path: root/gs/src/sfxstdio.c

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/*Id: sfxstdio.c  */
/* File stream implementation using stdio */
#include "stdio_.h"		/* includes std.h */
#include "memory_.h"
#include "gdebug.h"
#include "gpcheck.h"
#include "stream.h"
#include "strimpl.h"

/* Forward references for file stream procedures */
private int
    s_file_available(P2(stream *, long *)), s_file_read_seek(P2(stream *, long)),
     s_file_read_close(P1(stream *)), s_file_read_process(P4(stream_state *, stream_cursor_read *,
					      stream_cursor_write *, bool));
private int
    s_file_write_seek(P2(stream *, long)), s_file_write_flush(P1(stream *)),
     s_file_write_close(P1(stream *)), s_file_write_process(P4(stream_state *, stream_cursor_read *,
					      stream_cursor_write *, bool));
private int
    s_file_switch(P2(stream *, bool));

/* ------ File streams ------ */

/* Initialize a stream for reading an OS file. */
void
sread_file(register stream * s, FILE * file, byte * buf, uint len)
{
    static const stream_procs p =
    {s_file_available, s_file_read_seek, s_std_read_reset,
     s_std_read_flush, s_file_read_close, s_file_read_process,
     s_file_switch
    };

    /*
     * There is no really portable way to test seekability,
     * but this should work on most systems.
     * Note that if our probe sets the ferror bit for the stream,
     * we have to clear it again to avoid trouble later.
     */
    int had_error = ferror(file);
    long curpos = ftell(file);
    bool seekable = (curpos != -1L && fseek(file, curpos, SEEK_SET) == 0);

    if (!had_error)
	clearerr(file);
    s_std_init(s, buf, len, &p,
	       (seekable ? s_mode_read + s_mode_seek : s_mode_read));
    if_debug1('s', "[s]read file=0x%lx\n", (ulong) file);
    s->file = file;
    s->file_modes = s->modes;
}
/* Procedures for reading from a file */
private int
s_file_available(register stream * s, long *pl)
{
    *pl = sbufavailable(s);
    if (sseekable(s)) {
	long pos, end;

	pos = ftell(s->file);
	if (fseek(s->file, 0L, SEEK_END))
	    return ERRC;
	end = ftell(s->file);
	if (fseek(s->file, pos, SEEK_SET))
	    return ERRC;
	*pl += end - pos;
	if (*pl == 0)
	    *pl = -1;		/* EOF */
    } else {
	if (*pl == 0 && feof(s->file))
	    *pl = -1;		/* EOF */
    }
    return 0;
}
private int
s_file_read_seek(register stream * s, long pos)
{
    uint end = s->srlimit - s->cbuf + 1;
    long offset = pos - s->position;

    if (offset >= 0 && offset <= end) {		/* Staying within the same buffer */
	s->srptr = s->cbuf + offset - 1;
	return 0;
    }
    if (fseek(s->file, pos, SEEK_SET) != 0)
	return ERRC;
    s->srptr = s->srlimit = s->cbuf - 1;
    s->end_status = 0;
    s->position = pos;
    return 0;
}
private int
s_file_read_close(stream * s)
{
    FILE *file = s->file;

    if (file != 0) {
	s->file = 0;
	return fclose(file);
    }
    return 0;
}

/* Initialize a stream for writing an OS file. */
void
swrite_file(register stream * s, FILE * file, byte * buf, uint len)
{
    static const stream_procs p =
    {s_std_noavailable, s_file_write_seek, s_std_write_reset,
     s_file_write_flush, s_file_write_close, s_file_write_process,
     s_file_switch
    };

    s_std_init(s, buf, len, &p,
	       (file == stdout ? s_mode_write : s_mode_write + s_mode_seek));
    if_debug1('s', "[s]write file=0x%lx\n", (ulong) file);
    s->file = file;
    s->file_modes = s->modes;
}
/* Initialize for appending to an OS file. */
void
sappend_file(register stream * s, FILE * file, byte * buf, uint len)
{
    swrite_file(s, file, buf, len);
    s->modes = s_mode_write + s_mode_append;	/* no seek */
    s->file_modes = s->modes;
    fseek(file, 0L, SEEK_END);
    s->position = ftell(file);
}
/* Procedures for writing on a file */
private int
s_file_write_seek(stream * s, long pos)
{				/* We must flush the buffer to reposition. */
    int code = sflush(s);

    if (code < 0)
	return code;
    if (fseek(s->file, pos, SEEK_SET) != 0)
	return ERRC;
    s->position = pos;
    return 0;
}
private int
s_file_write_flush(register stream * s)
{
    int result = s_process_write_buf(s, false);

    fflush(s->file);
    return result;
}
private int
s_file_write_close(register stream * s)
{
    s_process_write_buf(s, true);
    return s_file_read_close(s);
}

/* Process a buffer for a file reading stream. */
/* This is the first stream in the pipeline, so pr is irrelevant. */
private int
s_file_read_process(stream_state * st, stream_cursor_read * ignore_pr,
		    stream_cursor_write * pw, bool last)
{
    FILE *file = ((stream *) st)->file;
    int count = fread(pw->ptr + 1, 1, (uint) (pw->limit - pw->ptr), file);

    if (count < 0)
	count = 0;
    pw->ptr += count;
    process_interrupts();
    return (ferror(file) ? ERRC : feof(file) ? EOFC : 1);
}

/* Process a buffer for a file writing stream. */
/* This is the last stream in the pipeline, so pw is irrelevant. */
private int
s_file_write_process(stream_state * st, stream_cursor_read * pr,
		     stream_cursor_write * ignore_pw, bool last)
{				/* The DEC C library on AXP architectures gives an error on */
    /* fwrite if the count is zero! */
    uint count = pr->limit - pr->ptr;

    if (count != 0) {
	FILE *file = ((stream *) st)->file;
	int written = fwrite(pr->ptr + 1, 1, count, file);

	if (written < 0)
	    written = 0;
	pr->ptr += written;
	process_interrupts();
	return (ferror(file) ? ERRC : 0);
    } else {
	process_interrupts();
	return 0;
    }
}

/* Switch a file stream to reading or writing. */
private int
s_file_switch(stream * s, bool writing)
{
    uint modes = s->file_modes;
    FILE *file = s->file;
    long pos;

    if (writing) {
	if (!(s->file_modes & s_mode_write))
	    return ERRC;
	pos = stell(s);
	if_debug2('s', "[s]switch 0x%lx to write at %ld\n",
		  (ulong) s, pos);
	fseek(file, pos, SEEK_SET);
	if (modes & s_mode_append) {
	    sappend_file(s, file, s->cbuf, s->cbsize);	/* sets position */
	} else {
	    swrite_file(s, file, s->cbuf, s->cbsize);
	    s->position = pos;
	}
	s->modes = modes;
    } else {
	if (!(s->file_modes & s_mode_read))
	    return ERRC;
	pos = stell(s);
	if_debug2('s', "[s]switch 0x%lx to read at %ld\n",
		  (ulong) s, pos);
	if (sflush(s) < 0)
	    return ERRC;
	fseek(file, 0L, SEEK_CUR);	/* pacify C library */
	sread_file(s, file, s->cbuf, s->cbsize);
	s->modes |= modes & s_mode_append;	/* don't lose append info */
	s->position = pos;
    }
    s->file_modes = modes;
    return 0;
}