Why memory is empty

[996ccs]

I imported the wasm file to parse the wasm output data. The memory is empty.

wat file

(module
 (type $0 (func (result i32)))
 (memory $0 1)
 (data $0 (i32.const 1036) ",")
 (data $0.1 (i32.const 1048) "\02\00\00\00\16\00\00\00h\00e\00l\00l\00o\00 \00w\00o\00r\00l\00d")
 (export "getHelloWorld" (func $assembly/index/getHelloWorld))
 (export "memory" (memory $0))
 (func $assembly/index/getHelloWorld (result i32)
  i32.const 1056
 )
)

Module(types: [WasmKit.FunctionType(parameters: [], results: [i32])], functions: [WasmKit.GuestFunction(type: 0, defaultLocals: UnsafeBufferPointer(start: 0x00006000022583a0, count: 0), _bodyStorage: nil, materializer: (Function))], tables: [], memories: [WasmKit.Memory(type: WasmKit.Limits(min: 1, max: nil, isMemory64: false))], globals: [], elements: [], dataCount: Optional(2), data: [WasmKit.DataSegment.active(WasmKit.DataSegment.Active(index: 0, offset: [WasmKit.Instruction.numericConst(I32(1036))], initializer: ArraySlice([44]))), WasmKit.DataSegment.active(WasmKit.DataSegment.Active(index: 0, offset: [WasmKit.Instruction.numericConst(I32(1048))], initializer: ArraySlice([2, 0, 0, 0, 22, 0, 0, 0, 104, 0, 101, 0, 108, 0, 108, 0, 111, 0, 32, 0, 119, 0, 111, 0, 114, 0, 108, 0, 100])))], start: nil, imports: [], exports: [WasmKit.Export(name: "hello_world", descriptor: WasmKit.ExportDescriptor.function(0)), WasmKit.Export(name: "memory", descriptor: WasmKit.ExportDescriptor.memory(0))], customSections: [WasmKit.CustomSection(name: "sourceMappingURL", bytes: ArraySlice([18, 46, 47, 114, 101, 108, 101, 97, 115, 101, 46, 119, 97, 115, 109, 46, 109, 97, 112]))])

[kateinoigakukun]

What do you mean "memory is empty"? The parsed module has WasmKit.Memory in memories and WasmKit.DataSegment in data.

[996ccs]

What do you mean "memory is empty"? The parsed module has WasmKit.Memory in memories and WasmKit.DataSegment in data.

Yes, look at the output of WasmKit.Export(name: "memory", descriptor: WasmKit.ExportDescriptor.memory(0))]

[kateinoigakukun]

@996ccs WasmKit.ExportDescriptor.memory(0) means the export entry points to the index 0 of memories

[996ccs]

@996ccs WasmKit.ExportDescriptor.memory(0) means the export entry points to the index 0 of memories

Thank you very much for your reply. Please tell me how to obtain the initializer data in WasmKit.DataSegment. Like this data WasmKit.DataSegment.Active(index: 0, offset: [WasmKit.Instruction.numericConst(I32(1048))], initializer: ArraySlice([2, 0, 0, 0, 22, 0, 0, 0 , 104, 0, 101, 0, 108, 0, 108, 0, 111, 0, 32, 0, 119, 0, 111, 0, 114, 0, 108, 0, 100]))) How do I get initializer.

[kateinoigakukun]

I don't understand what you are trying to do but you can get the data segment initializer by something like below:

let initializer = switch dataSegment {
case .active(let active): Array(active.initializer)
case .passive(let initializer): initializer
}

[996ccs]

I don't understand what you are trying to do but you can get the data segment initializer by something like below:

let initializer = switch dataSegment {
case .active(let active): Array(active.initializer)
case .passive(let initializer): initializer
}

I used the code you provided and encountered the same problem myself. The error message 'initializer' is inaccessible due to 'internal' protection level

[kateinoigakukun]

Could you try it again with main branch of WasmKit?

[996ccs]

Could you try it again with main branch of WasmKit?

I updated version 0.04, and now the data under the module cannot be accessed. My need is to get the initializer: ArraySlice in WasmParser.DataSegment.active. Can it be exposed? Thanks

[kateinoigakukun]

Ah, sorry. If you just want to extract data segment, you can use WasmParser module directly.

[996ccs]

Ah, sorry. If you just want to extract data segment, you can use WasmParser module directly.

Can you tell me what I should do? Because I am not good at wasmkit and swift development

[kateinoigakukun]

I added several API documents on WasmParser: https://swiftpackageindex.com/swiftwasm/WasmKit/main/documentation/wasmparser
(It may take a few hours to be up-to-date)

And I think the following code snippet works for your use case as is. Feel free to re-open again if you have more question. Thanks.

import WasmParser

let bytes = try Array(Data(contentsOf: URL(fileURLWithPath: "wasm/hello.wasm")))

var parser = WasmParser.Parser(bytes: bytes)
while let payload = try parser.parseNext() {
    switch payload {
    case .dataSection(let dataSection):
        for segment in dataSection {
            switch segment {
            case .passive(let data):
                print("Data segment: \(data)")
            case .active(let active):
                print("Data segment: \(active.index) \(active.offset) \(active.initializer)")
            }
        }
    default: break
    }
}