C++ string_view::front方法代码示例

void test_strview_basics(const string_view& sv, const char *p, size_t n) {
    ASSERT_EQ(p, sv.data());
    ASSERT_EQ(n, sv.size());
    ASSERT_EQ(n, sv.length());
    ASSERT_EQ((n == 0), sv.empty());

    ASSERT_EQ(p, sv.cbegin());
    ASSERT_EQ(p, sv.begin());
    ASSERT_EQ(p + n, sv.cend());
    ASSERT_EQ(p + n, sv.end());

    using reviter_t = std::reverse_iterator<string_view::const_iterator>;

    ASSERT_EQ(reviter_t(sv.end()),    sv.rbegin());
    ASSERT_EQ(reviter_t(sv.begin()),  sv.rend());
    ASSERT_EQ(reviter_t(sv.cend()),   sv.crbegin());
    ASSERT_EQ(reviter_t(sv.cbegin()), sv.crend());

    for (size_t i = 0; i < n; ++i) {
        ASSERT_EQ(p[i], sv[i]);
        ASSERT_EQ(p[i], sv.at(i));
    }
    ASSERT_THROW(sv.at(n), std::out_of_range);
    ASSERT_THROW(sv.at(string_view::npos), std::out_of_range);

    if (n > 0) {
        ASSERT_EQ(p,         &(sv.front()));
        ASSERT_EQ(p + (n-1), &(sv.back()));
        ASSERT_EQ(p[0],        sv.front());
        ASSERT_EQ(p[n-1],      sv.back());
    }
}

static string ProcessMetasymbols(string_view Str, subst_data& Data)
{
	string Result;
	Result.reserve(Str.size());

	while (!Str.empty())
	{
		if (Str.front() == L'!')
		{
			Str = ProcessMetasymbol(Str, Data, Result);
		}
		else
		{
			Result.push_back(Str.front());
			Str.remove_prefix(1);
		}
	}

	return Result;
}

// Add the attribute -- figure out the type
void
parse_param(string_view paramname, string_view val, ImageSpec& spec)
{
    TypeDesc type;  // start out unknown

    // If the param string starts with a type name, that's what it is
    if (size_t typeportion = type.fromstring(paramname)) {
        paramname.remove_prefix(typeportion);
        Strutil::skip_whitespace(paramname);
    }
    // If the value string starts with a type name, that's what it is
    else if (size_t typeportion = type.fromstring(val)) {
        val.remove_prefix(typeportion);
        Strutil::skip_whitespace(val);
    }

    if (type.basetype == TypeDesc::UNKNOWN) {
        // If we didn't find a type name, try to guess
        if (val.size() >= 2 && val.front() == '\"' && val.back() == '\"') {
            // Surrounded by quotes? it's a string (strip off the quotes)
            val.remove_prefix(1);
            val.remove_suffix(1);
            type = TypeDesc::TypeString;
        } else if (Strutil::string_is<int>(val)) {
            // Looks like an int, is an int
            type = TypeDesc::TypeInt;
        } else if (Strutil::string_is<float>(val)) {
            // Looks like a float, is a float
            type = TypeDesc::TypeFloat;
        } else {
            // Everything else is assumed a string
            type = TypeDesc::TypeString;
        }
    }

    // Read the values and set the attribute
    int n = type.numelements() * type.aggregate;
    if (type.basetype == TypeDesc::INT) {
        std::vector<int> values(n);
        for (int i = 0; i < n; ++i) {
            Strutil::parse_int(val, values[i]);
            Strutil::parse_char(val, ',');  // optional
        }
        if (n > 0)
            spec.attribute(paramname, type, &values[0]);
    }
    if (type.basetype == TypeDesc::FLOAT) {
        std::vector<float> values(n);
        for (int i = 0; i < n; ++i) {
            Strutil::parse_float(val, values[i]);
            Strutil::parse_char(val, ',');  // optional
        }
        if (n > 0)
            spec.attribute(paramname, type, &values[0]);
    } else if (type.basetype == TypeDesc::STRING) {
        std::vector<ustring> values(n);
        for (int i = 0; i < n; ++i) {
            string_view v;
            Strutil::parse_string(val, v);
            Strutil::parse_char(val, ',');  // optional
            values[i] = v;
        }
        if (n > 0)
            spec.attribute(paramname, type, &values[0]);
    }
}

static void MixToFullPath(const string_view stPath, string& Dest, const string_view stCurrentDir)
{
		string strDest;
		string_view pstCurrentDir;
		bool blIgnore = false;
		size_t PathDirOffset = 0;
		const auto PathType = ParsePath(stPath, &PathDirOffset);
		size_t PathOffset = PathDirOffset;
		switch (PathType)
		{
			case root_type::unknown:
			{
				if (HasPathPrefix(stPath)) // \\?\<ANY_UNKNOWN_FORMAT>
				{
					blIgnore = true;
				}
				else if (!stPath.empty() && IsSlash(stPath.front())) //"\" or "\abc"
				{
					++PathOffset;
					if (!stCurrentDir.empty())
					{
						size_t CurDirDirOffset = 0;
						if (ParsePath(stCurrentDir, &CurDirDirOffset) != root_type::unknown)
						{
							assign(strDest, stCurrentDir.substr(0, CurDirDirOffset));
						}
					}
				}
				else //"abc" or whatever
				{
					pstCurrentDir = stCurrentDir;
				}
			}
			break;
			case root_type::drive_letter: //"C:" or "C:abc"
			{
				if(stPath.size() > 2 && IsSlash(stPath[2]))
				{
					PathOffset = 0;
				}
				else
				{
					const auto Drive = os::fs::get_drive(stPath[0]);
					const auto Value = os::env::get(L'=' + Drive);

					if (!Value.empty())
					{
						strDest = Value;
					}
					else
					{
						if (upper(stPath[0])==upper(stCurrentDir[0]))
						{
							assign(strDest, stCurrentDir);
						}
						else
						{
							strDest = Drive;
						}
					}
					AddEndSlash(strDest);
				}
			}
			break;
			case root_type::remote: //"\\abc"
			{
				PathOffset = 0;
			}
			break;
			case root_type::unc_drive_letter: //"\\?\whatever"
			case root_type::unc_remote:
			case root_type::volume:
			case root_type::pipe:
			{
				blIgnore=true;
				PathOffset = 0;
			}
			break;
		}

		if (!pstCurrentDir.empty())
		{
			append(strDest, pstCurrentDir);
			AddEndSlash(strDest);
		}

		append(strDest, stPath.substr(PathOffset));

		if (!blIgnore && !HasPathPrefix(strDest))
			MixToFullPath(strDest);

		Dest = std::move(strDest);
}