diff --git a/src/util.h b/src/util.h
index 090a4a0..8435ccf 100644
--- a/src/util.h
+++ b/src/util.h
@@ -8,6 +8,7 @@
 #include "defs.h"
 
 int stream_rewind(struct stream * const restrict in);
+int stream_skip(struct stream * const restrict in);
 int split(struct stream * const src, struct stream * const A, struct stream * const B);
 int print_data(struct stream * const in);