Merge bitcoin#12704: base58: use map instead of strchr() when decode

bcab47b use base58 map instead of strchr() (Kevin Pan)

Pull request description:

  Use array map instead of find string position.

  Test code snippet:

  ```cpp

  #include <assert.h>
  #include <stdint.h>
  #include <stdio.h>
  #include <stdlib.h>

  #include <string>

  int main(int argc, const char * argv[]) {

    static const char* pszBase58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
    static const int8_t mapBase58[] = {
      -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, 0, 1, 2, 3, 4, 5, 6,  7, 8,-1,-1,-1,-1,-1,-1,
      -1, 9,10,11,12,13,14,15, 16,-1,17,18,19,20,21,-1,
      22,23,24,25,26,27,28,29, 30,31,32,-1,-1,-1,-1,-1,
      -1,33,34,35,36,37,38,39, 40,41,42,43,-1,44,45,46,
      47,48,49,50,51,52,53,54, 55,56,57,-1,-1,-1,-1,-1,
    };

    const std::string b58Str(pszBase58);

    for (size_t i = 0; i < b58Str.length(); i++) {
      const char *ch = strchr(pszBase58, b58Str[i]);
      printf("%d - %d\n", ch - pszBase58, mapBase58[(uint8_t)b58Str[i]]);
      assert(ch - pszBase58 == mapBase58[(uint8_t)b58Str[i]]);
    }

    assert(mapBase58['1'] == 0);
    assert(mapBase58['z'] == 57);

    /** All alphanumeric characters except for "0", "I", "O", and "l" */
    assert(mapBase58['0'] == -1);
    assert(mapBase58['I'] == -1);
    assert(mapBase58['O'] == -1);
    assert(mapBase58['l'] == -1);

    return 0;
  }

  ```

Tree-SHA512: c28376dc8c92cc4a770c3282db4a568ae5f5a08e27f714183eb3d8755421dc7aa11d7b45afa55e70eba46565f378062aac53dc8f150eeeab12ce7b5db5af89c5

Author: laanwj

src/base58.cpp

@@ -14,6 +14,24 @@
 
 /** All alphanumeric characters except for "0", "I", "O", and "l" */
 static const char* pszBase58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
+static const int8_t mapBase58[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, 0, 1, 2, 3, 4, 5, 6,  7, 8,-1,-1,-1,-1,-1,-1,
+    -1, 9,10,11,12,13,14,15, 16,-1,17,18,19,20,21,-1,
+    22,23,24,25,26,27,28,29, 30,31,32,-1,-1,-1,-1,-1,
+    -1,33,34,35,36,37,38,39, 40,41,42,43,-1,44,45,46,
+    47,48,49,50,51,52,53,54, 55,56,57,-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,-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,-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,
+};
 
 bool DecodeBase58(const char* psz, std::vector<unsigned char>& vch)
 {
@@ -31,13 +49,12 @@ bool DecodeBase58(const char* psz, std::vector<unsigned char>& vch)
     int size = strlen(psz) * 733 /1000 + 1; // log(58) / log(256), rounded up.
     std::vector<unsigned char> b256(size);
     // Process the characters.
+    static_assert(sizeof(mapBase58)/sizeof(mapBase58[0]) == 256, "mapBase58.size() should be 256"); // guarantee not out of range
     while (*psz && !isspace(*psz)) {
         // Decode base58 character
-        const char* ch = strchr(pszBase58, *psz);
-        if (ch == nullptr)
+        int carry = mapBase58[(uint8_t)*psz];
+        if (carry == -1)  // Invalid b58 character
             return false;
-        // Apply "b256 = b256 * 58 + ch".
-        int carry = ch - pszBase58;
         int i = 0;
         for (std::vector<unsigned char>::reverse_iterator it = b256.rbegin(); (carry != 0 || i < length) && (it != b256.rend()); ++it, ++i) {
             carry += 58 * (*it);

src/test/data/base58_encode_decode.json

@@ -10,5 +10,7 @@
 ["572e4794", "3EFU7m"],
 ["ecac89cad93923c02321", "EJDM8drfXA6uyA"],
 ["10c8511e", "Rt5zm"],
-["00000000000000000000", "1111111111"]
+["00000000000000000000", "1111111111"],
+["000111d38e5fc9071ffcd20b4a763cc9ae4f252bb4e48fd66a835e252ada93ff480d6dd43dc62a641155a5", "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"],
+["000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f404142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9fa0a1a2a3a4a5a6a7a8a9aaabacadaeafb0b1b2b3b4b5b6b7b8b9babbbcbdbebfc0c1c2c3c4c5c6c7c8c9cacbcccdcecfd0d1d2d3d4d5d6d7d8d9dadbdcdddedfe0e1e2e3e4e5e6e7e8e9eaebecedeeeff0f1f2f3f4f5f6f7f8f9fafbfcfdfeff", "1cWB5HCBdLjAuqGGReWE3R3CguuwSjw6RHn39s2yuDRTS5NsBgNiFpWgAnEx6VQi8csexkgYw3mdYrMHr8x9i7aEwP8kZ7vccXWqKDvGv3u1GxFKPuAkn8JCPPGDMf3vMMnbzm6Nh9zh1gcNsMvH3ZNLmP5fSG6DGbbi2tuwMWPthr4boWwCxf7ewSgNQeacyozhKDDQQ1qL5fQFUW52QKUZDZ5fw3KXNQJMcNTcaB723LchjeKun7MuGW5qyCBZYzA1KjofN1gYBV3NqyhQJ3Ns746GNuf9N2pQPmHz4xpnSrrfCvy6TVVz5d4PdrjeshsWQwpZsZGzvbdAdN8MKV5QsBDY"]
 ]