add libbb functions

include/libbb.h

@@ -0,0 +1,9 @@
+
+#ifndef __LIBBB_H
+#define __LIBBB_H
+char *concat_path_file(const char *path, const char *filename);
+int execable_file(const char *name);
+char *find_execable(const char *filename);
+char* last_char_is(const char *s, int c);
+
+#endif /* __LIBBB_H */

lib/Makefile

@@ -11,6 +11,7 @@ obj-y			+= xfuncs.o
 obj-y			+= getopt.o
 obj-y 			+= readkey.o
 obj-y			+= kfifo.o
+obj-y			+= libbb.o
 obj-$(CONFIG_BZLIB)	+= bzlib.o bzlib_crctable.o bzlib_decompress.o bzlib_huffman.o bzlib_randtable.o
 obj-$(CONFIG_ZLIB)	+= zlib.o gunzip.o
 obj-$(CONFIG_CRC32)	+= crc32.o

lib/libbb.c

@@ -0,0 +1,87 @@
+/* vi: set sw=8 ts=8: */
+/*
+ * Utility routines.
+ *
+ * Copyright (C) many different people.
+ * If you wrote this, please acknowledge your work.
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+#include <common.h>
+#include <libbb.h>
+#include <linux/stat.h>
+#include <fs.h>
+#include <xfuncs.h>
+#include <malloc.h>
+#include <environment.h>
+
+/* concatenate path and file name to new allocation buffer,
+ * not adding '/' if path name already has '/'
+*/
+char *concat_path_file(const char *path, const char *filename)
+{
+	char *lc, *str;
+
+	if (!path)
+		path = "";
+	lc = last_char_is(path, '/');
+	while (*filename == '/')
+		filename++;
+
+	str = xmalloc(strlen(path) + (lc==0 ? 1 : 0) + strlen(filename) + 1);
+	sprintf(str, "%s%s%s", path, (lc==NULL ? "/" : ""), filename);
+
+	return str;
+}
+
+/* check if path points to an executable file;
+ * return 1 if found;
+ * return 0 otherwise;
+ */
+int execable_file(const char *name)
+{
+	struct stat s;
+	return (!stat(name, &s) && S_ISREG(s.st_mode));
+}
+
+/* search $PATH for an executable file;
+ * return allocated string containing full path if found;
+ * return NULL otherwise;
+ */
+char *find_execable(const char *filename)
+{
+	char *path, *p, *n;
+
+	p = path = strdup(getenv("PATH"));
+	while (p) {
+		n = strchr(p, ':');
+		if (n)
+			*n++ = '\0';
+		if (*p != '\0') { /* it's not a PATH="foo::bar" situation */
+			p = concat_path_file(p, filename);
+			if (execable_file(p)) {
+				free(path);
+				return p;
+			}
+			free(p);
+		}
+		p = n;
+	}
+	free(path);
+	return NULL;
+}
+
+/* Find out if the last character of a string matches the one given.
+ * Don't underrun the buffer if the string length is 0.
+ */
+char* last_char_is(const char *s, int c)
+{
+	if (s && *s) {
+		size_t sz = strlen(s) - 1;
+		s += sz;
+		if ( (unsigned char)*s == c)
+			return (char*)s;
+	}
+	return NULL;
+}