From 4abab5ad6c8465a7528ccdd5f49367da05f78bbd Mon Sep 17 00:00:00 2001
From: Vladimir Azarov <avm@intermediate-node.net>
Date: Tue, 1 Oct 2024 15:47:05 +0200
Subject: Initial version

---
 src/stdio/open_memstream.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 src/stdio/open_memstream.c

(limited to 'src/stdio/open_memstream.c')

diff --git a/src/stdio/open_memstream.c b/src/stdio/open_memstream.c
new file mode 100644
index 0000000..600d277
--- /dev/null
+++ b/src/stdio/open_memstream.c
@@ -0,0 +1,99 @@
+#include "stdio_impl.h"
+#include <errno.h>
+#include <limits.h>
+#include <string.h>
+#include <stdlib.h>
+#include "libc.h"
+
+struct cookie {
+	char **bufp;
+	size_t *sizep;
+	size_t pos;
+	char *buf;
+	size_t len;
+	size_t space;
+};
+
+struct ms_FILE {
+	FILE f;
+	struct cookie c;
+	unsigned char buf[BUFSIZ];
+};
+
+static off_t ms_seek(FILE *f, off_t off, int whence)
+{
+	ssize_t base;
+	struct cookie *c = f->cookie;
+	if (whence>2U) {
+fail:
+		errno = EINVAL;
+		return -1;
+	}
+	base = (size_t [3]){0, c->pos, c->len}[whence];
+	if (off < -base || off > SSIZE_MAX-base) goto fail;
+	return c->pos = base+off;
+}
+
+static size_t ms_write(FILE *f, const unsigned char *buf, size_t len)
+{
+	struct cookie *c = f->cookie;
+	size_t len2 = f->wpos - f->wbase;
+	char *newbuf;
+	if (len2) {
+		f->wpos = f->wbase;
+		if (ms_write(f, f->wbase, len2) < len2) return 0;
+	}
+	if (len + c->pos >= c->space) {
+		len2 = 2*c->space+1 | c->pos+len+1;
+		newbuf = realloc(c->buf, len2);
+		if (!newbuf) return 0;
+		*c->bufp = c->buf = newbuf;
+		memset(c->buf + c->space, 0, len2 - c->space);
+		c->space = len2;
+	}
+	memcpy(c->buf+c->pos, buf, len);
+	c->pos += len;
+	if (c->pos >= c->len) c->len = c->pos;
+	*c->sizep = c->pos;
+	return len;
+}
+
+static int ms_close(FILE *f)
+{
+	return 0;
+}
+
+FILE *open_memstream(char **bufp, size_t *sizep)
+{
+	struct ms_FILE *f;
+	char *buf;
+
+	if (!(f=malloc(sizeof *f))) return 0;
+	if (!(buf=malloc(sizeof *buf))) {
+		free(f);
+		return 0;
+	}
+	memset(&f->f, 0, sizeof f->f);
+	memset(&f->c, 0, sizeof f->c);
+	f->f.cookie = &f->c;
+
+	f->c.bufp = bufp;
+	f->c.sizep = sizep;
+	f->c.pos = f->c.len = f->c.space = *sizep = 0;
+	f->c.buf = *bufp = buf;
+	*buf = 0;
+
+	f->f.flags = F_NORD;
+	f->f.fd = -1;
+	f->f.buf = f->buf;
+	f->f.buf_size = sizeof f->buf;
+	f->f.lbf = EOF;
+	f->f.write = ms_write;
+	f->f.seek = ms_seek;
+	f->f.close = ms_close;
+	f->f.mode = -1;
+
+	if (!libc.threaded) f->f.lock = -1;
+
+	return __ofl_add(&f->f);
+}
-- 
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