util-math: Add SizeFromString method

Converts a String to an std::pair of int64_t (long long), which contain the size or 0 if none could be parsed. Any delimiter except digits(0-9), a minus sign(-) or a plus sign(+) between width and height are allowed. If a plus or minus sign is used as a delimiter, it must immediately be followed by the second size number. This allows for formats such as: 100x100, 100:100, 100p100, 100@100, 100+100 and so on, but not formats such as 100+:100, 100ThisIsSomeReall+yLongText100, etc.

The parameter 'allowSquare' also determines what to do when the height parameter is not found. A value of true will have the function return <width,width> instead of <width,0>.

source/util-math.cpp

@@ -20,8 +20,10 @@
 #include "util-math.h"
 #include "util-memory.h"
 #include <malloc.h>
+#include <stdlib.h>
+#include <cctype>
 
-void* util::vec3a::operator new(size_t count){
+void* util::vec3a::operator new(size_t count) {
 	return _aligned_malloc(count, 16);
 }
 
@@ -37,7 +39,7 @@ void util::vec3a::operator delete[](void* p) {
 	_aligned_free(p);
 }
 
-void* util::vec4a::operator new(size_t count){
+void* util::vec4a::operator new(size_t count) {
 	return _aligned_malloc(count, 16);
 }
 
@@ -52,3 +54,42 @@ void util::vec4a::operator delete(void* p) {
 void util::vec4a::operator delete[](void* p) {
 	_aligned_free(p);
 }
+
+std::pair<int64_t, int64_t> util::SizeFromString(std::string text, bool allowSquare) {
+	int64_t width, height;
+
+	const char* begin = text.c_str();
+	const char* end = text.c_str() + text.size() + 1;
+	char* here = const_cast<char*>(end);
+
+	long long res = strtoll(begin, &here, 0);
+	if (errno == ERANGE) {
+		return { 0, 0 };
+	}
+	width = res;
+
+	while (here != end) {
+		if (isdigit(*here) || (*here == '-') || (*here == '+')) {
+			break;
+		}
+		here++;
+	}
+	if (here == end) {
+		// Are we allowed to return a square?
+		if (allowSquare) {
+			// Yes: Return width,width.
+			return { width, width };
+		} else {
+			// No: Return width,0.
+			return { width, 0 };
+		}
+	}
+
+	res = strtoll(here, nullptr, 0);
+	if (errno == ERANGE) {
+		return { width, 0 };
+	}
+	height = res;
+
+	return { width, height };
+}

source/util-math.h

@@ -20,6 +20,8 @@
 #pragma once
 #include <math.h>
 #include <inttypes.h>
+#include <utility>
+#include <string>
 
 // OBS
 #include <libobs/graphics/vec2.h>
@@ -60,4 +62,6 @@ namespace util {
 		static void vec4a::operator delete(void* p);
 		static void vec4a::operator delete[](void* p);
 	};
+
+	std::pair<int64_t, int64_t> SizeFromString(std::string text, bool allowSquare = true);
 }