("" < 3.4) always evaluates to true, which unconditionally

[dragonfly.git] / contrib / less-381 / ch.c

/*
 * Copyright (C) 1984-2002  Mark Nudelman
 *
 * You may distribute under the terms of either the GNU General Public
 * License or the Less License, as specified in the README file.
 *
 * For more information about less, or for information on how to 
 * contact the author, see the README file.
 */


/*
 * Low level character input from the input file.
 * We use these special purpose routines which optimize moving
 * both forward and backward from the current read pointer.
 */

#include "less.h"
#if MSDOS_COMPILER==WIN32C
#include <errno.h>
#include <windows.h>
#endif

typedef POSITION BLOCKNUM;

public int ignore_eoi;

/*
 * Pool of buffers holding the most recently used blocks of the input file.
 * The buffer pool is kept as a doubly-linked circular list,
 * in order from most- to least-recently used.
 * The circular list is anchored by the file state "thisfile".
 */
#define LBUFSIZE        8192
struct buf {
        struct buf *next, *prev;
        struct buf *hnext, *hprev;
        BLOCKNUM block;
        unsigned int datasize;
        unsigned char data[LBUFSIZE];
};

struct buflist {
        /* -- Following members must match struct buf */
        struct buf *buf_next, *buf_prev;
        struct buf *buf_hnext, *buf_hprev;
};

/*
 * The file state is maintained in a filestate structure.
 * A pointer to the filestate is kept in the ifile structure.
 */
#define BUFHASH_SIZE    64
struct filestate {
        struct buf *buf_next, *buf_prev;
        struct buflist hashtbl[BUFHASH_SIZE];
        int file;
        int flags;
        POSITION fpos;
        int nbufs;
        BLOCKNUM block;
        unsigned int offset;
        POSITION fsize;
};

#define ch_bufhead      thisfile->buf_next
#define ch_buftail      thisfile->buf_prev
#define ch_nbufs        thisfile->nbufs
#define ch_block        thisfile->block
#define ch_offset       thisfile->offset
#define ch_fpos         thisfile->fpos
#define ch_fsize        thisfile->fsize
#define ch_flags        thisfile->flags
#define ch_file         thisfile->file

#define END_OF_CHAIN    ((struct buf *)&thisfile->buf_next)
#define END_OF_HCHAIN(h) ((struct buf *)&thisfile->hashtbl[h])
#define BUFHASH(blk)    ((blk) & (BUFHASH_SIZE-1))

#define FOR_BUFS_IN_CHAIN(h,bp) \
        for (bp = thisfile->hashtbl[h].buf_hnext;  \
             bp != END_OF_HCHAIN(h);  bp = bp->hnext)

#define HASH_RM(bp) \
        (bp)->hnext->hprev = (bp)->hprev; \
        (bp)->hprev->hnext = (bp)->hnext;

#define HASH_INS(bp,h) \
        (bp)->hnext = thisfile->hashtbl[h].buf_hnext; \
        (bp)->hprev = END_OF_HCHAIN(h); \
        thisfile->hashtbl[h].buf_hnext->hprev = (bp); \
        thisfile->hashtbl[h].buf_hnext = (bp);

static struct filestate *thisfile;
static int ch_ungotchar = -1;
static int maxbufs = -1;

extern int autobuf;
extern int sigs;
extern int secure;
extern constant char helpdata[];
extern constant int size_helpdata;
extern IFILE curr_ifile;
#if LOGFILE
extern int logfile;
extern char *namelogfile;
#endif

static int ch_addbuf();


/*
 * Get the character pointed to by the read pointer.
 * ch_get() is a macro which is more efficient to call
 * than fch_get (the function), in the usual case 
 * that the block desired is at the head of the chain.
 */
#define ch_get()   ((ch_block == ch_bufhead->block && \
                     ch_offset < ch_bufhead->datasize) ? \
                        ch_bufhead->data[ch_offset] : fch_get())
        int
fch_get()
{
        register struct buf *bp;
        register int n;
        register int slept;
        register int h;
        POSITION pos;
        POSITION len;

        slept = FALSE;

