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Author: Andrew Bower <andrew@bower.uk>
Description: Fix reverse reading of incomplete trailing record
Last-Update: 2025-09-22
Bug: https://savannah.gnu.org/bugs/?56282
Bug: https://savannah.gnu.org/bugs/?56285
Bug: https://savannah.gnu.org/bugs/?49930
Bug-Debian: https://bugs.debian.org/715840
Bug-Debian: https://bugs.debian.org/715841
Bug-Debian: https://bugs.debian.org/506701
Forwarded: https://file.savannah.gnu.org/file/fix-reverse-read-incomplete-record.patch?file_id=57676
---
file_rd.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/file_rd.c b/file_rd.c
index ac2a754..6c2b324 100644
--- a/file_rd.c
+++ b/file_rd.c
@@ -106,13 +106,23 @@ char *file_reader_get_entry(struct file_rd_info *fri)
{
off_t offset, max_recs, recs_to_read;
- if ((offset = ftello (fri->fp)) <= 0)
+ if ((offset = ftello (fri->fp)) < 0) {
+ perror("get_entry: error determining file position");
+ offset = 0;
+ }
+
+ max_recs = offset / (off_t) fri->record_size;
+ if (max_recs * (off_t) fri->record_size != offset) {
+ fprintf(stderr, "warning: data beyond last complete record\n");
+ offset = max_recs * (off_t) fri->record_size;
+ }
+
+ if (offset == 0)
goto no_more_records;
/* Read as many records as possible, up to
FRI->BUFFERED_RECORDS */
- max_recs = offset / (long) fri->record_size;
recs_to_read = ((max_recs < fri->buffered_records)
? max_recs
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