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Tier1: properly implement UtlString methods

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Determine proper stack buf size for ssize_t += operator. If its 64bits then the buf should be doubled to accommodate for the maximum number of digits in a 64bit decimal number. Also properly determine stack buf size of double += operator. For FormatV, instead of a fixed stack buffer, perform a dry run to determine required buflen, reserve num char bytes of memory and write into it again on the next call.
This commit is contained in:
Kawe Mazidjatari 2024-02-06 14:48:11 +01:00
parent b094040c64
commit fe32055f7c
1 changed files with 39 additions and 10 deletions
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49
r5dev/tier1/utlstring.cpp
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@ -365,10 +365,14 @@ CUtlString &CUtlString::operator+=( char c )
CUtlString &CUtlString::operator+=( ssize_t rhs )
{
Assert( !m_Storage.IsReadOnly() );
Assert( sizeof( rhs ) == 4 );
Assert( sizeof( rhs ) == sizeof( ssize_t ) );
char tmpBuf[ 12 ]; // Sufficient for a signed 32 bit integer [ -2147483648 to +2147483647 ]
Q_snprintf( tmpBuf, sizeof( tmpBuf ), "%lld", rhs );
// 12 = sufficient for a signed 32 bit integer [ -2147483648 to +2147483647 ]
// 22 = sufficient for a signed 64 bit integer [ -9223372036854775807 to +9223372036854775807 ]
const size_t bufLen = sizeof( ssize_t ) == 4 ? 12 : 22;
char tmpBuf[ bufLen ];
Q_snprintf( tmpBuf, sizeof( tmpBuf ), "%zd", rhs );
tmpBuf[ sizeof( tmpBuf ) - 1 ] = '\0';
return operator+=( tmpBuf );
@ -378,7 +382,17 @@ CUtlString &CUtlString::operator+=( double rhs )
{
Assert( !m_Storage.IsReadOnly() );
char tmpBuf[ 256 ]; // How big can doubles be??? Dunno.
// from: https://stackoverflow.com/questions/1701055/what-is-the-maximum-length-in-chars-needed-to-represent-any-double-value
//
// The longest number is actually the smallest representable negative
// number: it needs enough digits to cover both the exponent and the
// mantissa. This value is -pow(2, DBL_MIN_EXP - DBL_MANT_DIG), where
// DBL_MIN_EXP is negative. It's fairly easy to see (and prove by
// induction) that -pow(2,-N) needs 3+N characters for a non-scientific
// decimal representation ("-0.", followed by N digits).
const size_t maxDigits = ( sizeof( "-0." ) - 1 ) + DBL_MANT_DIG - DBL_MIN_EXP;
char tmpBuf[ maxDigits + 1 ]; // +1 for terminating NULL.
Q_snprintf( tmpBuf, sizeof( tmpBuf ), "%lg", rhs );
tmpBuf[ sizeof( tmpBuf ) - 1 ] = '\0';
@ -411,13 +425,28 @@ int CUtlString::Format( const char *pFormat, ... )
int CUtlString::FormatV( const char *pFormat, va_list marker )
{
char tmpBuf[ 4096 ]; //< Nice big 4k buffer, as much memory as my first computer had, a Radio Shack Color Computer
// Initialize use of the variable argument array.
va_list argsCopy;
va_copy( argsCopy, marker );
//va_start( marker, pFormat );
int len = V_vsprintf_safe( tmpBuf, pFormat, marker );
//va_end( marker );
Set( tmpBuf );
return len;
// Dry run to obtain required buffer size.
const int iLen = vsnprintf( nullptr, 0, pFormat, argsCopy );
va_end( argsCopy );
assert( iLen >= 0 );
if ( iLen <= 0 )
{
Clear();
}
else
{
// NOTE: SetLength already adds +1 to account for the terminating NULL.
SetLength( iLen );
vsnprintf( (char*)m_Storage.Get(), m_Storage.Length(), pFormat, marker );
}
return iLen;
}
//-----------------------------------------------------------------------------