From 491594ef0f56dcafd9a1aaba7b66ec23c9f18af4 Mon Sep 17 00:00:00 2001
From: lawnjelly <lawnjelly@gmail.com>
Date: Mon, 12 Dec 2022 15:14:39 +0000
Subject: [PATCH] VariantParser make readahead optional

It turns out some areas are independently moving / reading filepointers outside of the VariantParser, which can cause the readahead caching to get out of sync.

This PR makes the VariantParser readahead to be optional to allow for these use cases.
---
 core/variant/variant_parser.cpp          | 17 ++++++++++++++++-
 core/variant/variant_parser.h            | 10 +++++++---
 scene/resources/resource_format_text.cpp |  3 ++-
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/core/variant/variant_parser.cpp b/core/variant/variant_parser.cpp
index 9f500dbf5e1f..f122ed5f8f81 100644
--- a/core/variant/variant_parser.cpp
+++ b/core/variant/variant_parser.cpp
@@ -42,7 +42,7 @@ char32_t VariantParser::Stream::get_char() {
 	}
 
 	// attempt to readahead
-	readahead_filled = _read_buffer(readahead_buffer, READAHEAD_SIZE);
+	readahead_filled = _read_buffer(readahead_buffer, readahead_enabled ? READAHEAD_SIZE : 1);
 	if (readahead_filled) {
 		readahead_pointer = 0;
 	} else {
@@ -54,10 +54,21 @@ char32_t VariantParser::Stream::get_char() {
 	return get_char();
 }
 
+bool VariantParser::Stream::is_eof() const {
+	if (readahead_enabled) {
+		return eof;
+	}
+	return _is_eof();
+}
+
 bool VariantParser::StreamFile::is_utf8() const {
 	return true;
 }
 
+bool VariantParser::StreamFile::_is_eof() const {
+	return f->eof_reached();
+}
+
 uint32_t VariantParser::StreamFile::_read_buffer(char32_t *p_buffer, uint32_t p_num_chars) {
 	// The buffer is assumed to include at least one character (for null terminator)
 	ERR_FAIL_COND_V(!p_num_chars, 0);
@@ -79,6 +90,10 @@ bool VariantParser::StreamString::is_utf8() const {
 	return false;
 }
 
+bool VariantParser::StreamString::_is_eof() const {
+	return pos > s.length();
+}
+
 uint32_t VariantParser::StreamString::_read_buffer(char32_t *p_buffer, uint32_t p_num_chars) {
 	// The buffer is assumed to include at least one character (for null terminator)
 	ERR_FAIL_COND_V(!p_num_chars, 0);
diff --git a/core/variant/variant_parser.h b/core/variant/variant_parser.h
index 6b1d095ab562..fdea355c4b16 100644
--- a/core/variant/variant_parser.h
+++ b/core/variant/variant_parser.h
@@ -46,14 +46,16 @@ public:
 		bool eof = false;
 
 	protected:
+		bool readahead_enabled = true;
 		virtual uint32_t _read_buffer(char32_t *p_buffer, uint32_t p_num_chars) = 0;
+		virtual bool _is_eof() const = 0;
 
 	public:
 		char32_t saved = 0;
 
 		char32_t get_char();
 		virtual bool is_utf8() const = 0;
-		bool is_eof() const { return eof; }
+		bool is_eof() const;
 
 		Stream() {}
 		virtual ~Stream() {}
@@ -62,13 +64,14 @@ public:
 	struct StreamFile : public Stream {
 	protected:
 		virtual uint32_t _read_buffer(char32_t *p_buffer, uint32_t p_num_chars) override;
+		virtual bool _is_eof() const override;
 
 	public:
 		Ref<FileAccess> f;
 
 		virtual bool is_utf8() const override;
 
-		StreamFile() {}
+		StreamFile(bool p_readahead_enabled = true) { readahead_enabled = p_readahead_enabled; }
 	};
 
 	struct StreamString : public Stream {
@@ -79,10 +82,11 @@ public:
 
 	protected:
 		virtual uint32_t _read_buffer(char32_t *p_buffer, uint32_t p_num_chars) override;
+		virtual bool _is_eof() const override;
 
 	public:
 		virtual bool is_utf8() const override;
-		StreamString() {}
+		StreamString(bool p_readahead_enabled = true) { readahead_enabled = p_readahead_enabled; }
 	};
 
 	typedef Error (*ParseResourceFunc)(void *p_self, Stream *p_stream, Ref<Resource> &r_res, int &line, String &r_err_str);
diff --git a/scene/resources/resource_format_text.cpp b/scene/resources/resource_format_text.cpp
index 36e4a8ea37f1..e871ca007ca5 100644
--- a/scene/resources/resource_format_text.cpp
+++ b/scene/resources/resource_format_text.cpp
@@ -836,7 +836,8 @@ void ResourceLoaderText::set_translation_remapped(bool p_remapped) {
 	translation_remapped = p_remapped;
 }
 
-ResourceLoaderText::ResourceLoaderText() {}
+ResourceLoaderText::ResourceLoaderText() :
+		stream(false) {}
 
 void ResourceLoaderText::get_dependencies(Ref<FileAccess> p_f, List<String> *p_dependencies, bool p_add_types) {
 	open(p_f);