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(svn r9883) -Fix (r4965): [NewGRF] Check for overflow and carry over when adding to the existing value.

This commit is contained in:
peter1138 2007-05-19 22:37:24 +00:00
parent 707bc97c03
commit 1ce633b894
1 changed files with 8 additions and 1 deletions
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9
src/newgrf.cpp
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@ -3094,11 +3094,18 @@ static void CfgApply(byte *buf, int len)
grfmsg(8, "CfgApply: Applying %u bytes from parameter 0x%02X at offset 0x%04X", param_size, param_num, offset);
bool carry = false;
for (i = 0; i < param_size; i++) {
uint32 value = GetParamVal(param_num + i / 4, NULL);
/* Reset carry flag for each iteration of the variable (only really
* matters if param_size is greater than 4) */
if (i == 0) carry = false;
if (add_value) {
_preload_sprite[offset + i] += GB(value, (i % 4) * 8, 8);
uint new_value = _preload_sprite[offset + i] + GB(value, (i % 4) * 8, 8) + (carry ? 1 : 0);
_preload_sprite[offset + i] = GB(new_value, 0, 8);
/* Check if the addition overflowed */
carry = new_value >= 256;
} else {
_preload_sprite[offset + i] = GB(value, (i % 4) * 8, 8);
}