//----------------------------------------------------------------------
// If a pair of valid hex digits exist at the head of the
// StringExtractor they are decoded into an unsigned byte and returned
// by this function
//
// If there is not a pair of valid hex digits at the head of the
// StringExtractor, it is left unchanged and -1 is returned
//----------------------------------------------------------------------
int StringExtractor::DecodeHexU8() {
SkipSpaces();
if (GetBytesLeft() < 2) {
return -1;
}
const int hi_nibble = xdigit_to_sint(m_packet[m_index]);
const int lo_nibble = xdigit_to_sint(m_packet[m_index + 1]);
if (hi_nibble == -1 || lo_nibble == -1) {
return -1;
}
m_index += 2;
return (uint8_t)((hi_nibble << 4) + lo_nibble);
}
uint64_t StringExtractor::GetHexMaxU64(bool little_endian,
uint64_t fail_value) {
uint64_t result = 0;
uint32_t nibble_count = 0;
SkipSpaces();
if (little_endian) {
uint32_t shift_amount = 0;
while (m_index < m_packet.size() && ::isxdigit(m_packet[m_index])) {
// Make sure we don't exceed the size of a uint64_t...
if (nibble_count >= (sizeof(uint64_t) * 2)) {
m_index = UINT64_MAX;
return fail_value;
}
uint8_t nibble_lo;
uint8_t nibble_hi = xdigit_to_sint(m_packet[m_index]);
++m_index;
if (m_index < m_packet.size() && ::isxdigit(m_packet[m_index])) {
nibble_lo = xdigit_to_sint(m_packet[m_index]);
++m_index;
result |= ((uint64_t)nibble_hi << (shift_amount + 4));
result |= ((uint64_t)nibble_lo << shift_amount);
nibble_count += 2;
shift_amount += 8;
} else {
result |= ((uint64_t)nibble_hi << shift_amount);
nibble_count += 1;
shift_amount += 4;
}
}
} else {
while (m_index < m_packet.size() && ::isxdigit(m_packet[m_index])) {
// Make sure we don't exceed the size of a uint64_t...
if (nibble_count >= (sizeof(uint64_t) * 2)) {
m_index = UINT64_MAX;
return fail_value;
}
uint8_t nibble = xdigit_to_sint(m_packet[m_index]);
// Big Endian
result <<= 4;
result |= nibble;
++m_index;
++nibble_count;
}
}
return result;
}
//----------------------------------------------------------------------
// Extract a signed character from two hex ASCII chars in the packet
// string
//----------------------------------------------------------------------
int8_t
StringExtractor::GetHexS8 (int8_t fail_value)
{
if (GetNumHexASCIICharsAtFilePos(2))
{
char hi_nibble_char = m_packet[m_index];
char lo_nibble_char = m_packet[m_index+1];
if (isxdigit(hi_nibble_char) && isxdigit(lo_nibble_char))
{
char hi_nibble = xdigit_to_sint (hi_nibble_char);
char lo_nibble = xdigit_to_sint (lo_nibble_char);
m_index += 2;
return (hi_nibble << 4) + lo_nibble;
}
}
m_index = UINT32_MAX;
return fail_value;
}
