95 lines
3.6 KiB
C
95 lines
3.6 KiB
C
#ifndef VLIBC_STDIO_STDIO_IMPL_H
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#define VLIBC_STDIO_STDIO_IMPL_H
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/*
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* vlibc — internal FILE layout and stream helpers (todo 15).
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*
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* struct vlibc_FILE is the object behind the opaque FILE of <stdio.h>.
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* Position invariant (authoritative):
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*
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* - Read mode: `pos` is the file offset of buf[0]. The logical position
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* (offset of the byte at rpos) is pos + (rpos - buf), and the kernel
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* position is pos + (rstop - buf); with an empty buffer
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* (rpos == rstop) the kernel sits exactly at the logical position.
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* - Write mode: `pos` is the file offset of buf[0]; the next written byte
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* lands at pos + (wpos - buf). With an empty buffer the kernel sits at
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* pos. A flush advances pos by the number of bytes written.
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*
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* Mode switching: reading while write data is pending flushes it first;
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* writing while unread buffered data is pending seeks the kernel back to
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* the logical position (discarding the unread data). F_PUSHED marks the
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* single guaranteed ungetc pushback byte in `ungot`; a successful seek
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* discards it.
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*
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* The helper prototypes below are shared with the formatted-I/O todos
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* (16: vfprintf, 17: vfscanf) so they operate on the same buffer state.
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*/
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#include <stdio.h>
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#include "../internal/libc.h"
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struct vlibc_FILE
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{
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unsigned char *buf; /* buffer base: library- or user-supplied */
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unsigned char *rpos; /* read mode: next byte to deliver */
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unsigned char *rstop; /* read mode: end of valid buffered data */
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unsigned char *wpos; /* write mode: next byte to store */
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unsigned char *wstop; /* write mode: end of the buffer */
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int fd; /* underlying descriptor; -1 when closed */
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int flags; /* F_* bits below */
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size_t buf_size; /* usable buffer size; 0 = not yet sized */
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off_t pos; /* position per the invariant above */
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struct vlibc_FILE *next; /* registry link for fflush(NULL) */
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unsigned char ungot; /* pushed-back byte when F_PUSHED */
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};
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/* Stream flags. */
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#define F_READ 0x001 /* reads are enabled by the open mode */
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#define F_WRITE 0x002 /* writes are enabled by the open mode */
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#define F_EOF 0x004 /* end of file has been seen */
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#define F_ERR 0x008 /* an I/O error occurred */
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#define F_LINEBUF 0x010 /* line buffered: flush on newline */
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#define F_UNBUF 0x020 /* unbuffered: 1-byte buffer */
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#define F_APPEND 0x040 /* append mode: writes land at end of file */
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#define F_OWNBUF 0x080 /* buf was allocated by the library */
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#define F_HEAP 0x100 /* the FILE struct itself is heap-allocated */
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#define F_PUSHED 0x200 /* ungot holds a pushed-back byte */
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/* Flush pending write data; returns 0, or -1 with F_ERR set. */
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hidden int
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stdio_flush(FILE *f);
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/* Refill the read buffer from the descriptor (read mode only). */
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hidden void
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stdio_refill(FILE *f);
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/* Discard unread buffered data, seeking the kernel back to pos. */
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hidden int
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stdio_discard_read(FILE *f);
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/* Allocate the buffer lazily (std streams, setvbuf with NULL). */
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hidden void
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stdio_init_if_needed(FILE *f);
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/* Allocate and register a FILE over an open descriptor. */
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hidden FILE *
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stdio_alloc_file(int fd, int m);
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/*
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* Parse a fopen-style mode string. On success stores the F_READ/F_WRITE
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* capability bits in *m, the openat flags in *oflags, and returns 1;
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* returns 0 for an invalid mode.
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*/
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hidden int
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stdio_parse_mode(const char *mode, int *m, int *oflags);
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/*
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* Raw lseek with errno translation. Separate from syscall_ret() because
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* syscall_ret narrows results to int and would truncate large offsets.
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*/
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hidden off_t
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stdio_lseek(int fd, off_t off, int whence);
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#endif /* VLIBC_STDIO_STDIO_IMPL_H */
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