WebAssembly学习笔记（一）

先下载代码
cd /usr/local
git clone https://github.com/emscripten-core/emsdk.git

激活
cd emsdk
./emsdk install latest
./emsdk activate latest

设置环境变量
source ./emsdk_env.sh --build=Release

测试
$ mkdir hello
$ cd hello
$ cat << EOF > hello.cc

#include <stdio.h>
int main(int argc, char ** argv) {
  printf("Hello, world!\n");
}
EOF

编译
emcc hello.cc -o hello.html

运行
emrun --no_browser --port 8080 .
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 代码改成

// Copyright 2011 The Emscripten Authors. All rights reserved. // Emscripten is available under two separate licenses, the MIT license and the // University of Illinois/NCSA Open Source License. Both these licenses can be // found in the LICENSE file. #include <stdio.h> #include <SDL/SDL.h> #ifdef __EMSCRIPTEN__ #include <emscripten.h> #endif extern "C" int main(int argc, char** argv) { printf("hello, world!\n"); SDL_Init(SDL_INIT_VIDEO); SDL_Surface *screen = SDL_SetVideoMode(256, 256, 32, SDL_SWSURFACE); #ifdef TEST_SDL_LOCK_OPTS EM_ASM("SDL.defaults.copyOnLock = false; SDL.defaults.discardOnLock = true; SDL.defaults.opaqueFrontBuffer = false;"); #endif if (SDL_MUSTLOCK(screen)) SDL_LockSurface(screen); for (int i = 0; i < 256; i++) { for (int j = 0; j < 256; j++) { #ifdef TEST_SDL_LOCK_OPTS // Alpha behaves like in the browser, so write proper opaque pixels. int alpha = 255; #else // To emulate native behavior with blitting to screen, alpha component is ignored. Test that it is so by outputting // data (and testing that it does get discarded) int alpha = (i+j) % 255; #endif *((Uint32*)screen->pixels + i * 256 + j) = SDL_MapRGBA(screen->format, i, j, 255-i, alpha); } } if (SDL_MUSTLOCK(screen)) SDL_UnlockSurface(screen); SDL_Flip(screen); printf("you should see a smoothly-colored square - no sharp lines but the square borders!\n"); printf("and here is some text that should be HTML-friendly: amp: |&| double-quote: |\"| quote: |'| less-than, greater-than, html-like tags: |<cheez></cheez>|\nanother line.\n"); SDL_Quit(); return 0; }