Node.js – v8.deserializer.readHeader() Method

The v8.deserializer.readHeader() method is used for reading and validating the headers. It also checks the format version. An error is thrown when an invalid or unsupported wire format is encountered.

Syntax

v8.deserializer.readHeader()

Parameters

Since it read headers from the internal buffer, it does not need any input parameters. It will return True after deserializing the headers.

Example 1

Create a file with the name "readHeader.js" and copy the following code snippet.After creating the file, use the command "node readHeader.js" to run this code.

// v8.deserializer.readHeader() Demo Example

// Importing the v8 module
const v8 = require('v8');

// Defining the serializer object
const serializer = new v8.Serializer();

// Writing the headers to the internal buffer
serializer.writeHeader();

// Defining the deserializer object
const deserializer = new v8.Deserializer(serializer.releaseBuffer());

// Reading the headers from internal buffer
console.log(deserializer.readHeader());

// Printing the header values from internal buffer
console.log(serializer.releaseBuffer());

Output

C:\home
ode>> node readHeader.js
undefined
<Buffer ff 0d 22 1a 57 65 6c 63 6f 6d 65 20 74 6f 20 54 75 74 6f 72 69 61 6c 73 20 50 6f 69 6e 74>

Example 2

Let’s have a look at one more example

// v8.serializer.readHeader() Demo Example

// Importing the v8 module
const v8 = require('v8');

// Defining the serializer object
const serializer = new v8.Serializer();

// Writing some value using writeUint32
console.log(serializer.writeUint32(7869));

// Writing the headers to the internal buffer
serializer.writeHeader();

// Defining the deserializer object
const deserializer = new
v8.Deserializer(serializer.releaseBuffer());

// Reading the headers from internal buffer
console.log(deserializer.readHeader());

// Printing the header values from internal buffer
console.log(serializer.releaseBuffer());

Output

C:\home
ode>> node readHeader.js
undefined
/home/mayankaggarwal/mysql-test/util.js:18
console.log(deserializer.readHeader());
                        ^
Error: Unable to deserialize cloned data due to invalid or
unsupported version.
   at Object. (/home/node/readHeader .js:18:26)
   at Module._compile (internal/modules/cjs/loader.js:778:30)
   at Object.Module._extensions..js
(internal/modules/cjs/loader.js:789:10)
   at Module.load (internal/modules/cjs/loader.js:653:32)
   at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
   at Function.Module._load
(internal/modules/cjs/loader.js:585:3)
   at Function.Module.runMain
(internal/modules/cjs/loader.js:831:12)
   at startup (internal/bootstrap/node.js:283:19)
   at bootstrapNodeJSCore (internal/bootstrap/node.js:623:3)

Mayank Agarwal

Updated on: 18-Aug-2021

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