/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <limits>
#include <sstream>
#include <string>
#include <vector>
#include <stdint.h>
#include <cmath>
namespace android
{
namespace utilities
{
/**
* Convert a given source type to a given destination type.
*
* String conversion to T reads the value of the type T in the given string.
* The function does not allow to have white spaces around the value to parse
* and tries to parse the whole string, which means that if some bytes were not
* read in the string, the function fails.
* Hexadecimal representation (ie. numbers starting with 0x) is supported only
* for integral types conversions.
*
* Numeric conversion to string formats the source value to decimal space.
*
* Vector to vector conversion calls convertTo on each element.
*
* @tparam srcType source type, default value is string type
* @tparam dstType destination type
* @param[in] input The source to convert from.
* @param[out] result Converted value if success, undefined on failure.
*
* @return true if conversion was successful, false otherwise.
*/
template <typename srcType, typename dstType>
static inline bool convertTo(const srcType &input, dstType &result);
/* details namespace is here to hide implementation details to header end user. It
* is NOT intended to be used outside. */
namespace details
{
/** Helper class to limit instantiation of templates */
template <typename T>
struct ConversionFromStringAllowed;
template <typename T>
struct ConversionToStringAllowed;
/* List of allowed types for conversion */
template <>
struct ConversionFromStringAllowed<bool> {};
template <>
struct ConversionFromStringAllowed<uint64_t> {};
template <>
struct ConversionFromStringAllowed<int64_t> {};
template <>
struct ConversionFromStringAllowed<uint32_t> {};
template <>
struct ConversionFromStringAllowed<int32_t> {};
template <>
struct ConversionFromStringAllowed<uint16_t> {};
template <>
struct ConversionFromStringAllowed<int16_t> {};
template <>
struct ConversionFromStringAllowed<float> {};
template <>
struct ConversionFromStringAllowed<double> {};
template <>
struct ConversionToStringAllowed<int64_t> {};
template <>
struct ConversionToStringAllowed<uint64_t> {};
template <>
struct ConversionToStringAllowed<uint32_t> {};
template <>
struct ConversionToStringAllowed<int32_t> {};
template <>
struct ConversionToStringAllowed<double> {};
template <>
struct ConversionToStringAllowed<float> {};
/**
* Set the decimal precision to 10 digits.
* Note that this setting is aligned with Android Audio Parameter
* policy concerning float storage into string.
*/
static const uint32_t gFloatPrecision = 10;
template <typename T>
static inline bool fromString(const std::string &str, T &result)
{
/* Check that conversion to that type is allowed.
* If this fails, this means that this template was not intended to be used
* with this type, thus that the result is undefined. */
ConversionFromStringAllowed<T>();
if (str.find_first_of(std::string("\r\n\t\v ")) != std::string::npos) {
return false;
}
/* Check for a '-' in string. If type is unsigned and a - is found, the
* parsing fails. This is made necessary because "-1" is read as 65535 for
* uint16_t, for example */
if (str.find('-') != std::string::npos
&& !std::numeric_limits<T>::is_signed) {
return false;
}
std::stringstream ss(str);
/* Sadly, the stream conversion does not handle hexadecimal format, thus
* check is done manually */
if (str.substr(0, 2) == "0x") {
if (std::numeric_limits<T>::is_integer) {
ss >> std::hex >> result;
} else {
/* Conversion undefined for non integers */
return false;
}
} else {
ss >> result;
}
return ss.eof() && !ss.fail() && !ss.bad();
}
template <typename T>
static inline bool toString(const T &value, std::string &str)
{
/* Check that conversion from that type is allowed.
* If this fails, this means that this template was not intended to be used
* with this type, thus that the result is undefined. */
ConversionToStringAllowed<T>();
std::stringstream oss;
oss.precision(gFloatPrecision);
oss << value;
str = oss.str();
return !oss.fail() && !oss.bad();
}
template <typename srcType, typename dstType>
class Converter;
template <typename dstType>
class Converter<std::string, dstType>
{
public:
static inline bool run(const std::string &str, dstType &result)
{
return fromString<dstType>(str, result);
}
};
template <typename srcType>
class Converter<srcType, std::string>
{
public:
static inline bool run(const srcType &str, std::string &result)
{
return toString<srcType>(str, result);
}
};
/** Convert a vector by applying convertTo on each element.
*
* @tparam SrcElem Type of the src elements.
* @tparam DstElem Type of the destination elements.
