off_t beg_offset = !NILP (beg) ? file_offset (beg) : 0;
off_t end_offset = !NILP (end) ? file_offset (end) : TYPE_MAXIMUM (off_t);
+ /* END_OFFSET should never be less than BEG_OFFSET,
+ so that code can assume that END_OFFSET - BEG_OFFSET is nonnegative.
+ So set END_OFFSET = max (END_OFFSET, BEG_OFFSET)
+ whenever setting either variable,
+ unless it is already known that BEG_OFFSET <= END_OFFSET. */
+ end_offset = max (end_offset, beg_offset);
+
filename = ENCODE_FILE (filename);
fd = emacs_fd_open (SSDATA (filename), O_RDONLY, 0);
: get_stat_mtime (&st));
}
- /* The initial input position, or -1 if the file is not seekable. */
- off_t begpos = emacs_fd_lseek (fd, beg_offset,
- !NILP (beg) ? SEEK_SET : SEEK_CUR);
-
- /* Whether the file is seekable via SEEK_CUR and SEEK_SET.
- SEEK_END is trickier as it is not reliable on /proc files,
- so it is tested separately below. */
- bool seekable = 0 <= begpos;
-
- /* The current input position if the file is seekable,
- otherwise the number of bytes read. */
- off_t curpos = seekable ? begpos : 0;
-
- if (!seekable && beg_offset != 0)
- report_file_error ("Setting file position", orig_filename);
-
/* The REPLACE code will need to be changed in order to work on
named pipes, and it's probably just not worth it. So we should
at least signal an error. */
orig_filename);
}
- if (end_offset <= beg_offset)
- goto handled;
-
/* Check now whether the buffer will become too large,
in the likely case where the file's length is not changing.
This saves a lot of needless work before a buffer overflow.
/* Prevent redisplay optimizations. */
current_buffer->clip_changed = true;
+ /* The current input position if known, -1 otherwise. */
+ off_t curpos = -1;
+
if (EQ (Vcoding_system_for_read, Qauto_save_coding))
{
coding_system = coding_inherit_eol_type (Qutf_8_emacs, Qunix);
specification if it is not a regular file. */
if (regular && !NILP (Vset_auto_coding_function))
{
+ if (!NILP (beg))
+ curpos = xlseek (fd, beg_offset, SEEK_SET, orig_filename);
+ else
+ {
+ beg_offset = curpos = xlseek (fd, 0, SEEK_CUR, orig_filename);
+ end_offset = max (end_offset, beg_offset);
+ }
+
/* Find a coding system specified in the heading two
lines or in the tailing several lines of the file.
Assume that the 1 KiB and 3 KiB for heading
purpose. Because the file may be in /proc,
do not use st_size or report any SEEK_END failure. */
static_assert (4 * 1024 < sizeof read_buf);
- ptrdiff_t nread = emacs_full_read (fd, read_buf, 4 * 1024);
- if (nread < 4 * 1024)
- curpos = nread;
- else
+ ptrdiff_t
+ trial = min (end_offset - beg_offset, 4 * 1024),
+ nread = trial ? emacs_full_read (fd, read_buf, trial) : 0;
+ curpos += nread;
+
+ if (nread == 4 * 1024 && curpos < end_offset)
{
curpos = emacs_fd_lseek (fd, - 3 * 1024, SEEK_END);
if (curpos < 0)
- curpos = nread;
+ curpos = beg_offset + nread;
+ else
+ {
+ off_t curmax = end_offset - 3 * 1024;
+ if (curmax < curpos)
+ curpos = xlseek (fd, curmax, SEEK_SET, orig_filename);
+ }
/* When appending the last 3 KiB, read extra bytes
without trusting SEEK_END, as the file may be growing.
