os: add missing is_opened checks to File.read* functions (fix #26096) (#26413)

Author: gechandesu

vlib/os/file.c.v

@@ -208,6 +208,9 @@ pub fn (mut f File) reopen(path string, mode string) ! {
 
 // read implements the Reader interface.
 pub fn (f &File) read(mut buf []u8) !int {
+	if !f.is_opened {
+		return error_file_not_opened()
+	}
 	if buf.len == 0 {
 		return Eof{}
 	}
@@ -390,6 +393,9 @@ pub fn (f &File) read_bytes_at(size int, pos u64) []u8 {
 // A read call is either stopped, if the buffer is full, a newline was read or EOF.
 // On EOF, the method returns 0. The methods will also return any IO error encountered.
 pub fn (f &File) read_bytes_with_newline(mut buf []u8) !int {
+	if !f.is_opened {
+		return error_file_not_opened()
+	}
 	if buf.len == 0 {
 		return error(@FN + ': `buf.len` == 0')
 	}
@@ -429,6 +435,9 @@ pub fn (f &File) read_bytes_with_newline(mut buf []u8) !int {
 // `buf` *must* have length greater than zero.
 // Returns the number of read bytes, or an error.
 pub fn (f &File) read_bytes_into(pos u64, mut buf []u8) !int {
+	if !f.is_opened {
+		return error_file_not_opened()
+	}
 	if buf.len == 0 {
 		return error(@FN + ': `buf.len` == 0')
 	}
@@ -440,6 +449,9 @@ pub fn (f &File) read_bytes_into(pos u64, mut buf []u8) !int {
 
 // read_from implements the RandomReader interface.
 pub fn (f &File) read_from(pos u64, mut buf []u8) !int {
+	if !f.is_opened {
+		return error_file_not_opened()
+	}
 	if buf.len == 0 {
 		return 0
 	}
@@ -451,6 +463,9 @@ pub fn (f &File) read_from(pos u64, mut buf []u8) !int {
 // read_into_ptr reads at most `max_size` bytes from the file and writes it into ptr.
 // Returns the amount of bytes read or an error.
 pub fn (f &File) read_into_ptr(ptr &u8, max_size int) !int {
+	if !f.is_opened {
+		return error_file_not_opened()
+	}
 	return fread(ptr, 1, max_size, f.cfile)
 }
 

vlib/os/file_test.v

@@ -518,3 +518,11 @@ fn test_write_lines() {
 	assert c1 == c2
 	assert c1.split_into_lines() == some_lines_content.split_into_lines()
 }
+
+fn test_read_from_closed_file() {
+	os.write_file(tfile, 'test')!
+	mut f := os.open(tfile)!
+	f.close()
+	mut buf := []u8{len: 64}
+	assert f.read(mut buf) or { -1 } == -1
+}