Implement method kj::StringPtr:parseAs<NUMBER_TYPE>

This method provides kj-ish interface to parse numbers.

Moves code from capnp json decoder to kj::StringPtr.

c++/src/capnp/compat/json.c++

@@ -384,31 +384,6 @@ void JsonCodec::encodeField(StructSchema::Field field, DynamicValue::Reader inpu
 }
 
 namespace {
-int64_t parseInt64(kj::StringPtr s) {
-  char *endPtr;
-  errno = 0;
-  int64_t value = strtoll(s.begin(), &endPtr, 10);
-  KJ_REQUIRE(endPtr == s.end(), "String does not contain valid number", s);
-  KJ_REQUIRE(errno != ERANGE, "Value out-of-range", s);
-  return value;
-}
-
-uint64_t parseUInt64(kj::StringPtr s) {
-  char *endPtr;
-  errno = 0;
-  uint64_t value = strtoull(s.begin(), &endPtr, 10);
-  KJ_REQUIRE(endPtr == s.end(), "String does not contain valid number", s);
-  KJ_REQUIRE(errno != ERANGE, "Value out-of-range", s);
-  return value;
-}
-
-double parseFloat64(kj::StringPtr s) {
-  char *endPtr;
-  errno = 0;
-  double value = strtod(s.begin(), &endPtr);
-  KJ_REQUIRE(endPtr == s.end(), "String does not contain valid floating number", s);
-  return value;
-}
 
 template <typename SetFn, typename DecodeArrayFn, typename DecodeObjectFn>
 void decodeField(Type type, JsonValue::Reader value, SetFn setFn, DecodeArrayFn decodeArrayFn,
@@ -436,7 +411,7 @@ void decodeField(Type type, JsonValue::Reader value, SetFn setFn, DecodeArrayFn
           setFn(value.getNumber());
           break;
         case JsonValue::STRING:
-          setFn(parseInt64(value.getString()));
+          setFn(value.getString().parseAs<int64_t>());
           break;
         default:
           KJ_FAIL_REQUIRE("Expected integer value");
@@ -452,7 +427,7 @@ void decodeField(Type type, JsonValue::Reader value, SetFn setFn, DecodeArrayFn
           setFn(value.getNumber());
           break;
         case JsonValue::STRING:
-          setFn(parseUInt64(value.getString()));
+          setFn(value.getString().parseAs<uint64_t>());
           break;
         default:
           KJ_FAIL_REQUIRE("Expected integer value");
@@ -468,7 +443,7 @@ void decodeField(Type type, JsonValue::Reader value, SetFn setFn, DecodeArrayFn
           setFn(value.getNumber());
           break;
         case JsonValue::STRING:
-          setFn(parseFloat64(value.getString()));
+          setFn(value.getString().parseAs<double>());
           break;
         default:
           KJ_FAIL_REQUIRE("Expected float value");

c++/src/kj/string-test.c++

@@ -67,6 +67,83 @@ TEST(String, StartsEndsWith) {
   EXPECT_TRUE(StringPtr("foobar").endsWith(""));
 }
 
