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Fix strtol(3) quality.

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This commit is contained in:
Jonas 'Sortie' Termansen 2014-09-14 20:03:16 +02:00
parent 228bf52b49
commit 513c5f242d
1 changed files with 91 additions and 54 deletions
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145
libc/stdlib/strtol.cpp
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@ -1,6 +1,6 @@
/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2011, 2013.
Copyright(C) Jonas 'Sortie' Termansen 2011, 2013, 2014.
This file is part of the Sortix C Library.
@ -73,6 +73,10 @@ static bool would_multiplication_overflow(T_INT a, T_INT b)
if ( !a || !b )
return false;
// Trivial cases.
if ( a == 1 || b == 1 )
return false;
// Check if we have a 64-bit integer that it is large enough.
if ( sizeof(T_INT)*2 <= sizeof(int64_t) )
{
@ -111,7 +115,7 @@ static bool would_multiplication_overflow(T_INT a, T_INT b)
T_UNSIGNED_INT b_abs = b < 0 ? - (T_UNSIGNED_INT) b : b;
T_UNSIGNED_INT min_abs = - (T_UNSIGNED_INT) T_INT_MIN;
T_UNSIGNED_INT max_abs = T_INT_MAX;
T_UNSIGNED_INT limit_pos = (0 <= a && 0 <= b) || ( a < 0 && b < 0 );
T_UNSIGNED_INT limit_pos = (0 <= a && 0 <= b) || (a < 0 && b < 0);
T_UNSIGNED_INT limit = limit_pos ? max_abs : min_abs;
T_UNSIGNED_INT max_b = a_abs / limit;
return max_b < b_abs;
@ -120,24 +124,23 @@ static bool would_multiplication_overflow(T_INT a, T_INT b)
extern "C"
STRTOL_INT STRTOL(const STRTOL_CHAR* restrict str,
STRTOL_CHAR** restrict endptr,
STRTOL_CHAR** restrict end_ptr,
int base)
{
const STRTOL_CHAR* origstr = str;
int origbase = base;
// Reject bad bases.
if ( base < 0 || base == 1 || 36 < base )
{
if ( end_ptr )
*end_ptr = (STRTOL_CHAR*) str;
return errno = EINVAL, 0;
}
const STRTOL_CHAR* original_str = str;
// Skip any leading white space.
while ( STRTOL_ISSPACE(*str) )
str++;
// Reject bad bases.
if ( base < 0 || 36 < base )
{
if ( endptr )
*endptr = (STRTOL_CHAR*) str;
return errno = EINVAL, 0;
}
bool negative = false;
STRTOL_CHAR c = *str;
@ -147,43 +150,52 @@ STRTOL_INT STRTOL(const STRTOL_CHAR* restrict str,
else if ( c == STRTOL_L('+') )
str++, negative = false;
// Autodetect base 8 or base 16.
if ( !base && str[0] == STRTOL_L('0') )
bool actually_negative = !STRTOL_INT_IS_UNSIGNED && negative;
// Autodetect base if requested.
if ( base == 0 )
{
if ( (str[1] == STRTOL_L('x') || str[1] == STRTOL_L('X')) &&
(str[2] && debase(str[2]) < 16) )
if ( str[0] == STRTOL_L('0') &&
(str[1] == STRTOL_L('x') || str[1] == STRTOL_L('X')) &&
(0 <= debase(str[2]) && debase(str[2]) < 16) )
str += 2, base = 16;
else if ( 0 <= debase(str[1]) )
else if ( str[0] == STRTOL_L('0') &&
0 <= debase(str[1]) && debase(str[1]) < 8 )
str++, base = 8;
else
base = 10;
}
// Default to base 10.
if ( !base )
base = 10;
// Skip the leading '0x' prefix in base 16 for hexadecimal integers.
if ( origbase == 16 &&
str[0] == STRTOL_L('0') &&
(str[1] == STRTOL_L('x') || str[1] == STRTOL_L('X')) &&
(0 <= debase(str[2]) && debase(str[2]) < 16) )
str += 2;
else if ( base == 16 )
{
if ( str[0] == STRTOL_L('0') &&
(str[1] == STRTOL_L('x') || str[1] == STRTOL_L('X')) &&
(0 <= debase(str[2]) && debase(str[2]) < 16) )
str += 2;
}
// Determine what value will be returned on overflow/underflow.
