From 5cb23bf245ef1461fa080c2d8aeee8972720f3e5 Mon Sep 17 00:00:00 2001
From: Mia Herkt <mia@0x0.st>
Date: Wed, 7 Dec 2022 23:51:13 +0100
Subject: [PATCH] 07: C: Use mmap instead of fgets

---
 07/solution.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/07/solution.c b/07/solution.c
index 5e0027a..534340a 100644
--- a/07/solution.c
+++ b/07/solution.c
@@ -2,6 +2,9 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdint.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
 
 uint32_t fnv1a_32(const char *buf, size_t len)
 {
@@ -22,7 +25,7 @@ typedef struct entry {
 } entry;
 
 entry *findent(entry *e, const char *name) {
-    uint32_t id = fnv1a_32(name, strlen(name));
+    uint32_t id = fnv1a_32(name, strchr(name, '\n') - name);
     for (size_t i = 0; i < e->n_entries; i++) {
         if (e->entries[i]->id == id)
             return e->entries[i];
@@ -42,19 +45,29 @@ entry *addent(entry *parent, const char *name) {
     parent->n_entries++;
 
     entry *e = parent->entries[parent->n_entries - 1] = calloc(1, sizeof(entry));
-    e->id = fnv1a_32(name, strlen(name));
+    e->id = fnv1a_32(name, strchr(name, '\n') - name);
     e->parent = parent;
 
     return e;
 }
 
 int main(int argc, char **argv) {
-    char l[64];
+    if (argc < 2) return 1;
+
     entry *root = calloc(1, sizeof(entry));
     entry *current = root;
     size_t S = 0, G = 0, required = 0;
 
-    while (fgets(l, 64, stdin)) {
+    struct stat s;
+    if (stat(argv[1], &s) == -1) return 1;
+    int fd = open(argv[1], O_RDONLY);
+    if (fd == -1) return 1;
+
+    char *in = mmap(NULL, s.st_size, PROT_READ, MAP_SHARED, fd, 0);
+    if (in == MAP_FAILED) return 1;
+    char *l = in;
+
+    while (l - in < s.st_size) {
         if (l[0] == '$') {
             if (l[2] == 'c') {
                 if (l[5] == '/')
@@ -73,11 +86,12 @@ int main(int argc, char **argv) {
                 f->size += sz;
             f->size += sz;
         }
+        l = strchr(l, '\n') + 1;
     }
 
     current = root;
-    if (argc == 3)
-        required = strtoul(argv[2], NULL, 10) - (strtoul(argv[1], NULL, 10) - root->size);
+    if (argc == 4)
+        required = strtoul(argv[3], NULL, 10) - (strtoul(argv[2], NULL, 10) - root->size);
     else
         required = 30000000UL - (70000000UL - root->size);
     do {