Although this may yield more than 4 KiB of data total,
and the trailing data may not be from file end if
the file is growing, it is good enough. */
- nread = emacs_full_read (fd, read_buf + 1024,
- sizeof read_buf - 1024);
+ ptrdiff_t trial = min (end_offset - curpos,
+ sizeof read_buf - 1024);
+ nread = emacs_full_read (fd, read_buf + 1024, trial);
if (0 <= nread)
{
curpos += nread;
bool giveup_match_end = false;
if (beg_offset != curpos)
- curpos = xlseek (fd, beg_offset, SEEK_SET, orig_filename);
+ {
+ if (!NILP (beg) || 0 <= curpos)
+ curpos = xlseek (fd, beg_offset, SEEK_SET, orig_filename);
+ else
+ {
+ beg_offset = curpos = xlseek (fd, 0, SEEK_CUR, orig_filename);
+ end_offset = max (end_offset, beg_offset);
+ }
+ }
/* Count how many chars at the start of the file
match the text at the beginning of the buffer. */
while (true)
{
- off_t bytes_to_read = sizeof read_buf;
- bytes_to_read = min (bytes_to_read, end_offset - curpos);
- ptrdiff_t nread = (bytes_to_read <= 0
- ? 0
- : emacs_fd_read (fd, read_buf, bytes_to_read));
+ ptrdiff_t trial = min (end_offset - curpos, sizeof read_buf);
+ ptrdiff_t nread = trial ? emacs_fd_read (fd, read_buf, trial) : 0;
if (nread < 0)
report_file_error ("Read error", orig_filename);
else if (nread == 0)
/* Arrange to read only the nonmatching middle part of the file. */
beg_offset += same_at_start - BEGV_BYTE;
end_offset = endpos - (ZV_BYTE - same_at_end);
+ eassert (beg_offset <= end_offset);
if (!NILP (visit) && BEG == BEGV && Z == ZV)
/* This binding is to avoid ask-user-about-supersession-threat
CONVERSION_BUFFER. */
if (beg_offset != curpos)
- curpos = xlseek (fd, beg_offset, SEEK_SET, orig_filename);
+ {
+ if (!NILP (beg) || 0 <= curpos)
+ curpos = xlseek (fd, beg_offset, SEEK_SET, orig_filename);
+ else
+ {
+ beg_offset = curpos = xlseek (fd, 0, SEEK_CUR, orig_filename);
+ end_offset = max (end_offset, beg_offset);
+ }
+ }
inserted = 0; /* Bytes put into CONVERSION_BUFFER so far. */
unprocessed = 0; /* Bytes not processed in previous loop. */
/* Read one buffer a time, to allow
quitting while reading a huge file. */
- ptrdiff_t trial = sizeof read_buf - unprocessed;
- this = emacs_fd_read (fd, read_buf + unprocessed, trial);
+ ptrdiff_t trial = min (end_offset - curpos,
+ sizeof read_buf - unprocessed);
+ this = trial ? emacs_fd_read (fd, read_buf + unprocessed, trial) : 0;
if (this < 0)
report_file_error ("Read error", orig_filename);
if (this == 0)
goto handled;
}
+ if (beg_offset != curpos)
+ {
+ if (!NILP (beg) || 0 <= curpos)
+ xlseek (fd, beg_offset, SEEK_SET, orig_filename);
+ else if (end_offset != TYPE_MAXIMUM (off_t))
+ {
+ curpos = emacs_fd_lseek (fd, 0, SEEK_CUR);
+ beg_offset = max (0, curpos);
+ end_offset = max (end_offset, beg_offset);
+ }
+ }
+ /* curpos effectively goes out of scope now, as it is no longer needed,
+ so do not bother to update curpos from now on. */
+
total = end_offset - beg_offset;
if (NILP (visit) && total > 0)
make_gap (growth);
}
- if (beg_offset != curpos)
- xlseek (fd, beg_offset, SEEK_SET, orig_filename);
- /* curpos effectively goes out of scope now, as it is no longer needed,
- so not bother to update curpos from now on. */
-
/* Total bytes inserted. */
inserted = 0;
projects / emacs.git / commitdiff