util: add ParseUInt16(), use it in SplitHostPort()

src/util/strencodings.cpp

@@ -115,8 +115,8 @@ void SplitHostPort(std::string in, uint16_t& portOut, std::string& hostOut)
     bool fBracketed = fHaveColon && (in[0]=='[' && in[colon-1]==']'); // if there is a colon, and in[0]=='[', colon is not 0, so in[colon-1] is safe
     bool fMultiColon = fHaveColon && (in.find_last_of(':',colon-1) != in.npos);
     if (fHaveColon && (colon==0 || fBracketed || !fMultiColon)) {
-        int32_t n;
-        if (ParseInt32(in.substr(colon + 1), &n) && n > 0 && n < 0x10000) {
+        uint16_t n;
+        if (ParseUInt16(in.substr(colon + 1), &n)) {
             in = in.substr(0, colon);
             portOut = n;
         }
@@ -335,6 +335,18 @@ bool ParseUInt8(const std::string& str, uint8_t *out)
     return true;
 }
 
+bool ParseUInt16(const std::string& str, uint16_t* out)
+{
+    uint32_t u32;
+    if (!ParseUInt32(str, &u32) || u32 > std::numeric_limits<uint16_t>::max()) {
+        return false;
+    }
+    if (out != nullptr) {
+        *out = static_cast<uint16_t>(u32);
+    }
+    return true;
+}
+
 bool ParseUInt32(const std::string& str, uint32_t *out)
 {
     if (!ParsePrechecks(str))

src/util/strencodings.h

@@ -115,6 +115,13 @@ constexpr inline bool IsSpace(char c) noexcept {
  */
 [[nodiscard]] bool ParseUInt8(const std::string& str, uint8_t *out);
 
+/**
+ * Convert decimal string to unsigned 16-bit integer with strict parse error feedback.
+ * @returns true if the entire string could be parsed as valid integer,
+ *   false if the entire string could not be parsed or if overflow or underflow occurred.
+ */
+[[nodiscard]] bool ParseUInt16(const std::string& str, uint16_t* out);
+
 /**
  * Convert decimal string to unsigned 32-bit integer with strict parse error feedback.
  * @returns true if the entire string could be parsed as valid integer,