godot/modules/text_server_adv/script_iterator.cpp

/*************************************************************************/
/*  script_iterator.cpp                                                  */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
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#include "script_iterator.h"

// This implementation is derived from ICU: icu4c/source/extra/scrptrun/scrptrun.cpp

bool ScriptIterator::same_script(int32_t p_script_one, int32_t p_script_two) {
	return p_script_one <= USCRIPT_INHERITED || p_script_two <= USCRIPT_INHERITED || p_script_one == p_script_two;
}

ScriptIterator::ScriptIterator(const String &p_string, int p_start, int p_length) {
	struct ParenStackEntry {
		int pair_index;
		UScriptCode script_code;
	};

	if (p_start >= p_length) {
		p_start = p_length - 1;
	}

	if (p_start < 0) {
		p_start = 0;
	}

	int paren_size = PAREN_STACK_DEPTH;
	ParenStackEntry *paren_stack = static_cast<ParenStackEntry *>(memalloc(paren_size * sizeof(ParenStackEntry)));

	int script_start;
	int script_end = p_start;
	UScriptCode script_code;
	int paren_sp = -1;
	int start_sp = paren_sp;
	UErrorCode err = U_ZERO_ERROR;
	const char32_t *str = p_string.ptr();

	do {
		script_code = USCRIPT_COMMON;
		for (script_start = script_end; script_end < p_length; script_end++) {
			UChar32 ch = str[script_end];
			UScriptCode sc = uscript_getScript(ch, &err);
			if (U_FAILURE(err)) {
				memfree(paren_stack);
				ERR_FAIL_MSG(u_errorName(err));
			}
			if (u_getIntPropertyValue(ch, UCHAR_BIDI_PAIRED_BRACKET_TYPE) != U_BPT_NONE) {
				if (u_getIntPropertyValue(ch, UCHAR_BIDI_PAIRED_BRACKET_TYPE) == U_BPT_OPEN) {
					// If it's an open character, push it onto the stack.
					paren_sp++;
					if (unlikely(paren_sp >= paren_size)) {
						// If the stack is full, allocate more space to handle deeply nested parentheses. This is unlikely to happen with any real text.
						paren_size += PAREN_STACK_DEPTH;
						paren_stack = static_cast<ParenStackEntry *>(memrealloc(paren_stack, paren_size * sizeof(ParenStackEntry)));
					}
					paren_stack[paren_sp].pair_index = ch;
					paren_stack[paren_sp].script_code = script_code;
				} else if (paren_sp >= 0) {
					// If it's a close character, find the matching open on the stack, and use that script code. Any non-matching open characters above it on the stack will be popped.
					UChar32 paired_ch = u_getBidiPairedBracket(ch);
					while (paren_sp >= 0 && paren_stack[paren_sp].pair_index != paired_ch) {
						paren_sp -= 1;
					}
					if (paren_sp < start_sp) {
						start_sp = paren_sp;
					}
					if (paren_sp >= 0) {
						sc = paren_stack[paren_sp].script_code;
					}
				}
			}

			if (same_script(script_code, sc)) {
				if (script_code <= USCRIPT_INHERITED && sc > USCRIPT_INHERITED) {
					script_code = sc;
					// Now that we have a final script code, fix any open characters we pushed before we knew the script code.
					while (start_sp < paren_sp) {
						paren_stack[++start_sp].script_code = script_code;
					}
				}
				if ((u_getIntPropertyValue(ch, UCHAR_BIDI_PAIRED_BRACKET_TYPE) == U_BPT_CLOSE) && paren_sp >= 0) {
					// If this character is a close paired character pop the matching open character from the stack.
					paren_sp -= 1;
					if (start_sp >= 0) {
						start_sp -= 1;
					}
				}
			} else {
				break;
			}
		}

		ScriptRange rng;
		rng.script = hb_icu_script_to_script(script_code);
		rng.start = script_start;
		rng.end = script_end;

		script_ranges.push_back(rng);
	} while (script_end < p_length);

	memfree(paren_stack);
}