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</li> <li class="version-picker"> <a href="#">View another version <span>▼</span></a> <ol class="version-picker"><li><a href="https://nodejs.org/docs/latest-v12.x/api/buffer.html">12.x</a></li> <li><a href="https://nodejs.org/docs/latest-v11.x/api/buffer.html">11.x</a></li> <li><a href="https://nodejs.org/docs/latest-v10.x/api/buffer.html">10.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v9.x/api/buffer.html">9.x</a></li> <li><a href="https://nodejs.org/docs/latest-v8.x/api/buffer.html">8.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v7.x/api/buffer.html">7.x</a></li> <li><a href="https://nodejs.org/docs/latest-v6.x/api/buffer.html">6.x</a></li> <li><a href="https://nodejs.org/docs/latest-v5.x/api/buffer.html">5.x</a></li> <li><a href="https://nodejs.org/docs/latest-v4.x/api/buffer.html">4.x</a></li> <li><a href="https://nodejs.org/docs/latest-v0.12.x/api/buffer.html">0.12.x</a></li> <li><a href="https://nodejs.org/docs/latest-v0.10.x/api/buffer.html">0.10.x</a></li></ol> </li> <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/master/doc/api/buffer.md"><span class="github_icon"><svg height="16" width="16" viewBox="0 0 16.1 16.1" fill="currentColor"><path d="M8 0a8 8 0 0 0-2.5 15.6c.4 0 .5-.2.5-.4v-1.5c-2 .4-2.5-.5-2.7-1 0-.1-.5-.9-.8-1-.3-.2-.7-.6 0-.6.6 0 1 .6 1.2.8.7 1.2 1.9 1 2.4.7 0-.5.2-.9.5-1-1.8-.3-3.7-1-3.7-4 0-.9.3-1.6.8-2.2 0-.2-.3-1 .1-2 0 0 .7-.3 2.2.7a7.4 7.4 0 0 1 4 0c1.5-1 2.2-.8 2.2-.8.5 1.1.2 2 .1 2.1.5.6.8 1.3.8 2.2 0 3-1.9 3.7-3.6 4 .3.2.5.7.5 1.4v2.2c0 .2.1.5.5.4A8 8 0 0 0 16 8a8 8 0 0 0-8-8z"></path></svg></span>Edit on GitHub</a></li> </ul> </div> <hr> </header> <div id="toc"> <h2>Table of Contents</h2> <ul> <li> <p><span class="stability_2"><a href="#buffer_buffer">Buffer</a></span></p> <ul> <li> <p><a href="#buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe"><code>Buffer.from()</code>, <code>Buffer.alloc()</code>, and <code>Buffer.allocUnsafe()</code></a></p> <ul> <li><a href="#buffer_the_zero_fill_buffers_command_line_option">The <code>--zero-fill-buffers</code> command line option</a></li> <li><a href="#buffer_what_makes_buffer_allocunsafe_and_buffer_allocunsafeslow_unsafe">What makes <code>Buffer.allocUnsafe()</code> and <code>Buffer.allocUnsafeSlow()</code> "unsafe"?</a></li> </ul> </li> <li><a href="#buffer_buffers_and_character_encodings">Buffers and Character Encodings</a></li> <li><a href="#buffer_buffers_and_typedarray">Buffers and TypedArray</a></li> <li><a href="#buffer_buffers_and_iteration">Buffers and iteration</a></li> <li> <p><a href="#buffer_class_buffer">Class: Buffer</a></p> <ul> <li><span class="stability_0"><a href="#buffer_new_buffer_array">new Buffer(array)</a></span></li> <li><span class="stability_0"><a href="#buffer_new_buffer_arraybuffer_byteoffset_length">new Buffer(arrayBuffer[, byteOffset[, length]])</a></span></li> <li><span class="stability_0"><a href="#buffer_new_buffer_buffer">new Buffer(buffer)</a></span></li> <li><span class="stability_0"><a href="#buffer_new_buffer_size">new Buffer(size)</a></span></li> <li><span class="stability_0"><a href="#buffer_new_buffer_string_encoding">new Buffer(string[, encoding])</a></span></li> <li><a href="#buffer_class_method_buffer_alloc_size_fill_encoding">Class Method: Buffer.alloc(size[, fill[, encoding]])</a></li> <li><a href="#buffer_class_method_buffer_allocunsafe_size">Class Method: Buffer.allocUnsafe(size)</a></li> <li><a href="#buffer_class_method_buffer_allocunsafeslow_size">Class Method: Buffer.allocUnsafeSlow(size)</a></li> <li><a href="#buffer_class_method_buffer_bytelength_string_encoding">Class Method: Buffer.byteLength(string[, encoding])</a></li> <li><a href="#buffer_class_method_buffer_compare_buf1_buf2">Class Method: Buffer.compare(buf1, buf2)</a></li> <li><a href="#buffer_class_method_buffer_concat_list_totallength">Class Method: