[review v4] Add a string_view version of startswith

[Tom Tromey (Code Review)]

The original change was created by Christian Biesinger.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/126
......................................................................

Add a string_view version of startswith

Makes sure that the string is longer than prefix, so that strncmp will
do the right thing even if the string is not null-terminated.

For use in my string_view conversion patch:
https://sourceware.org/ml/gdb-patches/2019-10/msg00030.html

gdb/ChangeLog:

2019-10-01  Christian Biesinger  <cbiesinger@google.com>

	* gdbsupport/common-utils.h (startswith): Add an overloaded version
	that takes gdb::string_view arguments.

Change-Id: I5389855de2fd70e7065a789a79374b0693651b71
---
M gdb/gdbsupport/common-utils.h
1 file changed, 12 insertions(+), 0 deletions(-)



diff --git a/gdb/gdbsupport/common-utils.h b/gdb/gdbsupport/common-utils.h
index e96fc21..23bf354 100644
--- a/gdb/gdbsupport/common-utils.h
+++ b/gdb/gdbsupport/common-utils.h
@@ -43,6 +43,8 @@
 #endif
 #endif
 
+#include "gdb_string_view.h"
+
 /* xmalloc(), xrealloc() and xcalloc() have already been declared in
    "libiberty.h". */
 
@@ -118,6 +120,16 @@
   return strncmp (string, pattern, strlen (pattern)) == 0;
 }
 
+/* Version of startswith that takes string_view arguments.  See comment
+   above.  */
+
+static inline bool
+startswith (gdb::string_view string, gdb::string_view pattern)
+{
+  return (string.length () >= pattern.length ()
+	  && strncmp (string.data (), pattern.data (), pattern.length ()) == 0);
+}
+
 ULONGEST strtoulst (const char *num, const char **trailer, int base);
 
 /* Skip leading whitespace characters in INP, returning an updated

-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I5389855de2fd70e7065a789a79374b0693651b71
Gerrit-Change-Number: 126
Gerrit-PatchSet: 4
Gerrit-Owner: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Tom Tromey <tromey@sourceware.org>
Gerrit-CC: Simon Marchi <simon.marchi@polymtl.ca>
Gerrit-MessageType: newpatchset