Merge bitcoin/bitcoin#28172: refactor: use string_view for passing string literals to Parse{Hash,Hex}

bb91131 doc: remove out-of-date external link in src/util/strencodings.h (Jon Atack)
7d494a4 refactor: use string_view to pass string literals to Parse{Hash,Hex} (Jon Atack)

Pull request description:

  as `string_view` is optimized to be trivially copiable, whereas the current code creates a `std::string` copy at each call.

  These utility methods are called by quite a few RPCs and tests, as well as by each other.

  ```
  $ git grep "ParseHashV\|ParseHashO\|ParseHexV\|ParseHexO" | wc -l
  61
  ```

  Also remove an out-of-date external link.

ACKs for top commit:
  jonatack:
    Rebased per `git range-diff c9273f6 b94581a bb91131` for an include header from the merge of bitcoin/bitcoin#28230. Should be trivial to re-ACK.
  maflcko:
    lgtm ACK bb91131
  ns-xvrn:
    ACK bitcoin/bitcoin@bb91131
  achow101:
    ACK bb91131
  brunoerg:
    crACK bb91131

Tree-SHA512: 9734fe022c9e43fd93c23a917770d332dbbd3132c80a234059714c32faa6469391e59349954749fc86c4ef0b18d5fd99bf8f4b7b82d9f799943799c1253272ae

Author: achow101

src/rpc/util.cpp

@@ -20,6 +20,7 @@
 #include <util/string.h>
 #include <util/translation.h>
 
+#include <string_view>
 #include <tuple>
 
 const std::string UNIX_EPOCH_TIME = "UNIX epoch time";
@@ -74,29 +75,29 @@ CAmount AmountFromValue(const UniValue& value, int decimals)
     return amount;
 }
 
-uint256 ParseHashV(const UniValue& v, std::string strName)
+uint256 ParseHashV(const UniValue& v, std::string_view name)
 {
     const std::string& strHex(v.get_str());
     if (64 != strHex.length())
-        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("%s must be of length %d (not %d, for '%s')", strName, 64, strHex.length(), strHex));
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("%s must be of length %d (not %d, for '%s')", name, 64, strHex.length(), strHex));
     if (!IsHex(strHex)) // Note: IsHex("") is false
-        throw JSONRPCError(RPC_INVALID_PARAMETER, strName+" must be hexadecimal string (not '"+strHex+"')");
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("%s must be hexadecimal string (not '%s')", name, strHex));
     return uint256S(strHex);
 }
-uint256 ParseHashO(const UniValue& o, std::string strKey)
+uint256 ParseHashO(const UniValue& o, std::string_view strKey)
 {
     return ParseHashV(o.find_value(strKey), strKey);
 }
-std::vector<unsigned char> ParseHexV(const UniValue& v, std::string strName)
+std::vector<unsigned char> ParseHexV(const UniValue& v, std::string_view name)
 {
     std::string strHex;
     if (v.isStr())
         strHex = v.get_str();
     if (!IsHex(strHex))
-        throw JSONRPCError(RPC_INVALID_PARAMETER, strName+" must be hexadecimal string (not '"+strHex+"')");
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("%s must be hexadecimal string (not '%s')", name, strHex));
     return ParseHex(strHex);
 }
-std::vector<unsigned char> ParseHexO(const UniValue& o, std::string strKey)
+std::vector<unsigned char> ParseHexO(const UniValue& o, std::string_view strKey)
 {
     return ParseHexV(o.find_value(strKey), strKey);
 }

src/rpc/util.h

@@ -26,6 +26,7 @@
 #include <map>
 #include <optional>
 #include <string>
+#include <string_view>
 #include <type_traits>
 #include <utility>
 #include <variant>
@@ -91,10 +92,10 @@ void RPCTypeCheckObj(const UniValue& o,
  * Utilities: convert hex-encoded Values
  * (throws error if not hex).
  */
-uint256 ParseHashV(const UniValue& v, std::string strName);
-uint256 ParseHashO(const UniValue& o, std::string strKey);
-std::vector<unsigned char> ParseHexV(const UniValue& v, std::string strName);
-std::vector<unsigned char> ParseHexO(const UniValue& o, std::string strKey);
+uint256 ParseHashV(const UniValue& v, std::string_view name);
+uint256 ParseHashO(const UniValue& o, std::string_view strKey);
+std::vector<unsigned char> ParseHexV(const UniValue& v, std::string_view name);
+std::vector<unsigned char> ParseHexO(const UniValue& o, std::string_view strKey);
 
 /**
  * Validate and return a CAmount from a UniValue number or string.

src/util/strencodings.h

@@ -260,7 +260,6 @@ bool TimingResistantEqual(const T& a, const T& b)
 }
 
 /** Parse number as fixed point according to JSON number syntax.
- * See https://json.org/number.gif
  * @returns true on success, false on error.
  * @note The result must be in the range (-10^18,10^18), otherwise an overflow error will trigger.
  */