libio: remove buffer_offset from istream_t

Instead, make the buffer const, let the user adjust the pointer and
size. The offset can then be inferred in precache.

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

1 files changed, 11 insertions, 13 deletions

diff --git a/lib/io/src/win32/istream.c b/lib/io/src/win32/istream.c
index 918b868..94c8584 100644
--- a/lib/io/src/win32/istream.c
+++ b/lib/io/src/win32/istream.c
@@ -23,27 +23,25 @@ static int file_precache(istream_t *strm)
 	DWORD diff, actual;
 	HANDLE hnd;
 
-	if (strm->buffer_offset >= strm->buffer_used) {
-		strm->buffer_offset = 0;
-		strm->buffer_used = 0;
-	} else if (strm->buffer_offset > 0) {
-		memmove(strm->buffer,
-			strm->buffer + strm->buffer_offset,
-			strm->buffer_used - strm->buffer_offset);
-
-		strm->buffer_used -= strm->buffer_offset;
-		strm->buffer_offset = 0;
-	}
-
 	if (strm->eof)
 		return 0;
 
+	assert(strm->buffer >= file->buffer);
+	assert(strm->buffer <= (file->buffer + BUFSZ));
+	assert(strm->buffer_used <= BUFSZ);
+	assert((size_t)(strm->buffer - file->buffer) <=
+	       (BUFSZ - strm->buffer_used));
+
+	if (strm->buffer_used > 0)
+		memmove(file->buffer, strm->buffer, strm->buffer_used);
+
+	strm->buffer = file->buffer;
 	hnd = file->path == NULL ? GetStdHandle(STD_INPUT_HANDLE) : file->hnd;
 
 	while (strm->buffer_used < sizeof(file->buffer)) {
 		diff = sizeof(file->buffer) - strm->buffer_used;
 
-		if (!ReadFile(hnd, strm->buffer + strm->buffer_used,
+		if (!ReadFile(hnd, file->buffer + strm->buffer_used,
 			      diff, &actual, NULL)) {
 			DWORD error = GetLastError();