libc/stdio: Rework custom streams interface similar to glibc.

Save 20 bytes per FILE structure, avoid indirect call for
read/write/seek/close operations for normal streams.
Additionally, custom streams has fileno = -2 now, like in glibc.

bloat-o-meter report (UCLIBC_HAS_GLIBC_CUSTOM_STREAMS=y):
function                                             old     new   delta
fopencookie                                           69     131     +62
ftello64                                             233     260     +27
fseeko64                                             298     319     +21
fclose                                               423     442     +19
.rodata                                            16696   16708     +12
fileno_unlocked                                       53      45      -8
__ns_name_pack                                       859     851      -8
vswscanf                                             184     144     -40
vdprintf                                             231     187     -44
vsscanf                                              210     151     -59
vswprintf                                            269     201     -68
vsnprintf                                            249     181     -68
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/7 up/down: 141/-295)         Total: -154 bytes

Signed-off-by: Leonid Lisovskiy <lly.dev@gmail.com>
Signed-off-by: Waldemar Brodkorb <wbx@uclibc-ng.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/test/stdio/tst-fmemopen.c b/test/stdio/tst-fmemopen.c
new file mode 100644
index 000000000..384faa1c9
--- /dev/null
+++ b/test/stdio/tst-fmemopen.c
@@ -0,0 +1,53 @@
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static char *text_input = "1 23 43";
+
+static const char *good_answer = "1 529 1849 ";
+
+
+static int
+do_test (void)
+{
+    FILE *out, *in;
+    int v, s;
+    size_t size;
+    char *ptr;
+
+    in = fmemopen(text_input, strlen(text_input), "r");
+    if (in == NULL) {
+        perror("fmemopen");
+	return 1;
+    }
+
+    out = open_memstream(&ptr, &size);
+    if (out == NULL) {
+        perror("open_memstream");
+	return 1;
+    }
+
+    for (;;) {
+        s = fscanf(in, "%d", &v);
+        if (s <= 0)
+            break;
+
+        s = fprintf(out, "%d ", v * v);
+        if (s == -1) {
+            puts("fprintf failed");
+	    exit(1);
+	}
+    }
+    fclose(in);
+    fclose(out);
+
+    if (size != strlen(good_answer) || strcmp(good_answer, ptr) != 0) {
+	printf("failed: size=%zu; ptr=%s\n", size, ptr);
+	exit(1);
+    }
+    free(ptr);
+    exit(0);
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"