WebAssembly 入门教程 c++、go、python编译wasm - ToB企服应用市场:ToB评测及商务社交产业平台

需要安装CMake，VS，python2.7及以上

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# Get the emsdk repo
git clone https://github.com/emscripten-core/emsdk.git
# Enter that directory
cd emsdk

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emsdk.bat install latest
emsdk.bat activate latest
在cmd窗口运行如上，有时需要./

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emsdk_evn.bat

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emcc --check
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.59 (0e4c5994eb5b8defd38367a416d0703fd506ad81)
shared:INFO: (Emscripten: Running sanity checks)

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#include <stdio.h>
int main() {
printf("Hello World\n");
return 0;
}

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emcc hello.c -o hello.html

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$ npx serve .

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$ python3 -m http.server

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#include <stdio.h>
#include <emscripten/emscripten.h>
int main() {
printf("Hello World\n");
return 0;
}
#ifdef __cplusplus
#define EXTERN extern "C"
#else
#define EXTERN
#endif
EXTERN EMSCRIPTEN_KEEPALIVE void greet(char* name) {
printf("Hello, %s!\n", name);
}
// Fibonacci function
EXTERN int EMSCRIPTEN_KEEPALIVE fibonacci(int n) {
if (n <= 1) {
return n;
} else {
return fibonacci(n - 1) + fibonacci(n - 2);
}
}

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emcc -o greet.html greet.c -s NO_EXIT_RUNTIME=1 -s EXPORTED_RUNTIME_METHODS=ccall

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<input type="text" id="myinput" value=10>
<button id="mybutton">Click me!</button>

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document.getElementById("mybutton").addEventListener("click", () => {
const result = Module.ccall(
"greet", // name of C function
null, // return type
["string"], // argument types
["WebAssembly"] // arguments
);
const n = parseInt(document.getElementById("myinput").value, 10);
const result2 = Module.ccall(
"fibonacci", // name of C function
"number", // return type
["number"], // argument types
[n] // arguments
);
console.log("The Fibonacci number is: " + result2);
});

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Uncaught RuntimeError: memory access out of bounds

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#include <stdio.h>
int output()
{
return 1;
}
int add(int a, int b)
{
return a + b;
}
emcc testWebAssembly.c -Os -s WASM=1 -s SIDE_MODULE=1 -o testWebAssembly.wasm

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WebAssembly.Instance(): Import #0 module="wasi_snapshot_preview1" error: module is not an object or function

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const fs = require('fs');
const wasmCode = fs.readFileSync('./testWebAssembly.wasm');
// 编译WebAssembly二进制代码
const wasmModule = new WebAssembly.Module(toUint8Array(wasmCode));
// 实例化WebAssembly模块
const wasmInstance = new WebAssembly.Instance(wasmModule, {});
const lib = wasmInstance.exports;
// `Wasm` does **not** understand node buffers, but thankfully a node buffer
// is easy to convert to a native Uint8Array.
function toUint8Array(buf) {
const u = new Uint8Array(buf.length);
for (let i = 0; i < buf.length; ++i) {
u[i] = buf[i];
}
return u;
}
console.log(lib.add(5, 5));
console.log(lib.output());

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[/code] [code]py2wasm pystone.py -o pystone.wasm

