Escape a string for use in any FS using C++11

escape_str.cpp

#include <assert.h>

#include <string>
#include <time.h>
#include <stdlib.h>
#include <vector>


std::string UriDecode(const std::string & src)
{
    // Note from RFC1630:  "Sequences which start with a percent sign
    // but are not followed by two hexadecimal characters (0-9, A-F) are reserved
    // for future extension"

    std::string out;    
    out.reserve(src.length());

    auto inserter = std::back_insert_iterator<std::string>(out);

    for (auto iter = src.begin(); iter != src.end(); ++iter)
    {
        if (*iter == '%')
        {
            ++iter;
            std::string charCode(iter , iter + 2);
            char ret = std::stoi(charCode, NULL, 16);
            inserter = ret;
            iter += 1;
        }
        else
        {
            inserter = *iter;
        }
    }

    return out;
}

// Only alphanum is safe.
static const char SAFE[256] =
{
    /*      0 1 2 3  4 5 6 7  8 9 A B  C D E F */
    /* 0 */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
    /* 1 */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
    /* 2 */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
    /* 3 */ 1,1,1,1, 1,1,1,1, 1,1,0,0, 0,0,0,0,
    
    /* 4 */ 0,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1,
    /* 5 */ 1,1,1,1, 1,1,1,1, 1,1,1,0, 0,0,0,0,
    /* 6 */ 0,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1,
    /* 7 */ 1,1,1,1, 1,1,1,1, 1,1,1,0, 0,0,0,0,
    
    /* 8 */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
    /* 9 */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
    /* A */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
    /* B */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
    
    /* C */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
    /* D */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
    /* E */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
    /* F */ 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
};

#include <iterator>

std::string UriEncode(const std::string & src)
{
    static const char DEC2HEX[] = "0123456789ABCDEF";

    std::string out;    
    out.reserve(src.length());
    auto inserter = std::back_insert_iterator<std::string>(out);

    for (auto iter = src.begin(); iter != src.end(); ++iter)
    {
        if (SAFE[*iter])
        {
            inserter = *iter;
        }
        else
        {
            inserter = '%';
            inserter = DEC2HEX[(*iter >> 4) & 0xF];
            inserter = DEC2HEX[*iter & 0xF];
        }
    }

    return out;
}

void encodeDecodeTest(void)
{
    TEST_ASSERT_EQUAL_STRING(UriEncode("ABC").c_str(), "ABC");
    
    std::vector<char> v = {0, 1, 2};
    const std::string ORG(v.begin(), v.end());
    const std::string ENC("%00%01%02");
    TEST_ASSERT_EQUAL_STRING(UriEncode(ORG).c_str(), ENC.c_str());
    TEST_ASSERT_EQUAL_STRING(UriDecode(ENC).c_str(), ORG.c_str());

    TEST_ASSERT_EQUAL_STRING(UriEncode("\xFF").c_str(), "%FF");
    TEST_ASSERT_EQUAL_STRING(UriDecode("%FF").c_str(), "\xFF");
    TEST_ASSERT_EQUAL_STRING(UriDecode("%ff").c_str(), "\xFF");

    // unsafe chars test, RFC1738
    const std::string UNSAFE(" <>#{}|\\^~[]`");
    std::string sUnsafeEnc = UriEncode(UNSAFE);
    TEST_ASSERT_EQUAL(std::string::npos, sUnsafeEnc.find_first_of(UNSAFE));
    TEST_ASSERT_EQUAL_STRING(UriDecode(sUnsafeEnc).c_str(), UNSAFE.c_str());

    // random test
    const int MAX_LEN = 128;
    char a[MAX_LEN];
    srand((unsigned)time(NULL));
    for (int i = 0; i < 100; i++)
    {
        for (int j = 0; j < MAX_LEN; j++)
            a[j] = rand() % (1 << 8);
        int nLen = rand() % MAX_LEN;
        std::string sOrg(a, nLen);
        std::string sEnc = UriEncode(sOrg);
        TEST_ASSERT_EQUAL_STRING(sOrg.c_str(), UriDecode(sEnc).c_str());
    }
}