stm32/mboot/gzstream: Fix lost data decompressing final part of file.

Prior to this fix, the final piece of data in a compressed file may have
been lost when decompressing.
Signed-off-by: Damien George <damien@micropython.org>

ports/stm32/mboot/gzstream.c

@@ -38,7 +38,7 @@
 typedef struct _gz_stream_t {
     void *stream_data;
     stream_read_t stream_read;
-    TINF_DATA tinf;
+    struct uzlib_uncomp tinf;
     uint8_t buf[512];
     uint8_t dict[DICT_SIZE];
 } gz_stream_t;
@@ -66,7 +66,7 @@ int gz_stream_init(void *stream_data, stream_read_t stream_read) {
     gz_stream.stream_read = stream_read;
 
     memset(&gz_stream.tinf, 0, sizeof(gz_stream.tinf));
-    gz_stream.tinf.readSource = gz_stream_read_src;
+    gz_stream.tinf.source_read_cb = gz_stream_read_src;
 
     int st = uzlib_gzip_parse_header(&gz_stream.tinf);
     if (st != TINF_OK) {
@@ -79,15 +79,21 @@ int gz_stream_init(void *stream_data, stream_read_t stream_read) {
 }
 
 int gz_stream_read(size_t len, uint8_t *buf) {
+    if (gz_stream.tinf.source == NULL && gz_stream.tinf.source_read_cb == NULL) {
+        // End of stream.
+        return 0;
+    }
     gz_stream.tinf.dest = buf;
     gz_stream.tinf.dest_limit = buf + len;
     int st = uzlib_uncompress_chksum(&gz_stream.tinf);
-    if (st == TINF_DONE) {
-        return 0;
-    }
     if (st < 0) {
         return st;
     }
+    if (st == TINF_DONE) {
+        // Indicate end-of-stream for subsequent calls.
+        gz_stream.tinf.source = NULL;
+        gz_stream.tinf.source_read_cb = NULL;
+    }
     return gz_stream.tinf.dest - buf;
 }