git ssb

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const inject = require('./injectGettersSetters.js')
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/**
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 * Prepares a binary by injecting getter and setter function for memory, globals and tables.
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 * @param {ArrayBuffer} binary - a wasm binary
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 * @param {Object} include
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 * @param {Boolean} [include.memory=true] - whether or not to included memory
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 * @param {Boolean} [include.table=true] - whether or not to included the function table
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 * @param {Array.<Boolean>} [include.globals=Array.<true>] - whether or not to
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 * included a given global. Each index in the array stands for a global index.
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 * Indexes that are set to false or left undefined will not be persisted. By
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 * default all globals are persisted.
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 * @param {String} [symbol = '_'] - a sting used to prefix the injected setter and getter functions
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 * @return {ArrayBuffer} the resulting wasm binary
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 */
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function prepare (binary, include = {memory: true, table: true}, symbol = '_') {
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  return inject(binary, include, symbol)
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}
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/**
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 * Given a wasm Instance this will produce an Object containing the current state of
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 * the instance
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 * @param {Webassembly.Instance} instance
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 * @param {String} symbol - the symbol that will be used to find the injected functions
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 * @returns {Object} the state of the wasm instance
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 */
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function hibernate (instance, symbol = '_') {
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  const json = {
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    globals: [],
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    table: [],
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    symbol
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  }
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  for (const key in instance.exports) {
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    const val = instance.exports[key]
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    if (key.startsWith(symbol)) {
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      const keyElems = key.slice(symbol.length).split('_')
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      // save the memory
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      if (val instanceof WebAssembly.Memory) {
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        json.memory = new Uint32Array(val.buffer)
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      } else if (val instanceof WebAssembly.Table) {
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        // mark the tables, (do something for external function?)
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        // the external functions should have a callback
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        for (let i = 0; i < val.length; i++) {
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          const func = val.get(i)
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          if (func === instance.exports[`${symbol}func_${func.name}`]) {
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            json.table.push(func.name)
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          }
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        }
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      } else if (keyElems[0] === 'global' && keyElems[1] === 'getter') {
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        // save the globals
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        const last = keyElems.pop()
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        if (last === 'high') {
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          json.globals.push([instance.exports[key]()])
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        } else if (last === 'low') {
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          json.globals[json.globals.length - 1].push(instance.exports[key]())
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        } else {
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          json.globals.push(instance.exports[key]())
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        }
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      }
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    }
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  }
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  instance.__hibrenated = true
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  return json
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}
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/**
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 * resumes a prevously hibranted webassembly instance
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 * @param {WebAssemby.Instance} instance
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 * @param {Object} state - the pervous state of the wasm instance
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 * @retrun {WebAssembly.Instance}
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 */
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function resume (instance, state) {
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  if (instance.__hibrenated) {
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    instance.__hibrenated = false
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  } else {
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    // initailize memory
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    const mem = instance.exports[`${state.symbol}memory`]
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    if (mem) {
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      // console.log(mem.length)
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      (new Uint32Array(mem.buffer)).set(state.memory, 0)
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    }
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    // initailize table
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    if (instance.exports._table) {
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      for (const index in state.table) {
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        const funcIndex = state.table[index]
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        instance.exports._table.set(index, instance.exports[`${state.symbol}func_${funcIndex}`])
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      }
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    }
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    // intialize globals
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    for (const index in state.globals) {
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      const val = state.globals[index]
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      if (Array.isArray(val)) {
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        instance.exports[`${state.symbol}global_setter_i64_${index}`](val[1], val[0])
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      } else {
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        instance.exports[`${state.symbol}global_setter_i32_${index}`](val)
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      }
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    }
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  }
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  return instance
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}
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module.exports = {
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  prepare,
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  hibernate,
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  resume
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}
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