[API/SDK] Add ASCII helpers and remove regex from InstrumentMetaDataValidator

CHANGELOG.md

@@ -15,6 +15,9 @@ Increment the:
 
 ## [Unreleased]
 
+* [API/SDK] Add ASCII helpers and remove regex from InstrumentMetaDataValidator
+  [#4715](https://github.com/open-telemetry/opentelemetry-cpp/pull/4715)
+
 * [SDK] Release provider mutexes before construction-failure diagnostics so
   custom log handlers can retrieve cached or noop tracers, loggers, and meters
   from the same provider without deadlocking.

api/include/opentelemetry/baggage/baggage.h

@@ -3,8 +3,7 @@
 
 #pragma once
 
-#include <cctype>
-
+#include "opentelemetry/common/detail/ascii.h"
 #include "opentelemetry/common/kv_properties.h"
 #include "opentelemetry/common/macros.h"
 #include "opentelemetry/nostd/shared_ptr.h"
@@ -215,16 +214,11 @@ class OPENTELEMETRY_EXPORT Baggage
   // Implementation inspired from : https://golang.org/src/net/url/url.go?s=7851:7884#L264
   static std::string UrlEncode(nostd::string_view str)
   {
-    auto to_hex = [](char c) -> char {
-      static const char *hex = "0123456789ABCDEF";
-      return hex[c & 15];
-    };
-
     std::string ret;
 
     for (auto c : str)
     {
-      if (std::isalnum(c) || c == '-' || c == '_' || c == '.' || c == '~')
+      if (common::detail::IsAsciiAlnum(c) || c == '-' || c == '_' || c == '.' || c == '~')
       {
         ret.push_back(c);
       }
@@ -235,8 +229,8 @@ class OPENTELEMETRY_EXPORT Baggage
       else
       {
         ret.push_back('%');
-        ret.push_back(to_hex(static_cast<char>(c >> 4)));
-        ret.push_back(to_hex(static_cast<char>(c & 15)));
+        ret.push_back(common::detail::UpperHexDigit(static_cast<unsigned char>(c) >> 4));
+        ret.push_back(common::detail::UpperHexDigit(c));
       }
     }
 
@@ -246,29 +240,21 @@ class OPENTELEMETRY_EXPORT Baggage
   // Uri decode key value pairs after extracting from header
   static std::string UrlDecode(nostd::string_view str, bool &err)
   {
-    auto IsHex = [](char c) {
-      return std::isdigit(c) || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
-    };
-
-    auto from_hex = [](char c) -> char {
-      // c - '0' produces integer type which could trigger error/warning when casting to char,
-      // but the cast is safe here.
-      return static_cast<char>(std::isdigit(c) ? c - '0' : std::toupper(c) - 'A' + 10);
-    };
-
     std::string ret;
     ret.reserve(str.size());
 
     for (size_t i = 0; i < str.size(); i++)
     {
       if (str[i] == '%')
       {
-        if (i + 2 >= str.size() || !IsHex(str[i + 1]) || !IsHex(str[i + 2]))
+        if (i + 2 >= str.size() || !common::detail::IsAsciiHexDigit(str[i + 1]) ||
+            !common::detail::IsAsciiHexDigit(str[i + 2]))
         {
           err = true;
           return "";
         }
-        ret.push_back(static_cast<char>(from_hex(str[i + 1]) << 4 | from_hex(str[i + 2])));
+        ret.push_back(static_cast<char>(common::detail::HexDigitValue(str[i + 1]) << 4 |
+                                        common::detail::HexDigitValue(str[i + 2])));
         i += 2;
       }
       else if (str[i] == '+')

