From 33e0c9fce238d334f160ee9dbaa29dea5a412718 Mon Sep 17 00:00:00 2001
From: Lucas Bajolet <r4pass@hotmail.com>
Date: Thu, 27 Aug 2015 14:09:33 -0400
Subject: [PATCH] lib/standard/text: Added methods for bytes to char position
 translation

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
---
 lib/standard/text/flat.nit   |   37 +++++++++++++++++++++++++++++++++++++
 lib/standard/text/native.nit |   23 +++++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/lib/standard/text/flat.nit b/lib/standard/text/flat.nit
index 917b0e5..75cf729 100644
--- a/lib/standard/text/flat.nit
+++ b/lib/standard/text/flat.nit
@@ -84,6 +84,43 @@ redef class FlatText
 		return ns_i
 	end
 
+	private fun byte_to_char_index(index: Int): Int do
+		var ln = bytelen
+		assert index >= 0
+		assert index < bytelen
+
+		# Find best insertion point
+		var delta_begin = index
+		var delta_end = (ln - 1) - index
+		var delta_cache = (bytepos - index).abs
+		var min = delta_begin
+		var its = items
+
+		if delta_cache < min then min = delta_cache
+		if delta_end < min then min = delta_end
+
+		var ns_i: Int
+		var my_i: Int
+
+		if min == delta_begin then
+			ns_i = first_byte
+			my_i = 0
+		else if min == delta_cache then
+			ns_i = bytepos
+			my_i = position
+		else
+			ns_i = its.find_beginning_of_char_at(last_byte)
+			my_i = length - 1
+		end
+
+		my_i = its.byte_to_char_index_cached(index, my_i, ns_i)
+
+		position = my_i
+		bytepos = index
+
+		return my_i
+	end
+
 	redef fun [](index) do return items.char_at(char_to_byte_index(index))
 end
 
diff --git a/lib/standard/text/native.nit b/lib/standard/text/native.nit
index 170b196..11c8d34 100644
--- a/lib/standard/text/native.nit
+++ b/lib/standard/text/native.nit
@@ -130,6 +130,29 @@ extern class NativeString `{ char* `}
 		return ns_i
 	end
 
+	# Gets the byte index of char at position `n` in UTF-8 String
+	#
+	# `char_from` and `byte_from` are cached values to seek from.
+	#
+	# NOTE: char_from and byte_from are not guaranteed to be valid cache values
+	# It it up to the client to ensure the validity of the information
+	fun byte_to_char_index_cached(n, char_from, byte_from: Int): Int do
+		var ns_i = byte_from
+		var my_i = char_from
+
+		while ns_i < n do
+			ns_i += length_of_char_at(ns_i)
+			my_i += 1
+		end
+
+		while ns_i > n do
+			ns_i = find_beginning_of_char_at(ns_i - 1)
+			my_i -= 1
+		end
+
+		return my_i
+	end
+
 	# Returns the beginning position of the char at position `pos`
 	#
 	# If the char is invalid UTF-8, `pos` is returned as-is
-- 
1.7.9.5