+TEST(String, parseAs) {
+  EXPECT_EQ(StringPtr("0").parseAs<double>(), 0.0);
+  EXPECT_EQ(StringPtr("0.0").parseAs<double>(), 0.0);
+  EXPECT_EQ(StringPtr("1").parseAs<double>(), 1.0);
+  EXPECT_EQ(StringPtr("1.0").parseAs<double>(), 1.0);
+  EXPECT_EQ(StringPtr("1e100").parseAs<double>(), 1e100);
+  EXPECT_EQ(StringPtr("inf").parseAs<double>(), inf());
+  EXPECT_EQ(StringPtr("infinity").parseAs<double>(), inf());
+  EXPECT_EQ(StringPtr("INF").parseAs<double>(), inf());
+  EXPECT_EQ(StringPtr("INFINITY").parseAs<double>(), inf());
+  EXPECT_EQ(StringPtr("1e100000").parseAs<double>(), inf());
+  EXPECT_EQ(StringPtr("-inf").parseAs<double>(), -inf());
+  EXPECT_EQ(StringPtr("-infinity").parseAs<double>(), -inf());
+  EXPECT_EQ(StringPtr("-INF").parseAs<double>(), -inf());
+  EXPECT_EQ(StringPtr("-INFINITY").parseAs<double>(), -inf());
+  EXPECT_EQ(StringPtr("-1e100000").parseAs<double>(), -inf());
+  EXPECT_TRUE(isNaN(StringPtr("nan").parseAs<double>()));
+  EXPECT_TRUE(isNaN(StringPtr("NAN").parseAs<double>()));
+  EXPECT_TRUE(isNaN(StringPtr("NaN").parseAs<double>()));
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("").parseAs<double>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("a").parseAs<double>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("1a").parseAs<double>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("+-1").parseAs<double>());
+
+  EXPECT_EQ(StringPtr("1").parseAs<float>(), 1.0);
+
+  EXPECT_EQ(StringPtr("1").parseAs<int64_t>(), 1);
+  EXPECT_EQ(StringPtr("9223372036854775807").parseAs<int64_t>(), 9223372036854775807LL);
+  EXPECT_EQ(StringPtr("-9223372036854775808").parseAs<int64_t>(), -9223372036854775808ULL);
+  KJ_EXPECT_THROW_MESSAGE("out-of-range", StringPtr("9223372036854775808").parseAs<int64_t>());
+  KJ_EXPECT_THROW_MESSAGE("out-of-range", StringPtr("-9223372036854775809").parseAs<int64_t>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("").parseAs<int64_t>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("a").parseAs<int64_t>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("1a").parseAs<int64_t>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("+-1").parseAs<int64_t>());
+
+  EXPECT_EQ(StringPtr("1").parseAs<uint64_t>(), 1);
+  EXPECT_EQ(StringPtr("0").parseAs<uint64_t>(), 0);
+  EXPECT_EQ(StringPtr("18446744073709551615").parseAs<uint64_t>(), 18446744073709551615ULL);
+  KJ_EXPECT_THROW_MESSAGE("out-of-range", StringPtr("-1").parseAs<uint64_t>());
+  KJ_EXPECT_THROW_MESSAGE("out-of-range", StringPtr("18446744073709551616").parseAs<uint64_t>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("").parseAs<uint64_t>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("a").parseAs<uint64_t>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("1a").parseAs<uint64_t>());
+  KJ_EXPECT_THROW_MESSAGE("not contain valid", StringPtr("+-1").parseAs<uint64_t>());
+
+  EXPECT_EQ(StringPtr("1").parseAs<int32_t>(), 1);
+  EXPECT_EQ(StringPtr("2147483647").parseAs<int32_t>(), 2147483647);
+  EXPECT_EQ(StringPtr("-2147483648").parseAs<int32_t>(), -2147483648);
+  KJ_EXPECT_THROW_MESSAGE("out-of-range", StringPtr("2147483648").parseAs<int32_t>());
+  KJ_EXPECT_THROW_MESSAGE("out-of-range", StringPtr("-2147483649").parseAs<int32_t>());
+
+  EXPECT_EQ(StringPtr("1").parseAs<uint32_t>(), 1);
+  EXPECT_EQ(StringPtr("0").parseAs<uint32_t>(), 0U);
+  EXPECT_EQ(StringPtr("4294967295").parseAs<uint32_t>(), 4294967295U);
+  KJ_EXPECT_THROW_MESSAGE("out-of-range", StringPtr("-1").parseAs<uint32_t>());
+  KJ_EXPECT_THROW_MESSAGE("out-of-range", StringPtr("4294967296").parseAs<uint32_t>());
+
+  EXPECT_EQ(StringPtr("1").parseAs<int16_t>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<uint16_t>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<int8_t>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<uint8_t>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<char>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<signed char>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<unsigned char>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<short>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<unsigned short>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<int>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<unsigned>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<long>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<unsigned long>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<long long>(), 1);
+  EXPECT_EQ(StringPtr("1").parseAs<unsigned long long>(), 1);
+
+  EXPECT_EQ(heapString("1").parseAs<int>(), 1);
+}
+
 #if KJ_COMPILER_SUPPORTS_STL_STRING_INTEROP
 TEST(String, StlInterop) {
   std::string foo = "foo";

c++/src/kj/string.c++

@@ -25,6 +25,7 @@
 #include <float.h>
 #include <errno.h>
 #include <stdlib.h>
+#include <limits>
 
 namespace kj {
 
@@ -33,6 +34,71 @@ namespace kj {
 // Warns that sprintf() is buffer-overrunny. We know that, it's cool.
 #endif
 
