{"id":77,"date":"2019-09-22T13:34:17","date_gmt":"2019-09-22T13:34:17","guid":{"rendered":"https:\/\/www.kindsonthegenius.com\/nodejs\/?p=77"},"modified":"2019-09-22T13:34:17","modified_gmt":"2019-09-22T13:34:17","slug":"working-with-buffers","status":"publish","type":"post","link":"https:\/\/kindsonthegenius.com\/nodejs\/working-with-buffers\/","title":{"rendered":"Working with Buffers"},"content":{"rendered":"

In this tutorial, we would cover Buffers in Node.js under the following sub-topics:<\/p>\n

    \n
  1. Introduction to Buffers<\/a><\/li>\n
  2. How to Create Buffers<\/a><\/li>\n
  3. Writing to Buffers<\/a><\/li>\n
  4. Reading from Buffers<\/a><\/li>\n
  5. Converting Buffers To JSON<\/a><\/li>\n
  6. Concatenating Buffers<\/a><\/li>\n
  7. Comparing Buffers<\/a><\/li>\n
  8. Copying Buffers<\/a><\/li>\n
  9. Slicing Buffers<\/a><\/li>\n
  10. Other Buffer Class Methods<\/a><\/li>\n<\/ol>\n

     <\/p>\n

    1. Introduction to Buffers<\/strong><\/p>\n

    The buffer class is provided by Node.js to data from streams. For instance, streams of data from file system or from network.<\/p>\n

    This is raw data similar to an array of integers. However, they corresponds to a raw memory allocation that is outside the V8<\/a> memory heap. Learn about V8 here<\/a>.<\/p>\n

    The Buffer class in Node.js is a global class. I can be accessed in your application without having to import the buffer module.<\/p>\n

