如何理解 PlaySound 函数 API 文档并在 MASM 中实现？

Question

I know that putting 20001h in PlaySound function as the last parameter can make the music play synchronously. But why is 20001h? I also wanted the music played in the background "repeatedly" but I couldn't understand the API document since it does not mention 20001h stands for SND_SYNC nor show what stands for SND_LOOP. Need some enlightenment, big thank!

This is my code:

includelib Winmm.lib
PlaySound PROTO,
        pszSound:PTR BYTE, 
        hmod:DWORD, 
        fdwSound:DWORD

file BYTE "test.wav",0
SND_SYNC DWORD 0

main proc
    mov SND_SYNC, 20001H 
    INVOKE PlaySound, OFFSET file, NULL, SND_SYNC

.......

Answer 1

I know that putting 20001h in PlaySound function as the last parameter can make the music play synchronously.

That is incorrect. It plays the file asynchronously .

The last parameter is a bitmask, it can hold multiple flags OR'ed together. SND_SYNC is defined as 00000h (the absence of any other flags), whereas 20001h is a combination of SND_ASYNC ( 00001h ) OR'ed with SND_FILENAME ( 20000h ).

SND_LOOP ( 00008h ) can only be used in combination with SND_ASYNC .

So, to accomplish what you want:

I also wanted the music played in the background "repeatedly"

You need to combine the SND_FILENAME , SND_ASYNC , and SND_LOOP flags. That numeric value is 20009h .

Here are all of the flags you can use with PlaySound() . Their meanings are explained in PlaySound 's documentation ¹ :

Name	Value
SND_SYNC	0x00000000
SND_ASYNC	0x00000001
SND_NODEFAULT	0x00000002
SND_MEMORY	0x00000004
SND_LOOP	0x00000008
SND_NOSTOP	0x00000010
SND_PURGE	0x00000040
SND_APPLICATION	0x00000080
SND_NOWAIT	0x00002000
SND_ALIAS	0x00010000
SND_ALIAS_ID	0x00110000
SND_FILENAME	0x00020000
SND_RESOURCE	0x00040000
SND_SENTRY	0x00080000
SND_RING	0x00100000
SND_SYSTEM	0x00200000

¹ Note: SND_RING is undocumented, but you can see that SND_ALIAS_ID is a combination of SND_RING OR'ed with SND_ALIAS .