How to use @webassemblyjs/helper-buffer - 9 common examples

const oldNodeSize = encodeNode(oldNode).length;
          const bodySizeDeltaBytes = replacementByteArray.length - oldNodeSize;

          if (bodySizeDeltaBytes !== 0) {
            const newValue = node.metadata.bodySize + bodySizeDeltaBytes;
            const newByteArray = encodeU32(newValue);

            debug("resize func body newValue=%d", newValue);

            // function body size byte
            // FIXME(sven): only handles one byte u32
            const start = node.loc.start.column;
            const end = start + 1;

            uint8Buffer = overrideBytesInBuffer(
              uint8Buffer,
              start,
              end,
              newByteArray
            );
          }
        }
      }
    });

* Add nodes
   */
  const newByteArray = encodeNode(node);

  // The size of the section doesn't include the storage of the size itself
  // we need to manually add it here
  const start = getEndOfSection(sectionMetadata);

  const end = start;

  /**
   * Update section
   */
  const deltaBytes = newByteArray.length;

  uint8Buffer = overrideBytesInBuffer(uint8Buffer, start, end, newByteArray);

  node.loc = {
    start: { line: -1, column: start },
    end: { line: -1, column: start + deltaBytes }
  };

  // for func add the additional metadata in the AST
  if (node.type === "Func") {
    // the size is the first byte
    // FIXME(sven): handle LEB128 correctly here
    const bodySize = newByteArray[0];

    node.metadata = { bodySize };
  }

  if (node.type !== "IndexInFuncSection") {

/**
     * The start section only contains one element,
     * we need to remove the whole section
     */
    uint8Buffer = removeSection(ast, uint8Buffer, "start");

    const deltaBytes = -(sectionMetadata.size.value + 1) /* section id */;

    return { uint8Buffer, deltaBytes, deltaElements };
  }

  // replacement is nothing
  const replacement = [];

  uint8Buffer = overrideBytesInBuffer(
    uint8Buffer,
    // $FlowIgnore: assertHasLoc ensures that
    node.loc.start.column,
    // $FlowIgnore: assertHasLoc ensures that
    node.loc.end.column,
    replacement
  );

  /**
   * Update section
   */

  // $FlowIgnore: assertHasLoc ensures that
  const deltaBytes = -(node.loc.end.column - node.loc.start.column);

  return { uint8Buffer, deltaBytes, deltaElements };

column: start + 1
  }; // 1 byte for the empty vector

  var size = t.withLoc(t.numberLiteralFromRaw(1), sizeEndLoc, sizeStartLoc);
  var vectorOfSizeStartLoc = {
    line: -1,
    column: sizeEndLoc.column
  };
  var vectorOfSizeEndLoc = {
    line: -1,
    column: sizeEndLoc.column + 1
  };
  var vectorOfSize = t.withLoc(t.numberLiteralFromRaw(0), vectorOfSizeEndLoc, vectorOfSizeStartLoc);
  var sectionMetadata = t.sectionMetadata(section, start, size, vectorOfSize);
  var sectionBytes = encodeNode(sectionMetadata);
  uint8Buffer = overrideBytesInBuffer(uint8Buffer, start - 1, end, sectionBytes); // Add section into the AST for later lookups

  if (_typeof(ast.body[0].metadata) === "object") {
    // $FlowIgnore: metadata can not be empty
    ast.body[0].metadata.sections.push(sectionMetadata);
    t.sortSectionMetadata(ast.body[0]);
  }
  /**
   * Update AST
   */
  // Once we hit our section every that is after needs to be shifted by the delta


  var deltaBytes = +sectionBytes.length;
  var encounteredSection = false;
  t.traverse(ast, {
    SectionMetadata: function SectionMetadata(path) {

