From: Ben Pfaff <blp@cs.stanford.edu>
Date: Mon, 26 Nov 2018 00:41:44 +0000 (-0800)
Subject: str: New functions ss_starts_with() and ss_find_substring().
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?p=pspp;a=commitdiff_plain;h=c1a772dd16c825866b0b1b4cfa5c1ba57a9fa48f

str: New functions ss_starts_with() and ss_find_substring().

These will have their first users in an upcoming commit.
---

diff --git a/src/libpspp/str.c b/src/libpspp/str.c
index 5aa7e41594..f31677b929 100644
--- a/src/libpspp/str.c
+++ b/src/libpspp/str.c
@@ -691,6 +691,14 @@ ss_last (struct substring ss)
   return ss.length > 0 ? (unsigned char) ss.string[ss.length - 1] : EOF;
 }
 
+/* Returns true if SS starts with PREFIX, false otherwise. */
+bool
+ss_starts_with (struct substring ss, struct substring prefix)
+{
+  return (ss.length >= prefix.length
+          && !memcmp (ss.string, prefix.string, prefix.length));
+}
+
 /* Returns true if SS ends with SUFFIX, false otherwise. */
 bool
 ss_ends_with (struct substring ss, struct substring suffix)
@@ -733,6 +741,16 @@ ss_find_byte (struct substring ss, char c)
   return p != NULL ? p - ss.string : SIZE_MAX;
 }
 
+/* Returns the offset in HAYSTACK of the first instance of NEEDLE,
+   or SIZE_MAX if NEEDLE does not occur in HAYSTACK. */
+size_t
+ss_find_substring (struct substring haystack, struct substring needle)
+{
+  const char *p = memmem (haystack.string, haystack.length,
+                          needle.string, needle.length);
+  return p != NULL ? p - haystack.string : SIZE_MAX;
+}
+
 /* Compares A and B and returns a strcmp()-type comparison
    result. */
 int
diff --git a/src/libpspp/str.h b/src/libpspp/str.h
index dd41ede819..66552a3964 100644
--- a/src/libpspp/str.h
+++ b/src/libpspp/str.h
@@ -122,10 +122,12 @@ char *ss_end (struct substring);
 int ss_at (struct substring, size_t idx);
 int ss_first (struct substring);
 int ss_last (struct substring);
+bool ss_starts_with (struct substring, struct substring prefix);
 bool ss_ends_with (struct substring, struct substring suffix);
 size_t ss_span (struct substring, struct substring skip_set);
 size_t ss_cspan (struct substring, struct substring stop_set);
 size_t ss_find_byte (struct substring, char);
+size_t ss_find_substring (struct substring, struct substring);
 int ss_compare (struct substring, struct substring);
 int ss_compare_case (struct substring, struct substring);
 int ss_equals (struct substring, struct substring);