diff options
| -rw-r--r-- | device.vala | 60 |
1 files changed, 59 insertions, 1 deletions
diff --git a/device.vala b/device.vala index 454e79b..0fd6719 100644 --- a/device.vala +++ b/device.vala @@ -137,13 +137,71 @@ public class Device { } else { if(detected.length > 0) { detected += '\0'; - return (string) detected; + + if(((string) detected).has_prefix("USER ")) { + if(!check_code39_checksum((string) detected)) + return "SCANNER RETURNED INCORRECT DATA"; + else /* remove checksum */ + detected[detected.length-2] = '\0'; + } + + return ((string) detected); } } } } } + private bool check_code39_checksum(string data) { + int result = 0; + + for(int i = 0; i<data.length-1; i++) { + if(data[i] >= '0' && data[i] <= '9') + result += data[i] - '0'; + else if(data[i] >= 'A' && data[i] <= 'Z') + result += data[i] - 'A' + 10; + else + switch(data[i]) { + case '-': + result += 36; break; + case '.': + result += 37; break; + case ' ': + result += 38; break; + case '$': + result += 39; break; + case '/': + result += 40; break; + case '+': + result += 41; break; + case '%': + result += 42; break; + default: + /* invalid character */ + return false; + } + + result %= 43; + } + + if(result < 10) + result = result + '0'; + else if(result < 36) + result = result - 10 + 'A'; + else + switch(result) { + case 36: result = '-'; break; + case 37: result = '.'; break; + case 38: result = ' '; break; + case 39: result = '$'; break; + case 40: result = '/'; break; + case 41: result = '+'; break; + case 42: result = '%'; break; + } + + return (data[data.length-1] == result); + } + /** * @param duration duration of the blink in 0.1 seconds */ |