From 10e031ba9e0f5c803fd4678f6e46628514cf0671 Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Mon, 24 Feb 2025 15:54:52 +0000
Subject: [PATCH] add byte-wise i/o to tags open in sequential write-only mode

---
 src/tag.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 src/tag.h | 14 ++++++--
 2 files changed, 107 insertions(+), 6 deletions(-)

diff --git a/src/tag.c b/src/tag.c
index 9e41f0a..453f579 100644
--- a/src/tag.c
+++ b/src/tag.c
@@ -8,6 +8,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+static enum ec3_status flush_seq_buffer(struct ec3_tag_ioctx *tag);
+
 static enum ec3_status init_seq_write_temp_files(struct ec3_tag_ioctx *tag)
 {
 	b_status status = b_file_open_temp(
@@ -78,6 +80,17 @@ enum ec3_status ec3_tag_ioctx_create(
 
 enum ec3_status ec3_tag_ioctx_close(struct ec3_tag_ioctx *tag)
 {
+	enum ec3_status status = EC3_SUCCESS;
+
+	if ((tag->io_mode & (EC3_TAG_IO_SEQUENTIAL))
+	    && tag->io_seq_data_ptr > 0) {
+		status = flush_seq_buffer(tag);
+	}
+
+	if (status != EC3_SUCCESS) {
+		return status;
+	}
+
 	enum ec3_tag_ioctx_mode mode = tag->io_mode;
 	tag->io_mode |= EC3_TAG_IO_CLOSED;
 
@@ -146,6 +159,12 @@ enum ec3_status ec3_tag_ioctx_read_cluster(
 		cluster_id,
 		&physical_cluster_id);
 
+	if (status == EC3_ERR_OUT_OF_BOUNDS) {
+		/* reached the end of the tag data */
+		*nr_read = 0;
+		return EC3_SUCCESS;
+	}
+
 	if (status != EC3_SUCCESS) {
 		return status;
 	}
@@ -166,7 +185,8 @@ enum ec3_status ec3_tag_ioctx_read_cluster(
 		return EC3_ERR_BAD_FORMAT;
 	}
 
-	size_t offset = tag->io_cluster_data_offset + cluster_info.c_base;
+	size_t offset = tag->io_parent->io_header.img_cluster_data_offset
+	              + cluster_info.c_base;
 	size_t r;
 	enum b_status status2 = b_file_read(
 		tag->io_f_image,
@@ -198,7 +218,7 @@ enum ec3_status ec3_tag_ioctx_read_cluster(
 enum ec3_status ec3_tag_ioctx_write_cluster(
 	struct ec3_tag_ioctx *tag,
 	size_t cluster_id,
-	void *buf,
+	const void *buf,
 	size_t len,
 	size_t *nr_written)
 {
@@ -210,7 +230,7 @@ enum ec3_status ec3_tag_ioctx_write_cluster(
 
 	if (!(tag->io_mode & EC3_TAG_IO_SEQUENTIAL)) {
 		status = cluster_cache_put(
-			tag->io_cluster_buf,
+			&tag->io_cache,
 			cluster_id,
 			buf,
 			len);
@@ -264,6 +284,79 @@ enum ec3_status ec3_tag_ioctx_write_cluster(
 	return EC3_SUCCESS;
 }
 
+static enum ec3_status flush_seq_buffer(struct ec3_tag_ioctx *tag)
+{
+	size_t nr_written = 0;
+	enum ec3_status status = ec3_tag_ioctx_write_cluster(
+		tag,
+		tag->io_seq_cluster_id,
+		tag->io_cluster_buf,
+		tag->io_seq_data_ptr,
+		&nr_written);
+
+	if (status != EC3_SUCCESS) {
+		return status;
+	}
+
+	tag->io_seq_data_ptr = 0;
+
+	return status;
+}
+
+enum ec3_status ec3_tag_ioctx_write(
+	struct ec3_tag_ioctx *tag,
+	const void *p,
+	size_t len,
+	size_t *nr_written)
+{
+	if (!(tag->io_mode & EC3_TAG_IO_WRITE)) {
+		return EC3_ERR_NOT_SUPPORTED;
+	}
+
+	if (!(tag->io_mode & EC3_TAG_IO_SEQUENTIAL)) {
+		return EC3_ERR_NOT_SUPPORTED;
+	}
+
+	enum ec3_status status = EC3_SUCCESS;
+	size_t cluster_size = tag->io_parent->io_header.img_cluster_size;
+
+	const unsigned char *buf = p;
+	size_t written = 0;
+
+	while (len > 0) {
+		size_t space_remaining = cluster_size - tag->io_seq_data_ptr;
+
+		size_t to_copy = len;
+		if (to_copy > space_remaining) {
+			to_copy = space_remaining;
+		}
+
+		const unsigned char *src = buf + written;
+		unsigned char *dest
+			= tag->io_cluster_buf + tag->io_seq_data_ptr;
+
+		memcpy(dest, src, to_copy);
+
+		tag->io_seq_data_ptr += to_copy;
+		written += to_copy;
+
+		len -= to_copy;
+		space_remaining -= to_copy;
+
+		if (space_remaining == 0) {
+			status = flush_seq_buffer(tag);
+		}
+
+		if (status != EC3_SUCCESS) {
+			return status;
+		}
+	}
+
+	*nr_written = written;
+
+	return EC3_SUCCESS;
+}
+
 enum ec3_status ec3_tag_ioctx_get_nr_clusters(
 	struct ec3_tag_ioctx *tag,
 	size_t *out_nr_clusters)
diff --git a/src/tag.h b/src/tag.h
index 6e86cbb..f9be46a 100644
--- a/src/tag.h
+++ b/src/tag.h
@@ -36,8 +36,6 @@ struct ec3_tag_ioctx {
 
 	/* temp buffer of cluster size, used for pipeline operations */
 	void *io_cluster_buf;
-	/* the offset to the start of the cluster table in io_f_rotag */
-	size_t io_cluster_data_offset;
 
 	/* this points to memory belonging to ec3_image_ioctx */
 	struct ec3_tag_info io_tag_info;
@@ -82,6 +80,10 @@ struct ec3_tag_ioctx {
 	struct cluster_table io_cluster_table;
 	/* how many clusters have been written sequentially to this tag */
 	size_t io_seq_cluster_id;
+	/* how many bytes have been written to io_cluster_buf using
+	 * ec3_tag_ioctx_write. when this reaches the cluster size (or
+	 * ec3_tag_ioctx_close is called) this is reset to 0. */
+	size_t io_seq_data_ptr;
 };
 
 extern enum ec3_status ec3_tag_ioctx_create(
@@ -98,7 +100,13 @@ extern enum ec3_status ec3_tag_ioctx_read_cluster(
 extern enum ec3_status ec3_tag_ioctx_write_cluster(
 	struct ec3_tag_ioctx *tag,
 	size_t cluster_id,
-	void *buf,
+	const void *buf,
+	size_t len,
+	size_t *nr_written);
+
+extern enum ec3_status ec3_tag_ioctx_write(
+	struct ec3_tag_ioctx *tag,
+	const void *buf,
 	size_t len,
 	size_t *nr_written);