API Parameter types:
|
boolean |
Four bytes are passed. The object must be a Boolean. This corresponds to type BOOL in C. |
|
double |
Eight bytes are passed. This type is intended for use with double-precision floating-point arguments such as class Float. |
|
handle |
The first four bytes of the object are passed. The object can be a variableByteSubclass and will usually be an ExternalHandle (or one of its subclasses).long Four bytes are passed. The object may be an integer in the range of -2147483648 .. +2147483647 (0x80000000 .. 0x7FFFFFFF), or it can be a byte object, and the first four bytes are passed. This corresponds to type LONG in C. |
|
self |
The object pointer itself is passed. This is used by user-defined DLL functions. |
|
short |
Four bytes are passed. The object may be an integer in the range of -32768 .. +32767 (0x8000 .. 0x7FFF), or it can be a byte object, and the first two bytes are passed. This corresponds to type SHORT in C. |
|
struct |
The four-byte address of the bytes of the object are passed. The object must be a variableByteSubclass and will usually be an ExternalBuffer. This type is used when the C argument is a pointer, such as a PSZ. |
|
structIn |
A struct pointer argument which is an IN parameter, i.e., the caller makes no changes to the structure. This is a performance optimization of the existing struct argument type. |
|
structOut |
A struct pointer argument which is an OUT parameter, i.e., the initial state of the structure is not specified and the caller will set the values. This is a performance optimization of the existing struct argument type. |
|
structValue |
This is a structure argument which is passed by value. For example, a POINTL argument is an 8-byte structure passed by value on the call stack, in contrast to a PPOINTL argument, which is a pointer to a POINTL structure |
|
ulong |
Four bytes are passed. The object may be a positive integer the range of 0..4294967295 (0xFFFFFFFF), or it can be a byte object, and the first four bytes are passed. This corresponds to type ULONG in C |
|
ushort |
Four bytes are passed. The object may be a positive integer in the range of 0 to 65535 (0xFFFF), or it can be a byte object and the first two bytes are passed. This corresponds to type USHORT in C. |
API return types:
|
hresult |
A 32-bit return value of type HRESULT. This return type is used extensively in OLE, but can also be used in non-OLE API’s. |
|
none |
Is specified if the function does not return a value. This is equivalent to declaring VOID in C |
|
short |
A 2-byte Integer, signed |
|
ushort |
A 2-byte Integer, unsigned |
|
boolean |
A 4-byte Boolean |
|
long |
A 4-byte Integer, signed |
|
ulong |
A 4-byte String, representing an unsigned integer quantity |
|
ulongReturn |
A 4-byte Integer, unsigned |
|
double |
An 8-byte Float, signed |
|
handle |
A variableByteObject (String) from which an appropriate ExternalHandle can be obtained via fromBytes: (Note: handle is actually the same as ulong) |
Documentation of the api parameter types is taken from Smalltalk for Windows Manual – Copyright by Cincom Inc.
API parameter encoding:
Compiled methods that contain the api: keyword have two special literals in their variable part:
- a string with the name of the API function
- a byte array that encodes the arguments and return types and also caches the address of the api call. The first four bytes of this array are the address cache. The next byte is the number of arguments plus one (the return type), followed by a corresponding number of bytes each indicating the argument type / return type according to this table:
|
short |
1 |
|
long |
2 |
|
boolean |
3 |
|
ushort |
4 |
|
ulong |
5 |
|
struct |
6 |
|
handle |
7 |
|
self |
8 |
|
none |
9 |
|
double |
10 |
|
ulongReturn |
11 |
|
selfIndirect |
12 |
|
structValue |
13 |
|
structIn |
14 |
|
structOut |
15 |
|
hresult |
16 |