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os: fix file read end-of-file detection (#10070)

pull/10099/head
Leigh McCulloch 2021-05-12 23:48:55 -07:00 committed by GitHub
parent ebe58dcafa
commit 49deeac71e
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 110 additions and 63 deletions
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100
vlib/os/file.c.v
View File

@ -321,6 +321,31 @@ pub fn (mut f File) write_ptr_at(data voidptr, size int, pos u64) int {
}
// **************************** Read ops ***************************
// fread wraps C.fread and handles error and end-of-file detection.
fn fread(ptr voidptr, item_size int, items int, stream &C.FILE) ?int {
nbytes := int(C.fread(ptr, item_size, items, stream))
// If no bytes were read, check for errors and end-of-file.
if nbytes <= 0 {
// If fread encountered end-of-file return the none error. Note that fread
// may read data and encounter the end-of-file, but we shouldn't return none
// in that case which is why we only check for end-of-file if no data was
// read. The caller will get none on their next call because there will be
// no data available and the end-of-file will be encountered again.
if C.feof(stream) != 0 {
return none
}
// If fread encountered an error, return it. Note that fread and ferror do
// not tell us what the error was, so we can't return anything more specific
// than there was an error. This is because fread and ferror do not set
// errno.
if C.ferror(stream) != 0 {
return error('file read error')
}
}
return nbytes
}
// read_bytes reads bytes from the beginning of the file.
// Utility method, same as .read_bytes_at(size, 0).
pub fn (f &File) read_bytes(size int) []byte {
@ -348,23 +373,14 @@ pub fn (f &File) read_bytes_into(pos u64, mut buf []byte) ?int {
$if windows {
// Note: fseek errors if pos == os.file_size, which we accept
C._fseeki64(f.cfile, pos, C.SEEK_SET)
// errno is only set if fread fails, so clear it first to tell
C.errno = 0
nbytes := int(C.fread(buf.data, 1, buf.len, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes := fread(buf.data, 1, buf.len, f.cfile) ?
$if debug {
C._fseeki64(f.cfile, 0, C.SEEK_SET)
}
return nbytes
} $else {
C.fseeko(f.cfile, pos, C.SEEK_SET)
C.errno = 0
nbytes := int(C.fread(buf.data, 1, buf.len, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes := fread(buf.data, 1, buf.len, f.cfile) ?
$if debug {
C.fseeko(f.cfile, 0, C.SEEK_SET)
}
@ -373,11 +389,7 @@ pub fn (f &File) read_bytes_into(pos u64, mut buf []byte) ?int {
}
$if x32 {
C.fseek(f.cfile, pos, C.SEEK_SET)
C.errno = 0
nbytes := int(C.fread(buf.data, 1, buf.len, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes := fread(buf.data, 1, buf.len, f.cfile) ?
$if debug {
C.fseek(f.cfile, 0, C.SEEK_SET)
}
@ -391,11 +403,7 @@ pub fn (f &File) read(mut buf []byte) ?int {
if buf.len == 0 {
return 0
}
C.errno = 0
nbytes := int(C.fread(buf.data, 1, buf.len, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes := fread(buf.data, 1, buf.len, f.cfile) ?
return nbytes
}
@ -417,20 +425,12 @@ pub fn (f &File) read_from(pos u64, mut buf []byte) ?int {
C.fseeko(f.cfile, pos, C.SEEK_SET)
}
C.errno = 0
nbytes := int(C.fread(buf.data, 1, buf.len, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes := fread(buf.data, 1, buf.len, f.cfile) ?
return nbytes
}
$if x32 {
C.fseek(f.cfile, pos, C.SEEK_SET)
C.errno = 0
nbytes := int(C.fread(buf.data, 1, buf.len, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes := fread(buf.data, 1, buf.len, f.cfile) ?
return nbytes
}
return error('Could not read file')
@ -461,11 +461,7 @@ pub fn (mut f File) read_struct<T>(mut t T) ? {
if tsize == 0 {
return none
}
C.errno = 0
nbytes := int(C.fread(t, 1, tsize, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes := fread(t, 1, tsize, f.cfile) ?
if nbytes != tsize {
return error_with_code('incomplete struct read', nbytes)
}
@ -480,27 +476,23 @@ pub fn (mut f File) read_struct_at<T>(mut t T, pos u64) ? {
if tsize == 0 {
return none
}
C.errno = 0
mut nbytes := 0
$if x64 {
$if windows {
C._fseeki64(f.cfile, pos, C.SEEK_SET)
nbytes = int(C.fread(t, 1, tsize, f.cfile))
nbytes = fread(t, 1, tsize, f.cfile) ?
C._fseeki64(f.cfile, 0, C.SEEK_END)
} $else {
C.fseeko(f.cfile, pos, C.SEEK_SET)
nbytes = int(C.fread(t, 1, tsize, f.cfile))
nbytes = fread(t, 1, tsize, f.cfile) ?
C.fseeko(f.cfile, 0, C.SEEK_END)
}
}
$if x32 {
C.fseek(f.cfile, pos, C.SEEK_SET)
nbytes = int(C.fread(t, 1, tsize, f.cfile))
nbytes = fread(t, 1, tsize, f.cfile) ?
C.fseek(f.cfile, 0, C.SEEK_END)
}
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
if nbytes != tsize {
return error_with_code('incomplete struct read', nbytes)
}
@ -515,12 +507,8 @@ pub fn (mut f File) read_raw<T>() ?T {
if tsize == 0 {
return none
}
C.errno = 0
mut t := T{}
nbytes := int(C.fread(&t, 1, tsize, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes := fread(&t, 1, tsize, f.cfile) ?
if nbytes != tsize {
return error_with_code('incomplete struct read', nbytes)
}
@ -536,7 +524,6 @@ pub fn (mut f File) read_raw_at<T>(pos u64) ?T {
if tsize == 0 {
return none
}
C.errno = 0
mut nbytes := 0
mut t := T{}
$if x64 {
@ -544,10 +531,7 @@ pub fn (mut f File) read_raw_at<T>(pos u64) ?T {
if C._fseeki64(f.cfile, pos, C.SEEK_SET) != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes = int(C.fread(&t, 1, tsize, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes = fread(&t, 1, tsize, f.cfile) ?
if C._fseeki64(f.cfile, 0, C.SEEK_END) != 0 {
return error(posix_get_error_msg(C.errno))
}
@ -555,10 +539,7 @@ pub fn (mut f File) read_raw_at<T>(pos u64) ?T {
if C.fseeko(f.cfile, pos, C.SEEK_SET) != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes = int(C.fread(&t, 1, tsize, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes = fread(&t, 1, tsize, f.cfile) ?
if C.fseeko(f.cfile, 0, C.SEEK_END) != 0 {
return error(posix_get_error_msg(C.errno))
}
@ -568,10 +549,7 @@ pub fn (mut f File) read_raw_at<T>(pos u64) ?T {
if C.fseek(f.cfile, pos, C.SEEK_SET) != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes = int(C.fread(&t, 1, tsize, f.cfile))
if C.errno != 0 {
return error(posix_get_error_msg(C.errno))
}
nbytes = fread(&t, 1, tsize, f.cfile) ?
if C.fseek(f.cfile, 0, C.SEEK_END) != 0 {
return error(posix_get_error_msg(C.errno))
}

