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Improve performance by constructing yytext as a std::string

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o Return its contents when necessary.  In many cases, this avoids
  construction of multiple copies of the yytext token.  Exceeds
  performance of current develop branch.
This commit is contained in:
Perry Kundert 2017-10-04 08:40:32 -07:00
parent 7c523338c5
commit 97a388802d
1 changed files with 10 additions and 21 deletions
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31
src/json.hpp
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@ -1795,9 +1795,9 @@ class lexer
@brief scan a string literal
This function scans a string according to Sect. 7 of RFC 7159. While
scanning, bytes are escaped and copied into buffer yytext. Then the
function returns successfully, yytext is null-terminated and yylen
contains the number of bytes in the string.
scanning, bytes are escaped and copied into buffer yytext. Then the function
returns successfully, yytext is *not* null-terminated (as it may contain \0
bytes), and yytext.size() is the number of bytes in the string.
@return token_type::value_string if string could be successfully scanned,
token_type::parse_error otherwise
@ -2582,7 +2582,7 @@ scan_number_done:
const auto x = std::strtoull(yytext.data(), &endptr, 10);
// we checked the number format before
assert(endptr == yytext.data() + yylen);
assert(endptr == yytext.data() + yytext.size());
if (errno == 0)
{
@ -2598,7 +2598,7 @@ scan_number_done:
const auto x = std::strtoll(yytext.data(), &endptr, 10);
// we checked the number format before
assert(endptr == yytext.data() + yylen);
assert(endptr == yytext.data() + yytext.size());
if (errno == 0)
{
@ -2615,7 +2615,7 @@ scan_number_done:
strtof(value_float, yytext.data(), &endptr);
// we checked the number format before
assert(endptr == yytext.data() + yylen);
assert(endptr == yytext.data() + yytext.size());
return token_type::value_float;
}
@ -2647,7 +2647,7 @@ scan_number_done:
/// reset yytext; current character is beginning of token
void reset() noexcept
{
yylen = 0;
yytext.clear();
token_string.clear();
token_string.push_back(static_cast<char>(current));
}
@ -2676,14 +2676,7 @@ scan_number_done:
/// add a character to yytext
void add(int c)
{
// resize yytext if necessary; this condition is deemed unlikely,
// because we start with a 1024-byte buffer
if (JSON_UNLIKELY((yylen + 1 > yytext.capacity())))
{
yytext.resize(2 * yytext.capacity(), '\0');
}
assert(yylen < yytext.size());
yytext[yylen++] = static_cast<char>(c);
yytext.push_back(static_cast<char>(c));
}
public:
@ -2712,9 +2705,7 @@ scan_number_done:
/// return string value
const std::string get_string()
{
// yytext cannot be returned as char*, because it may contain a null
// byte (parsed as "\u0000")
return std::string(yytext.data(), yylen);
return std::move( yytext );
}
/////////////////////
@ -2844,9 +2835,7 @@ scan_number_done:
std::vector<char> token_string = std::vector<char>();
/// buffer for variable-length tokens (numbers, strings)
std::vector<char> yytext = std::vector<char>(1024, '\0');
/// current index in yytext
std::size_t yylen = 0;
std::string yytext = "";
/// a description of occurred lexer errors
const char* error_message = "";