From 7f408c11de9e2cb4ef09070f17a4f5ff19b96195 Mon Sep 17 00:00:00 2001
From: boolean-false <booleanfalser@gmail.com>
Date: Sun, 20 Sep 2026 18:55:59 +0700
Subject: [PATCH] =?UTF-8?q?=D0=9F=D0=B5=D1=80=D0=B5=D0=B2=D0=B5=D0=BB=20pa?=
 =?UTF-8?q?rse=5Fdouble=20=D0=BD=D0=B0=20from=5Fchars?=
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---
 src/util/stringutil.cpp  | 41 +++++++++++++++++++++++-----------------
 test/util/stringutil.cpp |  8 ++++++++
 2 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/src/util/stringutil.cpp b/src/util/stringutil.cpp
index 8d80a82ab..a2743a8ba 100644
--- a/src/util/stringutil.cpp
+++ b/src/util/stringutil.cpp
@@ -1,9 +1,11 @@
-#include "stringutil.hpp"
-
-#include <algorithm>
-#include <cmath>
-#include <iomanip>
-#include <locale>
+#include "stringutil.hpp"
+
+#include <algorithm>
+#include <charconv>
+#include <cctype>
+#include <cmath>
+#include <iomanip>
+#include <locale>
 #include <sstream>
 #include <stdexcept>
 
@@ -509,17 +511,22 @@ int util::replaceAll(
     return replace_all(str, from, to);
 }
 
-// replace it with std::from_chars in the far far future
-double util::parse_double(const std::string& str) {
-    std::istringstream ss(str);
-    ss.imbue(std::locale("C"));
-    double d;
-    ss >> d;
-    if (ss.fail()) {
-        throw std::runtime_error("invalid number format");
-    }
-    return d;
-}
+double util::parse_double(const std::string& str) {
+    const char* begin = str.data();
+    const char* end = begin + str.size();
+    while (begin != end && std::isspace(static_cast<unsigned char>(*begin))) {
+        begin++;
+    }
+    if (begin != end && *begin == '+') {
+        begin++;
+    }
+    double d = 0.0;
+    const auto result = std::from_chars(begin, end, d);
+    if (result.ec != std::errc()) {
+        throw std::runtime_error("invalid number format");
+    }
+    return d;
+}
 
 double util::parse_double(const std::string& str, size_t offset, size_t len) {
     return parse_double(str.substr(offset, len));
diff --git a/test/util/stringutil.cpp b/test/util/stringutil.cpp
index a057d4e69..88915c58d 100644
--- a/test/util/stringutil.cpp
+++ b/test/util/stringutil.cpp
@@ -68,6 +68,14 @@ TEST(stringutil, base64_urlsafe) {
     }
 }
 
+TEST(stringutil, parse_double) {
+    EXPECT_DOUBLE_EQ(util::parse_double("53.125"), 53.125);
+    EXPECT_DOUBLE_EQ(util::parse_double("-0.25"), -0.25);
+    EXPECT_DOUBLE_EQ(util::parse_double("  +12.5"), 12.5);
+    EXPECT_DOUBLE_EQ(util::parse_double("xx1.75yy", 2, 4), 1.75);
+    EXPECT_THROW(util::parse_double("not-a-number"), std::runtime_error);
+}
+
 class StringParser : BasicParser<char> {
 public:
     StringParser(std::string_view source) : BasicParser("<string>", source) {}