diff options
| -rw-r--r-- | wiretap/file_wrappers.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/wiretap/file_wrappers.c b/wiretap/file_wrappers.c index 300f7348b6..210acc581b 100644 --- a/wiretap/file_wrappers.c +++ b/wiretap/file_wrappers.c @@ -928,9 +928,22 @@ file_seek(FILE_T file, gint64 offset, int whence, int *err) */ unsigned had = (unsigned)(file->next - file->out); if (-offset <= had) { - file->have -= (unsigned)offset; - file->next += offset; - file->pos += offset; + /* + * Offset is negative, so -offset is + * non-negative, and -offset is + * <= an unsigned and thus fits in an + * unsigned. Get that value and + * adjust appropriately. + * + * (Casting offset to unsigned makes + * it positive, which is not what we + * would want, so we cast -offset + * instead.) + */ + unsigned adjustment = (unsigned)(-offset); + file->have += adjustment; + file->next -= adjustment; + file->pos -= adjustment; return file->pos; } } |