From c6c7498562a47d80ebcbabba3e714ee37d2ca9c0 Mon Sep 17 00:00:00 2001
From: Simon Rozman <simon@rozman.si>
Date: Thu, 25 Apr 2024 12:41:08 +0200
Subject: [PATCH] mapping: add dst2src and src2dst

Signed-off-by: Simon Rozman <simon@rozman.si>
---
 include/stdex/mapping.hpp | 165 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 165 insertions(+)

diff --git a/include/stdex/mapping.hpp b/include/stdex/mapping.hpp
index 048f17c65..6f13cfca7 100644
--- a/include/stdex/mapping.hpp
+++ b/include/stdex/mapping.hpp
@@ -6,6 +6,7 @@
 #pragma once
 
 #include "compat.hpp"
+#include <algorithm>
 #include <vector>
 
 namespace stdex
@@ -71,4 +72,168 @@ namespace stdex
 
 	template <class T, class AX = std::allocator<mapping<T>>>
 	using mapping_vector = std::vector<mapping<T>, AX>;
+
+	///
+	/// Transforms destination index to source index
+	///
+	/// \param[in] mapping  Ordered vector of source to destination mappings
+	/// \param[in] to       Index in destination string
+	///
+	/// \returns Index in source string
+	///
+	template <class T, class AX = std::allocator<mapping<T>>>
+	T dst2src(_In_ const std::vector<stdex::mapping<T>, AX>& mapping, _In_ T to)
+	{
+		if (mapping.empty())
+			return to;
+
+		for (size_t l = 0, r = mapping.size();;) {
+			if (l < r) {
+				auto m = (l + r) / 2;
+				const auto& el = mapping[m];
+				if (to < el.to) r = m;
+				else if (el.to < to) l = m + 1;
+				else return el.from;
+			}
+			else if (l) {
+				const auto& el = mapping[l - 1];
+				return el.from + (to - el.to);
+			}
+			else {
+				const auto& el = mapping[0];
+				return std::min<T>(to, el.from);
+			}
+		}
+	}
+
+	///
+	/// Transforms destination index to source index
+	///
+	/// \param[in]     mapping  Ordered vector of source to destination mappings
+	/// \param[in]     to       Index in destination string
+	/// \param[in,out] m        Hint to speed-up bisection when calling this function in a loop and successive destination string indexes are in vicinity. Initialize to 0.
+	///
+	/// \returns Index in source string
+	///
+	template <class T, class AX = std::allocator<mapping<T>>>
+	T dst2src(_In_ const std::vector<stdex::mapping<T>, AX>& mapping, _In_ T to, _Inout_opt_ size_t& m)
+	{
+		if (mapping.empty())
+			return to;
+
+		size_t l, r;
+		const auto& el = mapping[m];
+		if (to < el.to) {
+			l = 0;
+			r = m;
+		}
+		else if (el.to < to) {
+			if (mapping.size() - 1 <= m || to < mapping[m + 1].to)
+				return el.from + (to - el.to);
+			l = m + 1;
+			r = mapping.size();
+		}
+		else
+			return el.from;
+
+		for (;;) {
+			if (l < r) {
+				m = (l + r) / 2;
+				const auto& el = mapping[m];
+				if (to < el.to) r = m;
+				else if (el.to < to) l = m + 1;
+				else return el.from;
+			}
+			else if (l) {
+				const auto& el = mapping[m = l - 1];
+				return el.from + (to - el.to);
+			}
+			else {
+				const auto& el = mapping[m = 0];
+				return std::min<T>(to, el.from);
+			}
+		}
+	}
+
+	///
+	/// Transforms source index to destination index
+	///
+	/// \param[in] mapping  Ordered vector of source to destination mappings
+	/// \param[in] from     Index in source string
+	///
+	/// \returns Index in destination string
+	///
+	template <class T, class AX = std::allocator<mapping<T>>>
+	T src2dst(_In_ const std::vector<stdex::mapping<T>, AX>& mapping, _In_ T from)
+	{
+		if (mapping.empty())
+			return from;
+
+		for (size_t l = 0, r = mapping.size();;) {
+			if (l < r) {
+				auto m = (l + r) / 2;
+				const auto& el = mapping[m];
+				if (from < el.from) r = m;
+				else if (el.from < from) l = m + 1;
+				else return el.to;
+			}
+			else if (l) {
+				const auto& el = mapping[l - 1];
+				return el.to + (from - el.from);
+			}
+			else {
+				const auto& el = mapping[0];
+				return std::min<T>(from, el.to);
+			}
+		}
+	}
+
+	///
+	/// Transforms source index to destination index
+	///
+	/// \param[in]     mapping  Ordered vector of source to destination mappings
+	/// \param[in]     from     Index in source string
+	/// \param[in,out] m        Hint to speed-up bisection when calling this function in a loop and successive source string indexes are in vicinity. Initialize to 0.
+	///
+	/// \returns Index in destination string
+	///
+	template <class T, class AX = std::allocator<mapping<T>>>
+	T src2dst(_In_ const std::vector<stdex::mapping<T>, AX>& mapping, _In_ T from, _Inout_opt_ size_t& m)
+	{
+		if (mapping.empty())
+			return from;
+
+		size_t l, r;
+		const auto& el = mapping[m];
+		if (from < el.from) {
+			l = 0;
+			r = m;
+		}
+		else if (el.from < from) {
+			if (mapping.size() - 1 <= m || from < mapping[m + 1].from)
+				return el.to + (from - el.from);
+			l = m + 1;
+			r = mapping.size();
+		}
+		else
+			return el.to;
+
+		for (;;) {
+			if (l < r) {
+				m = (l + r) / 2;
+				const auto& el = mapping[m];
+				if (from < el.from) r = m;
+				else if (el.from < from) l = m + 1;
+				else return el.to;
+			}
+			else if (l) {
+				const auto& el = mapping[m = l - 1];
+				return el.to + (from - el.from);
+			}
+			else {
+				const auto& el = mapping[m = 0];
+				return std::min<T>(from, el.to);
+			}
+		}
+	}
 }