Posts Tagged ‘Union’

Converting C structs and unions to Pascal (or Object Pascal / Delphi) records

I’ve been recently adding support for QuickTime TimeCode tracks to the JEDI QuickTime library’s “qt_QuickTimeComponents.pas” file and I thought I should share a quick reminder on how we convert C structs (records) and unions (sets) into Pascal (Delphi / Object Pascal in this case) records:


struct TimeCodeCounter {
long counter;
typedef struct TimeCodeCounter TimeCodeCounter;

long=integer; //in JEDI QuickTime I opted to create aliases for common C types to avoid converting them to Pascal equivalents everywhere
TimeCodeCounter = record


union TimeCodeRecord {
TimeCodeTime t;
TimeCodeCounter c;

type TimeCodeRecord = record
case integer of //C’s union
0: (t: TimeCodeTime);
1: (c: TimeCodeCounter);

Do note that you should use “packed record” in Pascal if the C code uses respective #pragma command to define 0-packing gap between record fields (the default for C and Pascal compilers is to do field alignment to word [16-bit] boundaries for optimization purposes)

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