     <\/p>\n

    2. How to Create Buffers<\/strong><\/p>\n

    Some of the methods of creating a buffer is given below<\/p>\n

    The code below creates a buffer of 10 octets that is uninitialized<\/p>\n

    <\/p>\n

    var<\/span> mybuffer =<\/span> new<\/span> Buffer(10<\/span>);\r\n<\/pre>\n
     <\/p>\n
    Here, a buffer is created from an array<\/p>\n
    <\/p>\n
    var<\/span> mybuffer =<\/span> new<\/span> Buffer([20<\/span>, 30<\/span>, 40<\/span>, 50<\/span>, 60<\/span>]);\r\n\r\n<\/pre>\n
     <\/p>\n
    Finally, in this code, a buffer is created from a string. You can pass the encoding as optional argument<\/p>\n
    <\/p>\n
    var<\/span> mybuffer =<\/span> new<\/span> Buffer(\"The Tech Pro\"<\/span>, \"utf-8\"<\/span>);\r\n<\/pre>\n
    Other encoding can be used as well. For example, “ascii”, “utf16e”, “hex” and “base64”.<\/p>\n
     <\/p>\n
    3. Writing to Buffers<\/strong><\/p>\n
    Once a buffer is created, then you can write to it. The syntax for writing to buffer is given below:<\/p>\n
    mybuffer.write(string[, offset][, length][, encoding]);\r\n<\/pre>\n
     <\/p>\n
    The parameters to the write() method are explained as follows:<\/p>\n
      \n
    • string<\/b> \u2212 The string data that is to be written to buffer.<\/li>\n
    • offset<\/b> \u2212 The index of the buffer from where to start writing at. The default value is 0.<\/li>\n
    • length<\/b> \u2212 The number of bytes to write into the buffer. Defaults to the length of the buffer, buffer.length.<\/li>\n
    • encoding<\/b> \u2212 The encoding to use. The default encoding is\u00a0‘utf8’ is.<\/li>\n<\/ul>\n
      The write method() returns the number of octets written. If there are no enough space in the buffer, then only a part of the string is written.<\/p>\n
       <\/p>\n
      Example\u00a0 of Writing to Buffer<\/strong><\/p>\n
      The code below writes a string to a buffer and outputs number of octets written.<\/p>\n
      mybuffer =<\/span> new<\/span> Buffer(256<\/span>);\r\nwritten =<\/span> mybuffer.write(\"The Tech Pro\"<\/span>);\r\n\r\nconsole.log(\"Number of Octets written : \"<\/span>+<\/span>  written);\r\n<\/pre>\n
       <\/p>\n
      4. Reading from Buffers<\/strong><\/p>\n
      You can also read from a buffer using the syntax below.<\/p>\n
      mybuffer.toString([encoding][, start][, end])\r\n<\/pre>\n
       <\/p>\n
      The parameters are described as follows:<\/p>\n
        \n
      • encoding<\/b> \u2212 The encoding to use. ‘utf8’ is the default.<\/li>\n
      • start<\/b> \u2212 The beginning index to start reading from, defaults is 0.<\/li>\n
      • end<\/b> \u2212 End index to end reading, defaults is the complete buffer.<\/li>\n<\/ul>\n
        The return value of the read method is a string form the buffer encoded with the given character encoding<\/p>\n
        mybuffer =<\/span> new<\/span> Buffer(26<\/span>);\r\nfor<\/span> (var<\/span> i =<\/span> 0<\/span> ; i <<\/span> 26<\/span> ; i++<\/span>) {\r\n    mybuffer[i] =<\/span> i +<\/span> 97<\/span>;\r\n}\r\n\r\nconsole.log( mybuffer.toString('ascii'<\/span>));       \/\/ output: abcdefghijklmnopqrstuvwxyz<\/span>\r\nconsole.log( mybuffer.toString('ascii'<\/span>,0<\/span>,5<\/span>));   \/\/ output: abcde<\/span>\r\nconsole.log( mybuffer.toString('utf8'<\/span>,0<\/span>,5<\/span>));    \/\/ output: abcde<\/span>\r\nconsole.log( mybuffer.toString(undefined<\/span>,0<\/span>,5<\/span>)); \/\/ encoding defaults to 'utf8', outputs abcde<\/span>\r\n<\/pre>\n
        I recommend you run the code to see the outputs.<\/p>\n
         <\/p>\n
        5. Converting Buffer to JSON<\/strong><\/p>\n
        To convert buffer to json simply use the toJSON()<\/em> <\/strong>method of the buffer object. This is as given below<\/p>\n
        mybuffer.toJSON()\r\n<\/pre>\n
         <\/p>\n
        6. Concatenating Buffers<\/strong><\/p>\n
        You can concatenate a two or more buffers using the concat()<\/em><\/strong> class method. The buffers to be concatenated are provided as an array list.<\/p>\n
        The syntax is given below:<\/p>\n
        Buffer.concat(list[, totalLength])\r\n<\/pre>\n
        The parameters are explained as follows:<\/p>\n
          \n
        • list<\/b> \u2212 An Array List of Buffer objects that is to be concatenated.<\/li>\n
        • totalLength<\/b> \u2212 The total length of the buffers when concatenated.<\/li>\n<\/ul>\n
          The return value is a buffer object made up of a combination of the buffers concatenated.<\/p>\n
          The code below shows a concatenation of two buffers, buffer1 and buffer2<\/p>\n
          var<\/span> buffer1 =<\/span> new<\/span> Buffer('The Tech Pro'<\/span>);\r\nvar<\/span> buffer2 =<\/span> new<\/span> Buffer('Learning made easy!'<\/span>);\r\nvar<\/span> buffer3 =<\/span> Buffer.concat([buffer1,buffer2]);\r\n\r\nconsole.log(\"buffer3 content: \"<\/span> +<\/span> buffer3.toString());\r\n<\/pre>\n
