git ssb

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const {findSections} = require('wasm-json-toolkit')
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const wantedSections = ['type', 'import', 'function', 'export', 'code']
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module.exports = function injectGlobals (json, globals) {
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  const iter = findSections(json, wantedSections)
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  const {value: type} = iter.next()
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  const getterType = type.entries.push(typeEntry()) - 1
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  const setterType = type.entries.push(typeEntry(Array(globals.length).fill('i32'))) - 1
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  const {value: imports = {entries: []}} = iter.next()
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  const {value: func} = iter.next()
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  const getterIndex = func.entries.push(getterType) - 1 + imports.entries.length
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  const setterIndex = func.entries.push(setterType) - 1 + imports.entries.length
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  const {value: exports} = iter.next()
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  exports.entries.push(exportEntry('getter_globals', getterIndex))
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  exports.entries.push(exportEntry('setter_globals', setterIndex))
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  const {value: code} = iter.next()
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  const getterCode = []
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  const setterCode = []
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  globals.forEach((global, index) => {
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    const globalIndex = global.index
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    // getter
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    getterCode.push(i32_const(index * 4))
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    getterCode.push(get_global(globalIndex))
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    getterCode.push(i32_store())
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    // setter
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    setterCode.push(get_local(index))
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    setterCode.push(set_global(globalIndex))
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  })
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  getterCode.push(end())
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  setterCode.push(end())
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  code.entries.push(section_code([], getterCode))
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  code.entries.push(section_code([], setterCode))
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  return json
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}
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function exportEntry (field_str, index) {
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  return {
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    field_str,
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    kind: 'function',
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    index
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  }
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}
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function typeEntry (params = []) {
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  return {
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    form: 'func',
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    params: params
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  }
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}
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function end () {
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  return {
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    name: 'end'
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  }
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}
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function get_local (index) {
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  return {
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    name: 'get_local',
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    immediates: index
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  }
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}
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function get_global (index) {
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  return {
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    name: 'get_global',
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    immediates: index
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  }
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}
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function set_global (index) {
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  return {
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    name: 'set_global',
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    immediates: index
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  }
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}
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function i32_const (num) {
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  return {
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    'return_type': 'i32',
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    'name': 'const',
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    'immediates': num
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  }
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}
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function i32_store () {
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  return {
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    'return_type': 'i32',
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    'name': 'store',
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    'immediates': {
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      'flags': 2,
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      'offset': 0
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    }
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  }
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}
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function section_code (locals, code) {
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  return {
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    locals: locals,
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    code: code
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  }
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}
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