MINOR: tools: function my_memmem() to lookup binary contents

This function simply looks for a memory block inside another one.

Signed-off-by: Baptiste Assmann <bedis9@gmail.com>

include/common/standard.h

@@ -519,6 +519,12 @@ int parse_binary(const char *source, char **binstr, int *binstrlen, char **err);
 /* copies at most <n> characters from <src> and always terminates with '\0' */
 char *my_strndup(const char *src, int n);
 
+/*
+ * search needle in haystack
+ * returns the pointer if found, returns NULL otherwise
+ */
+const void *my_memmem(const void *, size_t, const void *, size_t);
+
 /* This function returns the first unused key greater than or equal to <key> in
  * ID tree <root>. Zero is returned if no place is found.
  */

src/standard.c

@@ -1415,6 +1415,31 @@ char *my_strndup(const char *src, int n)
 	return ret;
 }
 
+/*
+ * search needle in haystack
+ * returns the pointer if found, returns NULL otherwise
+ */
+const void *my_memmem(const void *haystack, size_t haystacklen, const void *needle, size_t needlelen)
+{
+	const void *c = NULL;
+	unsigned char f;
+
+	if ((haystack == NULL) || (needle == NULL) || (haystacklen < needlelen))
+		return NULL;
+
+	f = *(char *)needle;
+	c = haystack;
+	while ((c = memchr(c, f, haystacklen - (c - haystack))) != NULL) {
+		if ((haystacklen - (c - haystack)) < needlelen)
+			return NULL;
+
+		if (memcmp(c, needle, needlelen) == 0)
+			return c;
+		++c;
+	}
+	return NULL;
+}
+
 /* This function returns the first unused key greater than or equal to <key> in
  * ID tree <root>. Zero is returned if no place is found.
  */