From c7eae87870da755586446fecb4eb30063c1d641c Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Date: Sun, 11 Jun 2023 17:59:21 +0200
Subject: libio: move istream buffer logic into interall callbacks

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
---
 lib/io/src/xfrm/istream.c | 64 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 47 insertions(+), 17 deletions(-)

(limited to 'lib/io/src/xfrm/istream.c')

diff --git a/lib/io/src/xfrm/istream.c b/lib/io/src/xfrm/istream.c
index bad3e22..c9bc41a 100644
--- a/lib/io/src/xfrm/istream.c
+++ b/lib/io/src/xfrm/istream.c
@@ -12,27 +12,28 @@ typedef struct istream_xfrm_t {
 	istream_t *wrapped;
 	xfrm_stream_t *xfrm;
 
+	size_t buffer_offset;
+	size_t buffer_used;
 	sqfs_u8 uncompressed[BUFSZ];
 } istream_xfrm_t;
 
-static int xfrm_precache(istream_t *base)
+static int precache(istream_t *base)
 {
 	istream_xfrm_t *xfrm = (istream_xfrm_t *)base;
 	int ret;
 
-	assert(base->buffer >= xfrm->uncompressed);
-	assert(base->buffer <= (xfrm->uncompressed + BUFSZ));
-	assert(base->buffer_used <= BUFSZ);
-	assert((size_t)(base->buffer - xfrm->uncompressed) <=
-	       (BUFSZ - base->buffer_used));
-
-	if (base->buffer_used > 0)
-		memmove(xfrm->uncompressed, base->buffer, base->buffer_used);
+	if (xfrm->buffer_offset > 0 &&
+	    xfrm->buffer_offset < xfrm->buffer_used) {
+		memmove(xfrm->uncompressed,
+			xfrm->uncompressed + xfrm->buffer_offset,
+			xfrm->buffer_used - xfrm->buffer_offset);
+	}
 
-	base->buffer = xfrm->uncompressed;
+	xfrm->buffer_used -= xfrm->buffer_offset;
+	xfrm->buffer_offset = 0;
 
 	for (;;) {
-		sqfs_u32 in_off = 0, out_off = base->buffer_used;
+		sqfs_u32 in_off = 0, out_off = xfrm->buffer_used;
 		int mode = XFRM_STREAM_FLUSH_NONE;
 		const sqfs_u8 *ptr;
 		size_t avail;
@@ -41,10 +42,8 @@ static int xfrm_precache(istream_t *base)
 						sizeof(xfrm->uncompressed));
 		if (ret < 0)
 			return ret;
-		if (ret > 0) {
+		if (ret > 0)
 			mode = XFRM_STREAM_FLUSH_FULL;
-			avail = 0;
-		}
 
 		ret = xfrm->xfrm->process_data(xfrm->xfrm,
 					       ptr, avail,
@@ -58,7 +57,7 @@ static int xfrm_precache(istream_t *base)
 			return -1;
 		}
 
-		base->buffer_used = out_off;
+		xfrm->buffer_used = out_off;
 		istream_advance_buffer(xfrm->wrapped, in_off);
 
 		if (ret == XFRM_STREAM_BUFFER_FULL || out_off >= BUFSZ)
@@ -71,6 +70,37 @@ static int xfrm_precache(istream_t *base)
 	return 0;
 }
 
+static int xfrm_get_buffered_data(istream_t *strm, const sqfs_u8 **out,
+				  size_t *size, size_t want)
+{
+	istream_xfrm_t *xfrm = (istream_xfrm_t *)strm;
+
+	if (want > BUFSZ)
+		want = BUFSZ;
+
+	if (xfrm->buffer_used == 0 ||
+	    (xfrm->buffer_used - xfrm->buffer_offset) < want) {
+		int ret = precache(strm);
+		if (ret)
+			return ret;
+	}
+
+	*out = xfrm->uncompressed + xfrm->buffer_offset;
+	*size = xfrm->buffer_used - xfrm->buffer_offset;
+	return (*size == 0) ? 1 : 0;
+}
+
+static void xfrm_advance_buffer(istream_t *strm, size_t count)
+{
+	istream_xfrm_t *xfrm = (istream_xfrm_t *)strm;
+
+	assert(count <= xfrm->buffer_used);
+
+	xfrm->buffer_offset += count;
+
+	assert(xfrm->buffer_offset <= xfrm->buffer_used);
+}
+
 static const char *xfrm_get_filename(istream_t *strm)
 {
 	istream_xfrm_t *xfrm = (istream_xfrm_t *)strm;
@@ -100,9 +130,9 @@ istream_t *istream_xfrm_create(istream_t *strm, xfrm_stream_t *xfrm)
 	stream->wrapped = sqfs_grab(strm);
 	stream->xfrm = sqfs_grab(xfrm);
 
-	base->precache = xfrm_precache;
+	base->get_buffered_data = xfrm_get_buffered_data;
+	base->advance_buffer = xfrm_advance_buffer;
 	base->get_filename = xfrm_get_filename;
-	base->buffer = stream->uncompressed;
 	return base;
 fail:
 	fprintf(stderr, "%s: error initializing decompressor stream.\n",
-- 
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