From 0ae2c768fc8b2e43d271284544af35a27dc2cd17 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 6 Jun 2022 11:27:32 +0200
Subject: Add trim_left() and trim_right() in addition to trim()

Also improve the trim() implementation.
---
 libbutl/utility.cxx | 41 +++++++++++++++++++++++++++++++++++------
 libbutl/utility.hxx | 18 ++++++++++++++++++
 2 files changed, 53 insertions(+), 6 deletions(-)

diff --git a/libbutl/utility.cxx b/libbutl/utility.cxx
index 78abbd8..b03a8f8 100644
--- a/libbutl/utility.cxx
+++ b/libbutl/utility.cxx
@@ -171,13 +171,42 @@ namespace butl
     for (; i != n && ws (l[i]);     ++i) ;
     for (; n != i && ws (l[n - 1]); --n) ;
 
-    if (i != 0)
+    if (n != l.size ()) l.resize (n);
+    if (i != 0)         l.erase (0, i);
+
+    return l;
+  }
+
+  string&
+  trim_left (string& l)
+  {
+    auto ws = [] (char c )
     {
-      string s (l, i, n - i);
-      l.swap (s);
-    }
-    else if (n != l.size ())
-      l.resize (n);
+      return c == ' ' || c == '\t' || c == '\n' || c == '\r';
+    };
+
+    size_t i (0), n (l.size ());
+
+    for (; i != n && ws (l[i]); ++i) ;
+
+    if (i != 0) l.erase (0, i);
+
+    return l;
+  }
+
+  string&
+  trim_right (string& l)
+  {
+    auto ws = [] (char c )
+    {
+      return c == ' ' || c == '\t' || c == '\n' || c == '\r';
+    };
+
+    size_t i (0), n (l.size ());
+
+    for (; n != i && ws (l[n - 1]); --n) ;
+
+    if (n != l.size ()) l.resize (n);
 
     return l;
   }
diff --git a/libbutl/utility.hxx b/libbutl/utility.hxx
index 49b61b3..95a7f78 100644
--- a/libbutl/utility.hxx
+++ b/libbutl/utility.hxx
@@ -146,12 +146,30 @@ namespace butl
   LIBBUTL_SYMEXPORT std::string&
   trim (std::string&);
 
+  LIBBUTL_SYMEXPORT std::string&
+  trim_left (std::string&);
+
+  LIBBUTL_SYMEXPORT std::string&
+  trim_right (std::string&);
+
   inline std::string
   trim (std::string&& s)
   {
     return move (trim (s));
   }
 
+  inline std::string
+  trim_left (std::string&& s)
+  {
+    return move (trim_left (s));
+  }
+
+  inline std::string
+  trim_right (std::string&& s)
+  {
+    return move (trim_right (s));
+  }
+
   // Find the beginning and end poistions of the next word. Return the size
   // of the word or 0 and set b = e = n if there are no more words. For
   // example:
-- 
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