tests/posix: add testcase for fmemopen(3)

tests/meson.build

@@ -49,6 +49,7 @@ all_test_cases = [
 	'posix/pwd',
 	'posix/fdopen',
 	'posix/fopencookie',
+	'posix/fmemopen',
 	'posix/getaddrinfo',
 	'posix/getdelim',
 	'posix/getnameinfo',

tests/posix/fmemopen.c

@@ -0,0 +1,119 @@
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <assert.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define BUFFER0_SIZE 0x1000
+#define BUFFER1 "Hello world"
+#define BUFFER1_SIZE (sizeof(BUFFER1))
+
+int main() {
+	// test seek with mode "r"
+	FILE *f = fmemopen(NULL, BUFFER0_SIZE, "r");
+	assert(f);
+
+	int ret = fseek(f, 0, SEEK_END);
+	assert(!ret);
+	long pos = ftell(f);
+	fprintf(stderr, "pos = %ld\n", pos);
+	// Despite the fact that this is correct behavior (see below),
+	// this sometimes fails on glibc; newlibs seems to get this wrong, too.
+	// to quote what posix says about it:
+	// > The stream shall also maintain the size of the current buffer contents;
+	// > use of fseek() or fseeko() on the stream with SEEK_END shall seek relative to this size.
+	// > For modes r and r+ the size shall be set to the value given by the size argument.
+#if !defined(__GLIBC__)
+	assert(pos == BUFFER0_SIZE);
+#endif
+
+	fclose(f);
+
+	// test seek with mode "w"
+	f = fmemopen(NULL, BUFFER0_SIZE, "w");
+	assert(f);
+
+	assert(!fseek(f, 0, SEEK_END));
+	pos = ftell(f);
+	assert(pos == 0);
+
+	fclose(f);
+
+	// test seek with mode "a" and a NULL buffer
+	f = fmemopen(NULL, BUFFER0_SIZE, "a");
+	assert(f);
+
+	assert(!fseek(f, 0, SEEK_END));
+	pos = ftell(f);
+	assert(pos == 0);
+
+	fclose(f);
+
+	// test seek with mode "a" and a buffer containing a '\0'
+	f = fmemopen(BUFFER1, BUFFER1_SIZE, "a");
+	assert(f);
+
+	assert(!fseek(f, 0, SEEK_END));
+	pos = ftell(f);
+	assert(pos == (long) (BUFFER1_SIZE - 1));
+
+	fclose(f);
+
+	// test seek with mode "a" and a buffer not containing a '\0'
+	f = fmemopen(BUFFER1, BUFFER1_SIZE - 2, "a");
+	assert(f);
+
+	assert(!fseek(f, 0, SEEK_END));
+	pos = ftell(f);
+	assert(pos == (long) (BUFFER1_SIZE - 2));
+
+	fclose(f);
+
+	f = fmemopen(BUFFER1, BUFFER1_SIZE, "r");
+	assert(f);
+
+	assert(!fseek(f, 0, SEEK_SET));
+
+	char buf[BUFFER1_SIZE];
+	int read = fread(buf, 1, BUFFER1_SIZE - 2, f);
+	assert(read == BUFFER1_SIZE - 2);
+	assert(!strncmp(BUFFER1, buf, BUFFER1_SIZE - 2));
+
+	fseek(f, 0, SEEK_END);
+
+	read = fread(buf, 1, 2, f);
+	assert(read == 0);
+	assert(feof(f));
+
+	fclose(f);
+
+	// Open a buffer for read+write
+	char *buf1 = strdup(BUFFER1);
+	f = fmemopen(buf1, BUFFER1_SIZE, "w+");
+	assert(f);
+	assert(strlen(BUFFER1) == BUFFER1_SIZE - 1);
+
+	// seek to somewhere in the middle of the buffer
+	fseek(f, BUFFER1_SIZE - 5, SEEK_SET);
+	// write as much data to it as possible
+	read = fwrite(BUFFER1, 1, 9, f);
+	rewind(f);
+
+	// seek the the same position in the middle of the buffer
+	ret = fseek(f, BUFFER1_SIZE - 5, SEEK_SET);
+	assert(!ret);
+	memset(buf, 0, BUFFER1_SIZE);
+	// read what we just wrote
+	read = fread(buf, 1, 5, f);
+	// check that the write got correctly truncated
+	assert(!strncmp(BUFFER1, buf, 4) && strlen(buf) == 4);
+
+	fclose(f);
+	free(buf1);
+
+	return 0;
+}