*/
template <typename SrcElem, typename DstElem>
class Converter<std::vector<SrcElem>, std::vector<DstElem> >
{
public:
typedef const std::vector<SrcElem> Src;
typedef std::vector<DstElem> Dst;
static inline bool run(Src &src, Dst &dst)
{
typedef typename Src::const_iterator SrcIt;
dst.clear();
dst.reserve(src.size());
for (SrcIt it = src.begin(); it != src.end(); ++it) {
DstElem dstElem;
if (not convertTo(*it, dstElem)) {
return false;
}
dst.push_back(dstElem);
}
return true;
}
};
} // namespace details
template <typename srcType, typename dstType>
static inline bool convertTo(const srcType &input, dstType &result)
{
return details::Converter<srcType, dstType>::run(input, result);
}
/**
* Specialization for int16_t of convertTo template function.
*
* This function follows the same paradigm than it's generic version.
*
* The specific implementation is made necessary because the stlport version of
* string streams is bugged and does not fail when giving overflowed values.
* This specialisation can be safely removed when stlport behaviour is fixed.
*
* @param[in] str the string to parse.
* @param[out] result reference to object where to store the result.
*
* @return true if conversion was successful, false otherwise.
*/
template <>
inline bool convertTo<std::string, int16_t>(const std::string &str, int16_t &result)
{
int64_t res;
if (!convertTo<std::string, int64_t>(str, res)) {
return false;
}
if (res > std::numeric_limits<int16_t>::max() || res < std::numeric_limits<int16_t>::min()) {
return false;
}
result = static_cast<int16_t>(res);
return true;
}
/**
* Specialization for float of convertTo template function.
*
* This function follows the same paradigm than it's generic version and is
* based on it but makes furthers checks on the returned value.
*
* The specific implementation is made necessary because the stlport conversion
* from string to float behaves differently than GNU STL: overflow produce
* +/-Infinity rather than an error.
*
* @param[in] str the string to parse.
* @param[out] result reference to object where to store the result.
*
* @return true if conversion was successful, false otherwise.
*/
template <>
inline bool convertTo<std::string, float>(const std::string &str, float &result)
{
if (!details::Converter<std::string, float>::run(str, result)) {
return false;
}
if (std::abs(result) == std::numeric_limits<float>::infinity() ||
result == std::numeric_limits<float>::quiet_NaN()) {
return false;
}
return true;
}
/**
* Specialization for double of convertTo template function.
*
* This function follows the same paradigm than it's generic version and is
* based on it but makes furthers checks on the returned value.
*
* The specific implementation is made necessary because the stlport conversion
* from string to double behaves differently than GNU STL: overflow produce
* +/-Infinity rather than an error.
*
* @param[in] str the string to parse.
* @param[out] result reference to object where to store the result.
*
* @return true if conversion was successful, false otherwise.
*/
template <>
inline bool convertTo<std::string, double>(const std::string &str, double &result)
{
if (!details::Converter<std::string, double>::run(str, result)) {
return false;
}
if (std::abs(result) == std::numeric_limits<double>::infinity() ||
result == std::numeric_limits<double>::quiet_NaN()) {
return false;
}
return true;
}
/**
* Specialization for boolean of convertTo template function.
*
* This function follows the same paradigm than it's generic version.
* This function accepts to parse boolean as "0/1" or "false/true" or
* "FALSE/TRUE".
* The specific implementation is made necessary because the behaviour of
* string streams when parsing boolean values is not sufficient to fit our
* requirements. Indeed, parsing "true" will correctly parse the value, but the
* end of stream is not reached which makes the ss.eof() fails in the generic
* implementation.
*
* @param[in] str the string to parse.
* @param[out] result reference to object where to store the result.
*
* @return true if conversion was successful, false otherwise.
*/
template <>
inline bool convertTo<std::string, bool>(const std::string &str, bool &result)
{
if (str == "0" || str == "FALSE" || str == "false") {
result = false;
return true;
}
if (str == "1" || str == "TRUE" || str == "true") {
result = true;
return true;
}
return false;
}
/**
* Specialization for boolean to string of convertTo template function.
*
* This function follows the same paradigm than it's generic version.
* This function arbitrarily decides to return "false/true".
* It is compatible with the specialization from string to boolean.
*
* @param[in] isSet boolean to convert to a string.
* @param[out] result reference to object where to store the result.
*
* @return true if conversion was successful, false otherwise.
*/
template <>
inline bool convertTo<bool, std::string>(const bool &isSet, std::string &result)
{
result = isSet ? "true" : "false";
return true;
}
/**
* Specialization for string to string of convertTo template function.
*
* This function is a dummy conversion from string to string.
* In case of clients using template as well, this implementation avoids adding extra
* specialization to bypass the conversion from string to string.
*
* @param[in] str the string to parse.
* @param[out] result reference to object where to store the result.
*
* @return true if conversion was successful, false otherwise.
*/
template <>
inline bool convertTo<std::string, std::string>(const std::string &str, std::string &result)
{
result = str;
return true;
}
} // namespace utilities
} // namespace android