Buffer.concat(list[, totalLength])</a></li> <li><a href="#buffer_class_method_buffer_from_array">Class Method: Buffer.from(array)</a></li> <li><a href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length">Class Method: Buffer.from(arrayBuffer[, byteOffset[, length]])</a></li> <li><a href="#buffer_class_method_buffer_from_buffer">Class Method: Buffer.from(buffer)</a></li> <li><a href="#buffer_class_method_buffer_from_object_offsetorencoding_length">Class Method: Buffer.from(object[, offsetOrEncoding[, length]])</a></li> <li><a href="#buffer_class_method_buffer_from_string_encoding">Class Method: Buffer.from(string[, encoding])</a></li> <li><a href="#buffer_class_method_buffer_isbuffer_obj">Class Method: Buffer.isBuffer(obj)</a></li> <li><a href="#buffer_class_method_buffer_isencoding_encoding">Class Method: Buffer.isEncoding(encoding)</a></li> <li><a href="#buffer_class_property_buffer_poolsize">Class Property: Buffer.poolSize</a></li> <li><a href="#buffer_buf_index">buf[index]</a></li> <li><a href="#buffer_buf_buffer">buf.buffer</a></li> <li><a href="#buffer_buf_byteoffset">buf.byteOffset</a></li> <li><a href="#buffer_buf_compare_target_targetstart_targetend_sourcestart_sourceend">buf.compare(target[, targetStart[, targetEnd[, sourceStart[, sourceEnd]]]])</a></li> <li><a href="#buffer_buf_copy_target_targetstart_sourcestart_sourceend">buf.copy(target[, targetStart[, sourceStart[, sourceEnd]]])</a></li> <li><a href="#buffer_buf_entries">buf.entries()</a></li> <li><a href="#buffer_buf_equals_otherbuffer">buf.equals(otherBuffer)</a></li> <li><a href="#buffer_buf_fill_value_offset_end_encoding">buf.fill(value[, offset[, end]][, encoding])</a></li> <li><a href="#buffer_buf_includes_value_byteoffset_encoding">buf.includes(value[, byteOffset][, encoding])</a></li> <li><a href="#buffer_buf_indexof_value_byteoffset_encoding">buf.indexOf(value[, byteOffset][, encoding])</a></li> <li><a href="#buffer_buf_keys">buf.keys()</a></li> <li><a href="#buffer_buf_lastindexof_value_byteoffset_encoding">buf.lastIndexOf(value[, byteOffset][, encoding])</a></li> <li><a href="#buffer_buf_length">buf.length</a></li> <li><span class="stability_0"><a href="#buffer_buf_parent">buf.parent</a></span></li> <li><a href="#buffer_buf_readbigint64be_offset">buf.readBigInt64BE([offset])</a></li> <li><a href="#buffer_buf_readbigint64le_offset">buf.readBigInt64LE([offset])</a></li> <li><a href="#buffer_buf_readbiguint64be_offset">buf.readBigUInt64BE([offset])</a></li> <li><a href="#buffer_buf_readbiguint64le_offset">buf.readBigUInt64LE([offset])</a></li> <li><a href="#buffer_buf_readdoublebe_offset">buf.readDoubleBE([offset])</a></li> <li><a href="#buffer_buf_readdoublele_offset">buf.readDoubleLE([offset])</a></li> <li><a href="#buffer_buf_readfloatbe_offset">buf.readFloatBE([offset])</a></li> <li><a href="#buffer_buf_readfloatle_offset">buf.readFloatLE([offset])</a></li> <li><a href="#buffer_buf_readint8_offset">buf.readInt8([offset])</a></li> <li><a href="#buffer_buf_readint16be_offset">buf.readInt16BE([offset])</a></li> <li><a href="#buffer_buf_readint16le_offset">buf.readInt16LE([offset])</a></li> <li><a href="#buffer_buf_readint32be_offset">buf.readInt32BE([offset])</a></li> <li><a href="#buffer_buf_readint32le_offset">buf.readInt32LE([offset])</a></li> <li><a href="#buffer_buf_readintbe_offset_bytelength">buf.readIntBE(offset, byteLength)</a></li> <li><a href="#buffer_buf_readintle_offset_bytelength">buf.readIntLE(offset, byteLength)</a></li> <li><a href="#buffer_buf_readuint8_offset">buf.readUInt8([offset])</a></li> <li><a href="#buffer_buf_readuint16be_offset">buf.readUInt16BE([offset])</a></li> <li><a href="#buffer_buf_readuint16le_offset">buf.readUInt16LE([offset])</a></li> <li><a href="#buffer_buf_readuint32be_offset">buf.readUInt32BE([offset])</a></li> <li><a href="#buffer_buf_readuint32le_offset">buf.readUInt32LE([offset])</a></li> <li><a