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Add semicolon and hex notation support to the MOS VDU command #118

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Add semicolon and hex notation support to the MOS VDU command #118

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f15d836
Add semicolon and hex notation support to VDU command.
HeathenUK Nov 21, 2023
5e73f2a
Don't try to strip 0x notation since strtol is designed to cope with it.
HeathenUK Nov 21, 2023
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64 changes: 54 additions & 10 deletions src/mos.c
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Original file line number Diff line number Diff line change
Expand Up @@ -640,16 +640,60 @@ int mos_cmdSET(char * ptr) {
// Returns:
// - MOS error code
//
int mos_cmdVDU(char *ptr) {
UINT24 value;

while(mos_parseNumber(NULL, &value)) {
if(value > 255) {
return 19; // Bad Parameter
}
putch(value);
}
return 0;
int mos_cmdVDU(char *ptr) {
char *value_str;
UINT24 value = 0;

while (mos_parseString(NULL, &value_str)) {
UINT8 isLong = 0;
UINT8 base = 10;
char *endPtr;
size_t len = strlen(value_str);

//Strip semicolon notation and set as Long
if (len > 0 && value_str[len - 1] == ';') {
value_str[len - 1] = '\0';
len--;
isLong = 1;
}

// Check for '0x' or '0X' prefix
if (len > 2 && (value_str[0] == '0' && tolower(value_str[1] == 'x'))) {
base = 16;
value_str += 2;
len -= 2;
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I think these 2 lines should be removed and let strtol() call below to deal with this prefix. Otherwise, the parsing code will allow input like 0x0xFE to be parsed as a valid number.

Also, the independent checks for prefix/suffix should probably be converted to sequence of if / elseif. The idea is to accept as valid only numbers with at most one prefix or suffix, not any combination of all possible prefixes/suffixes.

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Agreed on those two lines, since strtol can handle 0x prefixes there's no need.

We discussed the second point and it costs us nothing to deal with situations where a user may double up on notation.

}
// Check for '&' prefix
if (value_str[0] == '&') {
base = 16;
value_str++;
len--;
}
// Check for 'h' suffix
if (len > 0 && tolower(value_str[len - 1]) == 'h') {
value_str[len - 1] = '\0';
base = 16;
}

value = strtol(value_str, &endPtr, base);

if (*endPtr != '\0' || value > 65535) {
return 19;
}

if (value > 255) {
isLong = 1;
}

if (isLong) {
putch(value & 0xFF); // write LSB
putch(value >> 8); // write MSB
} else {
putch(value);
}
}

return 0;
}

// TIME
Expand Down