        /*
         * Look for a buffer holding the desired block.
         */
        h = BUFHASH(ch_block);
        FOR_BUFS_IN_CHAIN(h, bp)
        {
                if (bp->block == ch_block)
                {
                        if (ch_offset >= bp->datasize)
                                /*
                                 * Need more data in this buffer.
                                 */
                                goto read_more;
                        goto found;
                }
        }
        /*
         * Block is not in a buffer.  
         * Take the least recently used buffer 
         * and read the desired block into it.
         * If the LRU buffer has data in it, 
         * then maybe allocate a new buffer.
         */
        if (ch_buftail == END_OF_CHAIN || ch_buftail->block != -1)
        {
                /*
                 * There is no empty buffer to use.
                 * Allocate a new buffer if:
                 * 1. We can't seek on this file and -b is not in effect; or
                 * 2. We haven't allocated the max buffers for this file yet.
                 */
                if ((autobuf && !(ch_flags & CH_CANSEEK)) ||
                    (maxbufs < 0 || ch_nbufs < maxbufs))
                        if (ch_addbuf())
                                /*
                                 * Allocation failed: turn off autobuf.
                                 */
                                autobuf = OPT_OFF;
        }
        bp = ch_buftail;
        HASH_RM(bp); /* Remove from old hash chain. */
        bp->block = ch_block;
        bp->datasize = 0;
        HASH_INS(bp, h); /* Insert into new hash chain. */

    read_more:
        pos = (ch_block * LBUFSIZE) + bp->datasize;
        if ((len = ch_length()) != NULL_POSITION && pos >= len)
                /*
                 * At end of file.
                 */
                return (EOI);

        if (pos != ch_fpos)
        {
                /*
                 * Not at the correct position: must seek.
                 * If input is a pipe, we're in trouble (can't seek on a pipe).
                 * Some data has been lost: just return "?".
                 */
                if (!(ch_flags & CH_CANSEEK))
                        return ('?');
                if (lseek(ch_file, (off_t)pos, 0) == BAD_LSEEK)
                {
                        error("seek error", NULL_PARG);
                        clear_eol();
                        return (EOI);
                }
                ch_fpos = pos;
        }

        /*
         * Read the block.
         * If we read less than a full block, that's ok.
         * We use partial block and pick up the rest next time.
         */
        if (ch_ungotchar != -1)
        {
                bp->data[bp->datasize] = ch_ungotchar;
                n = 1;
                ch_ungotchar = -1;
        } else if (ch_flags & CH_HELPFILE)
        {
                bp->data[bp->datasize] = helpdata[ch_fpos];
                n = 1;
        } else
        {
                n = iread(ch_file, &bp->data[bp->datasize], 
                        (unsigned int)(LBUFSIZE - bp->datasize));
        }

        if (n == READ_INTR)
                return (EOI);
        if (n < 0)
        {
#if MSDOS_COMPILER==WIN32C
                if (errno != EPIPE)
#endif
                {
                        error("read error", NULL_PARG);
                        clear_eol();
                }
                n = 0;
        }

#if LOGFILE
        /*
         * If we have a log file, write the new data to it.
         */
        if (!secure && logfile >= 0 && n > 0)
                write(logfile, (char *) &bp->data[bp->datasize], n);
#endif

        ch_fpos += n;
        bp->datasize += n;

        /*
         * If we have read to end of file, set ch_fsize to indicate
         * the position of the end of file.
         */
        if (n == 0)
        {
                ch_fsize = pos;
                if (ignore_eoi)
                {
                        /*
                         * We are ignoring EOF.
                         * Wait a while, then try again.
                         */
                        if (!slept)
                        {
                                PARG parg;
                                parg.p_string = wait_message();
                                ierror("%s", &parg);
                        }
#if !MSDOS_COMPILER
                        sleep(1);
#else
#if MSDOS_COMPILER==WIN32C
                        Sleep(1000);
#endif
#endif
                        slept = TRUE;
                }
                if (sigs)
                        return (EOI);
        }

    found:
        if (ch_bufhead != bp)
        {
                /*
                 * Move the buffer to the head of the buffer chain.
                 * This orders the buffer chain, most- to least-recently used.
                 */
                bp->next->prev = bp->prev;
                bp->prev->next = bp->next;
                bp->next = ch_bufhead;
                bp->prev = END_OF_CHAIN;
                ch_bufhead->prev = bp;
                ch_bufhead = bp;