href="#buffer_buf_readuintbe_offset_bytelength">buf.readUIntBE(offset, byteLength)</a></li> <li><a href="#buffer_buf_readuintle_offset_bytelength">buf.readUIntLE(offset, byteLength)</a></li> <li><a href="#buffer_buf_subarray_start_end">buf.subarray([start[, end]])</a></li> <li><a href="#buffer_buf_slice_start_end">buf.slice([start[, end]])</a></li> <li><a href="#buffer_buf_swap16">buf.swap16()</a></li> <li><a href="#buffer_buf_swap32">buf.swap32()</a></li> <li><a href="#buffer_buf_swap64">buf.swap64()</a></li> <li><a href="#buffer_buf_tojson">buf.toJSON()</a></li> <li><a href="#buffer_buf_tostring_encoding_start_end">buf.toString([encoding[, start[, end]]])</a></li> <li><a href="#buffer_buf_values">buf.values()</a></li> <li><a href="#buffer_buf_write_string_offset_length_encoding">buf.write(string[, offset[, length]][, encoding])</a></li> <li><a href="#buffer_buf_writebigint64be_value_offset">buf.writeBigInt64BE(value[, offset])</a></li> <li><a href="#buffer_buf_writebigint64le_value_offset">buf.writeBigInt64LE(value[, offset])</a></li> <li><a href="#buffer_buf_writebiguint64be_value_offset">buf.writeBigUInt64BE(value[, offset])</a></li> <li><a href="#buffer_buf_writebiguint64le_value_offset">buf.writeBigUInt64LE(value[, offset])</a></li> <li><a href="#buffer_buf_writedoublebe_value_offset">buf.writeDoubleBE(value[, offset])</a></li> <li><a href="#buffer_buf_writedoublele_value_offset">buf.writeDoubleLE(value[, offset])</a></li> <li><a href="#buffer_buf_writefloatbe_value_offset">buf.writeFloatBE(value[, offset])</a></li> <li><a href="#buffer_buf_writefloatle_value_offset">buf.writeFloatLE(value[, offset])</a></li> <li><a href="#buffer_buf_writeint8_value_offset">buf.writeInt8(value[, offset])</a></li> <li><a href="#buffer_buf_writeint16be_value_offset">buf.writeInt16BE(value[, offset])</a></li> <li><a href="#buffer_buf_writeint16le_value_offset">buf.writeInt16LE(value[, offset])</a></li> <li><a href="#buffer_buf_writeint32be_value_offset">buf.writeInt32BE(value[, offset])</a></li> <li><a href="#buffer_buf_writeint32le_value_offset">buf.writeInt32LE(value[, offset])</a></li> <li><a href="#buffer_buf_writeintbe_value_offset_bytelength">buf.writeIntBE(value, offset, byteLength)</a></li> <li><a href="#buffer_buf_writeintle_value_offset_bytelength">buf.writeIntLE(value, offset, byteLength)</a></li> <li><a href="#buffer_buf_writeuint8_value_offset">buf.writeUInt8(value[, offset])</a></li> <li><a href="#buffer_buf_writeuint16be_value_offset">buf.writeUInt16BE(value[, offset])</a></li> <li><a href="#buffer_buf_writeuint16le_value_offset">buf.writeUInt16LE(value[, offset])</a></li> <li><a href="#buffer_buf_writeuint32be_value_offset">buf.writeUInt32BE(value[, offset])</a></li> <li><a href="#buffer_buf_writeuint32le_value_offset">buf.writeUInt32LE(value[, offset])</a></li> <li><a href="#buffer_buf_writeuintbe_value_offset_bytelength">buf.writeUIntBE(value, offset, byteLength)</a></li> <li><a href="#buffer_buf_writeuintle_value_offset_bytelength">buf.writeUIntLE(value, offset, byteLength)</a></li> </ul> </li> <li><a href="#buffer_buffer_inspect_max_bytes">buffer.INSPECT_MAX_BYTES</a></li> <li><a href="#buffer_buffer_kmaxlength">buffer.kMaxLength</a></li> <li><a href="#buffer_buffer_transcode_source_fromenc_toenc">buffer.transcode(source, fromEnc, toEnc)</a></li> <li> <p><span class="stability_0"><a href="#buffer_class_slowbuffer">Class: SlowBuffer</a></span></p> <ul> <li><span class="stability_0"><a href="#buffer_new_slowbuffer_size">new SlowBuffer(size)</a></span></li> </ul> </li> <li> <p><a href="#buffer_buffer_constants">Buffer Constants</a></p> <ul> <li><a href="#buffer_buffer_constants_max_length">buffer.constants.MAX_LENGTH</a></li> <li><a href="#buffer_buffer_constants_max_string_length">buffer.constants.MAX_STRING_LENGTH</a></li> </ul> </li> </ul> </li> </ul> </div> <div id="apicontent"> <h1>Buffer<span><a class="mark" href="#buffer_buffer" id="buffer_buffer">#</a></span></h1> <p></p><div class="api_stability api_stability_2"><a href="https://nodejs.org/api/documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> <p>Prior to the introduction of <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>, the JavaScript language had no mechanism for reading or manipulating streams of binary data. The <code>Buffer</code> class was introduced as part of the Node.js API to enable interaction with octet streams in TCP streams, file system operations, and other contexts.