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create.js
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Sun, Nov 10, 10:06

create.js
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function _typeof(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof = function _typeof(obj) { return typeof obj; }; } else { _typeof = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof(obj); }
import { encodeNode } from "@webassemblyjs/wasm-gen";
import { overrideBytesInBuffer } from "@webassemblyjs/helper-buffer";
import constants from "@webassemblyjs/helper-wasm-bytecode";
import * as t from "@webassemblyjs/ast";
function findLastSection(ast, forSection) {
var targetSectionId = constants.sections[forSection]; // $FlowIgnore: metadata can not be empty
var moduleSections = ast.body[0].metadata.sections;
var lastSection;
var lastId = 0;
for (var i = 0, len = moduleSections.length; i < len; i++) {
var section = moduleSections[i]; // Ignore custom section since they can actually occur everywhere
if (section.section === "custom") {
continue;
}
var sectionId = constants.sections[section.section];
if (targetSectionId > lastId && targetSectionId < sectionId) {
return lastSection;
}
lastId = sectionId;
lastSection = section;
}
return lastSection;
}
export function createEmptySection(ast, uint8Buffer, section) {
// previous section after which we are going to insert our section
var lastSection = findLastSection(ast, section);
var start, end;
/**
* It's the first section
*/
if (lastSection == null || lastSection.section === "custom") {
start = 8
/* wasm header size */
;
end = start;
} else {
start = lastSection.startOffset + lastSection.size.value + 1;
end = start;
} // section id
start += 1;
var sizeStartLoc = {
line: -1,
column: start
};
var sizeEndLoc = {
line: -1,
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) {
if (path.node.section === section) {
encounteredSection = true;
return;
}
if (encounteredSection === true) {
t.shiftSection(ast, path.node, deltaBytes);
}
}
});
return {
uint8Buffer: uint8Buffer,
sectionMetadata: sectionMetadata
};
}

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