libio: eliminate direct access of the interal buffer

Instead, go through helper functions, which in a next step can be
moved inside the implementation.

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

3 files changed, 70 insertions, 62 deletions

diff --git a/lib/io/src/get_line.c b/lib/io/src/get_line.c
index c764d04..a939a6c 100644
--- a/lib/io/src/get_line.c
+++ b/lib/io/src/get_line.c
@@ -46,12 +46,14 @@ int istream_get_line(istream_t *strm, char **out,
 
 	for (;;) {
 		bool have_line = false;
-		size_t i, count;
+		size_t i, count, avail;
+		const sqfs_u8 *ptr;
+		int ret;
 
-		if (istream_precache(strm))
+		ret = istream_get_buffered_data(strm, &ptr, &avail);
+		if (ret < 0)
 			goto fail_free;
-
-		if (strm->buffer_used == 0) {
+		if (ret > 0) {
 			if (line_len == 0)
 				goto out_eof;
 
@@ -62,12 +64,12 @@ int istream_get_line(istream_t *strm, char **out,
 			goto out_eof;
 		}
 
-		for (i = 0; i < strm->buffer_used; ++i) {
-			if (strm->buffer[i] == '\n')
+		for (i = 0; i < avail; ++i) {
+			if (ptr[i] == '\n')
 				break;
 		}
 
-		if (i < strm->buffer_used) {
+		if (i < avail) {
 			count = i++;
 			have_line = true;
 		} else {
@@ -79,12 +81,12 @@ int istream_get_line(istream_t *strm, char **out,
 			goto fail_errno;
 
 		line = new;
-		memcpy(line + line_len, strm->buffer, count);
+		memcpy(line + line_len, ptr, count);
 		line_len += count;
 		line[line_len] = '\0';
 
-		strm->buffer += i;
-		strm->buffer_used -= i;
+		if (istream_advance_buffer(strm, i))
+			goto fail_free;
 
 		if (have_line) {
 			if (line_len > 0 && line[line_len - 1] == '\r')
diff --git a/lib/io/src/istream.c b/lib/io/src/istream.c
index 0739fd6..6171f2c 100644
--- a/lib/io/src/istream.c
+++ b/lib/io/src/istream.c
@@ -10,30 +10,32 @@
 sqfs_s32 istream_read(istream_t *strm, void *data, size_t size)
 {
 	sqfs_s32 total = 0;
-	size_t diff;
 
 	if (size > 0x7FFFFFFF)
 		size = 0x7FFFFFFF;
 
 	while (size > 0) {
-		if (strm->buffer_used == 0) {
-			if (istream_precache(strm))
-				return -1;
+		const sqfs_u8 *ptr;
+		size_t diff;
+		int ret;
 
-			if (strm->buffer_used == 0)
-				break;
-		}
+		ret = istream_get_buffered_data(strm, &ptr, &diff);
+		if (ret > 0)
+			break;
+		if (ret < 0)
+			return ret;
 
-		diff = strm->buffer_used;
 		if (diff > size)
 			diff = size;
 
-		memcpy(data, strm->buffer, diff);
+		memcpy(data, ptr, diff);
 		data = (char *)data + diff;
-		strm->buffer += diff;
-		strm->buffer_used -= diff;
 		size -= diff;
 		total += diff;
+
+		ret = istream_advance_buffer(strm, diff);
+		if (ret)
+			return -1;
 	}
 
 	return total;
@@ -41,27 +43,27 @@ sqfs_s32 istream_read(istream_t *strm, void *data, size_t size)
 
 int istream_skip(istream_t *strm, sqfs_u64 size)
 {
-	size_t diff;
-
 	while (size > 0) {
-		if (strm->buffer_used == 0) {
-			if (istream_precache(strm))
-				return -1;
-
-			if (strm->buffer_used == 0) {
-				fprintf(stderr, "%s: unexpected end-of-file\n",
-					strm->get_filename(strm));
-				return -1;
-			}
+		const sqfs_u8 *ptr;
+		size_t diff;
+		int ret;
+
+		ret = istream_get_buffered_data(strm, &ptr, &diff);
+		if (ret < 0)
+			return ret;
+		if (ret > 0) {
+			fprintf(stderr, "%s: unexpected end-of-file\n",
+				strm->get_filename(strm));
+			return -1;
 		}
 
