lib: Added simple parser_base module for all hand-parsing related tasks

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>

diff --git a/lib/parser_base.nit b/lib/parser_base.nit
new file mode 100644 (file)
index 0000000..ac002fe
--- /dev/null
+++ b/lib/parser_base.nit
@@ -0,0 +1,94 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# This file is free software, which comes along with NIT.  This software is
+# distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+# without  even  the implied warranty of  MERCHANTABILITY or  FITNESS FOR A
+# PARTICULAR PURPOSE.  You can modify it is you want,  provided this header
+# is kept unaltered, and a notification of the changes is added.
+# You  are  allowed  to  redistribute it and sell it, alone or is a part of
+# another product.
+
+# Simple base for hand-made parsers of all kinds
+module parser_base
+
+# Basic facilities for common parser operations on String sources
+class StringProcessor
+       # Source document to parse
+       private var src: String
+
+       # Current position in `src`
+       private var pos = 0
+
+       # Position at which current line started
+       private var line_start = 0
+
+       # Current line in `src`
+       private var line = 1
+
+       # Offset in the current line
+       private fun line_offset: Int do return pos - line_start + 1
+
+       # Gives the current location in the `src`
+       fun current_location: Location do return new Location(line, line_offset)
+
+       # Advances in `src` until a non-whitespace character is encountered
+       private fun ignore_whitespaces do
+               var srclen = src.length
+               if pos >= srclen then return
+               var c = src[pos]
+               while c.is_whitespace do
+                       pos += 1
+                       if pos >= srclen then break
+                       if c == '\n' then
+                               line += 1
+                               line_start = pos
+                       end
+                       c = src[pos]
+               end
+       end
+
+       # Reads characters until pattern `s` is found
+       private fun ignore_until(s: String): Int do
+               if s.length == 0 then return pos
+               var srclen = src.length
+               if pos >= srclen then return -1
+               loop
+                       var c = s[0]
+                       var src_c = src[pos]
+                       while src_c != c do
+                               pos += 1
+                               if pos >= srclen then return -1
+                               if src_c == '\n' then
+                                       line += 1
+                                       line_start= pos
+                               end
+                               src_c = src[pos]
+                       end
+                       var relpos = pos
+                       var fnd = true
+                       for i in s do
+                               if relpos >= srclen then
+                                       fnd = false
+                                       break
+                               end
+                               if src[relpos] != i then
+                                       pos += 1
+                                       fnd = false
+                                       break
+                               end
+                               relpos += 1
+                       end
+                       if fnd then return pos
+               end
+       end
+end
+
+# Information about the location of an entity in a source document
+class Location
+       # Line in which the element is described
+       var line: Int
+       # Offset in the line at which the element is positioned
+       var offset: Int
+
+       redef fun to_s do return "line {line}, position {offset}"
+end