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/* $OpenBSD: test_fflush.c,v 1.3 2025/06/08 08:53:53 yasuoka Exp $ */
/*
* Copyright (c) 2025 YASUOKA Masahiko <yasuoka@yasuoka.net>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <assert.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wchar.h>
/* we use assert() */
#undef NDEBUG
#define TMPFILENAME "test_fflush.tmp"
void setup(void);
void test_fflush_read0(void);
void test_fflush_read1(void);
void test_fflush_read2(void);
void test_fflush_read3(void);
void test_fflush_read4(void);
void setupw(void);
void test_fflush_read5(void);
void test_fflush_read6(void);
void
setup(void)
{
FILE *fp;
/* common setup */
unlink(TMPFILENAME);
fp = fopen(TMPFILENAME, "w+");
assert(fp != NULL);
fputs("Hello world\n", fp);
fclose(fp);
}
/* fflush work with reading file and seekable */
void
test_fflush_read0(void)
{
int r;
char buf[80];
FILE *fp;
setup();
/* In POSIX 2008, fflush() must work with the file object for reading */
fp = fopen(TMPFILENAME, "r");
assert(fp != NULL);
assert(fgetc(fp) == 'H');
r = fflush(fp);
assert(r == 0);
/* the position is moved to 1 */
assert(ftell(fp) == 1);
/* can read rest of that */
fgets(buf, sizeof(buf), fp);
assert(strcmp(buf, "ello world\n") == 0);
r = fclose(fp);
assert(r == 0);
}
/* fflush work with reading file and seekable + unget */
void
test_fflush_read1(void)
{
int r;
char buf[80];
FILE *fp;
setup();
fp = fopen(TMPFILENAME, "r");
assert(fp != NULL);
assert(fgetc(fp) == 'H');
assert(fgetc(fp) == 'e');
assert(fgetc(fp) == 'l');
assert(fgetc(fp) == 'l');
assert(fgetc(fp) == 'o');
/* push the 'AAAA' back */
ungetc('A', fp);
ungetc('A', fp);
ungetc('A', fp);
ungetc('A', fp);
/* can read rest of that */
fgets(buf, sizeof(buf), fp);
assert(strcmp(buf, "AAAA world\n") == 0);
r = fclose(fp);
assert(r == 0);
/* do the same thing + fflush */
fp = fopen(TMPFILENAME, "r");
assert(fp != NULL);
assert(fgetc(fp) == 'H');
assert(fgetc(fp) == 'e');
assert(fgetc(fp) == 'l');
assert(fgetc(fp) == 'l');
assert(fgetc(fp) == 'o');
/* push 'AAAA' back */
ungetc('A', fp);
ungetc('A', fp);
ungetc('A', fp);
ungetc('A', fp);
/* then fflush */
r = fflush(fp);
assert(r == 0);
/* fllush() clears the all pushed back chars */
/* can read rest of that */
fgets(buf, sizeof(buf), fp);
assert(strcmp(buf, " world\n") == 0);
r = fclose(fp);
assert(r == 0);
}
/* fflush() to reading and non-seekable stream */
void
test_fflush_read2(void)
{
int r;
FILE *fp;
char buf[80];
/* In POSIX-2008, fflush() must work with the file object for reading */
fp = popen("echo Hello world", "r");
assert(fp != NULL);
assert(fgetc(fp) == 'H');
r = fflush(fp);
assert(r == 0);
/*
* FILE object for read and NOT seekable. In that case, fflush does
* nothing, but must keep the buffer.
