[#1] Add StringConvertUtil from Zserio C++ runtime

runtime/ClangTidySuppressions.txt

@@ -9,6 +9,14 @@ cppcoreguidelines-avoid-c-arrays:src/zserio/Span.h:174
 # This is necessary for low level implementation of Span to mimic standard C++20 'std::span' abstraction.
 cppcoreguidelines-pro-bounds-array-to-pointer-decay:src/zserio/Span.h:113
 
+# The following is filtered out because bounds are checked naturally by implementation. Therefore method 'at'
+# would only bring the performance drop.
+cppcoreguidelines-pro-bounds-constant-array-index:src/zserio/StringConvertUtil.h:44
+cppcoreguidelines-pro-bounds-constant-array-index:src/zserio/StringConvertUtil.h:45
+cppcoreguidelines-pro-bounds-constant-array-index:src/zserio/StringConvertUtil.h:50
+cppcoreguidelines-pro-bounds-constant-array-index:src/zserio/StringConvertUtil.h:55
+cppcoreguidelines-pro-bounds-constant-array-index:src/zserio/StringConvertUtil.h:56
+
 # This is necessary for low level implementation of Span to mimic standard C++20 'std::span' abstraction.
 google-explicit-constructor:src/zserio/Span.h:112
 google-explicit-constructor:src/zserio/Span.h:125

runtime/src/CMakeLists.txt

@@ -21,7 +21,10 @@ set(ZSERIO_CPP17_RUNTIME_LIB_SRCS
     zserio/BuiltInOperators.cpp
     zserio/BuiltInOperators.h
     zserio/CppRuntimeVersion.h
+    zserio/RebindAlloc.h
     zserio/Span.h
+    zserio/String.h
+    zserio/StringConvertUtil.h
     zserio/Types.h
 )
 

runtime/src/zserio/RebindAlloc.h

@@ -0,0 +1,14 @@
+#ifndef ZSERIO_REBIND_ALLOC_H_INC
+#define ZSERIO_REBIND_ALLOC_H_INC
+
+#include <memory>
+
+namespace zserio
+{
+
+template <typename ALLOC, typename T>
+using RebindAlloc = typename std::allocator_traits<ALLOC>::template rebind_alloc<T>;
+
+} // namespace zserio
+
+#endif // ZSERIO_REBIND_ALLOC_H_INC

runtime/src/zserio/String.h

@@ -0,0 +1,21 @@
+#ifndef ZSERIO_STRING_H_INC
+#define ZSERIO_STRING_H_INC
+
+#include <string>
+
+#include "zserio/RebindAlloc.h"
+
+namespace zserio
+{
+
+/**
+ * Typedef to std::string provided for convenience - using std::allocator<uint8_t>.
+ *
+ * Automatically rebinds the given allocator.
+ */
+template <typename ALLOC = std::allocator<char>>
+using string = std::basic_string<char, std::char_traits<char>, RebindAlloc<ALLOC, char>>;
+
+} // namespace zserio
+
+#endif // ZSERIO_STRING_H_INC