64
vlib/os/file_test.v
View File

@ -59,6 +59,70 @@ fn testsuite_end() ? {
assert !os.is_dir(tfolder)
}
// test_read_eof_last_read_partial_buffer_fill tests that when reading a file
// the end-of-file is detected and results in a none error being returned. This
// test simulates file reading where the end-of-file is reached inside an fread
// containing data.
fn test_read_eof_last_read_partial_buffer_fill() ? {
mut f := os.open_file(tfile, 'w') ?
bw := []byte{len: 199, init: 5}
f.write(bw) ?
f.close()
f = os.open_file(tfile, 'r') ?
mut br := []byte{len: 100}
// Read first 100 bytes of 199 byte file, should fill buffer with no error.
n0 := f.read(mut br) ?
assert n0 == 100
// Read remaining 99 bytes of 199 byte file, should fill buffer with no
// error, even though end-of-file was reached.
n1 := f.read(mut br) ?
assert n1 == 99
// Read again, end-of-file was previously reached so should return none
// error.
if _ := f.read(mut br) {
// This is not intended behavior because the read function should
// not return a number of bytes read when end-of-file is reached.
assert false
} else {
// Expect none to have been returned when end-of-file.
assert err is none
}
f.close()
}
// test_read_eof_last_read_full_buffer_fill tests that when reading a file the
// end-of-file is detected and results in a none error being returned. This test
// simulates file reading where the end-of-file is reached at the beinning of an
// fread that returns no data.
fn test_read_eof_last_read_full_buffer_fill() ? {
mut f := os.open_file(tfile, 'w') ?
bw := []byte{len: 200, init: 5}
f.write(bw) ?
f.close()
f = os.open_file(tfile, 'r') ?
mut br := []byte{len: 100}
// Read first 100 bytes of 200 byte file, should fill buffer with no error.
n0 := f.read(mut br) ?
assert n0 == 100
// Read remaining 100 bytes of 200 byte file, should fill buffer with no
// error. The end-of-file isn't reached yet, but there is no more data.
n1 := f.read(mut br) ?
assert n1 == 100
// Read again, end-of-file was previously reached so should return none
// error.
if _ := f.read(mut br) {
// This is not intended behavior because the read function should
// not return a number of bytes read when end-of-file is reached.
assert false
} else {
// Expect none to have been returned when end-of-file.
assert err is none
}
f.close()
}
fn test_write_struct() ? {
os.rm(tfile) or {} // FIXME This is a workaround for macos, because the file isn't truncated when open with 'w'
size_of_point := int(sizeof(Point))

9
vlib/os/os_test.v
View File

@ -160,8 +160,13 @@ fn test_write_and_read_bytes() {
// check that trying to read data from EOF doesn't error and returns 0
mut a := []byte{len: 5}
nread := file_read.read_bytes_into(5, mut a) or {
eprintln(err)
int(-1)
n := if err is none {
int(0)
} else {
eprintln(err)
int(-1)
}
n
}
assert nread == 0
file_read.close()