*/
/* can read rest of that */
fgets(buf, sizeof(buf), fp);
assert(strcmp(buf, "ello world\n") == 0);
r = pclose(fp);
assert(r == 0);
}
/* fflush() to the file which doesn't have any buffer */
void
test_fflush_read3(void)
{
int r;
FILE *fp;
setup();
/* In POSIX-2008, fflush() must work with the file object for reading */
fp = fopen(TMPFILENAME, "r");
assert(fp != NULL);
r = fflush(fp);
assert(r == 0);
r = fclose(fp);
assert(r == 0);
}
/* freopen() should call fflush() internal */
void
test_fflush_read4(void)
{
int r;
FILE *fp;
off_t pos;
char buf[80];
setup();
/* In POSIX-2008, fflush() must work with the file object for reading */
fp = fopen(TMPFILENAME, "r");
assert(fp != NULL);
assert(fgetc(fp) == 'H'); /* read 1 */
pos = lseek(fileno(fp), 0, SEEK_CUR);
assert(pos >= 1);
assert(pos > 1); /* this test assume the buffer is used */
/* freopen() should call fflush() internal */
fp = freopen(TMPFILENAME, "r", fp);
assert(fp != NULL);
/* can read rest of that on fp */
fgets(buf, sizeof(buf), fp);
assert(strcmp(buf, "Hello world\n") == 0);
r = fclose(fp);
assert(r == 0);
}
void
setupw(void)
{
FILE *fp;
/* common setup */
unlink(TMPFILENAME);
fp = fopen(TMPFILENAME, "w+");
assert(fp != NULL);
/* Konnitiwa Sekai(in Kanji) */
fputws(L"\u3053\u3093\u306b\u3061\u308f \u4e16\u754c\n", fp);
fclose(fp);
}
/* fflush work with reading file and seekable + ungetwc */
void
test_fflush_read5(void)
{
int r;
wchar_t buf[80];
FILE *fp;
setupw();
fp = fopen(TMPFILENAME, "r");
assert(fp != NULL);
assert(fgetwc(fp) == L'\u3053'); /* Ko */
assert(fgetwc(fp) == L'\u3093'); /* N */
assert(fgetwc(fp) == L'\u306b'); /* Ni */
assert(fgetwc(fp) == L'\u3061'); /* Ti */
assert(fgetwc(fp) == L'\u308f'); /* Wa */
/* push 263A(smile) back */
assert(ungetwc(L'\u263a', fp));
/* we support 1 push back wchar_t */
assert(fgetwc(fp) == L'\u263a');
/* can read reset of that */
fgetws(buf, sizeof(buf), fp);
assert(wcscmp(buf, L" \u4e16\u754c\n") == 0);
r = fclose(fp);
assert(r == 0);
/* do the same thing + fflush */
fp = fopen(TMPFILENAME, "r");
assert(fp != NULL);
assert(fgetwc(fp) == L'\u3053'); /* Ko */
assert(fgetwc(fp) == L'\u3093'); /* N */
assert(fgetwc(fp) == L'\u306b'); /* Ni */
assert(fgetwc(fp) == L'\u3061'); /* Ti */
assert(fgetwc(fp) == L'\u308f'); /* Wa */
/* push 263A(smile) back */
assert(ungetwc(L'\u263a', fp));
/* we support 1 push back wchar_t */
assert(fgetwc(fp) == L'\u263a');
/* then fflush */
r = fflush(fp);
assert(r == 0);
/* fllush() clears the all pushed back chars */
/* can read rest of that */
fgetws(buf, sizeof(buf), fp);
assert(wcscmp(buf, L" \u4e16\u754c\n") == 0);
r = fclose(fp);
assert(r == 0);
}
void
test_fflush_read6(void)
{
int r, c;
FILE *fp;
setup();
fp = fopen(TMPFILENAME, "r");
assert(fp != NULL);
/*
* https://pubs.opengroup.org/onlinepubs/9699919799/functions/fflush.html
* .. any characters pushed back onto the stream by ungetc() or ungetwc()
* that have not subsequently been read from the stream shall be discarded
* (without further changing the file offset).
*/
assert(fgetc(fp) == 'H');
c = getc(fp);
ungetc(c, fp); /* push back the character has been read */
r = fflush(fp);
assert(r == 0);
assert(getc(fp) == c);
fseek(fp, 0, SEEK_SET);
assert(fgetc(fp) == 'H');
c = getc(fp);
ungetc('X', fp); /* push back the character has not been read */
r = fflush(fp);
assert(r == 0);
assert(getc(fp) == 'l');
r = fclose(fp);
assert(r == 0);
}
int
main(int argc, char *argv[])
{
setlocale(LC_ALL, "C.UTF-8");
test_fflush_read0();
test_fflush_read1();
test_fflush_read2();
test_fflush_read3();
test_fflush_read4();
test_fflush_read5();
test_fflush_read6();
exit(0);
}
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