技术的魅力
最近在看比特币的源码，感觉它的开发人员，都是寻找最好的技术，最好的方案。在这里就来看看base58的表示，它就是比特币地址的字符串表示方式，它长度是最短的，又是最适合人看的方式。
由于我需要使用GUID，如果直接把GUID格式化为16进制表示，128位16个字节表示的GUID需要32个字符来表示，如果换成BASE58来表示，就只有22字符表示就可以了，省了10个字符。它的代码如下：
头文件：
#pragma once
#include
#include
class CBase58
{
public:
CBase58();
virtual ~CBase58();
std::string EncodeBase58(const unsigned char* pbegin, const unsigned char* pend);
std::wstring EncodeBase58W(const unsigned char* pbegin, const unsigned char* pend);
bool DecodeBase58(const char* psz, std::vector& vch);
std::string EncodeBase58(const std::vector& vch);
bool DecodeBase58(const std::string& str, std::vector& vchRet);
}; CPP文件：
#include "stdafx.h"
#include "Base58.h"
/** All alphanumeric characters except for "0", "I", "O", and "l" */
static const char* pszBase58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
static const char 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,
};
CBase58::CBase58()
{
}
CBase58::~CBase58()
{
}
std::string CBase58::EncodeBase58(const unsigned char* pbegin, const unsigned char* pend)
{
// Skip & count leading zeroes.
int zeroes = 0;
int length = 0;
while (pbegin != pend && *pbegin == 0) {
pbegin++;
zeroes++;
}
// Allocate enough space in big-endian base58 representation.
int size = (pend - pbegin) * 138 / 100 + 1; // log(256) / log(58), rounded up.
std::vector b58(size);
// Process the bytes.
while (pbegin != pend) {
int carry = *pbegin;
int i = 0;
// Apply "b58 = b58 * 256 + ch".
for (std::vector::reverse_iterator it = b58.rbegin(); (carry != 0 || i < length) && (it != b58.rend()); it++, i++) {
carry += 256 * (*it);
*it = carry % 58;
carry /= 58;
}
assert(carry == 0);
length = i;
pbegin++;
}
// Skip leading zeroes in base58 result.
std::vector::iterator it = b58.begin() + (size - length);
while (it != b58.end() && *it == 0)
it++;
// Translate the result into a string.
std::string str;
str.reserve(zeroes + (b58.end() - it));
str.assign(zeroes, '1');
while (it != b58.end())
str += pszBase58[*(it++)];
return str;
}
std::wstring CBase58::EncodeBase58W(const unsigned char* pbegin, const unsigned char* pend)
{
return std::wstring();
}
bool CBase58::DecodeBase58(const char* psz, std::vector& vch)
{
// Skip leading spaces.
while (*psz && isspace(*psz))
psz++;
// Skip and count leading '1's.
int zeroes = 0;
int length = 0;
while (*psz == '1') {
zeroes++;
psz++;
}
// Allocate enough space in big-endian base256 representation.
int size = strlen(psz) * 733 / 1000 + 1; // log(58) / log(256), rounded up.
std::vector 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
int carry = mapBase58[(uint8_t)*psz];
if (carry == -1) // Invalid b58 character
return false;
int i = 0;
for (std::vector::reverse_iterator it = b256.rbegin(); (carry != 0 || i < length) && (it != b256.rend()); ++it, ++i) {
carry += 58 * (*it);
*it = carry % 256;
carry /= 256;
}
assert(carry == 0);
length = i;
psz++;
}
// Skip trailing spaces.
while (isspace(*psz))
psz++;
if (*psz != 0)
return false;
// Skip leading zeroes in b256.
std::vector::iterator it = b256.begin() + (size - length);
while (it != b256.end() && *it == 0)
it++;
// Copy result into output vector.
vch.reserve(zeroes + (b256.end() - it));
vch.assign(zeroes, 0x00);
while (it != b256.end())
vch.push_back(*(it++));
return true;
}
std::string CBase58::EncodeBase58(const std::vector& vch)
{
return EncodeBase58(vch.data(), vch.data() + vch.size());
}
bool CBase58::DecodeBase58(const std::string& str, std::vector& vchRet)
{
return DecodeBase58(str.c_str(), vchRet);
} 这里是使用了比特币的源码base58算法，省掉了一些字符的base64的算法。