summaryrefslogtreecommitdiff
path: root/src/stdio/ungetc.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/stdio/ungetc.c')
-rw-r--r--src/stdio/ungetc.c33
1 files changed, 33 insertions, 0 deletions
diff --git a/src/stdio/ungetc.c b/src/stdio/ungetc.c
new file mode 100644
index 00000000..07181684
--- /dev/null
+++ b/src/stdio/ungetc.c
@@ -0,0 +1,33 @@
+#include "stdio_impl.h"
+
+int ungetc(int c, FILE *f)
+{
+ if (c == EOF) return c;
+
+ FLOCK(f);
+
+ /* Fail if unreadable or writing and unable to flush */
+ if ((f->flags & (F_ERR|F_NORD)) || (f->wpos && __oflow(f))) {
+ FUNLOCK(f);
+ return EOF;
+ }
+
+ /* Clear write mode */
+ f->wbase = f->wpos = f->wstop = f->wend = 0;
+
+ /* Put the file in read mode */
+ if (!f->rpos) f->rpos = f->rend = f->buf;
+
+ /* If unget buffer is already full, fail. */
+ if (f->rpos <= f->buf - UNGET) {
+ FUNLOCK(f);
+ return EOF;
+ }
+
+ /* Put a byte back into the buffer */
+ *--f->rpos = c;
+ f->flags &= ~F_EOF;
+
+ FUNLOCK(f);
+ return c;
+}