}) !== undefined; // Update func's body size if needed

        if (funcHasThisIntr === true) {
          // These are the old functions locations informations
          assertHasLoc(node);
          var oldNodeSize = encodeNode(oldNode).length;
          var bodySizeDeltaBytes = replacementByteArray.length - oldNodeSize;

          if (bodySizeDeltaBytes !== 0) {
            var newValue = node.metadata.bodySize + bodySizeDeltaBytes;
            var newByteArray = encodeU32(newValue); // function body size byte
            // FIXME(sven): only handles one byte u32

            var start = node.loc.start.column;
            var end = start + 1;
            uint8Buffer = overrideBytesInBuffer(uint8Buffer, start, end, newByteArray);
          }
        }
      }
    });

// These are the old functions locations informations
          assertHasLoc(node);

          const oldNodeSize = encodeNode(oldNode).length;
          const bodySizeDeltaBytes = replacementByteArray.length - oldNodeSize;

          if (bodySizeDeltaBytes !== 0) {
            const newValue = node.metadata.bodySize + bodySizeDeltaBytes;
            const newByteArray = encodeU32(newValue);

            // function body size byte
            // FIXME(sven): only handles one byte u32
            const start = node.loc.start.column;
            const end = start + 1;

            uint8Buffer = overrideBytesInBuffer(
              uint8Buffer,
              start,
              end,
              newByteArray
            );
          }
        }
      }
    });

function applyUpdate(
  ast: Program,
  uint8Buffer: Uint8Array,
  [oldNode, newNode]: [Node, Node]
): State {
  const deltaElements = 0;

  assertHasLoc(oldNode);

  const sectionName = getSectionForNode(newNode);
  const replacementByteArray = encodeNode(newNode);

  /**
   * Replace new node as bytes
   */
  uint8Buffer = overrideBytesInBuffer(
    uint8Buffer,
    // $FlowIgnore: assertHasLoc ensures that
    oldNode.loc.start.column,
    // $FlowIgnore: assertHasLoc ensures that
    oldNode.loc.end.column,
    replacementByteArray
  );

  /**
   * Update function body size if needed
   */
  if (sectionName === "code") {
    // Find the parent func
    traverse(ast, {
      Func({ node }) {
        const funcHasThisIntr =

function applyUpdate(ast, uint8Buffer, _ref) {
  var _ref2 = _slicedToArray(_ref, 2),
      oldNode = _ref2[0],
      newNode = _ref2[1];

  var deltaElements = 0;
  assertHasLoc(oldNode);
  var sectionName = getSectionForNode(newNode);
  var replacementByteArray = encodeNode(newNode);
  /**
   * Replace new node as bytes
   */

  uint8Buffer = overrideBytesInBuffer(uint8Buffer, // $FlowIgnore: assertHasLoc ensures that
  oldNode.loc.start.column, // $FlowIgnore: assertHasLoc ensures that
  oldNode.loc.end.column, replacementByteArray);
  /**
   * Update function body size if needed
   */

  if (sectionName === "code") {
    // Find the parent func
    traverse(ast, {
      Func: function Func(_ref3) {
        var node = _ref3.node;
        var funcHasThisIntr = node.body.find(function (n) {
          return n === newNode;
        }) !== undefined; // Update func's body size if needed

        if (funcHasThisIntr === true) {

SectionMetadata: function SectionMetadata(_ref2) {
      var node = _ref2.node;

      /**
       * Section size
       */
      {
        var newu32Encoded = encodeU32(node.size.value);
        var newu32EncodedLen = newu32Encoded.length;
        var start = node.size.loc.start.column;
        var end = node.size.loc.end.column;
        var oldu32EncodedLen = end - start;

        if (newu32EncodedLen !== oldu32EncodedLen) {
          var deltaInSizeEncoding = oldu32EncodedLen - newu32EncodedLen;
          uint8Buffer = overrideBytesInBuffer(uint8Buffer, start, end, newu32Encoded);
          shiftFollowingSections(ast, node, -deltaInSizeEncoding);
        }
      }
    }
  });