# All files / src/generator memory-assignment.js

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     // @flow
    import mapSyntax from './map-syntax';
    import mergeBlock from './merge-block';
    import opcode from '../emitter/opcode';
    import { TYPE_ARRAY } from '../semantics/metadata';
    import type { GeneratorType } from './flow/types';

    const generateMemoryAssignment: GeneratorType = (node, parent) => {
      const targetNode = node.params[0];
      const isArray = targetNode.params[0].meta[TYPE_ARRAY];
      let type = node.type;

      const block = node.params[0].params
        .map(mapSyntax(parent))
        .reduce(mergeBlock, []);

      if (isArray != null) {
        // For array types, the index is multiplied by the contained object size
        block.push.apply(block, [
          // TODO: fix this for user-defined types
          { kind: opcode.i32Const, params: [2] },
          { kind: opcode.i32Shl, params: [] },
        ]);
        type = isArray;
      }

      // The sequence of opcodes to perfrom a memory load is
      // get(Local|Global) base, i32Const offset[, i32Const size, i32Mul ], i32Add
      block.push({ kind: opcode.i32Add, params: [] });

      block.push.apply(
        block,
        node.params
          .slice(1)
          .map(mapSyntax(parent))
          .reduce(mergeBlock, [])
      );

      // The last piece is the WASM opcode. Either load or store
      block.push({
        kind: opcode[String(type) + 'Store'],
        params: [
          // Alignment
          // TODO: make this extendible
          2,
          // Memory. Always 0 in the WASM MVP
          0,
        ],
      });

      return block;
    };

    export default generateMemoryAssignment;