--- /dev/null
+#ifndef _STRING_UTIL_H
+#define _STRING_UTIL_H
+
+#include <string.h>
+
+/* like strtok(3), but without state, and doesn't modify s. Return
+ * value is indicated by pointer and length, not null terminator.
+ *
+ * Usage pattern:
+ *
+ * const char *tok = input;
+ * const char *delim = " \t";
+ * size_t tok_len = 0;
+ *
+ * while ((tok = strtok_len (tok + tok_len, delim, &tok_len)) != NULL) {
+ * // do stuff with string tok of length tok_len
+ * }
+ */
+
+char *strtok_len (char *s, const char *delim, size_t *len);
+
+/* Construct a boolean term query with the specified prefix (e.g.,
+ * "id") and search term, quoting term as necessary. Specifically, if
+ * term contains any non-printable ASCII characters, non-ASCII
+ * characters, close parenthesis or double quotes, it will be enclosed
+ * in double quotes and any internal double quotes will be doubled
+ * (e.g. a"b -> "a""b"). The result will be a valid notmuch query and
+ * can be parsed by parse_boolean_term.
+ *
+ * Output is into buf; it may be talloc_realloced.
+ * Return: 0 on success, -1 on error. errno will be set to ENOMEM if
+ * there is an allocation failure.
+ */
+int make_boolean_term (void *talloc_ctx, const char *prefix, const char *term,
+ char **buf, size_t *len);
+
+/* Parse a boolean term query consisting of a prefix, a colon, and a
+ * term that may be quoted as described for make_boolean_term. If the
+ * term is not quoted, then it ends at the first whitespace or close
+ * parenthesis. str may containing leading or trailing whitespace,
+ * but anything else is considered a parse error. This is compatible
+ * with anything produced by make_boolean_term, and supports a subset
+ * of the quoting styles supported by Xapian (and hence notmuch).
+ * *prefix_out and *term_out will be talloc'd with context ctx.
+ *
+ * Return: 0 on success, -1 on error. errno will be set to EINVAL if
+ * there is a parse error or ENOMEM if there is an allocation failure.
+ */
+int
+parse_boolean_term (void *ctx, const char *str,
+ char **prefix_out, char **term_out);
+
+#endif