Commit 3ce839e4 authored by Richard M. Stallman's avatar Richard M. Stallman
Browse files

(Fmake_temp_name): Complete rewrite.

parent 5feeeae2
......@@ -790,33 +790,108 @@ it returns a file name such as \"[X]Y.DIR.1\".")
return build_string (buf);
static char make_temp_name_tbl[64] =
static unsigned make_temp_name_count, make_temp_name_count_initialized_p;
DEFUN ("make-temp-name", Fmake_temp_name, Smake_temp_name, 1, 1, 0,
"Generate temporary file name (string) starting with PREFIX (a string).\n\
The Emacs process number forms part of the result,\n\
so there is no danger of generating a name being used by another process.\n\
In addition, this function makes an attempt to choose a name\n\
which has no existing file.")
which has no existing file. To make this work,\n\
PREFIX should be an absolute file name.")
Lisp_Object prefix;
char *temp;
Lisp_Object val;
#ifdef MSDOS
/* Don't use too many characters of the restricted 8+3 DOS
filename space. */
val = concat2 (prefix, build_string ("a.XXX"));
int len;
int pid;
unsigned char *p, *data;
char pidbuf[20];
int pidlen;
CHECK_STRING (prefix, 0);
/* VAL is created by adding 6 characters to PREFIX. The first
three are the PID of this process, in base 64, and the second
three are incremented if the file already exists. This ensures
262144 unique file names per PID per PREFIX. */
pid = (int) getpid ();
sprintf (pidbuf, "%d", pid);
pidlen = strlen (pidbuf);
val = concat2 (prefix, build_string ("XXXXXX"));
temp = mktemp (XSTRING (val)->data);
if (! temp)
error ("No temporary file names based on %s are available",
XSTRING (prefix)->data);
#ifdef DOS_NT
pidbuf[0] = make_temp_name_tbl[pid & 63], pid >>= 6;
pidbuf[1] = make_temp_name_tbl[pid & 63], pid >>= 6;
pidbuf[2] = make_temp_name_tbl[pid & 63], pid >>= 6;
pidlen = 3;
len = XSTRING (prefix)->size;
val = make_uninit_string (len + 3 + pidlen);
data = XSTRING (val)->data;
bcopy(XSTRING (prefix)->data, data, len);
p = data + len;
bcopy (pidbuf, p, pidlen);
p += pidlen;
/* Here we try to minimize useless stat'ing when this function is
invoked many times successively with the same PREFIX. We achieve
this by initializing count to a random value, and incrementing it
afterwards. */
if (!make_temp_name_count_initialized_p)
make_temp_name_count = (unsigned) time (NULL);
make_temp_name_count_initialized_p = 1;
while (1)
struct stat ignored;
unsigned num = make_temp_name_count++;
p[0] = make_temp_name_tbl[num & 63], num >>= 6;
p[1] = make_temp_name_tbl[num & 63], num >>= 6;
p[2] = make_temp_name_tbl[num & 63], num >>= 6;
if (stat (data, &ignored) < 0)
/* We want to return only if errno is ENOENT. */
if (errno == ENOENT)
return val;
/* The error here is dubious, but there is little else we
can do. The alternatives are to return nil, which is
as bad as (and in many cases worse than) throwing the
error, or to ignore the error, which will likely result
in looping through 262144 stat's, which is not only
SLOW, but also useless since it will fallback to the
errow below, anyway. */
report_file_error ("Cannot create temporary name for prefix `%s'",
Fcons (prefix, Qnil));
/* not reached */
error ("Cannot create temporary name for prefix `%s'",
XSTRING (prefix)->data);
return Qnil;
DEFUN ("expand-file-name", Fexpand_file_name, Sexpand_file_name, 1, 2, 0,
"Convert filename NAME to absolute, and canonicalize it.\n\
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