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#! /usr/bin/env python3
"""
"PYSTONE" Benchmark Program
Version: Python/1.1 (corresponds to C/1.1 plus 2 Pystone fixes)
Author: Reinhold P. Weicker, CACM Vol 27, No 10, 10/84 pg. 1013.
Translated from ADA to C by Rick Richardson.
Every method to preserve ADA-likeness has been used,
at the expense of C-ness.
Translated from C to Python by Guido van Rossum.
Version History:
Version 1.1 corrects two bugs in version 1.0:
First, it leaked memory: in Proc1(), NextRecord ends
up having a pointer to itself. I have corrected this
by zapping NextRecord.PtrComp at the end of Proc1().
Second, Proc3() used the operator != to compare a
record to None. This is rather inefficient and not
true to the intention of the original benchmark (where
a pointer comparison to None is intended; the !=
operator attempts to find a method __cmp__ to do value
comparison of the record). Version 1.1 runs 5-10
percent faster than version 1.0, so benchmark figures
of different versions can't be compared directly.
"""
LOOPS = 50000
from time import clock
__version__ = "1.1"
[Ident1, Ident2, Ident3, Ident4, Ident5] = range(1, 6)
class Record:
def __init__(self, PtrComp = None, Discr = 0, EnumComp = 0,
IntComp = 0, StringComp = 0):
self.PtrComp = PtrComp
self.Discr = Discr
self.EnumComp = EnumComp
self.IntComp = IntComp
self.StringComp = StringComp
def copy(self):
return Record(self.PtrComp, self.Discr, self.EnumComp,
self.IntComp, self.StringComp)
TRUE = 1
FALSE = 0
def main(loops=LOOPS):
benchtime, stones = pystones(loops)
print("Pystone(%s) time for %d passes = %g" % \
(__version__, loops, benchtime))
print("This machine benchmarks at %g pystones/second" % stones)
def pystones(loops=LOOPS):
return Proc0(loops)
IntGlob = 0
BoolGlob = FALSE
Char1Glob = '\0'
Char2Glob = '\0'
Array1Glob = [0]*51
Array2Glob = [x[:] for x in [Array1Glob]*51]
PtrGlb = None
PtrGlbNext = None
def Proc0(loops=LOOPS):
global IntGlob
global BoolGlob
global Char1Glob
global Char2Glob
global Array1Glob
global Array2Glob
global PtrGlb
global PtrGlbNext
starttime = clock()
for i in range(loops):
pass
nulltime = clock() - starttime
PtrGlbNext = Record()
PtrGlb = Record()
PtrGlb.PtrComp = PtrGlbNext
PtrGlb.Discr = Ident1
PtrGlb.EnumComp = Ident3
PtrGlb.IntComp = 40
PtrGlb.StringComp = "DHRYSTONE PROGRAM, SOME STRING"
String1Loc = "DHRYSTONE PROGRAM, 1'ST STRING"
Array2Glob[8][7] = 10
starttime = clock()
for i in range(loops):
Proc5()
Proc4()
IntLoc1 = 2
IntLoc2 = 3
String2Loc = "DHRYSTONE PROGRAM, 2'ND STRING"
EnumLoc = Ident2
BoolGlob = not Func2(String1Loc, String2Loc)
while IntLoc1 < IntLoc2:
IntLoc3 = 5 * IntLoc1 - IntLoc2
IntLoc3 = Proc7(IntLoc1, IntLoc2)
IntLoc1 = IntLoc1 + 1
Proc8(Array1Glob, Array2Glob, IntLoc1, IntLoc3)
PtrGlb = Proc1(PtrGlb)
CharIndex = 'A'
while CharIndex <= Char2Glob:
if EnumLoc == Func1(CharIndex, 'C'):
EnumLoc = Proc6(Ident1)
CharIndex = chr(ord(CharIndex)+1)
IntLoc3 = IntLoc2 * IntLoc1
IntLoc2 = IntLoc3 / IntLoc1
IntLoc2 = 7 * (IntLoc3 - IntLoc2) - IntLoc1
IntLoc1 = Proc2(IntLoc1)
benchtime = clock() - starttime - nulltime
if benchtime == 0.0:
loopsPerBenchtime = 0.0
else:
loopsPerBenchtime = (loops / benchtime)
return benchtime, loopsPerBenchtime
def Proc1(PtrParIn):
PtrParIn.PtrComp = NextRecord = PtrGlb.copy()
PtrParIn.IntComp = 5
NextRecord.IntComp = PtrParIn.IntComp
NextRecord.PtrComp = PtrParIn.PtrComp
NextRecord.PtrComp = Proc3(NextRecord.PtrComp)
if NextRecord.Discr == Ident1:
NextRecord.IntComp = 6
NextRecord.EnumComp = Proc6(PtrParIn.EnumComp)
NextRecord.PtrComp = PtrGlb.PtrComp
NextRecord.IntComp = Proc7(NextRecord.IntComp, 10)
else:
PtrParIn = NextRecord.copy()
NextRecord.PtrComp = None
return PtrParIn
def Proc2(IntParIO):
IntLoc = IntParIO + 10
while 1:
if Char1Glob == 'A':
IntLoc = IntLoc - 1
IntParIO = IntLoc - IntGlob
EnumLoc = Ident1
if EnumLoc == Ident1:
break
return IntParIO
def Proc3(PtrParOut):
global IntGlob
if PtrGlb is not None:
PtrParOut = PtrGlb.PtrComp
else:
IntGlob = 100
PtrGlb.IntComp = Proc7(10, IntGlob)
return PtrParOut
def Proc4():
global Char2Glob
BoolLoc = Char1Glob == 'A'
BoolLoc = BoolLoc or BoolGlob
Char2Glob = 'B'
def Proc5():
global Char1Glob
global BoolGlob
Char1Glob = 'A'
BoolGlob = FALSE
def Proc6(EnumParIn):
EnumParOut = EnumParIn
if not Func3(EnumParIn):
EnumParOut = Ident4
if EnumParIn == Ident1:
EnumParOut = Ident1
elif EnumParIn == Ident2:
if IntGlob > 100:
EnumParOut = Ident1
else:
EnumParOut = Ident4
elif EnumParIn == Ident3:
EnumParOut = Ident2
elif EnumParIn == Ident4:
pass
elif EnumParIn == Ident5:
EnumParOut = Ident3
return EnumParOut
def Proc7(IntParI1, IntParI2):
IntLoc = IntParI1 + 2
IntParOut = IntParI2 + IntLoc
return IntParOut
def Proc8(Array1Par, Array2Par, IntParI1, IntParI2):
global IntGlob
IntLoc = IntParI1 + 5
Array1Par[IntLoc] = IntParI2
Array1Par[IntLoc+1] = Array1Par[IntLoc]
Array1Par[IntLoc+30] = IntLoc
for IntIndex in range(IntLoc, IntLoc+2):
Array2Par[IntLoc][IntIndex] = IntLoc
Array2Par[IntLoc][IntLoc-1] = Array2Par[IntLoc][IntLoc-1] + 1
Array2Par[IntLoc+20][IntLoc] = Array1Par[IntLoc]
IntGlob = 5
def Func1(CharPar1, CharPar2):
CharLoc1 = CharPar1
CharLoc2 = CharLoc1
if CharLoc2 != CharPar2:
return Ident1
else:
return Ident2
def Func2(StrParI1, StrParI2):
IntLoc = 1
while IntLoc <= 1:
if Func1(StrParI1[IntLoc], StrParI2[IntLoc+1]) == Ident1:
CharLoc = 'A'
IntLoc = IntLoc + 1
if CharLoc >= 'W' and CharLoc <= 'Z':
IntLoc = 7
if CharLoc == 'X':
return TRUE
else:
if StrParI1 > StrParI2:
IntLoc = IntLoc + 7
return TRUE
else:
return FALSE
def Func3(EnumParIn):
EnumLoc = EnumParIn
if EnumLoc == Ident3: return TRUE
return FALSE
if __name__ == '__main__':
import sys
def error(msg):
print(msg, end=' ', file=sys.stderr)
print("usage: %s [number_of_loops]" % sys.argv[0], file=sys.stderr)
sys.exit(100)
nargs = len(sys.argv) - 1
if nargs > 1:
error("%d arguments are too many;" % nargs)
elif nargs == 1:
try: loops = int(sys.argv[1])
except ValueError:
error("Invalid argument %r;" % sys.argv[1])
else:
loops = LOOPS
main(loops)