api/include/opentelemetry/common/detail/ascii.h

@@ -0,0 +1,106 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include <cstdint>
+
+#include "opentelemetry/version.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace common
+{
+namespace detail
+{
+
+// Character classes for protocol and specification text, which define them over
+// ASCII. The <cctype> functions depend on the global locale, and passing them a
+// negative char is undefined behavior.
+
+constexpr bool IsAsciiDigit(char c) noexcept
+{
+  return c >= '0' && c <= '9';
+}
+
+constexpr bool IsAsciiLower(char c) noexcept
+{
+  return c >= 'a' && c <= 'z';
+}
+
+constexpr bool IsAsciiUpper(char c) noexcept
+{
+  return c >= 'A' && c <= 'Z';
+}
+
+constexpr bool IsAsciiAlpha(char c) noexcept
+{
+  return IsAsciiLower(c) || IsAsciiUpper(c);
+}
+
+constexpr bool IsAsciiAlnum(char c) noexcept
+{
+  return IsAsciiAlpha(c) || IsAsciiDigit(c);
+}
+
+// Indexed by byte value: hexadecimal digits are decoded on the propagation hot
+// path, where a lookup is faster than range comparisons.
+constexpr int8_t kHexDigitValues[256] = {
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1};
+
+// Returns the value of a hexadecimal digit of either case, or -1 if c is not one.
+constexpr int HexDigitValue(char c) noexcept
+{
+  return kHexDigitValues[static_cast<unsigned char>(c)];
+}
+
+constexpr bool IsAsciiHexDigit(char c) noexcept
+{
+  return HexDigitValue(c) >= 0;
+}
+
+// Returns the hexadecimal digit for the low four bits of value.
+constexpr char LowerHexDigit(int value) noexcept
+{
+  return "0123456789abcdef"[value & 0xF];
+}
+
+constexpr char UpperHexDigit(int value) noexcept
+{
+  return "0123456789ABCDEF"[value & 0xF];
+}
+
+// 0x00 to 0x1F and 0x7F: what std::iscntrl accepts in the "C" locale.
+constexpr bool IsAsciiControl(char c) noexcept
+{
+  return static_cast<unsigned char>(c) < 0x20 || c == '\x7f';
+}
+
+// Space, \t, \n, \v, \f and \r: what std::isspace accepts in the "C" locale.
+constexpr bool IsAsciiSpace(char c) noexcept
+{
+  return c == ' ' || (c >= '\t' && c <= '\r');
+}
+
+constexpr char ToAsciiLower(char c) noexcept
+{
+  return IsAsciiUpper(c) ? static_cast<char>(c - 'A' + 'a') : c;
+}
+
+constexpr char ToAsciiUpper(char c) noexcept
+{
+  return IsAsciiLower(c) ? static_cast<char>(c - 'a' + 'A') : c;
+}
+
+}  // namespace detail
+}  // namespace common
+OPENTELEMETRY_END_NAMESPACE

api/include/opentelemetry/common/string_util.h

@@ -3,8 +3,7 @@
 
 #pragma once
 
-#include <cctype>
-
+#include "opentelemetry/common/detail/ascii.h"
 #include "opentelemetry/common/macros.h"
 
 #if OPENTELEMETRY_HAVE_EXCEPTIONS
@@ -29,11 +28,11 @@ class StringUtil
     {
       return nostd::string_view();
     }
-    while (left <= right && std::isspace(str[left]))
+    while (left <= right && detail::IsAsciiSpace(str[left]))
     {
       left++;
     }
-    while (left <= right && std::isspace(str[right]))
+    while (left <= right && detail::IsAsciiSpace(str[right]))
     {
       right--;
     }

api/include/opentelemetry/context/propagation/environment_carrier.h

@@ -8,6 +8,7 @@
 #include <memory>
 #include <string>
 
+#include "opentelemetry/common/detail/ascii.h"
 #include "opentelemetry/context/propagation/text_map_propagator.h"
 #include "opentelemetry/nostd/string_view.h"
 #include "opentelemetry/version.h"
@@ -135,17 +136,13 @@ class EnvironmentCarrier : public TextMapCarrier
     std::string result(key);
     for (auto &c : result)
     {
-      unsigned char uc = static_cast<unsigned char>(c);
-      if (uc >= 'a' && uc <= 'z')
-      {
-        c = static_cast<char>(uc - ('a' - 'A'));
-      }
-      else if (!((uc >= 'A' && uc <= 'Z') || (uc >= '0' && uc <= '9') || uc == '_'))
+      c = common::detail::ToAsciiUpper(c);
+      if (!common::detail::IsAsciiUpper(c) && !common::detail::IsAsciiDigit(c) && c != '_')
       {
         c = '_';
       }
     }
-    if (result[0] >= '0' && result[0] <= '9')
+    if (common::detail::IsAsciiDigit(result[0]))
     {
       result.insert(result.begin(), '_');
     }

api/include/opentelemetry/trace/propagation/detail/hex.h

@@ -7,6 +7,7 @@
 #include <cstdint>
 #include <cstring>
 
+#include "opentelemetry/common/detail/ascii.h"
 #include "opentelemetry/nostd/string_view.h"
 #include "opentelemetry/version.h"
 
@@ -20,28 +21,9 @@ namespace propagation
 namespace detail
 {
 
-constexpr int8_t kHexDigits[256] = {
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-};
-
-inline int8_t HexToInt(char c)
-{
-  return kHexDigits[static_cast<uint8_t>(c)];
-}
-
 inline bool IsValidHex(nostd::string_view s)
 {
-  return std::all_of(s.begin(), s.end(), [](char c) { return HexToInt(c) != -1; });
+  return std::all_of(s.begin(), s.end(), [](char c) { return common::detail::IsAsciiHexDigit(c); });
 }
 
