perf: 2.5x improvement in reading file (normal mode)

Rewritten reading function, yet there is always room for optimizations.

utils/io.cpp

@@ -128,6 +128,14 @@ inline void ins_b(char ch)
 	}
 }
 
+inline long whereis(const char *str,  char ch)
+{
+	const char *end = strchr(str, ch);
+	if (end == 0)
+		return -1;
+	return end - str + 1;
+}
+
 // read in single line
 void read_fread_sl(FILE *fi)
 {
@@ -140,11 +148,22 @@ void read_fread_sl(FILE *fi)
 void read_fread(FILE *fi)
 {
 	char tmp[SZ];
-	unsigned a;
-	while ((a = fread(tmp, sizeof(tmp[0]), SZ, fi)))
-		for (unsigned i = 0; i < a; ++i)
-			ins_b(tmp[i]);
-	// if last line does not have a newline, gap does not get updated
-	it->gps = it->len;
-	it->gpe = it->cpt;
+	unsigned a, j = 0;
+	while ((a = fread(tmp, sizeof(tmp[0]), SZ, fi))) {
+		long res = whereis(tmp, '\n');
+		if (res > 0) { // found newline
+			while ((res = whereis(tmp + j, '\n')) > -1) {
+				apnd_s(*it, tmp + j, res);
+				j += res;
+				if (++curnum >= txt_cpt) {
+					txt_cpt *= 2;
+					text.resize(txt_cpt);
+				}
+				++it;
+			}
+		}
+		// if last character is not a newline
+		apnd_s(*it, tmp + j, a - j);
+		j = 0;
+	}
 }