                /*
                 * Move to head of hash chain too.
                 */
                HASH_RM(bp);
                HASH_INS(bp, h);
        }

        if (ch_offset >= bp->datasize)
                /*
                 * After all that, we still don't have enough data.
                 * Go back and try again.
                 */
                goto read_more;

        return (bp->data[ch_offset]);
}

/*
 * ch_ungetchar is a rather kludgy and limited way to push 
 * a single char onto an input file descriptor.
 */
        public void
ch_ungetchar(c)
        int c;
{
        if (c != -1 && ch_ungotchar != -1)
                error("ch_ungetchar overrun", NULL_PARG);
        ch_ungotchar = c;
}

#if LOGFILE
/*
 * Close the logfile.
 * If we haven't read all of standard input into it, do that now.
 */
        public void
end_logfile()
{
        static int tried = FALSE;

        if (logfile < 0)
                return;
        if (!tried && ch_fsize == NULL_POSITION)
        {
                tried = TRUE;
                ierror("Finishing logfile", NULL_PARG);
                while (ch_forw_get() != EOI)
                        if (ABORT_SIGS())
                                break;
        }
        close(logfile);
        logfile = -1;
        namelogfile = NULL;
}

/*
 * Start a log file AFTER less has already been running.
 * Invoked from the - command; see toggle_option().
 * Write all the existing buffered data to the log file.
 */
        public void
sync_logfile()
{
        register struct buf *bp;
        int warned = FALSE;
        BLOCKNUM block;
        BLOCKNUM nblocks;

        nblocks = (ch_fpos + LBUFSIZE - 1) / LBUFSIZE;
        for (block = 0;  block < nblocks;  block++)
        {
                for (bp = ch_bufhead;  ;  bp = bp->next)
                {
                        if (bp == END_OF_CHAIN)
                        {
                                if (!warned)
                                {
                                        error("Warning: log file is incomplete",
                                                NULL_PARG);
                                        warned = TRUE;
                                }
                                break;
                        }
                        if (bp->block == block)
                        {
                                write(logfile, (char *) bp->data, bp->datasize);
                                break;
                        }
                }
        }
}

#endif

/*
 * Determine if a specific block is currently in one of the buffers.
 */
        static int
buffered(block)
        BLOCKNUM block;
{
        register struct buf *bp;
        register int h;

        h = BUFHASH(block);
        FOR_BUFS_IN_CHAIN(h, bp)
        {
                if (bp->block == block)
                        return (TRUE);
        }
        return (FALSE);
}

/*
 * Seek to a specified position in the file.
 * Return 0 if successful, non-zero if can't seek there.
 */
        public int
ch_seek(pos)
        register POSITION pos;
{
        BLOCKNUM new_block;
        POSITION len;

        len = ch_length();
        if (pos < ch_zero() || (len != NULL_POSITION && pos > len))
                return (1);

        new_block = pos / LBUFSIZE;
        if (!(ch_flags & CH_CANSEEK) && pos != ch_fpos && !buffered(new_block))
        {
                if (ch_fpos > pos)
                        return (1);
                while (ch_fpos < pos)
                {
                        if (ch_forw_get() == EOI)
                                return (1);
                        if (ABORT_SIGS())
                                return (1);
                }
                return (0);
        }
        /*
         * Set read pointer.
         */
        ch_block = new_block;
        ch_offset = pos % LBUFSIZE;
        return (0);
}

/*
 * Seek to the end of the file.
 */
        public int
ch_end_seek()
{
        POSITION len;

        if (ch_flags & CH_CANSEEK)
                ch_fsize = filesize(ch_file);

        len = ch_length();
        if (len != NULL_POSITION)
                return (ch_seek(len));

