epee: speedup word/number matching

Number matching semantics are slightly changed: since this is used
as a filter to check whether a number is signed and/or floating
point, we can speed this up further. strto* functions are called
afterwards and will error out where necessary. We now also accept
numbers like .4 which were not accepted before.

The strto* calls on a boost::string_ref will not access unallocated
memory since the parsers always stop at the first bad character,
and the original string is zero terminated.

in arbitrary time measurement units for some arbitrary test case:

match_number2: 235 -> 70
match_word2: 330 -> 108

1 files changed, 58 insertions, 14 deletions

diff --git a/contrib/epee/include/storages/parserse_base_utils.h b/contrib/epee/include/storages/parserse_base_utils.h
index d73fbde3a..69b650cd4 100644
--- a/contrib/epee/include/storages/parserse_base_utils.h
+++ b/contrib/epee/include/storages/parserse_base_utils.h
@@ -29,6 +29,7 @@
 #pragma once 
 
 #include <algorithm>
+#include <boost/utility/string_ref.hpp>
 
 namespace epee 
 {
@@ -36,6 +37,40 @@ namespace misc_utils
 {
   namespace parse
   {
+    // 1: digit
+    // 2: .eE (floating point)
+    // 4: alpha
+    // 8: whitespace
+    // 16: allowed in float but doesn't necessarily mean it's a float
+    static const constexpr uint8_t lut[256]={
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 8, 8, 8, 8, 0, 0, // 16
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 32
+      8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 16, 0, 16, 18, 0, // 48
+      17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 0, 0, 0, 0, 0, 0, // 64
+      0, 4, 4, 4, 4, 22, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, // 80
+      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, // 96
+      0, 4, 4, 4, 4, 22, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, // 112
+      4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, // 128
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    };
+
+    inline bool isspace(char c)
+    {
+      return lut[(uint8_t)c] & 8;
+    }
+
+    inline bool isdigit(char c)
+    {
+      return lut[(uint8_t)c] & 1;
+    }
+
     inline std::string transform_to_escape_sequence(const std::string& src)
     {
       static const char escaped[] = "\b\f\n\r\t\v\"\\/";
@@ -159,25 +194,34 @@ namespace misc_utils
           return false;
         }
       }
-      inline void match_number2(std::string::const_iterator& star_end_string, std::string::const_iterator buf_end, std::string& val, bool& is_float_val, bool& is_signed_val)
+      inline void match_number2(std::string::const_iterator& star_end_string, std::string::const_iterator buf_end, boost::string_ref& val, bool& is_float_val, bool& is_signed_val)
       {
         val.clear();
-        is_float_val = false;
-        for(std::string::const_iterator it = star_end_string;it != buf_end;it++)
+        uint8_t float_flag = 0;
+        is_signed_val = false;
+        size_t chars = 0;
+        std::string::const_iterator it = star_end_string;
+        if (it != buf_end && *it == '-')
+        {
+          is_signed_val = true;
+          ++chars;
+          ++it;
+        }
+        for(;it != buf_end;it++)
         {
-          if(isdigit(*it) || (it == star_end_string && *it == '-') || (val.size() && *it == '.' ) || (is_float_val && (*it == 'e' || *it == 'E' || *it == '-' || *it == '+' )) )
+          const uint8_t flags = lut[(uint8_t)*it];
+          if (flags & 16)
           {
-            if(!val.size() &&  *it == '-')
-              is_signed_val = true;
-            if(*it == '.' ) 
-              is_float_val = true;
-            val.push_back(*it);
+            float_flag |= flags;
+            ++chars;
           }
           else
           {
+            val = boost::string_ref(&*star_end_string, chars);
             if(val.size())
             {
               star_end_string = --it;
+              is_float_val = !!(float_flag & 2);
               return;
             }
             else 
@@ -186,7 +230,7 @@ namespace misc_utils
         }
         ASSERT_MES_AND_THROW("wrong number in json entry: " << std::string(star_end_string, buf_end));
       }
-      inline bool match_number(std::string::const_iterator& star_end_string, std::string::const_iterator buf_end, std::string& val)
+      inline bool match_number(std::string::const_iterator& star_end_string, std::string::const_iterator buf_end, boost::string_ref& val)
       {
         try
         {
@@ -199,15 +243,15 @@ namespace misc_utils
           return false;
         }
       }
-      inline void match_word2(std::string::const_iterator& star_end_string, std::string::const_iterator buf_end, std::string& val)
+      inline void match_word2(std::string::const_iterator& star_end_string, std::string::const_iterator buf_end, boost::string_ref& val)
       {
         val.clear();
 
         for(std::string::const_iterator it = star_end_string;it != buf_end;it++)
         {
-          if(!isalpha(*it))
+          if (!(lut[(uint8_t)*it] & 4))
           {
-            val.assign(star_end_string, it);
+            val = boost::string_ref(&*star_end_string, std::distance(star_end_string, it));
             if(val.size())
             {
               star_end_string = --it;
@@ -218,7 +262,7 @@ namespace misc_utils
         }
         ASSERT_MES_AND_THROW("failed to match word number in json entry: " << std::string(star_end_string, buf_end));
       }
-      inline bool match_word(std::string::const_iterator& star_end_string, std::string::const_iterator buf_end, std::string& val)
+      inline bool match_word(std::string::const_iterator& star_end_string, std::string::const_iterator buf_end, boost::string_ref& val)
       {
         try
         {