libio: add desired read size to istream_get_buffered_data

This properly maps to all of our use cases and makes istream_precache
obsolete.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

6 files changed, 26 insertions, 49 deletions

diff --git a/include/io/istream.h b/include/io/istream.h
index f091aa1..8edd61d 100644
--- a/include/io/istream.h
+++ b/include/io/istream.h
@@ -82,24 +82,6 @@ SQFS_INTERNAL int istream_get_line(istream_t *strm, char **out,
 SQFS_INTERNAL sqfs_s32 istream_read(istream_t *strm, void *data, size_t size);
 
 /**
- * @brief Adjust and refill the internal buffer of an input stream
- *
- * @memberof istream_t
- *
- * This function resets the buffer offset of an input stream (moving any unread
- * data up front if it has to) and calls an internal callback of the input
- * stream to fill the rest of the buffer to the extent possible.
- *
- * @param strm A pointer to an input stream.
- *
- * @return 0 on success, -1 on failure.
- */
-SQFS_INLINE int istream_precache(istream_t *strm)
-{
-	return strm->precache(strm);
-}
-
-/**
  * @brief Get the underlying filename of an input stream.
  *
  * @memberof istream_t
@@ -129,14 +111,17 @@ SQFS_INLINE const char *istream_get_filename(istream_t *strm)
  * @param strm A pointer to an istream_t implementation.
  * @param out Returns a pointer into an internal buffer on success.
  * @param size Returns the number of bytes available in the buffer.
+ * @param want A number of bytes that the reader would like to have. If there is
+ *             less than this available, the implementation can choose to do a
+ *             blocking precache.
  *
  * @return Zero on success, a negative error code on failure,
  *         a postive number on EOF.
  */
 SQFS_INLINE int istream_get_buffered_data(istream_t *strm, const sqfs_u8 **out,
-					  size_t *size)
+					  size_t *size, size_t want)
 {
-	if (strm->buffer_used == 0) {
+	if (strm->buffer_used == 0 || strm->buffer_used < want) {
 		int ret = strm->precache(strm);
 		if (ret)
 			return ret;
diff --git a/lib/io/src/get_line.c b/lib/io/src/get_line.c
index a939a6c..94ae9ce 100644
--- a/lib/io/src/get_line.c
+++ b/lib/io/src/get_line.c
@@ -50,7 +50,7 @@ int istream_get_line(istream_t *strm, char **out,
 		const sqfs_u8 *ptr;
 		int ret;
 
-		ret = istream_get_buffered_data(strm, &ptr, &avail);
+		ret = istream_get_buffered_data(strm, &ptr, &avail, 0);
 		if (ret < 0)
 			goto fail_free;
 		if (ret > 0) {
diff --git a/lib/io/src/istream.c b/lib/io/src/istream.c
index 6171f2c..b4c709c 100644
--- a/lib/io/src/istream.c
+++ b/lib/io/src/istream.c
@@ -19,7 +19,7 @@ sqfs_s32 istream_read(istream_t *strm, void *data, size_t size)
 		size_t diff;
 		int ret;
 
-		ret = istream_get_buffered_data(strm, &ptr, &diff);
+		ret = istream_get_buffered_data(strm, &ptr, &diff, size);
 		if (ret > 0)
 			break;
 		if (ret < 0)
@@ -48,7 +48,7 @@ int istream_skip(istream_t *strm, sqfs_u64 size)
 		size_t diff;
 		int ret;
 
-		ret = istream_get_buffered_data(strm, &ptr, &diff);
+		ret = istream_get_buffered_data(strm, &ptr, &diff, size);
 		if (ret < 0)
 			return ret;
 		if (ret > 0) {
@@ -81,7 +81,7 @@ sqfs_s32 istream_splice(istream_t *in, ostream_t *out, sqfs_u32 size)
 		size_t diff;
 		int ret;
 
-		ret = istream_get_buffered_data(in, &ptr, &diff);
+		ret = istream_get_buffered_data(in, &ptr, &diff, size);
 		if (ret < 0)
 			return ret;
 		if (ret > 0)
diff --git a/lib/io/src/xfrm/istream.c b/lib/io/src/xfrm/istream.c
index 2ada5db..8755cb6 100644
--- a/lib/io/src/xfrm/istream.c
+++ b/lib/io/src/xfrm/istream.c
@@ -37,11 +37,8 @@ static int xfrm_precache(istream_t *base)
 		const sqfs_u8 *ptr;
 		size_t avail;
 
