From 0259de8caf917f5f7f9832ffbd2616ec8f93a8c4 Mon Sep 17 00:00:00 2001
From: "Michael D. Lowis" <mike@mdlowis.com>
Date: Tue, 23 Sep 2014 22:24:11 -0400
Subject: [PATCH] fixed EOF handling

---
 source/sclpl/lexer.c   | 18 ++++++++++--------
 source/sclpl/lexer.h   |  2 +-
 source/sclpl/main.c    | 17 +++++++++--------
 source/sclpl/scanner.c |  9 ++++++---
 4 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/source/sclpl/lexer.c b/source/sclpl/lexer.c
index 04c92e4..4523414 100644
--- a/source/sclpl/lexer.c
+++ b/source/sclpl/lexer.c
@@ -44,15 +44,17 @@ lex_tok_t* lexer_read(lexer_t* p_lexer) {
     mpc_result_t r;
     lex_tok_t* p_tok = NULL;
     char* text = scanner_read(p_lexer->scanner);
-    if (mpc_parse("<stdin>", text, p_lexer->lexrule, &r)) {
-        mpc_ast_print(((mpc_ast_t*)r.output)->children[1]);
-        p_tok = lexer_translate( ((mpc_ast_t*)r.output)->children[1] );
-        mpc_ast_delete(r.output);
-    } else {
-        mpc_err_print(r.error);
-        mpc_err_delete(r.error);
+    if (NULL != text) {
+        if (mpc_parse("<stdin>", text, p_lexer->lexrule, &r)) {
+            mpc_ast_print(((mpc_ast_t*)r.output)->children[1]);
+            p_tok = lexer_translate( ((mpc_ast_t*)r.output)->children[1] );
+            mpc_ast_delete(r.output);
+        } else {
+            mpc_err_print(r.error);
+            mpc_err_delete(r.error);
+        }
+        free(text);
     }
-    free(text);
     return p_tok;
 }
 
diff --git a/source/sclpl/lexer.h b/source/sclpl/lexer.h
index 9233b91..4013142 100644
--- a/source/sclpl/lexer.h
+++ b/source/sclpl/lexer.h
@@ -20,7 +20,7 @@ typedef struct {
 
 typedef enum {
     END, STRING, CHAR, INT, FLOAT, BOOL, LBRACE, RBRACE, LBRACK, RBRACK, LPAR,
-    RPAR, COMMA, VAR
+    RPAR, COMMA, VAR, END_FILE
 } lex_tok_type_t;
 
 typedef struct {
diff --git a/source/sclpl/main.c b/source/sclpl/main.c
index 430c260..43c1a11 100644
--- a/source/sclpl/main.c
+++ b/source/sclpl/main.c
@@ -9,6 +9,8 @@ typedef struct {
     lex_tok_t* p_tok;
 } parser_t;
 
+lex_tok_t tok_eof = { END_FILE, NULL, 0, 0, NULL };
+
 parser_t* parser_new(char* p_prompt, FILE* input)
 {
     parser_t* p_parser = (parser_t*)malloc(sizeof(parser_t));
@@ -20,6 +22,8 @@ parser_t* parser_new(char* p_prompt, FILE* input)
 void parser_fetch(parser_t* p_parser)
 {
     p_parser->p_tok = lexer_read(p_parser->p_lexer);
+    if (NULL == p_parser->p_tok)
+        p_parser->p_tok = &tok_eof;
 }
 
 lex_tok_t* parser_peek(parser_t* p_parser)
@@ -29,6 +33,10 @@ lex_tok_t* parser_peek(parser_t* p_parser)
     return p_parser->p_tok;
 }
 
+bool parser_eof(parser_t* p_parser) {
+    return (parser_peek(p_parser)->type == END_FILE);
+}
+
 void parser_error(parser_t* p_parser, const char* p_text)
 {
     (void)p_parser;
@@ -193,7 +201,6 @@ void parser_fn_stmnt(parser_t* p_parser)
  *****************************************************************************/
 /* TODO:
 
-    * Gracefully handle EOF
     * Formalize grammar for parser
     * Paren for function application must be on same line as variable in REPL
     * "end" and ';' must be equivalent
@@ -209,14 +216,8 @@ int main(int argc, char **argv) {
     (void)argc;
     (void)argv;
 
-    //scanner_t* p_scanner = scanner_new(":> ", stdin);
-    //while(!scanner_eof(p_scanner)) {
-    //    printf("TOK: '%s'\n", scanner_read(p_scanner) );
-    //    puts("OK.");
-    //}
-
     parser_t* p_parser = parser_new(":> ", stdin);
-    while(true) {
+    while(!parser_eof(p_parser)) {
         parser_toplevel(p_parser);
         puts("OK.");
     }
diff --git a/source/sclpl/scanner.c b/source/sclpl/scanner.c
index fcfe78f..e6fafb4 100644
--- a/source/sclpl/scanner.c
+++ b/source/sclpl/scanner.c
@@ -89,11 +89,14 @@ static void scanner_skip_ws(scanner_t* p_scanner) {
     /* If we haven't read a line yet, read one now */
     if (NULL == p_scanner->p_line)
         scanner_getline(p_scanner);
-    while('\0' == scanner_current(p_scanner) || scanner_oneof(p_scanner, " \t\r\n")) {
-        if ('\0' == scanner_current(p_scanner) && !scanner_eof(p_scanner)) {
+    /* Fast forward past whitespace and read a newline if necessary  */
+    while(!scanner_eof(p_scanner)) {
+        if ('\0' == scanner_current(p_scanner)) {
             scanner_getline(p_scanner);
-        } else {
+        } else if (scanner_oneof(p_scanner, " \t\r\n")) {
             p_scanner->index++;
+        } else {
+            break;
         }
     }
 }
-- 
2.52.0