runtime/src/zserio/StringConvertUtil.h

@@ -0,0 +1,213 @@
+#ifndef ZSERIO_STRING_CONVERT_UTIL_H_INC
+#define ZSERIO_STRING_CONVERT_UTIL_H_INC
+
+#include <array>
+#include <limits>
+#include <sstream>
+#include <string_view>
+
+#include "zserio/String.h"
+
+namespace zserio
+{
+
+namespace detail
+{
+
+/**
+ * Converts integer value to string into the given buffer.
+ *
+ * The string is filled from backwards starting at the 24th byte.
+ *
+ * \return Beginning of the resulting string which is null-terminated.
+ */
+template <typename T,
+        typename std::enable_if<std::is_unsigned<T>::value && !std::is_same<T, bool>::value, int>::type = 0>
+const char* convertIntToString(std::array<char, 24>& buffer, T value, bool isNegative)
+{
+    static const std::array<char, 201> DIGITS_100_10 = {
+            "0001020304050607080910111213141516171819"
+            "2021222324252627282930313233343536373839"
+            "4041424344454647484950515253545556575859"
+            "6061626364656667686970717273747576777879"
+            "8081828384858687888990919293949596979899"};
+    static const std::array<char, 11> DIGITS_1 = {"0123456789"};
+
+    auto bufferEnd = buffer.end();
+    *(--bufferEnd) = '\0'; // always terminate with '\0'
+
+    while (value >= 100)
+    {
+        const unsigned int index = static_cast<unsigned int>((value % 100) * 2);
+        value /= 100;
+        *(--bufferEnd) = DIGITS_100_10[index + 1];
+        *(--bufferEnd) = DIGITS_100_10[index];
+    }
+
+    if (value < 10)
+    {
+        *(--bufferEnd) = DIGITS_1[static_cast<unsigned int>(value)];
+    }
+    else
+    {
+        const unsigned int index = static_cast<unsigned int>(value * 2);
+        *(--bufferEnd) = DIGITS_100_10[index + 1];
+        *(--bufferEnd) = DIGITS_100_10[index];
+    }
+
+    if (isNegative)
+    {
+        *(--bufferEnd) = '-';
+    }
+
+    return &(*bufferEnd);
+}
+
+} // namespace detail
+
+/**
+ * Converts unsigned integral value to string and writes the result to the given buffer.
+ *
+ * Note that the buffer is filled from behind.
+ *
+ * \param buffer Buffer to fill with the string representation of the given value.
+ * \param value  Value to convert.
+ *
+ * \return Pointer to the beginning of the resulting string.
+ */
+template <typename T, typename std::enable_if<std::is_unsigned<T>::value, int>::type = 0>
+const char* convertIntToString(std::array<char, 24>& buffer, T value)
+{
+    return detail::convertIntToString(buffer, value, false);
+}
+
+/**
+ * Converts signed integral value to string and writes the result to the given buffer.
+ *
+ * Note that the buffer is filled from behind.
+ *
+ * \param buffer Buffer to fill with the string representation of the given value.
+ * \param value  Value to convert.
+ *
+ * \return Pointer to the beginning of the resulting string.
+ */
+template <typename T, typename std::enable_if<std::is_signed<T>::value, int>::type = 0>
+const char* convertIntToString(std::array<char, 24>& buffer, T value)
+{
+    using unsigned_type = typename std::make_unsigned<T>::type;
+    unsigned_type absValue = static_cast<unsigned_type>(value);
+    const bool isNegative = value < 0;
+    if (isNegative)
+    {
+        absValue = static_cast<unsigned_type>(0 - absValue);
+    }
+
+    return detail::convertIntToString(buffer, absValue, isNegative);
+}
+
+/**
+ * Converts float to string and writes the result to the given buffer.
+ *
+ * Note that only five three digits after point are used and that the buffers are filled from behind.
+ *
+ * \param integerPartBuffer Buffer to fill with the string representation of the integer part.
+ * \param floatingPartBuffer Buffer to fill with the string representation of the floating part.
+ * \param value Value to convert.
+ * \param floatingPartString Reference where to fill pointer to the beginning of the floating part in string.
+ * \param integerPartString Reference where to fill pointer to the beginning of the integer part in string.
+ */
+inline void convertFloatToString(std::array<char, 24>& integerPartBuffer,
+        std::array<char, 24>& floatingPartBuffer, float value, const char*& integerPartString,
+        const char*& floatingPartString)
+{
+    if (value >= static_cast<float>(std::numeric_limits<int64_t>::max()))
+    {
+        integerPartString = "+Inf";
+        floatingPartString = nullptr;
+    }
+    else if (value <= static_cast<float>(std::numeric_limits<int64_t>::min()))
+    {
+        integerPartString = "-Inf";
+        floatingPartString = nullptr;
+    }
+    else
+    {
+        const int64_t integerPart = static_cast<int64_t>(value);
+        const int64_t floatingPart =
+                static_cast<int64_t>((value - static_cast<float>(integerPart)) * 1e3F); // 3 digits
+        const int64_t floatingPartAbs = (floatingPart < 0) ? 0 - floatingPart : floatingPart;
+        integerPartString = convertIntToString(integerPartBuffer, integerPart);
+        floatingPartString = convertIntToString(floatingPartBuffer, floatingPartAbs);
+    }
+}
+
+/**
+ * Converts bool value to boolalpha C-string ("true" or "false").
+ *
+ * \param value Value to convert.
+ *
+ * \return C-string representation of the given bool value.
+ */
+inline const char* convertBoolToString(bool value)
+{
+    return value ? "true" : "false";
+}
+
+/**
+ * Converts an integral value to string using the given allocator. Defined for convenience.
+ *
+ * \param value     Value to convert.
+ * \param allocator Allocator to use for the string allocation.
+ *
+ * \return String representation of the given integral value.
+ */
+template <typename ALLOC, typename T>
+string<ALLOC> toString(T value, const ALLOC& allocator = ALLOC())
+{
+    std::array<char, 24> buffer = {};
+    return string<ALLOC>(convertIntToString(buffer, value), allocator);
+}
+
+/**
+ * Converts a boolean value to string using the given allocator. Defined for convenience.
+ *
+ * Note that in contrast to std::to_string, this behaves as STL streams with boolalpha flag and produces
+ * "true" and "false" strings.
+ *
+ * \param value Value to convert.
+ * \param allocator Allocator to use for the string allocation.
+ */
+template <typename ALLOC>
+string<ALLOC> toString(bool value, const ALLOC& allocator = ALLOC())
+{
+    return string<ALLOC>(convertBoolToString(value), allocator);
+}
+
+/**
+ * Converts a string view to string using the given allocator. Defined for convenience.
+ *
+ * \param value String view to convert.
+ * \param allocator Allocator to use for the string allocation.
+ */
+template <typename ALLOC>
+string<ALLOC> toString(std::string_view value, const ALLOC& allocator = ALLOC())
+{
+    return string<ALLOC>(value, allocator);
+}
+
+/**
+ * Converts an integral (or a boolean) value to string. Convenience wrapper to call without allocator.
+ *
+ * \param value Value to convert.
+ *
+ * \return String representation of the given value.
+ */
+template <typename T>
+string<std::allocator<char>> toString(T value)
+{
+    return toString<std::allocator<char>>(value);
+}
+
+} // namespace zserio
+
+#endif // ifndef ZSERIO_STRING_CONVERT_UTIL_H_INC

runtime/test/CMakeLists.txt

@@ -14,6 +14,7 @@ gtest_add_library("${ZSERIO_CPP17_PROJECT_ROOT}/3rdparty/cpp/googletest")
 set(ZSERIO_CPP17_RUNTIME_TEST_SRCS
     zserio/BuiltInOperatorsTest.cpp
     zserio/SpanTest.cpp
+    zserio/StringConvertUtilTest.cpp
 )
 
 add_executable(${PROJECT_NAME} ${ZSERIO_CPP17_RUNTIME_TEST_SRCS})