src/etc/wasm32-shim.js

   1 // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // This is a small "shim" program which is used when wasm32 unit tests are run
  12 // in this repository. This program is intended to be run in node.js and will
  13 // load a wasm module into memory, instantiate it with a set of imports, and
  14 // then run it.
  15 //
  16 // There's a bunch of helper functions defined here in `imports.env`, but note
  17 // that most of them aren't actually needed to execute most programs. Many of
  18 // these are just intended for completeness or debugging. Hopefully over time
  19 // nothing here is needed for completeness.
  20
  21 const fs = require('fs');
  22 const process = require('process');
  23 const buffer = fs.readFileSync(process.argv[2]);
  24
  25 Error.stackTraceLimit = 20;
  26
  27 let m = new WebAssembly.Module(buffer);
  28
  29 let memory = null;
  30
  31 function copystr(a, b) {
  32   if (memory === null) {
  33     return null
  34   }
  35   let view = new Uint8Array(memory.buffer).slice(a, a + b);
  36   return String.fromCharCode.apply(null, view);
  37 }
  38
  39 let imports = {};
  40 imports.env = {
  41   // These are generated by LLVM itself for various intrinsic calls. Hopefully
  42   // one day this is not necessary and something will automatically do this.
  43   fmod: function(x, y) { return x % y; },
  44   exp2: function(x) { return Math.pow(2, x); },
  45   exp2f: function(x) { return Math.pow(2, x); },
  46   ldexp: function(x, y) { return x * Math.pow(2, y); },
  47   ldexpf: function(x, y) { return x * Math.pow(2, y); },
  48   log10: Math.log10,
  49   log10f: Math.log10,
  50
  51   // These are called in src/libstd/sys/wasm/stdio.rs and are used when
  52   // debugging is enabled.
  53   rust_wasm_write_stdout: function(a, b) {
  54     let s = copystr(a, b);
  55     if (s !== null) {
  56       process.stdout.write(s);
  57     }
  58   },
  59   rust_wasm_write_stderr: function(a, b) {
  60     let s = copystr(a, b);
  61     if (s !== null) {
  62       process.stderr.write(s);
  63     }
  64   },
  65
  66   // These are called in src/libstd/sys/wasm/args.rs and are used when
  67   // debugging is enabled.
  68   rust_wasm_args_count: function() {
  69     if (memory === null)
  70       return 0;
  71     return process.argv.length - 2;
  72   },
  73   rust_wasm_args_arg_size: function(i) {
  74     return Buffer.byteLength(process.argv[i + 2]);
  75   },
  76   rust_wasm_args_arg_fill: function(idx, ptr) {
  77     let arg = process.argv[idx + 2];
  78     let view = new Uint8Array(memory.buffer);
  79     Buffer.from(arg).copy(view, ptr);
  80   },
  81
  82   // These are called in src/libstd/sys/wasm/os.rs and are used when
  83   // debugging is enabled.
  84   rust_wasm_getenv_len: function(a, b) {
  85     let key = copystr(a, b);
  86     if (key === null) {
  87       return -1;
  88     }
  89     if (!(key in process.env)) {
  90       return -1;
  91     }
  92     return Buffer.byteLength(process.env[key]);
  93   },
  94   rust_wasm_getenv_data: function(a, b, ptr) {
  95     let key = copystr(a, b);
  96     let value = process.env[key];
  97     let view = new Uint8Array(memory.buffer);
  98     Buffer.from(value).copy(view, ptr);
  99   },
 100 };
 101
 102 let module_imports = WebAssembly.Module.imports(m);
 103
 104 for (var i = 0; i < module_imports.length; i++) {
 105   let imp = module_imports[i];
 106   if (imp.module != 'env') {
 107     continue
 108   }
 109   if (imp.name == 'memory' && imp.kind == 'memory') {
 110     memory = new WebAssembly.Memory({initial: 20});
 111     imports.env.memory = memory;
 112   }
 113 }
 114
 115 let instance = new WebAssembly.Instance(m, imports);