feat(unistd): file I/O syscall wrappers
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#ifndef VLIBC_UNISTD_H
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#define VLIBC_UNISTD_H
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/*
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* vlibc — <unistd.h>.
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*
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* File descriptors, file I/O, and the access/whence symbolic constants
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* (POSIX.1-2008). Every function here is an unbuffered pass-through to the
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* kernel: failures are reported as -1 (or the fd/offset on success) with
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* errno set by the syscall layer.
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*
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* Level 1 (onlyposix): read, write, pread, pwrite, open, openat, close,
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* lseek, dup, dup2, pipe, fsync, fdatasync, ftruncate,
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* sync, access, faccessat.
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* Level 2 (muslmimic): dup3, pipe2 (Linux extensions), truncate (XSI),
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* lseek64 (glibc LFS alias of lseek on x86_64).
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*
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* The open-flag constants (O_RDONLY, O_CREAT, O_CLOEXEC, ...) belong to
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* <fcntl.h> and are deliberately not defined here; the oflag arguments below
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* are plain int and take their values from that header. The optional mode
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* argument of open/openat is a mode_t supplied only when oflag contains
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* O_CREAT or O_TMPFILE.
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*
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* None of these declarations carry an intent attribute: every function
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* performs I/O with side effects and reports failures through errno, so
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* const/pure would be unsound.
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*/
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#include <vlibc/features.h>
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#include <stddef.h>
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#include <sys/types.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Level 1 (POSIX base). */
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/* Access-check modes for access() and faccessat(). */
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#define F_OK 0 /* existence only */
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#define X_OK 1 /* execute (search for a directory) */
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#define W_OK 2 /* write */
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#define R_OK 4 /* read */
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/* whence values for lseek() and lseek64() (also defined by <stdio.h>). */
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#define SEEK_SET 0 /* from the beginning of the file */
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#define SEEK_CUR 1 /* from the current position */
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#define SEEK_END 2 /* from the end of the file */
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/*
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* Read up to nbyte bytes from fildes into buf and return the number of
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* bytes read, 0 at end of file, or -1 with errno set on error. Unbuffered.
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*/
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ssize_t
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read(int fildes, void *buf, size_t nbyte);
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/*
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* Write up to nbyte bytes from buf to fildes and return the number of
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* bytes written, or -1 with errno set on error. Unbuffered.
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*/
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ssize_t
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write(int fildes, const void *buf, size_t nbyte);
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/*
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* Read nbyte bytes from fildes starting at offset, without changing the
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* file position; return the number of bytes read, or -1 with errno set.
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*/
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ssize_t
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pread(int fildes, void *buf, size_t nbyte, off_t offset);
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/*
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* Write nbyte bytes from buf to fildes starting at offset, without
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* changing the file position; return the number of bytes written, or -1
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* with errno set.
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*/
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ssize_t
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pwrite(int fildes, const void *buf, size_t nbyte, off_t offset);
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/*
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* Open path with the oflag access mode (from <fcntl.h>) and return a file
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* descriptor, or -1 with errno set. A mode argument is required — and read
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* from the varargs — only when oflag contains O_CREAT or O_TMPFILE.
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*/
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int
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open(const char *path, int oflag, ...);
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/*
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* Like open(), but path is relative to the directory named by fd (use
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* AT_FDCWD from <fcntl.h> for the current working directory). The mode
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* varargs rule is the same as open().
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*/
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int
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openat(int fd, const char *path, int oflag, ...);
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/*
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* Close the file descriptor fildes; return 0, or -1 with errno set.
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*/
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int
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close(int fildes);
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/*
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* Reposition the file offset of fildes to offset per whence (SEEK_SET,
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* SEEK_CUR, SEEK_END) and return the resulting offset, or (off_t)-1 with
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* errno set. The full 64-bit offset is returned; errno is untouched on
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* success.
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*/
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off_t
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lseek(int fildes, off_t offset, int whence);
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/*
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* Duplicate fildes to the lowest-numbered free descriptor; return it, or
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* -1 with errno set. The copy shares the file description (position,
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* flags, locks) with the original.
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*/
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int
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dup(int fildes);
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/*
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* Duplicate fildes onto fildes2, closing fildes2 first if it was open;
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* return fildes2, or -1 with errno set. dup2(f, f) returns f without
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* doing anything (POSIX).
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*/
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int
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dup2(int fildes, int fildes2);
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/*
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* Create a pipe: fildes[0] becomes the read end, fildes[1] the write end.
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* Return 0, or -1 with errno set. No descriptor flags are set (unlike
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* pipe2, this is plain POSIX).
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*/
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int
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pipe(int fildes[2]);
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/*
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* Flush all buffered modifications of fildes and its metadata to stable
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* storage; return 0, or -1 with errno set.
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*/
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int
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fsync(int fildes);
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/*
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* Like fsync(), but may skip the metadata work needed only to preserve
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* file contents; return 0, or -1 with errno set.
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*/
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int
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fdatasync(int fildes);
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/*
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* Truncate fildes to length bytes; return 0, or -1 with errno set.
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*/
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int
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ftruncate(int fildes, off_t length);
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/*
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* Flush all filesystem caches to stable storage. Returns nothing.
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*/
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void
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sync(void);
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/*
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* Check accessibility of path under amode (R_OK, W_OK, X_OK, F_OK); return
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* 0, or -1 with errno set. Uses the real IDs of the calling process.
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*/
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int
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access(const char *path, int amode);
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/*
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* Like access(), but path is relative to the directory named by fd (use
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* AT_FDCWD for the current working directory) and flag may hold
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* AT_EACCESS; return 0, or -1 with errno set.
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*/
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int
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faccessat(int fd, const char *path, int amode, int flag);
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#if VLIBC_LEVEL_GE(2)
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/* Level 2 (muslmimic): Linux extensions + XSI. */
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/*
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* Like dup2(), but with descriptor flags (O_CLOEXEC from <fcntl.h>) applied
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* atomically; return fildes2, or -1 with errno set. Linux-specific.
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*/
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int
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dup3(int fildes, int fildes2, int flags);
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/*
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* Like pipe(), but with descriptor flags (e.g. O_CLOEXEC) applied
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* atomically; return 0, or -1 with errno set. Linux-specific.
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*/
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int
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pipe2(int fildes[2], int flags);
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/*
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* Truncate the file named by path to length bytes; return 0, or -1 with
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* errno set. XSI.
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*/
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int
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truncate(const char *path, off_t length);
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/*
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* glibc LFS alias of lseek(): on x86_64 the LFS and non-LFS off_t are
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* identical (both 64-bit), so this simply calls lseek(). Provided for
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* source compatibility only.
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*/
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off_t
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lseek64(int fildes, off_t offset, int whence);
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#endif /* VLIBC_LEVEL_GE(2) */
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#ifdef __cplusplus
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}
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#endif
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#endif /* VLIBC_UNISTD_H */
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