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diff --git a/internal/strings/util.h b/internal/strings/util.h
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+// Useful string functions and so forth.  This is a grab-bag file.
+//
+// You might also want to look at memutil.h, which holds mem*()
+// equivalents of a lot of the str*() functions in string.h,
+// eg memstr, mempbrk, etc.
+//
+// These functions work fine for UTF-8 strings as long as you can
+// consider them to be just byte strings.  For example, due to the
+// design of UTF-8 you do not need to worry about accidental matches,
+// as long as all your inputs are valid UTF-8 (use \uHHHH, not \xHH or \oOOO).
+//
+// Caveats:
+// * all the lengths in these routines refer to byte counts,
+//   not character counts.
+// * case-insensitivity in these routines assumes that all the letters
+//   in question are in the range A-Z or a-z.
+//
+// If you need Unicode specific processing (for example being aware of
+// Unicode character boundaries, or knowledge of Unicode casing rules,
+// or various forms of equivalence and normalization), take a look at
+// files in i18n/utf8.
+
+#ifndef DYNAMIC_DEPTH_INTERNAL_STRINGS_UTIL_H_  // NOLINT
+#define DYNAMIC_DEPTH_INTERNAL_STRINGS_UTIL_H_  // NOLINT
+
+#include <string>
+
+#include "base/port.h"
+#include "fastmem.h"
+
+namespace dynamic_depth {
+
+// Returns whether str begins with prefix.
+inline bool HasPrefixString(const string& str, const string& prefix) {
+  return str.length() >= prefix.length() &&
+         ::dynamic_depth::strings::memeq(&str[0], &prefix[0], prefix.length());
+}
+
+// Returns whether str ends with suffix.
+inline bool HasSuffixString(const string& str, const string& suffix) {
+  return str.length() >= suffix.length() &&
+         ::dynamic_depth::strings::memeq(
+             &str[0] + (str.length() - suffix.length()), &suffix[0],
+             suffix.length());
+}
+
+}  // namespace dynamic_depth
+
+#endif  // DYNAMIC_DEPTH_INTERNAL_STRINGS_UTIL_H_  // NOLINT