FFI: How to pass a pointer to a char pointer?

// ffi.ts
const library = Deno.dlopen("./mylib.so", {
  my_func: {
    parameters: ["buffer", "usize"],
    result: "void",
  },
});

const buffer = new Uint8Array(128); // allocate a buffer
library.symbols.my_func(buffer, buffer.length);

// ffi.ts
const library = Deno.dlopen("./mylib.so", {
  my_func: {
    parameters: ["buffer", "usize"],
    result: "void",
  },
});

const buffer = new Uint8Array(128); // allocate a buffer
library.symbols.my_func(buffer, buffer.length);

const DECL = {
  method: {
    parameters: [
      "i32",
      "buf",
      "buf"
    ],
    result: "void",
  }
};

// ...

const AIndex = 12;

const outPtrs = new ArrayBuffer(16);
const outPtrValues = new BigUint64Array(outPtrs);
const sResposta = new Uint8Array(outPtrs, 0, 8);
const esTamanho = new Uint8Array(outPtrs, 8, 8);

lib.symbols.method(AIndex, sReposta, esTamanho);

console.log("sResposta address:", outPtrValues[0]);
console.log("es Tamanho value:", Number(outPtrValues[1]));
const sRepostaPtr = Deno.UnsafePointer.create(outPtrValues[0]);
const sRepostaBuffer = Deno.UnsafePointerView.getArrayBuffer(sRepostaPtr, Number(outPtrValues[1]));
const sRespotaString = new TextDecoder().decode(new Uint8Array(sRepostaBuffer));

const DECL = {
  method: {
    parameters: [
      "i32",
      "buf",
      "buf"
    ],
    result: "void",
  }
};

// ...

const AIndex = 12;

const outPtrs = new ArrayBuffer(16);
const outPtrValues = new BigUint64Array(outPtrs);
const sResposta = new Uint8Array(outPtrs, 0, 8);
const esTamanho = new Uint8Array(outPtrs, 8, 8);

lib.symbols.method(AIndex, sReposta, esTamanho);

console.log("sResposta address:", outPtrValues[0]);
console.log("es Tamanho value:", Number(outPtrValues[1]));
const sRepostaPtr = Deno.UnsafePointer.create(outPtrValues[0]);
const sRepostaBuffer = Deno.UnsafePointerView.getArrayBuffer(sRepostaPtr, Number(outPtrValues[1]));
const sRespotaString = new TextDecoder().decode(new Uint8Array(sRepostaBuffer));

this.NFE_ObterXml = this.lib.func("int16_t NFE_ObterXml(int16_t AIndex, char **sResposta, int16_t *esTamanho)") 
obtemXml(lista){
        let aloc_sResposta = Buffer.alloc(256);
        let aloc_esTamanho = ref.alloc("int", 256);

        this.NFe.NFE_ObterXml(
            0,
            aloc_sResposta,
            aloc_esTamanho
        )

        if(256 < aloc_esTamanho.readInt32LE(0)){
            aloc_sResposta = Buffer.alloc(aloc_esTamanho.readInt32LE(0));
            this.NFe.NFE_UltimoRetorno(aloc_sResposta, aloc_esTamanho)
            console.log(aloc_sResposta.toString('utf-8', 0, aloc_esTamanho.readInt32LE(0)))
        }

        return aloc_sResposta.toString('utf-8', 0, aloc_esTamanho.readInt32LE(0))

this.NFE_ObterXml = this.lib.func("int16_t NFE_ObterXml(int16_t AIndex, char **sResposta, int16_t *esTamanho)") 
obtemXml(lista){
        let aloc_sResposta = Buffer.alloc(256);
        let aloc_esTamanho = ref.alloc("int", 256);

        this.NFe.NFE_ObterXml(
            0,
            aloc_sResposta,
            aloc_esTamanho
        )

        if(256 < aloc_esTamanho.readInt32LE(0)){
            aloc_sResposta = Buffer.alloc(aloc_esTamanho.readInt32LE(0));
            this.NFe.NFE_UltimoRetorno(aloc_sResposta, aloc_esTamanho)
            console.log(aloc_sResposta.toString('utf-8', 0, aloc_esTamanho.readInt32LE(0)))
        }

        return aloc_sResposta.toString('utf-8', 0, aloc_esTamanho.readInt32LE(0))

const outPtrs = new ArrayBuffer(10); // Allocate 8 + 2 bytes, that is one 64 bit pointer's worth + one 16 bit integer's worth.
const sResposta = new Uint8Array(outPtrs, 0, 8); // Create an out-pointer buffer pointing to the first 8 bytes (64 bits).
const esTamanho = new Uint8Array(outPtrs, 8, 2); // Create an out-pointer buffer pointing to the last 2 bytes (16 bits).

lib.NFe.symbols.NFE_ObterXML(
  0, sResposta, esTamanho
);

console.log(sResposta);
console.log(new Uint16Array(outPtrs, 8, 1)[0]); // es Tamanho is a Uint16

const outPtrs = new ArrayBuffer(10); // Allocate 8 + 2 bytes, that is one 64 bit pointer's worth + one 16 bit integer's worth.
const sResposta = new Uint8Array(outPtrs, 0, 8); // Create an out-pointer buffer pointing to the first 8 bytes (64 bits).
const esTamanho = new Uint8Array(outPtrs, 8, 2); // Create an out-pointer buffer pointing to the last 2 bytes (16 bits).