 /**
@@ -66,12 +48,13 @@ inline bool HexToBinary(nostd::string_view hex, uint8_t *buffer, size_t buffer_s
 
   if (is_hex_size_odd)
   {
-    buffer[buffer_pos++] = HexToInt(hex[i++]);
+    buffer[buffer_pos++] = static_cast<uint8_t>(common::detail::HexDigitValue(hex[i++]));
   }
 
   for (; i < last_hex_pos; i += 2)
   {
-    buffer[buffer_pos++] = (HexToInt(hex[i]) << 4) | HexToInt(hex[i + 1]);
+    buffer[buffer_pos++] = static_cast<uint8_t>((common::detail::HexDigitValue(hex[i]) << 4) |
+                                                common::detail::HexDigitValue(hex[i + 1]));
   }
 
   return true;

api/include/opentelemetry/trace/span_id.h

@@ -6,6 +6,7 @@
 #include <cstdint>
 #include <cstring>
 
+#include "opentelemetry/common/detail/ascii.h"
 #include "opentelemetry/nostd/span.h"
 #include "opentelemetry/version.h"
 
@@ -31,11 +32,10 @@ class SpanId final
   // Populates the buffer with the lowercase base16 representation of the ID.
   void ToLowerBase16(nostd::span<char, 2 * kSize> buffer) const noexcept
   {
-    constexpr char kHex[] = "0123456789abcdef";
     for (size_t i = 0; i < kSize; ++i)
     {
-      buffer[i * 2 + 0] = kHex[(rep_[i] >> 4) & 0xF];
-      buffer[i * 2 + 1] = kHex[(rep_[i] >> 0) & 0xF];
+      buffer[i * 2 + 0] = common::detail::LowerHexDigit(rep_[i] >> 4);
+      buffer[i * 2 + 1] = common::detail::LowerHexDigit(rep_[i]);
     }
   }
 

api/include/opentelemetry/trace/trace_flags.h

@@ -5,6 +5,7 @@
 
 #include <cstdint>
 
+#include "opentelemetry/common/detail/ascii.h"
 #include "opentelemetry/nostd/span.h"
 #include "opentelemetry/version.h"
 
@@ -44,9 +45,8 @@ class TraceFlags final
   // Populates the buffer with the lowercase base16 representation of the flags.
   void ToLowerBase16(nostd::span<char, 2> buffer) const noexcept
   {
-    constexpr char kHex[] = "0123456789ABCDEF";
-    buffer[0]             = kHex[(rep_ >> 4) & 0xF];
-    buffer[1]             = kHex[(rep_ >> 0) & 0xF];
+    buffer[0] = common::detail::UpperHexDigit(rep_ >> 4);
+    buffer[1] = common::detail::UpperHexDigit(rep_);
   }
 
   uint8_t flags() const noexcept { return rep_; }

api/include/opentelemetry/trace/trace_id.h

@@ -6,6 +6,7 @@
 #include <cstdint>
 #include <cstring>
 
+#include "opentelemetry/common/detail/ascii.h"
 #include "opentelemetry/nostd/span.h"
 #include "opentelemetry/version.h"
 
@@ -34,11 +35,10 @@ class TraceId final
   // Populates the buffer with the lowercase base16 representation of the ID.
   void ToLowerBase16(nostd::span<char, 2 * kSize> buffer) const noexcept
   {
-    constexpr char kHex[] = "0123456789abcdef";
     for (size_t i = 0; i < kSize; ++i)
     {
-      buffer[i * 2 + 0] = kHex[(rep_[i] >> 4) & 0xF];
-      buffer[i * 2 + 1] = kHex[(rep_[i] >> 0) & 0xF];
+      buffer[i * 2 + 0] = common::detail::LowerHexDigit(rep_[i] >> 4);
+      buffer[i * 2 + 1] = common::detail::LowerHexDigit(rep_[i]);
     }
   }
 

api/include/opentelemetry/trace/trace_state.h

@@ -3,11 +3,11 @@
 
 #pragma once
 
-#include <cctype>
 #include <cstddef>
 #include <string>
 #include <vector>
 
+#include "opentelemetry/common/detail/ascii.h"
 #include "opentelemetry/common/kv_properties.h"
 #include "opentelemetry/nostd/function_ref.h"
 #include "opentelemetry/nostd/shared_ptr.h"
@@ -298,7 +298,7 @@ class OPENTELEMETRY_EXPORT TraceState
 
   static bool IsLowerCaseAlphaOrDigit(char c) noexcept
   {
-    return std::isdigit(c) || std::islower(c);
+    return common::detail::IsAsciiDigit(c) || common::detail::IsAsciiLower(c);
   }
 
 private: