1 files changed, 52 insertions, 0 deletions
diff --git a/src/stdio/__overflow.c b/src/stdio/__overflow.c
new file mode 100644
index 00000000..e35104de
--- /dev/null
+++ b/src/stdio/__overflow.c
@@ -0,0 +1,52 @@
+#include "stdio_impl.h"
+
+static int overflow(FILE *f, int c)
+{
+	/* Initialize if we're not already writing */
+	if (!f->wend) {
+		/* Fail if we're in error state or unwritable. */
+		if (f->flags & (F_ERR|F_NOWR)) return EOF;
+
+		/* Set byte orientation -1,0=>-1; 1=>1 */
+		f->mode |= f->mode-1;
+
+		/* Clear read buffer (easier than summoning nasal demons) */
+		f->rpos = f->rend = f->rstop = 0;
+
+		/* Activate write through the buffer */
+		f->wpos = f->wbase = f->buf;
+		f->wend = f->buf + f->buf_size;
+		f->wstop = (f->lbf < 0) ? f->wend - 1 : 0;
+	}
+
+	/* Buffer can always hold at least 1 byte... */
+	if (c != EOF) {
+		*f->wpos++ = c;
+		if (f->wpos <= f->wstop && c != f->lbf) return c;
+	}
+	/* ...since if the next call fails, buffer is empty. */
+	if (f->write(f, f->wbase, f->wpos - f->wbase) < 0) {
+		f->flags |= F_ERR;
+		f->wpos = f->wbase = f->wend = f->wstop = 0;
+		return EOF;
+	}
+
+	/* Buffer is empty so reset position to beginning */
+	f->wpos = f->wbase;
+
+	return c;
+}
+
+int __overflow(FILE *f, int c)
+{
+	return overflow(f, c & 0xff);
+}
+
+int __oflow(FILE *f)
+{
+	overflow(f, EOF);
+	return (f->flags & F_ERR) ? EOF : 0;
+}
+
+/* Link flush-on-exit code iff any stdio write functions are linked. */
+int (*const __fflush_on_exit)(FILE *) = fflush;