Create fgetc.[ch]

1 files changed, 37 insertions, 0 deletions

diff --git a/fgetc.c b/fgetc.c
new file mode 100644
index 0000000..4aaffeb
--- /dev/null
+++ b/fgetc.c
@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include "fgetc.h"
+
+/* ************************************************************************ */
+/* Custom fgetc/ungetc implementation able to unget more than one character */
+/* ************************************************************************ */
+
+enum
+{
+  GETC_BUFF_SIZE = 16
+};
+
+static char getc_buffer[GETC_BUFF_SIZE] = { '\0' };
+
+static long next_buffer_pos = 0; /* next free position in the getc buffer */
+
+/* ====================================== */
+/* Get a (possibly pushed-back) character */
+/* ====================================== */
+int
+my_fgetc(FILE * input)
+{
+  return (next_buffer_pos > 0) ? getc_buffer[--next_buffer_pos] : fgetc(input);
+}
+
+/* ============================ */
+/* Push character back on input */
+/* ============================ */
+void
+my_ungetc(int c)
+{
+  if (next_buffer_pos >= GETC_BUFF_SIZE)
+    fprintf(stderr, "Error: cannot push back more than %d characters\n",
+            GETC_BUFF_SIZE);
+  else
+    getc_buffer[next_buffer_pos++] = c;
+}