[hackers] [blind] Fix support for tiny frames in blind-reverse || Mattias Andrée

[git]

commit a2eb10b156eafd5fc900471dded83c78adc5d46d
Author:     Mattias Andrée <maand...@kth.se>
AuthorDate: Tue May 2 00:08:33 2017 +0200
Commit:     Mattias Andrée <maand...@kth.se>
CommitDate: Tue May 2 00:08:33 2017 +0200

    Fix support for tiny frames in blind-reverse
    
    Signed-off-by: Mattias Andrée <maand...@kth.se>

diff --git a/src/blind-reverse.c b/src/blind-reverse.c
index 0bbe766..69013bb 100644
--- a/src/blind-reverse.c
+++ b/src/blind-reverse.c
@@ -18,7 +18,7 @@ to_stdout(struct stream *stream, size_t frame_size)
                ptr = stream->frames * frame_size + stream->headlen;
                end = ptr + frame_size;
                while (ptr < end) {
-                       if (!(r = epread(stream->fd, buf, sizeof(buf), ptr, 
stream->file)))
+                       if (!(r = epread(stream->fd, buf, MIN(sizeof(buf), end 
- ptr), ptr, stream->file)))
                                eprintf("%s: file is shorter than expected\n", 
stream->file);
                        ptr += n = (size_t)r;
                        ewriteall(STDOUT_FILENO, buf, n, "<stdout>");
@@ -35,6 +35,21 @@ elseek_set(int fd, off_t offset, const char *fname)
 }
 
 static void
+epread_frame(struct stream *stream, char *buf, off_t off, size_t n)
+{
+       stream->ptr = stream->xptr = 0;
+       elseek_set(stream->fd, off, stream->file);
+       eread_frame(stream, buf, n);
+}
+
+static void
+epwrite_frame(struct stream *stream, char *buf, off_t off, size_t n)
+{
+       elseek_set(stream->fd, off, stream->file);
+       ewriteall(stream->fd, buf, n, stream->file);
+}
+
+static void
 in_place(struct stream *stream, size_t frame_size)
 {
        size_t f, fm = stream->frames - 1;
@@ -47,13 +62,12 @@ in_place(struct stream *stream, size_t frame_size)
        for (f = 0; f < stream->frames >> 1; f++) {
                pa = f        * frame_size + stream->headlen;
                pb = (fm - f) * frame_size + stream->headlen;
-               eread_frame(stream, bufa, frame_size);
-               elseek_set(stream->fd, pb, stream->file);
-               eread_frame(stream, bufb, frame_size);
-               elseek_set(stream->fd, pb, stream->file);
-               ewriteall(stream->fd, bufa, frame_size, stream->file);
-               elseek_set(stream->fd, pa, stream->file);
-               ewriteall(stream->fd, bufb, frame_size, stream->file);
+
+               epread_frame(stream, bufa, pa, frame_size);
+               epread_frame(stream, bufb, pb, frame_size);
+
+               epwrite_frame(stream, bufa, pb, frame_size);
+               epwrite_frame(stream, bufb, pa, frame_size);
        }
 
        free(bufa);