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lib/commonio.c: Use block I/O for backup copies #1565

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lib/commonio.c: Use block I/O for backup copies #1565

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28 changes: 20 additions & 8 deletions lib/commonio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -247,7 +247,6 @@ static int create_backup (const char *name, FILE * fp)
struct stat sb;
struct utimbuf ub;
FILE *bkfp;
int c;

stprintf_a(tmpf, "%s.cioXXXXXX", name);
if (fstat (fileno (fp), &sb) != 0) {
Expand All @@ -259,16 +258,29 @@ static int create_backup (const char *name, FILE * fp)
return -1;
}

/* TODO: faster copy, not one-char-at-a-time. --marekm */
c = 0;
if (fseek (fp, 0, SEEK_SET) == 0) {
while ((c = getc (fp)) != EOF) {
if (putc (c, bkfp) == EOF) {
break;
if (fseek (fp, 0, SEEK_SET) != 0) {
(void) fclose (bkfp);
unlink(tmpf);
return -1;
}
{
char buf[BUFSIZ];
size_t n;

while ((n = fread (buf, 1, sizeof buf, fp)) > 0) {
if (fwrite (buf, 1, n, bkfp) != n) {
(void) fclose (bkfp);
unlink(tmpf);
return -1;
}
}
if (ferror (fp) != 0) {
(void) fclose (bkfp);
unlink(tmpf);
return -1;
}
}
if ((c != EOF) || (ferror (fp) != 0) || (fflush (bkfp) != 0)) {
if (fflush (bkfp) != 0) {
Comment on lines -262 to +283
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@alejandro-colomar alejandro-colomar Mar 7, 2026

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Did you notice any performance issues or issues of other kind? Otherwise, I see this as a readability pessimization, which has a high chance of having bugs in there.

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@alejandro-colomar alejandro-colomar Mar 7, 2026 •
edited
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You may be interested in this instead:

(void) fclose (bkfp);
unlink(tmpf);
return -1;
Expand Down