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//go:build js && wasm
package main
import (
"fmt"
"math/rand"
"os"
"runtime"
"syscall"
"syscall/js"
"time"
)
func getFileAttr(path string) (string, error) {
fi, err := os.Stat(path)
if err != nil {
return "", err
}
return fmt.Sprintf("Mode: %s\nOwner: %d\nGroup: %d\nSize: %d\nModified: %s\nIsDir: %t",
fi.Mode(),
fi.Sys().(*syscall.Stat_t).Uid,
fi.Sys().(*syscall.Stat_t).Gid,
fi.Size(),
fi.ModTime().String(),
fi.IsDir(),
), nil
}
func main() {
// **ERROR**: fsnotify is not supported in WASM
fmt.Println("testing...........")
_, err := os.Lstat("/tmp/test.txt")
if err != nil {
// as expected, lstat is not supported in WASM
fmt.Println(err.Error())
}
ret, err := getFileAttr("/tmp/test.txt")
if err != nil {
fmt.Println(err.Error())
}
fmt.Println(ret)
js.Global().Set("jsPI", jsPI())
js.Global().Call("alert", "this is an alerting!")
v := js.Global().Get("app")
fmt.Println(v.Get("title").String())
fmt.Println(v.Call("getAppTitle", "").String())
select {}
}
func pi(samples int) float64 {
cpus := runtime.NumCPU()
threadSamples := samples / cpus
results := make(chan float64, cpus)
for j := 0; j < cpus; j++ {
go func() {
var inside int
r := rand.New(rand.NewSource(time.Now().UnixNano()))
for i := 0; i < threadSamples; i++ {
x, y := r.Float64(), r.Float64()
if x*x+y*y <= 1 {
inside++
}
}
results <- float64(inside) / float64(threadSamples) * 4
}()
}
var total float64
for i := 0; i < cpus; i++ {
total += <-results
}
return total / float64(cpus)
}
func jsPI() js.Func {
return js.FuncOf(func(this js.Value, args []js.Value) any {
if len(args) != 1 {
return "Invalid no of arguments passed"
}
samples := args[0].Int()
return pi(samples)
})
}

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cp "$(go env GOROOT)/misc/wasm/wasm_exec.js" ./test/
cp "$(go env GOROOT)/misc/wasm/wasm_exec_node.js" ./test/
GOOS=js GOARCH=wasm go build -o ./bin/md-monitor.wasm

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'use strict'
// Try to execute the following code in browser or electron(Obsidian) console
const exec_wasm = require('./test/wasm_exec.js');
const go = new Go();
const fs = require('fs');
let content = undefined;
fs.readFile("./bin/md-monitor.wasm", (err, data) => { content = data });
WebAssembly.instantiate(content, go.importObject).then((ret) => { go.run(ret.instance); });
// call exported function which define in go module.
jsPI(3);

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