lib.NFe.symbols.NFE_ObterXML(
  0, sResposta, esTamanho
);

console.log(sResposta);
console.log(new Uint16Array(outPtrs, 8, 1)[0]); // es Tamanho is a Uint16

const DEFAULT_LENGTH = 256; // choose how much you want to pre-allocate; this should be large enough to cover the usual cases but not so large that you waste memory. Althought! If you can bear it, you can just do a single allocation and reuse that on every call, and that can then be pretty big.
const outPtrs = new ArrayBuffer(2 + DEFAULT_LENGTH); // Allocate 2 bytes for the 16 bit integer and then the above pre-allocation size.
const sResposta = new Uint8Array(outPtrs, 2, DEFAULT_LENGTH); // Out pointer for the string to be written into. Note that this is now offset by two bytes from outPtrs; the first two bytes are used for esTamanho.
const esTamanho = new Uint8Array(outPtrs, 0, 2); // Int/out pointer for the buffer length length to be written into, out-pointer for the string length that should be written in. Note that this is now at the beginning of outPtrs.
const esTamanhoView = new Uint16Array(outPtrs, 0, 1);
esTamanhoView[0] = DEFAULT_LENGTH;

lib.NFesymbols.NFE_ObterXML(
  0, sResposta, esTamanho
);

const sRespostaLength = esTamanhoView[0];
if (sRespostaLength > DEFAULT_LEGTH) {
  // library needed more room; need to reallocate.
  const realloc = new Uint8Array(sRespostaLength);
  this.NFe.NFE_UltimoRetorno(realloc, esTamanho);
  console.log(new TextDecoder().decode(realloc));
} else {
  const sRespostaString = new TextDecoder().decode(sResposta.subarray(0, sRespostaLength));
  console.log(sRespostaString);
}

const DEFAULT_LENGTH = 256; // choose how much you want to pre-allocate; this should be large enough to cover the usual cases but not so large that you waste memory. Althought! If you can bear it, you can just do a single allocation and reuse that on every call, and that can then be pretty big.
const outPtrs = new ArrayBuffer(2 + DEFAULT_LENGTH); // Allocate 2 bytes for the 16 bit integer and then the above pre-allocation size.
const sResposta = new Uint8Array(outPtrs, 2, DEFAULT_LENGTH); // Out pointer for the string to be written into. Note that this is now offset by two bytes from outPtrs; the first two bytes are used for esTamanho.
const esTamanho = new Uint8Array(outPtrs, 0, 2); // Int/out pointer for the buffer length length to be written into, out-pointer for the string length that should be written in. Note that this is now at the beginning of outPtrs.
const esTamanhoView = new Uint16Array(outPtrs, 0, 1);
esTamanhoView[0] = DEFAULT_LENGTH;

lib.NFesymbols.NFE_ObterXML(
  0, sResposta, esTamanho
);

const sRespostaLength = esTamanhoView[0];
if (sRespostaLength > DEFAULT_LEGTH) {
  // library needed more room; need to reallocate.
  const realloc = new Uint8Array(sRespostaLength);
  this.NFe.NFE_UltimoRetorno(realloc, esTamanho);
  console.log(new TextDecoder().decode(realloc));
} else {
  const sRespostaString = new TextDecoder().decode(sResposta.subarray(0, sRespostaLength));
  console.log(sRespostaString);
}

const DEFAULT_LENGTH = 9048;
const outPtrs = new ArrayBuffer(2 + DEFAULT_LENGTH);
const sResposta = new Uint8Array(outPtrs, 2, DEFAULT_LENGTH);
const esTamanho = new Uint8Array(outPtrs, 0, 2);
const esTamanhoView = new Uint16Array(outPtrs, 0, 1);
esTamanhoView[0] = DEFAULT_LENGTH;

lib.NFesymbols.NFE_ObterXML(
  0, sResposta, esTamanho
);

const esTamanhoValue = esTamanhoView[0];
if (esTamanhoValue > DEFAULT_LEGTH) {
  // library needed more room; need to reallocate.
  const realloc = new Uint8Array(sRespostaLength);
  this.NFe.NFE_UltimoRetorno(realloc, esTamanho);
  const sRespostaString = new TextDecoder().decode(realloc);
  console.log(sRespostaString);
} else {
  const sRespostaString = new TextDecoder().decode(sResposta.subarray(0, esTamanhoValue));
  console.log(sRespostaString);
}

const DEFAULT_LENGTH = 9048;
const outPtrs = new ArrayBuffer(2 + DEFAULT_LENGTH);
const sResposta = new Uint8Array(outPtrs, 2, DEFAULT_LENGTH);
const esTamanho = new Uint8Array(outPtrs, 0, 2);
const esTamanhoView = new Uint16Array(outPtrs, 0, 1);
esTamanhoView[0] = DEFAULT_LENGTH;

lib.NFesymbols.NFE_ObterXML(
  0, sResposta, esTamanho
);

const esTamanhoValue = esTamanhoView[0];
if (esTamanhoValue > DEFAULT_LEGTH) {
  // library needed more room; need to reallocate.
  const realloc = new Uint8Array(sRespostaLength);
  this.NFe.NFE_UltimoRetorno(realloc, esTamanho);
  const sRespostaString = new TextDecoder().decode(realloc);
  console.log(sRespostaString);
} else {
  const sRespostaString = new TextDecoder().decode(sResposta.subarray(0, esTamanhoValue));
  console.log(sRespostaString);
}