-		diff = strm->buffer_used;
 		if ((sqfs_u64)diff > size)
 			diff = size;
 
-		strm->buffer += diff;
-		strm->buffer_used -= diff;
 		size -= diff;
+
+		if (istream_advance_buffer(strm, diff))
+			return -1;
 	}
 
 	return 0;
@@ -70,31 +72,31 @@ int istream_skip(istream_t *strm, sqfs_u64 size)
 sqfs_s32 istream_splice(istream_t *in, ostream_t *out, sqfs_u32 size)
 {
 	sqfs_s32 total = 0;
-	size_t diff;
 
 	if (size > 0x7FFFFFFF)
 		size = 0x7FFFFFFF;
 
 	while (size > 0) {
-		if (in->buffer_used == 0) {
-			if (istream_precache(in))
-				return -1;
+		const sqfs_u8 *ptr;
+		size_t diff;
+		int ret;
 
-			if (in->buffer_used == 0)
-				break;
-		}
+		ret = istream_get_buffered_data(in, &ptr, &diff);
+		if (ret < 0)
+			return ret;
+		if (ret > 0)
+			break;
 
-		diff = in->buffer_used;
 		if (diff > size)
 			diff = size;
 
-		if (ostream_append(out, in->buffer, diff))
+		if (ostream_append(out, ptr, diff))
+			return -1;
+		if (istream_advance_buffer(in, diff))
 			return -1;
 
-		in->buffer += diff;
-		in->buffer_used -= diff;
-		size -= diff;
 		total += diff;
+		size -= diff;
 	}
 
 	return total;
diff --git a/lib/io/src/xfrm/istream.c b/lib/io/src/xfrm/istream.c
index 152563f..a89ac3d 100644
--- a/lib/io/src/xfrm/istream.c
+++ b/lib/io/src/xfrm/istream.c
@@ -18,7 +18,7 @@ typedef struct istream_xfrm_t {
 static int xfrm_precache(istream_t *base)
 {
 	istream_xfrm_t *xfrm = (istream_xfrm_t *)base;
-	int ret;
+	int ret, sret;
 
 	if (base->eof)
 		return 0;
@@ -34,20 +34,26 @@ static int xfrm_precache(istream_t *base)
 
 	base->buffer = xfrm->uncompressed;
 
-	ret = istream_precache(xfrm->wrapped);
-	if (ret != 0)
-		return ret;
-
 	for (;;) {
 		sqfs_u32 in_off = 0, out_off = base->buffer_used;
 		int mode = XFRM_STREAM_FLUSH_NONE;
+		const sqfs_u8 *ptr;
+		size_t avail;
+
+		ret = istream_precache(xfrm->wrapped);
+		if (ret != 0)
+			return ret;
 
-		if (xfrm->wrapped->eof)
+		ret = istream_get_buffered_data(xfrm->wrapped, &ptr, &avail);
+		if (ret < 0)
+			return ret;
+		if (ret > 0) {
 			mode = XFRM_STREAM_FLUSH_FULL;
+			avail = 0;
+		}
 
 		ret = xfrm->xfrm->process_data(xfrm->xfrm,
-					       xfrm->wrapped->buffer,
-					       xfrm->wrapped->buffer_used,
+					       ptr, avail,
 					       xfrm->uncompressed + out_off,
 					       BUFSZ - out_off,
 					       &in_off, &out_off, mode);
@@ -59,17 +65,15 @@ static int xfrm_precache(istream_t *base)
 		}
 
 		base->buffer_used = out_off;
-		xfrm->wrapped->buffer += in_off;
-		xfrm->wrapped->buffer_used -= in_off;
+
+		sret = istream_advance_buffer(xfrm->wrapped, in_off);
+		if (sret != 0)
+			return sret;
 
 		if (ret == XFRM_STREAM_BUFFER_FULL || out_off >= BUFSZ)
 			break;
 
-		ret = istream_precache(xfrm->wrapped);
-		if (ret != 0)
-			return ret;
-
-		if (xfrm->wrapped->eof && xfrm->wrapped->buffer_used == 0) {
+		if (mode == XFRM_STREAM_FLUSH_FULL) {
 			if (base->buffer_used == 0)
 				base->eof = true;
 			break;