}
}
-/* In FD, position to POS. If this fails, report an error with FILENAME. */
-static void
+/* In FD, position to POS. Return POS if successful, otherwise signal
+ an error with FILENAME. */
+static off_t
xlseek (emacs_fd fd, off_t pos, Lisp_Object filename)
{
if (emacs_fd_lseek (fd, pos, SEEK_SET) < 0)
report_file_error ("Setting file position", filename);
+ return pos;
}
/* A good blocksize to minimize system call overhead across most systems.
: get_stat_mtime (&st));
}
- /* The initial offset can be nonzero, e.g., /dev/stdin.
- If SEEK_CUR works, later code assumes SEEK_SET also works,
- but tests SEEK_END rather than relying on it
- as SEEK_END can fail on Linux /proc files. */
- off_t initial_offset = emacs_fd_lseek (fd, 0, SEEK_CUR);
- bool seekable = 0 <= initial_offset;
- if (seekable && NILP (beg))
- beg_offset = initial_offset;
- if (end_offset <= beg_offset)
- goto handled;
+ /* 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
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.
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 (4 * 1024 <= nread)
+ if (nread < 4 * 1024)
+ curpos = nread;
+ else
{
- off_t tailoff = emacs_fd_lseek (fd, - 3 * 1024, SEEK_END);
- if (tailoff < 0)
- tailoff = nread;
+ curpos = emacs_fd_lseek (fd, - 3 * 1024, SEEK_END);
+ if (curpos < 0)
+ curpos = nread;
/* When appending the last 3 KiB, read extra bytes
- without trusting tailoff, as the file may be growing. */
+ 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);
- if (nread == sizeof read_buf - 1024)
- {
- /* Give up reading the last 3 KiB; the file is
- growing too rapidly. */
- nread = 1024;
- }
- else if (0 <= nread)
+ if (0 <= nread)
{
+ curpos += nread;
nread += 1024;
- if (4 * 1024 < nread)
- {
- memmove (read_buf + 1024,
- read_buf + nread - 3 * 1024, 3 * 1024);
- nread = 4 * 1024;
- }
}
}
/* Discard the unwind protect for recovering the
current buffer. */
specpdl_ptr--;
-
- /* Rewind the file for the actual read done later. */
- xlseek (fd, initial_offset, orig_filename);
}
}
give up on handling REPLACE in the optimized way. */
bool giveup_match_end = false;
- if (beg_offset != initial_offset)
- xlseek (fd, beg_offset, orig_filename);
+ if (beg_offset != curpos)
+ curpos = xlseek (fd, beg_offset, orig_filename);
/* 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;
- off_t curpos = beg_offset + (same_at_start - BEGV_BYTE);
bytes_to_read = min (bytes_to_read, end_offset - curpos);
ptrdiff_t nread = (bytes_to_read <= 0
? 0
if (0 < nread)
{
+ curpos += nread;
+
if (CODING_REQUIRE_DETECTION (&coding))
{
coding_system
ptrdiff_t n = emacs_full_read (fd, read_buf, sizeof read_buf);
if (n < 0)
report_file_error ("Read error", orig_filename);
- endpos += n;
+ curpos = endpos += n;
/* Give up if the file grew more than even the test read. */
giveup_match_end = n == sizeof read_buf;
while (!giveup_match_end)
{
ptrdiff_t nread, bufpos, trial;
- off_t curpos;
-
- /* At what file position are we now scanning? */
- curpos = endpos - (ZV_BYTE - same_at_end);
/* How much can we scan in the next step? Compare with poslim
to prevent overlap of the matching head with the matching tail.
if (trial == 0)
break;
- curpos -= trial;
- xlseek (fd, curpos, orig_filename);
+ curpos = xlseek (fd, curpos - trial, orig_filename);
nread = emacs_full_read (fd, read_buf, trial);
+ curpos += nread;
if (nread < trial)
{
if (nread < 0)
/* First read the whole file, performing code conversion into
CONVERSION_BUFFER. */
- xlseek (fd, beg_offset, orig_filename);
+ if (beg_offset != curpos)
+ curpos = xlseek (fd, beg_offset, orig_filename);
inserted = 0; /* Bytes put into CONVERSION_BUFFER so far. */
unprocessed = 0; /* Bytes not processed in previous loop. */
report_file_error ("Read error", orig_filename);
if (this == 0)
break;
+ curpos += this;
BUF_TEMP_SET_PT (XBUFFER (conversion_buffer),
BUF_Z (XBUFFER (conversion_buffer)));
make_gap (growth);
}
- if (beg_offset != 0 || (!NILP (replace)
- && !BASE_EQ (replace, Qunbound)))
+ if (beg_offset != curpos)
xlseek (fd, beg_offset, 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