Expand - env! and option_env!

1 files changed, 76 insertions, 0 deletions

diff --git a/src/expand/env.cpp b/src/expand/env.cpp
new file mode 100644
index 00000000..989fbb7a
--- /dev/null
+++ b/src/expand/env.cpp
@@ -0,0 +1,76 @@
+/*
+ * MRustC - Rust Compiler
+ * - By John Hodge (Mutabah/thePowersGang)
+ *
+ * expand/env.cpp
+ * - env! and option_env! macros
+ */
+#include <synext_macro.hpp>
+#include <parse/common.hpp>
+#include <ast/expr.hpp> // ExprNode_*
+#include <synext.hpp>   // for Expand_BareExpr
+
+namespace {
+    // Read a string out of the input stream
+    ::std::string get_string(const Span& sp, const AST::Crate& crate, AST::Module& mod, const TokenTree& tt) {
+        auto lex = TTStream(tt);
+        
+        auto n = Parse_ExprVal(lex);
+        ASSERT_BUG(sp, n, "No expression returned");
+        if( lex.lookahead(0) != TOK_EOF ) {
+            ERROR(sp, E0000, "Unexpected token after string literal - " << lex.getToken());
+        }
+        Expand_BareExpr(crate, mod, n);
+
+        auto* string_np = dynamic_cast<AST::ExprNode_String*>(&*n);
+        if( !string_np ) {
+            ERROR(sp, E0000, "Expected a string literal - got " << *n);
+        }
+        return mv$( string_np->m_value );
+    }
+}
+
+class CExpanderEnv:
+    public ExpandProcMacro
+{
+    ::std::unique_ptr<TokenStream> expand(const Span& sp, const AST::Crate& crate, const ::std::string& ident, const TokenTree& tt, AST::Module& mod) override
+    {
+        if( ident != "" )
+            ERROR(sp, E0000, "env! doesn't take an ident");
+        ::std::string   varname = get_string(sp, crate, mod,  tt);
+        
+        const char* var_val_cstr = getenv(varname.c_str());
+        if( !var_val_cstr ) {
+            ERROR(sp, E0000, "Environment variable '" << varname << "' not defined");
+        }
+        return box$( TTStreamO(TokenTree(Token(TOK_STRING, var_val_cstr))) );
+    }
+};
+
+class CExpanderOptionEnv:
+    public ExpandProcMacro
+{
+    ::std::unique_ptr<TokenStream> expand(const Span& sp, const AST::Crate& crate, const ::std::string& ident, const TokenTree& tt, AST::Module& mod) override
+    {
+        if( ident != "" )
+            ERROR(sp, E0000, "option_env! doesn't take an ident");
+        ::std::string   varname = get_string(sp, crate, mod,  tt);
+        
+        const char* var_val_cstr = getenv(varname.c_str());
+        if( !var_val_cstr ) {
+            return box$( TTStreamO(TokenTree(Token(TOK_IDENT, "None"))) );
+        }
+        else {
+            ::std::vector< TokenTree>   rv;
+            rv.reserve(4);
+            rv.push_back( Token(TOK_IDENT, "Some") );
+            rv.push_back( Token(TOK_PAREN_OPEN) );
+            rv.push_back( Token(TOK_STRING, var_val_cstr) );
+            rv.push_back( Token(TOK_PAREN_CLOSE) );
+            return box$( TTStreamO(TokenTree( mv$(rv) )) );
+        }
+    }
+};
+
+STATIC_MACRO("env", CExpanderEnv);
+STATIC_MACRO("option_env", CExpanderOptionEnv);