1 files changed, 74 insertions, 0 deletions
diff --git a/gnu/lib/libf2c/libI77/backspace.c b/gnu/lib/libf2c/libI77/backspace.c
new file mode 100644
index 00000000000..848923912bf
--- /dev/null
+++ b/gnu/lib/libf2c/libI77/backspace.c
@@ -0,0 +1,74 @@
+#include "config.h"
+#include <sys/types.h>
+#include "f2c.h"
+#include "fio.h"
+#ifdef KR_headers
+integer f_back(a) alist *a;
+#else
+integer f_back(alist *a)
+#endif
+{	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;
+}