how to transfer a hexadecimal to decimal in Dtwain?

[madeline799]

for example,I want to use DTWAIN_CallDSMProc,the params DG_IMAGE which hexadecimal is 0x0002L,how to transfer to decimal?Becase It has no hexadecimal in Javascript.

[dynarithmic]

Hexadecimal 0x0002 is the same as decimal 2.

[madeline799]

Could you show me the Java example? Anthor,when I use the API DTWAIN_GetTwainAppID,the return value always is -1,Is the params not correct?Could you give me a hand?Is there any problem below? const ffi = require('ffi-napi'); const ArrayType = require('ref-array-napi'); const path = require('path'); const refstruct = require('ref-struct-napi')

const version = refstruct({ 'MajorNum': 'int', 'MinorNum': 'int', 'Language': 'int', 'Country': 'int', 'Info': 'string' }) const DTWAIN_IDENTITY = refstruct({ 'Id': 'long', 'Version': version, 'ProtocolMajor': 'long', 'ProtocolMinor': 'long', 'SupportedGroups': 'long', 'Manufacturer': 'string', 'ProductFamily': 'string', 'ProductName': 'string' }); const dtw = ffi.Library(path.join(__dirname, "dll/dtwain32.dll"), { "DTWAIN_GetTwainAppID": [DTWAIN_IDENTITY, []], });

[dynarithmic]

1) Sorry, but I am not familiar with the language you are using (it looks like nodejs), so I cannot really help you in interfacing to a C structure using your language. You will have to get a node expert to help you figure out the TW_IDENTITY defined by TWAIN.

2) The Java code that shows the usage of DTWAIN_GetTwainAppID() is here. Note that there is a TW_IDENTITY defined for Java, and that is used on the JNI side to be filled in with the TWAIN information. This is highly specialized for Java and JNI, so I don't think this will help you.

[dynarithmic]

Also, there is the undocumented DTWAIN_GetTwainAppIDEx function that is prototyped like this:

TWAIN_IDENTITY DLLENTRY_DEF DTWAIN_GetTwainAppIDEx(TW_IDENTITY* pIdentity)

The parameter passed in is a pointer to a TW_IDENTITY that is filled in by DTWAIN_GetTwainAppIDEx(). Maybe you should try to use this function instead of DTWAIN_GetTwainAppID().

There is also a corresponding DTWAIN_GetSourceIDEx(DTWAIN_SOURCE, TW_IDENTITY*) that basically does the same thing, with the only difference being that you provide the source handle, and a pointer to the TW_IDENTITY to fill in.

But again, your definition of TW_IDENTITY must match exactly, both in size, alignment, etc. with the C TW_IDENTITY version that I linked to in the previous message. Maybe you are getting bad results because you are using string when the TW_IDENTITY structure requires exactly a 34 byte field for the string data.

[madeline799]

Thanks a lot.I will see it.and I have a doubt.DTWAIN_GetTwainAppID return the code -1. Do you know what is this meaning?Cause I already define the return type is Struct.

[dynarithmic]

DTWAIN_GetTwainAppID returns a void *, which is either 4 bytes or 8 bytes, depending on whether the application is 32-bit or 64-bit. Since I do not know nodejs, you will need to figure out what is going on. The return type is no different than if you called DTWAIN_SelectSource, where a 4 or 8 byte pointer is returned to you on source selection.

Also, you should post your program -- you can't call any DTWAIN functions until you have called DTWAIN_SysInitialize, and in your case DTWAIN_StartTwainSession. So far I have no idea if you have done these steps, with these functions returning a success code. If you're calling DTWAIN_GetTwainAppID just by itself without initializing and starting a session, it isn't a surprise you are getting erroneous results.

[dynarithmic]

Closing issue, as the resolution is to declare the DTWAIN_GetTwainAppID similar to DTWAIN_SelectSource with respect to the return type.