STRTOL_INT overflow_value = negative && !STRTOL_INT_IS_UNSIGNED ?
STRTOL_INT_MIN :
STRTOL_INT_MAX;
STRTOL_INT overflow_value =
actually_negative ? STRTOL_INT_MIN : STRTOL_INT_MAX;
// Convert a single character at a time.
STRTOL_INT result = 0;
size_t numconvertedchars = 0;
size_t num_converted_chars = 0;
bool overflow_occured = false;
while ( (c = *str ) )
{
// Stop if we encounterd a character that doesn't fit in this base.
// Stop if we encounter a character that doesn't fit in this base.
int val = debase(c);
if ( val < 0 || base <= val )
break;
str++;
num_converted_chars++;
if ( overflow_occured )
continue;
// Attempt to multiply the accumulator with the current base.
if ( would_multiplication_overflow<STRTOL_INT,
STRTOL_INT_IS_UNSIGNED,
@ -191,47 +203,72 @@ STRTOL_INT STRTOL(const STRTOL_CHAR* restrict str,
STRTOL_INT_MIN,
STRTOL_INT_MAX>
(result, (STRTOL_INT) base) )
overflow_occured = true, result = overflow_value;
{
overflow_occured = true;
result = overflow_value;
errno = ERANGE;
continue;
}
else
{
STRTOL_INT new_result = result * (STRTOL_INT) base;
assert( negative || result <= new_result);
assert(!negative || result >= new_result);
assert( actually_negative || result <= new_result);
assert(!actually_negative || result >= new_result);
result = new_result;
}
// Nothing needs to be added if we are encountered a zero digit.
if ( val == 0 )
{
}
// Attempt to add the latest digit to the accumulator (positive).
if ( (STRTOL_INT_IS_UNSIGNED || !negative) &&
(STRTOL_INT) val <= (STRTOL_INT) (STRTOL_INT_MAX - result) )
else if ( !actually_negative &&
(STRTOL_INT) val <= (STRTOL_INT) (STRTOL_INT_MAX - result) )
{
result += (STRTOL_INT) val;
}
// Attempt to subtract the latest digit to the accumulator (negative).
else if ( (!STRTOL_INT_IS_UNSIGNED && negative) &&
(STRTOL_UNSIGNED_INT) val < ((STRTOL_UNSIGNED_INT) result - (STRTOL_UNSIGNED_INT) STRTOL_INT_MIN) )
else if ( actually_negative &&
(STRTOL_UNSIGNED_INT) val <
((STRTOL_UNSIGNED_INT) result -
(STRTOL_UNSIGNED_INT) STRTOL_INT_MIN) )
{
result -= (STRTOL_INT) val;
}
// Handle the case where the addition/subtract would overflow/underflow.
// Otherwise, the addition/subtract would overflow/underflow.
else
overflow_occured = true, result = overflow_value;
str++;
numconvertedchars++;
{
overflow_occured = true;
result = overflow_value;
errno = ERANGE;
continue;
}
}
// If no characters were successfully converted, rewind to the start, also
// rewinding past skipped whitespace and sign characters and such.
if ( !numconvertedchars )
str = origstr, result = 0;
// If no characters were successfully converted, rewind to the start.
if ( !num_converted_chars )
{
errno = EINVAL;
str = original_str;
}
// Let the caller know where we got to.
if ( endptr )
*endptr = (STRTOL_CHAR*) str;
if ( end_ptr )
*end_ptr = (STRTOL_CHAR*) str;
// Handle the special case where we are creating an unsigned integer and the
// string was negative and non-zero and no overflow occured, then we treat
// it as (the maximum value+1) minus (the negative string as integer).
if ( STRTOL_INT_IS_UNSIGNED && negative && result && !overflow_occured )
result = STRTOL_INT_MAX - (result-1);
// string was negative. The result is the negation assuming no overflow.
if ( STRTOL_INT_IS_UNSIGNED && negative )
{
if ( overflow_occured )
result = STRTOL_INT_MAX;
else
result = -result;
}
return result;
}