Add iterators to rexy::string_base

include/rexy/string_base.hpp

@@ -24,6 +24,7 @@
 #include <cstddef> //size_t,ptrdiff
 #include <cstring> //strlen
 #include <climits> //CHAR_BIT
+#include <iterator> //reverse_iterator
 
 #include "steal.hpp"
 #include "cx/utility.hpp"
@@ -48,14 +49,17 @@ namespace rexy{
 		using const_reference = const value_type&;
 		using iterator = pointer;
 		using const_iterator = const_pointer;
+		using reverse_iterator = std::reverse_iterator<iterator>;
+		using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
 	private:
 		static constexpr size_type EXTRA_SDATA_LEN = 0;
 
+		//represent long string
 		struct ldata{
-			unsigned char islong:1;
+			unsigned char islong:1; //common subsequence with short string
-			size_type capacity:(CHAR_BIT*sizeof(size_type)-1);
+			size_type capacity:(CHAR_BIT*sizeof(size_type)-1); //take away last bit from capacity for islong
-			size_type length;
+			size_type length; //length of string excluding null terminator
 			constexpr ldata(void)noexcept:
 				islong(0),
 				capacity(0),
@@ -63,25 +67,31 @@ namespace rexy{
 		};
 
 		static constexpr size_type MAX_SHORT_LEN = EXTRA_SDATA_LEN+sizeof(ldata)-2;
+		//represent short string
 		struct sdata{
-			unsigned char islong:1;
+			unsigned char islong:1; //common subsequenci with long string
-			unsigned char length:(CHAR_BIT-1);
+			unsigned char length:(CHAR_BIT-1); //take away last bit from length for islong, excludes null terminator
-			value_type data[MAX_SHORT_LEN+1];
+			value_type data[MAX_SHORT_LEN+1]; //char array for string storage
 			constexpr sdata(void)noexcept:
 				islong(0),
 				length(0),
 				data{}{}
 		};
+		//union of short and long string representations. Default to long representation for static_string's use case.
 		union combine_data{
 			ldata l;
 			sdata s;
 			constexpr combine_data(void)noexcept:
 				l(){}
 		}m_data;
+
+		//direct access to current string data regardless of representation. Increases access speed.
 		pointer m_raw = m_data.s.data;
 
 	protected:
+		//Functions for handling long vs short string manipulation. Use this instead of directly modifying m_data.
 		constexpr void set_islong_flag(bool b){
+			//although well defined to set either one at any time, constexpr functions cannot change active union member.
 			if(b)
 				m_data.l.islong = b;
 			else
@@ -187,9 +197,6 @@ namespace rexy{
 		//true if m_data is not empty
 		constexpr bool valid(void)const noexcept{return length() > 0;}
 
-		constexpr int compare(const string_base& s)const{return cx::strcmp(get(), s.get());}
-		constexpr int compare(const_pointer s)const{return cx::strcmp(get(), s);}
-
 		constexpr reference operator[](size_type i)noexcept{return get_pointer()[i];}
 		constexpr const_reference operator[](size_type i)const noexcept{return get_pointer()[i];}
 
@@ -198,6 +205,20 @@ namespace rexy{
 		constexpr bool compare(const string_base& s)const{return *this == s;}
 		constexpr bool compare(const_pointer c)const{return *this == c;}
 
+		constexpr iterator begin(void){return get_pointer();}
+		constexpr const_iterator begin(void)const{return get_pointer();}
+		constexpr iterator end(void){return get_pointer()+length();}
+		constexpr const_iterator end(void)const{return get_pointer()+length();}
+		constexpr const_iterator cbegin(void)const{return begin();}
+		constexpr const_iterator cend(void)const{return end();}
+
+		constexpr reverse_iterator rbegin(void){return reverse_iterator(get_pointer()+length());}
+		constexpr const_reverse_iterator rbegin(void)const{return const_reverse_iterator(get_pointer()+length());}
+		constexpr reverse_iterator rend(void){return reverse_iterator(get_pointer()-1);}
+		constexpr const_reverse_iterator rend(void)const{return const_reverse_iterator(get_pointer()-1);}
+		constexpr const_reverse_iterator crbegin(void)const{return rbegin();}
+		constexpr const_reverse_iterator crend(void)const{return rend();}
+
 		static constexpr bool uses_sso(void){return true;}
 		static constexpr size_type short_string_size(void){return MAX_SHORT_LEN;}
 	};