</p> <p>With <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> now available, the <code>Buffer</code> class implements the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> API in a manner that is more optimized and suitable for Node.js.</p> <p>Instances of the <code>Buffer</code> class are similar to arrays of integers from <code>0</code> to <code>255</code> (other integers are coerced to this range by <code>& 255</code> operation) but correspond to fixed-sized, raw memory allocations outside the V8 heap. The size of the <code>Buffer</code> is established when it is created and cannot be changed.</p> <p>The <code>Buffer</code> class is within the global scope, making it unlikely that one would need to ever use <code>require('buffer').Buffer</code>.</p> <pre><code class="language-js">// Creates a zero-filled Buffer of length 10. const buf1 = Buffer.alloc(10); // Creates a Buffer of length 10, filled with 0x1. const buf2 = Buffer.alloc(10, 1); // Creates an uninitialized buffer of length 10. // This is faster than calling Buffer.alloc() but the returned // Buffer instance might contain old data that needs to be // overwritten using either fill() or write(). const buf3 = Buffer.allocUnsafe(10); // Creates a Buffer containing [0x1, 0x2, 0x3]. const buf4 = Buffer.from([1, 2, 3]); // Creates a Buffer containing UTF-8 bytes [0x74, 0xc3, 0xa9, 0x73, 0x74]. const buf5 = Buffer.from('tést'); // Creates a Buffer containing Latin-1 bytes [0x74, 0xe9, 0x73, 0x74]. const buf6 = Buffer.from('tést', 'latin1'); </code></pre> <h2><code>Buffer.from()</code>, <code>Buffer.alloc()</code>, and <code>Buffer.allocUnsafe()</code><span><a class="mark" href="#buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe" id="buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe">#</a></span></h2> <p>In versions of Node.js prior to 6.0.0, <code>Buffer</code> instances were created using the <code>Buffer</code> constructor function, which allocates the returned <code>Buffer</code> differently based on what arguments are provided:</p> <ul> <li>Passing a number as the first argument to <code>Buffer()</code> (e.g. <code>new Buffer(10)</code>) allocates a new <code>Buffer</code> object of the specified size. Prior to Node.js 8.0.0, the memory allocated for such <code>Buffer</code> instances is <em>not</em> initialized and <em>can contain sensitive data</em>. Such <code>Buffer</code> instances <em>must</em> be subsequently initialized by using either <a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(0)</code></a> or by writing to the entire <code>Buffer</code>. While this behavior is <em>intentional</em> to improve performance, development experience has demonstrated that a more explicit distinction is required between creating a fast-but-uninitialized <code>Buffer</code> versus creating a slower-but-safer <code>Buffer</code>. Since Node.js 8.0.0, <code>Buffer(num)</code> and <code>new Buffer(num)</code> return a <code>Buffer</code> with initialized memory.</li> <li>Passing a string, array, or <code>Buffer</code> as the first argument copies the passed object's data into the <code>Buffer</code>.</li> <li>Passing an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> or a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> returns a <code>Buffer</code> that shares allocated memory with the given array buffer.