-		ret = istream_precache(xfrm->wrapped);
-		if (ret != 0)
-			return ret;
-
-		ret = istream_get_buffered_data(xfrm->wrapped, &ptr, &avail);
+		ret = istream_get_buffered_data(xfrm->wrapped, &ptr, &avail,
+						sizeof(xfrm->uncompressed));
 		if (ret < 0)
 			return ret;
 		if (ret > 0) {
diff --git a/lib/io/test/istream_mem.c b/lib/io/test/istream_mem.c
index 632b1f5..f1849dd 100644
--- a/lib/io/test/istream_mem.c
+++ b/lib/io/test/istream_mem.c
@@ -32,8 +32,9 @@ static void init_buffer(void)
 
 int main(int argc, char **argv)
 {
+	size_t i, diff, size;
 	bool eat_all = true;
-	size_t i, diff;
+	const sqfs_u8 *ptr;
 	istream_t *in;
 	int ret;
 	(void)argc; (void)argv;
@@ -45,33 +46,30 @@ int main(int argc, char **argv)
 	TEST_EQUAL_UI(((sqfs_object_t *)in)->refcount, 1);
 
 	TEST_STR_EQUAL(istream_get_filename(in), "memstream.txt");
-	TEST_NOT_NULL(in->buffer);
-	TEST_EQUAL_UI(in->buffer_used, 0);
 
 	for (i = 0; i < end2; i += diff) {
-		ret = istream_precache(in);
+		ret = istream_get_buffered_data(in, &ptr, &size, 61);
 		TEST_EQUAL_I(ret, 0);
 
 		if ((end2 - i) >= 61) {
-			TEST_NOT_NULL(in->buffer);
-			TEST_EQUAL_UI(in->buffer_used, 61);
+			TEST_NOT_NULL(ptr);
+			TEST_EQUAL_UI(size, 61);
 		} else {
-			TEST_NOT_NULL(in->buffer);
-			TEST_EQUAL_UI(in->buffer_used, (end2 - i));
+			TEST_NOT_NULL(ptr);
+			TEST_EQUAL_UI(size, (end2 - i));
 		}
 
-		for (size_t j = 0; j < in->buffer_used; ++j) {
-			TEST_EQUAL_UI(in->buffer[j], byte_at_offset(i + j));
+		for (size_t j = 0; j < size; ++j) {
+			TEST_EQUAL_UI(ptr[j], byte_at_offset(i + j));
 		}
 
-		diff = eat_all ? in->buffer_used : (in->buffer_used / 2);
+		diff = eat_all ? size : (size / 2);
 		eat_all = !eat_all;
 
-		in->buffer += diff;
-		in->buffer_used -= diff;
+		ret = istream_advance_buffer(in, diff);
+		TEST_EQUAL_I(ret, 0);
 	}
 
-	TEST_EQUAL_UI(in->buffer_used, 0);
 	sqfs_drop(in);
 	return EXIT_SUCCESS;
 }
diff --git a/lib/tar/src/iterator.c b/lib/tar/src/iterator.c
index 66b5dfc..f46a9c2 100644
--- a/lib/tar/src/iterator.c
+++ b/lib/tar/src/iterator.c
@@ -132,7 +132,7 @@ static int strm_precache(istream_t *strm)
 		int ret;
 
 		ret = istream_get_buffered_data(tar->parent->stream,
-						&strm->buffer, &avail);
+						&strm->buffer, &avail, diff);
 		if (ret > 0)
 			goto fail_borked;
 		if (ret < 0)
@@ -373,11 +373,8 @@ dir_iterator_t *tar_open_stream(istream_t *strm)
 	it->read_xattr = it_read_xattr;
 
 	/* proble if the stream is compressed */
-	ret = istream_precache(strm);
-	if (ret != 0)
-		goto out_strm;
-
-	ret = istream_get_buffered_data(strm, &ptr, &size);
+	ret = istream_get_buffered_data(strm, &ptr, &size,
+					sizeof(tar_header_t));
 	if (ret != 0)
 		goto out_strm;