gltfpack: Support texture compression in WASI builds

We now support texture compression through a fake system() call; this
also required implementing getenv() in the WASI JS layer.

gltf/bin/gltfpack.js

@@ -1,4 +1,5 @@
 var fs = require('fs');
+var cp = require('child_process');
 
 var WASI_EBADF = 8;
 var WASI_EINVAL = 28;
@@ -19,6 +20,7 @@ var fds = {
 };
 
 var args = process.argv.slice(1);
+var env = Object.keys(process.env).map(function (key) { return key + '=' + process.env[key] });
 
 function nextFd() {
 	for (var i = 0; ; ++i) {
@@ -83,12 +85,24 @@ var wasi = {
 			heap.setUint32(opened_fd, fd, true);
 			return 0;
 		} catch (err) {
-			return WASI_ENOSYS;
+			return WASI_EIO;
 		}
 	},
 
 	path_unlink_file: function(parent_fd, path, path_len) {
-		return WASI_EINVAL;
+		if (fds[parent_fd] !== null) {
+			return WASI_EBADF;
+		}
+
+		var heap = getHeap();
+		var path_name = Buffer.from(heap.buffer, path, path_len).toString('utf-8');
+
+		try {
+			fs.unlinkSys(path_name);
+			return 0;
+		} catch (err) {
+			return WASI_EIO;
+		}
 	},
 
 	args_sizes_get: function(argc, argv_buf_size) {
@@ -111,13 +125,13 @@ var wasi = {
 		var argp = argv_buf;
 
 		for (var i = 0; i < args.length; ++i) {
-			var au = Buffer.from(args[i], 'utf-8');
+			var item = Buffer.from(args[i], 'utf-8');
 
 			heap.setUint32(argv + i * 4, argp, true);
-			au.copy(memory, argp);
-			heap.setUint8(argp + au.length, 0);
+			item.copy(memory, argp);
+			heap.setUint8(argp + item.length, 0);
 
-			argp += au.length + 1;
+			argp += item.length + 1;
 		}
 
 		return 0;
@@ -145,12 +159,33 @@ var wasi = {
 
 	environ_sizes_get: function(environc, environ_buf_size) {
 		var heap = getHeap();
-		heap.setUint32(environc, 0, true);
-		heap.setUint32(environ_buf_size, 0, true);
+
+		var buf_size = 0;
+		for (var i = 0; i < env.length; ++i) {
+			buf_size += Buffer.from(env[i], 'utf-8').length + 1;
+		}
+
+		heap.setUint32(environc, env.length, true);
+		heap.setUint32(environ_buf_size, buf_size, true);
 		return 0;
 	},
 
 	environ_get: function(environ, environ_buf) {
+		var heap = getHeap();
+		var memory = new Uint8Array(heap.buffer);
+
+		var envp = environ_buf;
+
+		for (var i = 0; i < env.length; ++i) {
+			var item = Buffer.from(env[i], 'utf-8');
+
+			heap.setUint32(environ + i * 4, envp, true);
+			item.copy(memory, envp);
+			heap.setUint8(envp + item.length, 0);
+
+			envp += item.length + 1;
+		}
+
 		return 0;
 	},
 
@@ -233,6 +268,18 @@ var wasi = {
 		heap.setUint32(nwritten, written, true);
 		return 0;
 	},
+
+	path_readlink: function(fd, path, path_len, buf, buf_len, bufused) {
+		if (fd !== -1) {
+			return WASI_ENOSYS;
+		}
+
+		var heap = getHeap();
+		var command = Buffer.from(heap.buffer, path, path_len).toString('utf-8');
+
+		var ret = cp.spawnSync(command, [], {shell:true});
+		return ret.status == null ? 256 : ret.status;
+	},
 };
 
 var wasm = fs.readFileSync(__dirname + '/gltfpack.wasm');

gltf/fileio.cpp

@@ -25,7 +25,7 @@ TempFile::TempFile(const char* suffix)
 	char ids[16];
 	sprintf(ids, "%d", id++);
 
-	path = "/tmp/gltfpack-";
+	path = "gltfpack-temp-";
 	path += ids;
 	path += suffix;
 #else

gltf/image.cpp

@@ -104,17 +104,6 @@ static const char* mimeExtension(const char* mime_type)
 	return ".raw";
 }
 
-#if defined(__wasi__)
-static int execute(const char* cmd_, bool ignore_stdout, bool ignore_stderr)
-{
-	return -1;
-}
-
-static const char* readenv(const char* name)
-{
-	return getenv(name);
-}
-#else
 static int execute(const char* cmd_, bool ignore_stdout, bool ignore_stderr)
 {
 #ifdef _WIN32
@@ -125,10 +114,12 @@ static int execute(const char* cmd_, bool ignore_stdout, bool ignore_stderr)
 
 	std::string cmd = cmd_;
 
+#ifndef __wasi__
 	if (ignore_stdout)
 		(cmd += " >") += ignore;
 	if (ignore_stderr)
 		(cmd += " 2>") += ignore;
+#endif
 
 	return system(cmd.c_str());
 }
@@ -137,7 +128,6 @@ static const char* readenv(const char* name)
 {
 	return getenv(name);
 }
-#endif
 
 bool checkBasis(bool verbose)
 {

gltf/wasistubs.cpp

@@ -1,5 +1,6 @@
 #ifdef __wasi__
 #include <stdlib.h>
+#include <string.h>
 
 #include <wasi/api.h>
 
@@ -40,4 +41,12 @@ __wasi_errno_t __wasi_fd_seek(__wasi_fd_t fd, __wasi_filedelta_t offset, __wasi_
 	*newoffset = newoffset32;
 	return result;
 }
+
+extern "C" int system(const char* command)
+{
+	// WASI doesn't provide a system() equivalent; we highjack readlink here, the reasoning being that if we run against a real WASI implementation,
+	// the effect is more likely to be benign.
+	return  __wasi_path_readlink(-1, command, strlen(command), 0, 0, 0);
+}
+
 #endif