</li> </ul> <p>Because the behavior of <code>new Buffer()</code> is different depending on the type of the first argument, security and reliability issues can be inadvertently introduced into applications when argument validation or <code>Buffer</code> initialization is not performed.</p> <p>For example, if an attacker can cause an application to receive a number where a string is expected, the application may call <code>new Buffer(100)</code> instead of <code>new Buffer("100")</code>, it will allocate a 100 byte buffer instead of allocating a 3 byte buffer with content <code>"100"</code>. This is commonly possible using JSON API calls. Since JSON distinguishes between numeric and string types, it allows injection of numbers where a naive application might expect to always receive a string. Before Node.js 8.0.0, the 100 byte buffer might contain arbitrary pre-existing in-memory data, so may be used to expose in-memory secrets to a remote attacker. Since Node.js 8.0.0, exposure of memory cannot occur because the data is zero-filled. However, other attacks are still possible, such as causing very large buffers to be allocated by the server, leading to performance degradation or crashing on memory exhaustion.</p> <p>To make the creation of <code>Buffer</code> instances more reliable and less error-prone, the various forms of the <code>new Buffer()</code> constructor have been <strong>deprecated</strong> and replaced by separate <code>Buffer.from()</code>, <a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc()</code></a>, and <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> methods.</p> <p><em>Developers should migrate all existing uses of the <code>new Buffer()</code> constructors to one of these new APIs.</em></p> <ul> <li><a href="#buffer_class_method_buffer_from_array"><code>Buffer.from(array)</code></a> returns a new <code>Buffer</code> that <em>contains a copy</em> of the provided octets.</li> <li><a href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length"><code>Buffer.from(arrayBuffer[, byteOffset[, length]])</code></a> returns a new <code>Buffer</code> that <em>shares the same allocated memory</em> as the given <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a>.</li> <li><a href="#buffer_class_method_buffer_from_buffer"><code>Buffer.from(buffer)</code></a> returns a new <code>Buffer</code> that <em>contains a copy</em> of the contents of the given <code>Buffer</code>.</li> <li><a href="#buffer_class_method_buffer_from_string_encoding"><code>Buffer.from(string[, encoding])</code></a> returns a new <code>Buffer</code> that <em>contains a copy</em> of the provided string.</li> <li><a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc(size[, fill[, encoding]])</code></a> returns a new initialized <code>Buffer</code> of the specified size. This method is slower than <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe(size)</code></a> but guarantees that newly created <code>Buffer</code> instances never contain old data that is potentially sensitive. A <code>TypeError</code> will be thrown if <code>size</code> is not a number.</li> <li><a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe(size)</code></a> and <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow(size)</code></a> each return a new uninitialized <code>Buffer</code> of the specified <code>size</code>. Because the <code>Buffer</code> is uninitialized, the allocated segment of memory might contain old data that is potentially sensitive.</li> </ul> <p><code>Buffer</code> instances returned by <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> <em>may</em> be allocated off a shared internal memory pool if <code>size</code> is less than or equal to half <a href="#buffer_class_property_buffer_poolsize"><code>Buffer.poolSize</code></a>. Instances returned by <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a> <em>never</em> use the shared internal memory pool.