1 files changed, 81 insertions, 0 deletions
diff --git a/libf2c/libI77/backspace.c b/libf2c/libI77/backspace.c
new file mode 100644
index 0000000..c31e711
--- /dev/null
+++ b/libf2c/libI77/backspace.c
@@ -0,0 +1,81 @@
+#include "config.h"
+#include <sys/types.h>
+#include "f2c.h"
+#include "fio.h"
+integer
+f_back (alist * a)
+{
+  unit *b;
+  off_t v, w, x, y, z;
+  uiolen n;
+  FILE *f;
+
+  f__curunit = b = &f__units[a->aunit];	/* curunit for error messages */
+  if (f__init & 2)
+    f__fatal (131, "I/O recursion");
+  if (a->aunit >= MXUNIT || a->aunit < 0)
+    err (a->aerr, 101, "backspace");
+  if (b->useek == 0)
+    err (a->aerr, 106, "backspace");
+  if (b->ufd == NULL)
+    {
+      fk_open (1, 1, a->aunit);
+      return (0);
+    }
+  if (b->uend == 1)
+    {
+      b->uend = 0;
+      return (0);
+    }
+  if (b->uwrt)
+    {
+      t_runc (a);
+      if (f__nowreading (b))
+	err (a->aerr, errno, "backspace");
+    }
+  f = b->ufd;			/* may have changed in t_runc() */
+  if (b->url > 0)
+    {
+      x = FTELL (f);
+      y = x % b->url;
+      if (y == 0)
+	x--;
+      x /= b->url;
+      x *= b->url;
+      FSEEK (f, x, SEEK_SET);
+      return (0);
+    }
+
+  if (b->ufmt == 0)
+    {
+      FSEEK (f, -(off_t) sizeof (uiolen), SEEK_CUR);
+      fread ((char *) &n, sizeof (uiolen), 1, f);
+      FSEEK (f, -(off_t) n - 2 * sizeof (uiolen), SEEK_CUR);
+      return (0);
+    }
+  w = x = FTELL (f);
+  z = 0;
+loop:
+  while (x)
+    {
+      x -= x < 64 ? x : 64;
+      FSEEK (f, x, SEEK_SET);
+      for (y = x; y < w; y++)
+	{
+	  if (getc (f) != '\n')
+	    continue;
+	  v = FTELL (f);
+	  if (v == w)
+	    {
+	      if (z)
+		goto break2;
+	      goto loop;
+	    }
+	  z = v;
+	}
+      err (a->aerr, (EOF), "backspace");
+    }
+break2:
+  FSEEK (f, z, SEEK_SET);
+  return 0;
+}