+namespace {
+
+long long parseSigned(const StringPtr& s, long long min, long long max) {
+  KJ_REQUIRE(s != nullptr, "String does not contain valid number", s);
+  char *endPtr;
+  errno = 0;
+  auto value = strtoll(s.begin(), &endPtr, 10);
+  KJ_REQUIRE(endPtr == s.end(), "String does not contain valid number", s);
+  KJ_REQUIRE(errno != ERANGE, "Value out-of-range", s);
+  KJ_REQUIRE(value >= min && value <= max, "Value out-of-range", value, min, max);
+  return value;
+}
+
+unsigned long long parseUnsigned(const StringPtr& s, unsigned long long max) {
+  KJ_REQUIRE(s != nullptr, "String does not contain valid number", s);
+  char *endPtr;
+  errno = 0;
+  auto value = strtoull(s.begin(), &endPtr, 10);
+  KJ_REQUIRE(endPtr == s.end(), "String does not contain valid number", s);
+  KJ_REQUIRE(errno != ERANGE, "Value out-of-range", s);
+  KJ_REQUIRE(value <= max, "Value out-of-range", value, max);
+  KJ_REQUIRE(s[0] != '-', "Value out-of-range", s); //strtoull("-1") does not fail with ERANGE
+  return value;
+}
+
+template <typename T>
+T parseInteger(const StringPtr& s) {
+  if (std::numeric_limits<T>::is_signed) {
+    auto min = (long long) std::numeric_limits<T>::min();
+    auto max = (long long) std::numeric_limits<T>::max();
+    return static_cast<T>(parseSigned(s, min, max));
+  } else {
+    auto max = (unsigned long long) std::numeric_limits<T>::max();
+    return static_cast<T>(parseUnsigned(s, max));
+  }
+}
+
+double parseDouble(const StringPtr& s) {
+  KJ_REQUIRE(s != nullptr, "String does not contain valid number", s);
+  char *endPtr;
+  errno = 0;
+  auto value = strtod(s.begin(), &endPtr);
+  KJ_REQUIRE(endPtr == s.end(), "String does not contain valid floating number", s);
+  return value;
+}
+
+} // namespace
+
+#define PARSE_AS_INTEGER(T) \
+    template <> T StringPtr::parseAs<T>() const { return parseInteger<T>(*this); }
+PARSE_AS_INTEGER(char);
+PARSE_AS_INTEGER(signed char);
+PARSE_AS_INTEGER(unsigned char);
+PARSE_AS_INTEGER(short);
+PARSE_AS_INTEGER(unsigned short);
+PARSE_AS_INTEGER(int);
+PARSE_AS_INTEGER(unsigned int);
+PARSE_AS_INTEGER(long);
+PARSE_AS_INTEGER(unsigned long);
+PARSE_AS_INTEGER(long long);
+PARSE_AS_INTEGER(unsigned long long);
+#undef PARSE_AS_INTEGER
+template <> double StringPtr::parseAs<double>() const { return parseDouble(*this); }
+template <> float StringPtr::parseAs<float>() const { return parseDouble(*this); }
+
 String heapString(size_t size) {
   char* buffer = _::HeapArrayDisposer::allocate<char>(size + 1);
   buffer[size] = '\0';

c++/src/kj/string.h

@@ -112,6 +112,9 @@ public:
   inline Maybe<size_t> findFirst(char c) const;
   inline Maybe<size_t> findLast(char c) const;
 
+  template <typename T>
+  T parseAs() const;
+
 private:
   inline StringPtr(ArrayPtr<const char> content): content(content) {}
 
@@ -121,6 +124,20 @@ private:
 inline bool operator==(const char* a, const StringPtr& b) { return b == a; }
 inline bool operator!=(const char* a, const StringPtr& b) { return b != a; }
 
+template <> char StringPtr::parseAs<char>() const;
+template <> signed char StringPtr::parseAs<signed char>() const;
+template <> unsigned char StringPtr::parseAs<unsigned char>() const;
+template <> short StringPtr::parseAs<short>() const;
+template <> unsigned short StringPtr::parseAs<unsigned short>() const;
+template <> int StringPtr::parseAs<int>() const;
+template <> unsigned StringPtr::parseAs<unsigned>() const;
+template <> long StringPtr::parseAs<long>() const;
+template <> unsigned long StringPtr::parseAs<unsigned long>() const;
+template <> long long StringPtr::parseAs<long long>() const;
+template <> unsigned long long StringPtr::parseAs<unsigned long long>() const;
+template <> float StringPtr::parseAs<float>() const;
+template <> double StringPtr::parseAs<double>() const;
+
 // =======================================================================================
 // String -- A NUL-terminated Array<char> containing UTF-8 text.
 //
@@ -182,6 +199,10 @@ public:
   inline Maybe<size_t> findFirst(char c) const { return StringPtr(*this).findFirst(c); }
   inline Maybe<size_t> findLast(char c) const { return StringPtr(*this).findLast(c); }
 
+  template <typename T>
+  T parseAs() const { return StringPtr(*this).parseAs<T>(); }
+  // Parse as number
+
 private:
   Array<char> content;
 };