feat: read files and split them by lines

src/file.c

@@ -0,0 +1,47 @@
+#include "file.h"
+
+File* new_file(const char* path) {
+    if (!path) return NULL;
+    FILE* f = fopen(path, "rb");
+    if (!f) return NULL;
+
+    if (fseek(f, 0, SEEK_END) != 0) { fclose(f); return NULL; }
+    long sz = ftell(f);
+    if (sz < 0) { fclose(f); return NULL; }
+    if (fseek(f, 0, SEEK_SET) != 0) { fclose(f); return NULL; }
+
+    size_t n = (size_t)sz;
+    char* buf = (char *)calloc(n + 1, 1);
+    if (!buf) { fclose(f); return NULL; }
+
+    size_t got = fread(buf, 1, n, f);
+    fclose(f);
+
+    buf[got] = '\0';
+
+    size_t count = 1;
+    for (size_t i = 0; i < got; ++i) if (buf[i] == '\n') count++;
+    if (buf[got-1] == '\n') count--;
+
+    char** lines = count ? (char**)malloc(count * sizeof *lines) : NULL;
+    if (count && !lines) return NULL;
+
+    size_t idx = 0;
+    lines[idx++] = buf;
+
+    for (size_t i = 0; i < got; ++i) {
+        if (buf[i] == '\n') {
+            if (i > 0 && buf[i-1] == '\r') buf[i-1] = '\0';
+            buf[i] = '\0';
+            if (i+1 < got) lines[idx++] = &buf[i+1];
+        }
+    }
+
+    if (got > 0 && buf[got-1] == '\r') buf[got-1] = '\0';
+
+    File* file = calloc(1, sizeof(File));
+    file->content = lines;
+    file->lines = idx;
+
+    return file;
+}