        /*
         * Do it the slow way: read till end of data.
         */
        while (ch_forw_get() != EOI)
                if (ABORT_SIGS())
                        return (1);
        return (0);
}

/*
 * Seek to the beginning of the file, or as close to it as we can get.
 * We may not be able to seek there if input is a pipe and the
 * beginning of the pipe is no longer buffered.
 */
        public int
ch_beg_seek()
{
        register struct buf *bp, *firstbp;

        /*
         * Try a plain ch_seek first.
         */
        if (ch_seek(ch_zero()) == 0)
                return (0);

        /*
         * Can't get to position 0.
         * Look thru the buffers for the one closest to position 0.
         */
        firstbp = bp = ch_bufhead;
        if (bp == END_OF_CHAIN)
                return (1);
        while ((bp = bp->next) != END_OF_CHAIN)
                if (bp->block < firstbp->block)
                        firstbp = bp;
        ch_block = firstbp->block;
        ch_offset = 0;
        return (0);
}

/*
 * Return the length of the file, if known.
 */
        public POSITION
ch_length()
{
        if (ignore_eoi)
                return (NULL_POSITION);
        if (ch_flags & CH_HELPFILE)
                return (size_helpdata);
        return (ch_fsize);
}

/*
 * Return the current position in the file.
 */
        public POSITION
ch_tell()
{
        return (ch_block * LBUFSIZE) + ch_offset;
}

/*
 * Get the current char and post-increment the read pointer.
 */
        public int
ch_forw_get()
{
        register int c;

        c = ch_get();
        if (c == EOI)
                return (EOI);
        if (ch_offset < LBUFSIZE-1)
                ch_offset++;
        else
        {
                ch_block ++;
                ch_offset = 0;
        }
        return (c);
}

/*
 * Pre-decrement the read pointer and get the new current char.
 */
        public int
ch_back_get()
{
        if (ch_offset > 0)
                ch_offset --;
        else
        {
                if (ch_block <= 0)
                        return (EOI);
                if (!(ch_flags & CH_CANSEEK) && !buffered(ch_block-1))
                        return (EOI);
                ch_block--;
                ch_offset = LBUFSIZE-1;
        }
        return (ch_get());
}

/*
 * Set max amount of buffer space.
 * bufspace is in units of 1024 bytes.  -1 mean no limit.
 */
        public void
ch_setbufspace(bufspace)
        int bufspace;
{
        if (bufspace < 0)
                maxbufs = -1;
        else
        {
                maxbufs = ((bufspace * 1024) + LBUFSIZE-1) / LBUFSIZE;
                if (maxbufs < 1)
                        maxbufs = 1;
        }
}

/*
 * Flush (discard) any saved file state, including buffer contents.
 */
        public void
ch_flush()
{
        register struct buf *bp;

        if (!(ch_flags & CH_CANSEEK))
        {
                /*
                 * If input is a pipe, we don't flush buffer contents,
                 * since the contents can't be recovered.
                 */
                ch_fsize = NULL_POSITION;
                return;
        }

        /*
         * Initialize all the buffers.
         */
        for (bp = ch_bufhead;  bp != END_OF_CHAIN;  bp = bp->next)
                bp->block = -1;

        /*
         * Figure out the size of the file, if we can.
         */
        ch_fsize = filesize(ch_file);

        /*
         * Seek to a known position: the beginning of the file.
         */
        ch_fpos = 0;
        ch_block = 0; /* ch_fpos / LBUFSIZE; */
        ch_offset = 0; /* ch_fpos % LBUFSIZE; */

#if 1
        /*
         * This is a kludge to workaround a Linux kernel bug: files in
         * /proc have a size of 0 according to fstat() but have readable 
         * data.  They are sometimes, but not always, seekable.
         * Force them to be non-seekable here.
         */
        if (ch_fsize == 0)
        {
                ch_fsize = NULL_POSITION;
                ch_flags &= ~CH_CANSEEK;
        }
#endif

        if (lseek(ch_file, (off_t)0, 0) == BAD_LSEEK)
        {
                /*
                 * Warning only; even if the seek fails for some reason,
                 * there's a good chance we're at the beginning anyway.
                 * {{ I think this is bogus reasoning. }}
                 */
                error("seek error to 0", NULL_PARG);
        }
}

