mirrors/cosmopolitan
1
0
Fork 0
mirror of https://github.com/jart/cosmopolitan.git synced 2025-06-27 06:48:31 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

Share file offset across processes

Browse source 
This change ensures that if a file descriptor for an open disk file gets
shared by multiple processes within a process tree, then lseek() changes
will be visible across processes, and read() / write() are synchronized.
Note this only applies to Windows, because UNIX kernels already do this.
This commit is contained in:
Justine Tunney 2024-08-03 01:24:46 -07:00
parent a80ab3f8fe
commit 761c6ad615
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
15 changed files with 256 additions and 63 deletions
Download patch file Download diff file Expand all files Collapse all files

13
libc/calls/lseek-nt.c
View file

@ -31,7 +31,7 @@ static textwindows int64_t GetPosition(struct Fd *f, int whence) {
case SEEK_SET:
return 0;
case SEEK_CUR:
return f->pointer;
return f->shared->pointer;
case SEEK_END: {
struct NtByHandleFileInformation wst;
if (!GetFileInformationByHandle(f->handle, &wst)) {
@ -67,11 +67,14 @@ textwindows int64_t sys_lseek_nt(int fd, int64_t offset, int whence) {
} else if (__isfdkind(fd, kFdFile)) {
struct Fd *f = g_fds.p + fd;
int filetype = GetFileType(f->handle);
if (filetype != kNtFileTypePipe && filetype != kNtFileTypeChar) {
if (filetype != kNtFileTypePipe && //
filetype != kNtFileTypeChar && //
f->shared) {
int64_t res;
if ((res = Seek(f, offset, whence)) != -1) {
f->pointer = res;
}
__fd_lock(f);
if ((res = Seek(f, offset, whence)) != -1)
f->shared->pointer = res;
__fd_unlock(f);
return res;
} else {
return espipe();