lib: add mangle.c for mtab (fstab or swaps) encoding

Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/lib/mangle.c b/lib/mangle.c
new file mode 100644
index 000000000..766d479d6
--- /dev/null
+++ b/lib/mangle.c
@@ -0,0 +1,116 @@
+/*
+ * Functions for \oct encoding used in mtab/fstab/swaps/etc.
+ *
+ * Based on code from mount(8).
+ *
+ * Copyright (C) 2010 Karel Zak <kzak@redhat.com>
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+#include "mangle.h"
+
+#define isoctal(a) (((a) & ~7) == '0')
+
+static unsigned char need_escaping[] = { ' ', '\t', '\n', '\\' };
+
+char *mangle(const char *s)
+{
+	char *ss, *sp;
+	int n;
+
+	n = strlen(s);
+	ss = sp = malloc(4*n+1);
+	if (!sp)
+		return NULL;
+	while(1) {
+		for (n = 0; n < sizeof(need_escaping); n++) {
+			if (*s == need_escaping[n]) {
+				*sp++ = '\\';
+				*sp++ = '0' + ((*s & 0300) >> 6);
+				*sp++ = '0' + ((*s & 070) >> 3);
+				*sp++ = '0' + (*s & 07);
+				goto next;
+			}
+		}
+		*sp++ = *s;
+		if (*s == 0)
+			break;
+	next:
+		s++;
+	}
+	return ss;
+}
+
+void unmangle_to_buffer(char *s, char *buf, size_t len)
+{
+	size_t sz = 0;
+
+	while(*s && sz < len - 1) {
+		if (*s == '\\' && sz + 4 < len - 1 && isoctal(s[1]) &&
+		    isoctal(s[2]) && isoctal(s[3])) {
+
+			*buf++ = 64*(s[1] & 7) + 8*(s[2] & 7) + (s[3] & 7);
+			s += 4;
+			sz += 4;
+		} else {
+			*buf++ = *s++;
+			sz++;
+		}
+	}
+	*buf = '\0';
+}
+
+static inline char *skip_nonspaces(char *s)
+{
+	while (*s && !(*s == ' ' || *s == '\t'))
+		s++;
+	return s;
+}
+
+/*
+ * Returns mallocated buffer or NULL in case of error.
+ */
+char *unmangle(char *s)
+{
+	char *buf, *end;
+	size_t sz;
+
+	end = skip_nonspaces(s);
+	sz = end - s + 1;
+
+	buf = malloc(sz);
+	if (!buf)
+		return NULL;
+
+	unmangle_to_buffer(s, buf, sz);
+	return buf;
+}
+
+#ifdef TEST_PROGRAM
+#include <err.h>
+#include <errno.h>
+int main(int argc, char *argv[])
+{
+	if (argc < 3) {
+		fprintf(stderr, "usage: %s --mangle | --unmangle <string>\n",
+						program_invocation_short_name);
+		return EXIT_FAILURE;
+	}
+
+	if (!strcmp(argv[1], "--mangle"))
+		printf("mangled: '%s'\n", mangle(argv[2]));
+
+	else if (!strcmp(argv[1], "--unmangle")) {
+		char *x = unmangle(argv[2]);
+		if (x)
+			printf("unmangled: '%s'\n", x);
+		else
+			err(EXIT_FAILURE, "unmangle failed");
+	}
+
+	return EXIT_SUCCESS;
+}
+#endif /* TEST_PROGRAM */