From f5257e1823d0354666d8cbe72738d5821b461e4f Mon Sep 17 00:00:00 2001
From: Bruce Hill <bruce@bruce-hill.com>
Date: Thu, 24 Sep 2020 22:10:03 -0700
Subject: Added mmap()

---
 file_loader.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/file_loader.c b/file_loader.c
index 0ce4b4c..82f594b 100644
--- a/file_loader.c
+++ b/file_loader.c
@@ -7,6 +7,8 @@
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
 #include <unistd.h>
 
 #include "file_loader.h"
@@ -22,19 +24,33 @@ file_t *load_file(const char *filename)
     file_t *f = calloc(sizeof(file_t), 1);
     f->filename = strdup(filename);
     // TODO: use mmap when possible
+    struct stat sb;
+    if (fstat(fd, &sb) == -1)
+        goto skip_mmap;
+
+    f->contents = mmap(NULL, (size_t)sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+    if (f->contents == MAP_FAILED)
+        goto skip_mmap;
+
+    f->mmapped = 1;
+    f->length = (size_t)sb.st_size;
+    goto finished_loading;
+
+  skip_mmap:
     f->mmapped = 0;
     size_t capacity = 1000;
     f->length = 0;
-    f->contents = calloc(sizeof(char), capacity+1);
+    f->contents = calloc(sizeof(char), capacity);
     ssize_t just_read;
     while ((just_read=read(fd, &f->contents[f->length], capacity - f->length)) > 0) {
         f->length += (size_t)just_read;
         if (f->length >= capacity)
             f->contents = realloc(f->contents, sizeof(char)*(capacity *= 2) + 1);
     }
-    f->contents[f->length] = '\0';
-    f->end = &f->contents[f->length];
     close(fd);
+
+  finished_loading:
+    f->end = &f->contents[f->length];
     
     // Calculate line numbers:
     size_t linecap = 10;
@@ -64,7 +80,11 @@ void destroy_file(file_t **f)
         (*f)->lines = NULL;
     }
     if ((*f)->contents) {
-        free((*f)->contents);
+        if ((*f)->mmapped) {
+            munmap((*f)->contents, (*f)->length);
+        } else {
+            free((*f)->contents);
+        }
         (*f)->contents = NULL;
     }
     free(*f);
-- 
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