Merge bitcoin/bitcoin#25001: Modernize util/strencodings and util/string: string_view and optional

fa7078d84f scripted-diff: Rename ValidAsCString to ContainsNoNUL (MacroFake)
e7d2fbda63 Use std::string_view throughout util strencodings/string (Pieter Wuille)
8ffbd1412d Make DecodeBase{32,64} take string_view arguments (Pieter Wuille)
1a72d62152 Generalize ConvertBits to permit transforming the input (Pieter Wuille)
78f3ac51b7 Make DecodeBase{32,64} return optional instead of taking bool* (Pieter Wuille)
a65931e3ce Make DecodeBase{32,64} always return vector, not string (Pieter Wuille)
a4377a0843 Reject incorrect base64 in HTTP auth (Pieter Wuille)
d648b5120b Make SanitizeString use string_view (Pieter Wuille)
963bc9b576 Make IsHexNumber use string_view (Pieter Wuille)
40062997f2 Make IsHex use string_view (Pieter Wuille)
c1d165a8c2 Make ParseHex use string_view (Pieter Wuille)

Pull request description:

  Make use of `std::string_view` and `std::optional` in the util/{strencodings, string} files.

  This avoids many temporary string/vector objects being created, while making the interface easier to read. Changes include:
  * Make all input arguments in functions in util/strencodings and util/string take `std::string_view` instead of `std::string`.
  * Add `RemovePrefixView` and `TrimStringView` which also *return* `std::string_view` objects (the corresponding `RemovePrefix` and `TrimString` keep returning an `std::string`, as that's needed in many call sites still).
  * Stop returning `std::string` from `DecodeBase32` and `DecodeBase64`, but return vectors. Base32/64 are fundamentally algorithms for encoding bytes as strings; returning `std::string` from those (especially doing it conditionally based on the input arguments/types) is just bizarre.
  * Stop taking a `bool* pf_invalid` output argument pointer in `DecodeBase32` and `DecodeBase64`; return an `std::optional` instead.
  * Make `DecodeBase32` and `DecodeBase64` more efficient by doing the conversion from characters to integer symbols on-the-fly rather than through a temporary vector.

ACKs for top commit:
  MarcoFalke:
    re-ACK fa7078d84f only change is rebase and adding a scripted-diff 🍲
  martinus:
    Code review ACK fa7078d84f, found no issue
  laanwj:
    Code review ACK  fa7078d84f
  sipa:
    utACK fa7078d84f (as far as the commit that isn't mine goes)

Tree-SHA512: 5cf02e541caef0bcd100466747664bdb828a68a05dae568cbcd0632a53dd3a4c4e85cd8c48ebbd168d4247d5c9666689c16005f1c8ad75b0f057d8683931f664

src/qt/walletframe.cpp

@@ -194,16 +194,16 @@ void WalletFrame::gotoVerifyMessageTab(QString addr)
 
 void WalletFrame::gotoLoadPSBT(bool from_clipboard)
 {
-    std::string data;
+    std::vector<unsigned char> data;
 
     if (from_clipboard) {
         std::string raw = QApplication::clipboard()->text().toStdString();
-        bool invalid;
-        data = DecodeBase64(raw, &invalid);
-        if (invalid) {
+        auto result = DecodeBase64(raw);
+        if (!result) {
             Q_EMIT message(tr("Error"), tr("Unable to decode PSBT from clipboard (invalid base64)"), CClientUIInterface::MSG_ERROR);
             return;
         }
+        data = std::move(*result);
     } else {
         QString filename = GUIUtil::getOpenFileName(this,
             tr("Load Transaction Data"), QString(),
@@ -214,12 +214,12 @@ void WalletFrame::gotoLoadPSBT(bool from_clipboard)
             return;
         }
         std::ifstream in{filename.toLocal8Bit().data(), std::ios::binary};
-        data = std::string(std::istreambuf_iterator<char>{in}, {});
+        data.assign(std::istream_iterator<unsigned char>{in}, {});
     }
 
     std::string error;
     PartiallySignedTransaction psbtx;
-    if (!DecodeRawPSBT(psbtx, data, error)) {
+    if (!DecodeRawPSBT(psbtx, MakeByteSpan(data), error)) {
         Q_EMIT message(tr("Error"), tr("Unable to decode PSBT") + "\n" + QString::fromStdString(error), CClientUIInterface::MSG_ERROR);
         return;
     }