</p> <h3>The <code>--zero-fill-buffers</code> command line option<span><a class="mark" href="#buffer_the_zero_fill_buffers_command_line_option" id="buffer_the_zero_fill_buffers_command_line_option">#</a></span></h3> <div class="api_metadata"> <span>Added in: v5.10.0</span> </div> <p>Node.js can be started using the <code>--zero-fill-buffers</code> command line option to cause all newly allocated <code>Buffer</code> instances to be zero-filled upon creation by default. Before Node.js 8.0.0, this included buffers allocated by <code>new Buffer(size)</code>. Since Node.js 8.0.0, buffers allocated with <code>new</code> are always zero-filled, whether this option is used or not. <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a>, <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a>, and <code>new SlowBuffer(size)</code>. Use of this flag can have a significant negative impact on performance. Use of the <code>--zero-fill-buffers</code> option is recommended only when necessary to enforce that newly allocated <code>Buffer</code> instances cannot contain old data that is potentially sensitive.</p> <pre><code class="language-txt">$ node --zero-fill-buffers > Buffer.allocUnsafe(5); <Buffer 00 00 00 00 00> </code></pre> <h3>What makes <code>Buffer.allocUnsafe()</code> and <code>Buffer.allocUnsafeSlow()</code> "unsafe"?<span><a class="mark" href="#buffer_what_makes_buffer_allocunsafe_and_buffer_allocunsafeslow_unsafe" id="buffer_what_makes_buffer_allocunsafe_and_buffer_allocunsafeslow_unsafe">#</a></span></h3> <p>When calling <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> and <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a>, the segment of allocated memory is <em>uninitialized</em> (it is not zeroed-out). While this design makes the allocation of memory quite fast, the allocated segment of memory might contain old data that is potentially sensitive. Using a <code>Buffer</code> created by <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> without <em>completely</em> overwriting the memory can allow this old data to be leaked when the <code>Buffer</code> memory is read.</p> <p>While there are clear performance advantages to using <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a>, extra care <em>must</em> be taken in order to avoid introducing security vulnerabilities into an application.</p> <h2>Buffers and Character Encodings<span><a class="mark" href="#buffer_buffers_and_character_encodings" id="buffer_buffers_and_character_encodings">#</a></span></h2> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v6.4.0</td> <td><p>Introduced <code>latin1</code> as an alias for <code>binary</code>.</p></td></tr> <tr><td>v5.0.0</td> <td><p>Removed the deprecated <code>raw</code> and <code>raws</code> encodings.</p></td></tr> </tbody></table> </details> </div> <p>When string data is stored in or extracted out of a <code>Buffer</code> instance, a character encoding may be specified.</p> <pre><code class="language-js">const buf = Buffer.from('hello world', 'ascii'); console.log(buf.toString('hex')); // Prints: 68656c6c6f20776f726c64 console.log(buf.toString('base64')); // Prints: aGVsbG8gd29ybGQ= console.log(Buffer.from('fhqwhgads', 'ascii')); // Prints: <Buffer 66 68 71 77 68 67 61 64 73> console.log(Buffer.from('fhqwhgads', 'utf16le')); // Prints: <Buffer 66 00 68 00 71 00 77 00 68 00 67 00 61 00 64 00 73 00> </code></pre> <p>The character encodings currently supported by Node.js include:</p> <ul> <li> <p><code>'ascii'</code> - For 7-bit ASCII data only. This encoding is fast and will strip the high bit if set.</p> </li> <li> <p><code>'utf8'</code> - Multibyte encoded Unicode characters. Many web pages and other document formats use UTF-8.</p> </li> <li> <p><code>'utf16le'</code> - 2 or 4 bytes, little-endian encoded Unicode characters. Surrogate pairs (U+10000 to U+10FFFF) are supported.