✨ add native functions of subprocess

src/natives/subprocess.cpp

@@ -1,13 +1,62 @@
 #include "natives/subprocess.h"
 
+#include <cstdio>
+
 namespace nasal {
 
-var builtin_subprocess_run(context* ctx, gc* ngc) {
-    return nil;
+const auto subprocess_object_name = "subprocess";
+
+void subprocess_destructor(void* ptr) {
+    pclose(static_cast<FILE*>(ptr));
+}
+
+var builtin_subprocess_popen(context* ctx, gc* ngc) {
+    auto command = ctx->localr[1];
+    if (!command.is_str()) {
+        return nas_err("subprocess::popen", "expect a string as the command");
+    }
+
+    auto fd = popen(command.str().c_str(), "r");
+    if (fd == nullptr) {
+        return nas_err("subprocess::popen", "failed to create sub-process");
+    }
+
+    var ret = ngc->alloc(vm_type::vm_ghost);
+    ret.ghost().set(subprocess_object_name, subprocess_destructor, nullptr, fd);
+    return ret;
+}
+
+var builtin_subprocess_pclose(context* ctx, gc* ngc) {
+    auto fd = ctx->localr[1];
+    if (!fd.object_check(subprocess_object_name)) {
+        return nas_err("subprocess::pclose", "not a valid subprocess");
+    }
+    auto res = pclose(static_cast<FILE*>(fd.ghost().pointer));
+    fd.ghost().pointer = nullptr;
+    fd.ghost().clear();
+    return var::num(res);
+}
+
+var builtin_subprocess_read_stdout(context* ctx, gc* ngc) {
+    auto fd = ctx->localr[1];
+    if (!fd.object_check(subprocess_object_name)) {
+        return nas_err("subprocess::pclose", "not a valid subprocess");
+    }
+    char buffer[1025];
+    auto res = ngc->alloc(vm_type::vm_str);
+    while(fgets(
+        buffer,
+        sizeof(buffer)-1,
+        static_cast<FILE*>(fd.ghost().pointer))!=nullptr) {
+        res.str() += buffer;
+    }
+    return res;
 }
 
 nasal_builtin_table subprocess_native[] = {
-    {"__subprocess_run", builtin_subprocess_run},
+    {"__subprocess_popen", builtin_subprocess_popen},
+    {"__subprocess_pclose", builtin_subprocess_pclose},
+    {"__subprocess_read_stdout", builtin_subprocess_read_stdout},
     {nullptr, nullptr}
 };