          Try to run to code yourself to see the output.<\/p>\n
           <\/p>\n
           <\/p>\n
          7. Comparing two Buffers<\/strong><\/p>\n
          You can compare two buffers using the compare method of the buffer object. For example:<\/p>\n
          buffer1.compare(buffer2)\r\n<\/pre>\n
          The return value is either a positive number, negative number or zero.<\/p>\n
          Positive number indicates that buffer1 comes before buffer2<\/p>\n
          Negative number indicates buffer1 comes after buffer2<\/p>\n
          Zero means the two buffers are the same<\/p>\n
          The program below illustrates the result of comparing two buffers:
          \n<\/p>\n
          var<\/span> buffer1 =<\/span> new<\/span> Buffer('AB'<\/span>);\r\nvar<\/span> buffer2 =<\/span> new<\/span> Buffer('ABCDE'<\/span>);\r\nvar<\/span> result =<\/span> buffer1.compare(buffer2);\r\n\r\nif<\/span>(ret_val<<\/span> 0<\/span>) {\r\n   console.log(buffer1 +<\/span>\" comes before \"<\/span> +<\/span> buffer2);\r\n} else<\/span> if<\/span>(ret_val ===<\/span> 0<\/span>) {\r\n   console.log(buffer1 +<\/span>\" is same as \"<\/span> +<\/span> buffer2);\r\n} else<\/span> {\r\n   console.log(buffer1 +<\/span>\" comes after \"<\/span> +<\/span> buffer2);\r\n}\r\n<\/pre>\n
           <\/p>\n
          8. Copying Buffers<\/strong><\/p>\n
          You can copy buffer using the copy instance method of the buffer object. The syntax is given below:<\/p>\n
          buffer.copy(targetBuffer[, targetStart][, sourceStart][, sourceEnd])\r\n<\/pre>\n
          where:<\/p>\n
            \n
          • targetBuffer<\/b> \u2212 The buffer object where buffer will be copied to.<\/li>\n
          • targetStart<\/b> \u2212 Number, Optional, Default is 0<\/li>\n
          • sourceStart<\/b> \u2212 Number, Optional, Default is0<\/li>\n
          • sourceEnd<\/b>\u00a0\u2212 Number, Optional, Default: buffer.length<\/li>\n<\/ul>\n
            There is no return value.<\/p>\n
             <\/p>\n
            9. Slicing a Buffer<\/strong><\/p>\n
            Slicing a buffer means extracting a part of the buffer. The syntax is:<\/p>\n
            buf.slice([start][, end])\r\n<\/pre>\n
            It returns a new buffer which is part of the original buffer but references the same memory location as the original buffer.<\/p>\n
             <\/p>\n
            10. Other Buffer Class Methods<\/strong><\/p>\n
            There are yet other buffer methods I would like you to try out. Find them in the table below:<\/p>\n\n\n\n\n\n\n\n\n
            SN.<\/th>\nMethod and brief description<\/th>\n<\/tr>\n
            1<\/td>\nBuffer.isEncoding(encoding)<\/b><\/p>\n
            Returns true if the encoding is a valid encoding argument, otherwise it returns false.<\/td>\n<\/tr>\n
            2<\/td>\nBuffer.isBuffer(obj)<\/b><\/p>\n
            Checks if obj is a Buffer.<\/td>\n<\/tr>\n
            3<\/td>\nBuffer.byteLength(string[, encoding])<\/b><\/p>\n
            Gives the actual length of a string in byte. encoding default is ‘utf8’. This is not the same as String.prototype.length, becaise String.prototype.length returns the number of characters in a string.<\/td>\n<\/tr>\n
            4<\/td>\nBuffer.concat(list[, totalLength])<\/b><\/p>\n
            We already mentioned this. It returns a buffer which is the result of concatenating all the buffers in the list together.<\/td>\n<\/tr>\n
            5<\/td>\nBuffer.compare(buffer1, buffer2)<\/b><\/p>\n
            The same as buffer1.compare(buffer2). Used for sorting an array of buffers.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"excerpt":{"rendered":"
            In this tutorial, we would cover Buffers in Node.js under the following sub-topics: Introduction to Buffers How to Create Buffers Writing to Buffers Reading from … <\/p>\n","protected":false},"author":1,"featured_media":81,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"footnotes":""},"categories":[1],"tags":[10],"class_list":["post-77","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-buffers"],"_links":{"self":[{"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/posts\/77","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/comments?post=77"}],"version-history":[{"count":1,"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/posts\/77\/revisions"}],"predecessor-version":[{"id":82,"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/posts\/77\/revisions\/82"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/media\/81"}],"wp:attachment":[{"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/media?parent=77"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/categories?post=77"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kindsonthegenius.com\/nodejs\/wp-json\/wp\/v2\/tags?post=77"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}