</p> </li> <li> <p><code>'ucs2'</code> - Alias of <code>'utf16le'</code>.</p> </li> <li> <p><code>'base64'</code> - Base64 encoding. When creating a <code>Buffer</code> from a string, this encoding will also correctly accept "URL and Filename Safe Alphabet" as specified in <a href="https://tools.ietf.org/html/rfc4648#section-5">RFC 4648, Section 5</a>.</p> </li> <li> <p><code>'latin1'</code> - A way of encoding the <code>Buffer</code> into a one-byte encoded string (as defined by the IANA in <a href="https://tools.ietf.org/html/rfc1345">RFC 1345</a>, page 63, to be the Latin-1 supplement block and C0/C1 control codes).</p> </li> <li> <p><code>'binary'</code> - Alias for <code>'latin1'</code>.</p> </li> <li> <p><code>'hex'</code> - Encode each byte as two hexadecimal characters.</p> </li> </ul> <p>Modern Web browsers follow the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a> which aliases both <code>'latin1'</code> and <code>'ISO-8859-1'</code> to <code>'win-1252'</code>. This means that while doing something like <code>http.get()</code>, if the returned charset is one of those listed in the WHATWG specification it is possible that the server actually returned <code>'win-1252'</code>-encoded data, and using <code>'latin1'</code> encoding may incorrectly decode the characters.</p> <h2>Buffers and TypedArray<span><a class="mark" href="#buffer_buffers_and_typedarray" id="buffer_buffers_and_typedarray">#</a></span></h2> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v3.0.0</td> <td><p>The <code>Buffer</code>s class now inherits from <code>Uint8Array</code>.</p></td></tr> </tbody></table> </details> </div> <p><code>Buffer</code> instances are also <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> instances. However, there are subtle incompatibilities with <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>. For example, while <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/slice"><code>ArrayBuffer#slice()</code></a> creates a copy of the slice, the implementation of <a href="#buffer_buf_slice_start_end"><code>Buffer#slice()</code></a> creates a view over the existing <code>Buffer</code> without copying, making <a href="#buffer_buf_slice_start_end"><code>Buffer#slice()</code></a> far more efficient.</p> <p>It is also possible to create new <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instances from a <code>Buffer</code> with the following caveats:</p> <ol> <li> <p>The <code>Buffer</code> object's memory is copied to the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>, not shared.</p> </li> <li> <p>The <code>Buffer</code> object's memory is interpreted as an array of distinct elements, and not as a byte array of the target type. That is, <code>new Uint32Array(Buffer.from([1, 2, 3, 4]))</code> creates a 4-element <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array"><code>Uint32Array</code></a> with elements <code>[1, 2, 3, 4]</code>, not a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array"><code>Uint32Array</code></a> with a single element <code>[0x1020304]</code> or <code>[0x4030201]</code>.</p> </li> </ol> <p>It is possible to create a new <code>Buffer</code> that shares the same allocated memory as a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instance by using the <code>TypedArray</code> object's <code>.buffer</code> property.</p> <pre><code class="language-js">const arr = new Uint16Array(2); arr[0] = 5000; arr[1] = 4000; // Copies the contents of `arr`. const buf1 = Buffer.from(arr); // Shares memory with `arr`. const buf2 = Buffer.from(arr.buffer); console.log(buf1); // Prints: <Buffer 88 a0> console.log(buf2); // Prints: <Buffer 88 13 a0 0f> arr[1] = 6000; console.log(buf1); // Prints: <Buffer 88 a0> console.log(buf2); // Prints: <Buffer 88 13 70 17> </code></pre> <p>When creating a <code>Buffer</code> using a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_