Merge bitcoin/bitcoin#23756: refactor: Fix implicit integer sign changes in strencodings

fa5865a9e339e7fe4068fbcce2ac055ed49eddfd Reduce size of strencodings decode tables (MarcoFalke)
fad6761cf7875c7e91fd76398a71a9f9c6b3ea82 Fix implicit integer sign changes in strencodings (MarcoFalke)

Pull request description:

  This removes casts where they are nonsensical (ToUpper/ToLower) and adds them where needed. Then, remove the suppressions.

  Also, reduce static memory usage.

ACKs for top commit:
  shaavan:
    crACK fa5865a9e339e7fe4068fbcce2ac055ed49eddfd

Tree-SHA512: 29850fb616789befad17f71731f322b2238e94ec431cda293629de540f7ab02060a9fc5b7666168ca2592048df5a39a2975177f47771d4d8211d90321052549d

2 files changed, 8 insertions, 10 deletions

diff --git a/src/util/strencodings.cpp b/src/util/strencodings.cpp
index 430f1963ea..f4768d5bb6 100644
--- a/src/util/strencodings.cpp
+++ b/src/util/strencodings.cpp
@@ -92,7 +92,7 @@ std::vector<unsigned char> ParseHex(const char* psz)
         signed char c = HexDigit(*psz++);
         if (c == (signed char)-1)
             break;
-        unsigned char n = (c << 4);
+        auto n{uint8_t(c << 4)};
         c = HexDigit(*psz++);
         if (c == (signed char)-1)
             break;
@@ -141,8 +141,7 @@ std::string EncodeBase64(Span<const unsigned char> input)
 
 std::vector<unsigned char> DecodeBase64(const char* p, bool* pf_invalid)
 {
-    static const int decode64_table[256] =
-    {
+    static const int8_t decode64_table[256]{
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
         -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
@@ -164,7 +163,7 @@ std::vector<unsigned char> DecodeBase64(const char* p, bool* pf_invalid)
     while (*p != 0) {
         int x = decode64_table[(unsigned char)*p];
         if (x == -1) break;
-        val.push_back(x);
+        val.push_back(uint8_t(x));
         ++p;
     }
 
@@ -220,8 +219,7 @@ std::string EncodeBase32(const std::string& str, bool pad)
 
 std::vector<unsigned char> DecodeBase32(const char* p, bool* pf_invalid)
 {
-    static const int decode32_table[256] =
-    {
+    static const int8_t decode32_table[256]{
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1,
@@ -243,7 +241,7 @@ std::vector<unsigned char> DecodeBase32(const char* p, bool* pf_invalid)
     while (*p != 0) {
         int x = decode32_table[(unsigned char)*p];
         if (x == -1) break;
-        val.push_back(x);
+        val.push_back(uint8_t(x));
         ++p;
     }
 
@@ -491,14 +489,14 @@ bool ParseFixedPoint(const std::string &val, int decimals, int64_t *amount_out)
 std::string ToLower(const std::string& str)
 {
     std::string r;
-    for (auto ch : str) r += ToLower((unsigned char)ch);
+    for (auto ch : str) r += ToLower(ch);
     return r;
 }
 
 std::string ToUpper(const std::string& str)
 {
     std::string r;
-    for (auto ch : str) r += ToUpper((unsigned char)ch);
+    for (auto ch : str) r += ToUpper(ch);
     return r;
 }
 
diff --git a/src/util/strencodings.h b/src/util/strencodings.h
index 08a5465de1..5813e8d212 100644
--- a/src/util/strencodings.h
+++ b/src/util/strencodings.h
@@ -226,7 +226,7 @@ bool TimingResistantEqual(const T& a, const T& b)
     if (b.size() == 0) return a.size() == 0;
     size_t accumulator = a.size() ^ b.size();
     for (size_t i = 0; i < a.size(); i++)
-        accumulator |= a[i] ^ b[i%b.size()];
+        accumulator |= size_t(a[i] ^ b[i%b.size()]);
     return accumulator == 0;
 }