Add: helper output iterator for formatting strings
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/*
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* This file is part of OpenTTD.
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* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
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* OpenTTD 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.
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* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
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*/
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/** @file strings_interal.h Types and functions related to the internal workings of formatting OpenTTD's strings. */
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#ifndef STRINGS_INTERNAL_H
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#define STRINGS_INTERNAL_H
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/**
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* Equivalent to the std::back_insert_iterator in function, with some
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* convenience helpers for string concatenation.
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*
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* The formatter is currently backed by an external char buffer, and has some
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* extra functions to ease the migration from char buffers to std::string.
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*/
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class StringBuilder {
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char *current; ///< The current location to add strings
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const char *last; ///< The last element of the buffer.
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public:
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/* Required type for this to be an output_iterator; mimics std::back_insert_iterator. */
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using value_type = void;
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using difference_type = void;
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using iterator_category = std::output_iterator_tag;
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using pointer = void;
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using reference = void;
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/**
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* Create the builder of an external buffer.
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* @param start The start location to write to.
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* @param last The last location to write to.
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*/
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StringBuilder(char *start, const char *last) : current(start), last(last) {}
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/* Required operators for this to be an output_iterator; mimics std::back_insert_iterator, which has no-ops. */
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StringBuilder &operator++() { return *this; }
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StringBuilder operator++(int) { return *this; }
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StringBuilder &operator*() { return *this; }
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/**
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* Operator to add a character to the end of the buffer. Like the back
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* insert iterators this also increases the position of the end of the
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* buffer.
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* @param value The character to add.
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* @return Reference to this inserter.
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*/
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StringBuilder &operator=(const char value)
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{
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return this->operator+=(value);
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}
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/**
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* Operator to add a character to the end of the buffer.
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* @param value The character to add.
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* @return Reference to this inserter.
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*/
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StringBuilder &operator+=(const char value)
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{
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if (this->current != this->last) *this->current++ = value;
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return *this;
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}
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/**
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* Operator to append the given string to the output buffer.
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* @param str The string to add.
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* @return Reference to this inserter.
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*/
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StringBuilder &operator+=(const char *str)
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{
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this->current = strecpy(this->current, str, this->last);
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return *this;
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}
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/**
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* Operator to append the given string to the output buffer.
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* @param str The string to add.
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* @return Reference to this inserter.
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*/
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StringBuilder &operator+=(const std::string &str)
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{
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return this->operator+=(str.c_str());
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}
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/**
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* Encode the given Utf8 character into the output buffer.
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* @param c The character to encode.
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* @return true iff there was enough space and the character got added.
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*/
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bool Utf8Encode(WChar c)
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{
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if (this->Remaining() < Utf8CharLen(c)) return false;
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this->current += ::Utf8Encode(this->current, c);
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return true;
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}
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/**
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* Get the pointer to the this->last written element in the buffer.
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* This call does '\0' terminate the string, whereas other calls do not
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* (necessarily) do this.
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* @return The this->current end of the string.
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*/
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char *GetEnd()
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{
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*this->current = '\0';
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return this->current;
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}
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/**
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* Get the remaining number of characters that can be placed.
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* @return The number of characters.
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*/
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ptrdiff_t Remaining()
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{
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return (ptrdiff_t)(this->last - this->current);
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}
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};
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#endif /* STRINGS_INTERNAL_H */
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