From 2372fc41a8751e691a04fe16f0a873155b7f99d4 Mon Sep 17 00:00:00 2001
From: Nedko Arnaudov <nedko@nedk.org>
Date: Thu, 17 Aug 2023 03:06:35 +0300
Subject: [PATCH] termsize.c: Check return values of write() and read() calls

While error and short read or write conditions with so small buffers are hard to impossible to trigger,
Checking the values is proper formally so was the warning from the compiler
---
 termsize.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/termsize.c b/termsize.c
index 00fc3d0..9428ca0 100644
--- a/termsize.c
+++ b/termsize.c
@@ -15,9 +15,9 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <limits.h>
+#include <errno.h>
 
 int fd;
-const char * cmd;
 char buf[256];
 
 struct curpos
@@ -26,20 +26,41 @@ struct curpos
   int col;
 };
 
+void write_asciiz(const char * str)
+{
+  ssize_t sret;
+  size_t len;
+
+  len = strlen(str);
+loop:
+  sret = write(fd, str, len);
+  if (sret == -1) abort();
+  str += (size_t)sret;
+  len -= (size_t)sret;
+  if (len > 0) goto loop;
+}
 
 void get_cursor_position(struct curpos * pos)
 {
   int i;
   char * p;
+  ssize_t sret;
 
-  cmd = "\033[6n";
-  write(fd, cmd, strlen(cmd));
+  write_asciiz("\033[6n");
 
   i = 0;
 loop:
   if (i == sizeof(buf)) abort();
 
-  read(fd, buf + i, 1);
+  sret = read(fd, buf + i, 1);
+  if (sret == -1)
+  {
+    if (errno == EINTR) goto loop;
+    abort();
+  }
+  if (sret == 0) goto loop;
+  if (sret != 1) abort();
+
   if (buf[i] == 'R')
   {
     buf[i] = 0;
@@ -61,7 +82,7 @@ loop:
 void set_cursor_position(const struct curpos * pos)
 {
   sprintf(buf, "\033[%d;%dH", pos->row, pos->col);
-  write(fd, buf, strlen(buf));
+  write_asciiz(buf);
 }
 
 void get_terminal_size(struct curpos * size)
@@ -82,7 +103,6 @@ int main(void)
 {
   struct termios tty_save;
   struct termios tty;
-  const char * cmd;
   struct curpos size;
   struct winsize winsize;