/*
 * Allocate a new buffer.
 * The buffer is added to the tail of the buffer chain.
 */
        static int
ch_addbuf()
{
        register struct buf *bp;

        /*
         * Allocate and initialize a new buffer and link it 
         * onto the tail of the buffer list.
         */
        bp = (struct buf *) calloc(1, sizeof(struct buf));
        if (bp == NULL)
                return (1);
        ch_nbufs++;
        bp->block = -1;
        bp->next = END_OF_CHAIN;
        bp->prev = ch_buftail;
        ch_buftail->next = bp;
        ch_buftail = bp;
        HASH_INS(bp, 0);
        return (0);
}

/*
 *
 */
        static void
init_hashtbl()
{
        register int h;

        for (h = 0;  h < BUFHASH_SIZE;  h++)
        {
                thisfile->hashtbl[h].buf_hnext = END_OF_HCHAIN(h);
                thisfile->hashtbl[h].buf_hprev = END_OF_HCHAIN(h);
        }
}

/*
 * Delete all buffers for this file.
 */
        static void
ch_delbufs()
{
        register struct buf *bp;

        while (ch_bufhead != END_OF_CHAIN)
        {
                bp = ch_bufhead;
                bp->next->prev = bp->prev;;
                bp->prev->next = bp->next;
                free(bp);
        }
        ch_nbufs = 0;
        init_hashtbl();
}

/*
 * Is it possible to seek on a file descriptor?
 */
        public int
seekable(f)
        int f;
{
#if MSDOS_COMPILER
        extern int fd0;
        if (f == fd0 && !isatty(fd0))
        {
                /*
                 * In MS-DOS, pipes are seekable.  Check for
                 * standard input, and pretend it is not seekable.
                 */
                return (0);
        }
#endif
        return (lseek(f, (off_t)1, 0) != BAD_LSEEK);
}

/*
 * Initialize file state for a new file.
 */
        public void
ch_init(f, flags)
        int f;
        int flags;
{
        /*
         * See if we already have a filestate for this file.
         */
        thisfile = (struct filestate *) get_filestate(curr_ifile);
        if (thisfile == NULL)
        {
                /*
                 * Allocate and initialize a new filestate.
                 */
                thisfile = (struct filestate *) 
                                calloc(1, sizeof(struct filestate));
                thisfile->buf_next = thisfile->buf_prev = END_OF_CHAIN;
                thisfile->nbufs = 0;
                thisfile->flags = 0;
                thisfile->fpos = 0;
                thisfile->block = 0;
                thisfile->offset = 0;
                thisfile->file = -1;
                thisfile->fsize = NULL_POSITION;
                ch_flags = flags;
                init_hashtbl();
                /*
                 * Try to seek; set CH_CANSEEK if it works.
                 */
                if ((flags & CH_CANSEEK) && !seekable(f))
                        ch_flags &= ~CH_CANSEEK;
                set_filestate(curr_ifile, (void *) thisfile);
        }
        if (thisfile->file == -1)
                thisfile->file = f;
        ch_flush();
}

/*
 * Close a filestate.
 */
        public void
ch_close()
{
        int keepstate = FALSE;

        if (ch_flags & (CH_CANSEEK|CH_POPENED|CH_HELPFILE))
        {
                /*
                 * We can seek or re-open, so we don't need to keep buffers.
                 */
                ch_delbufs();
        } else
                keepstate = TRUE;
        if (!(ch_flags & CH_KEEPOPEN))
        {
                /*
                 * We don't need to keep the file descriptor open
                 * (because we can re-open it.)
                 * But don't really close it if it was opened via popen(),
                 * because pclose() wants to close it.
                 */
                if (!(ch_flags & (CH_POPENED|CH_HELPFILE)))
                        close(ch_file);
                ch_file = -1;
        } else
                keepstate = TRUE;
        if (!keepstate)
        {
                /*
                 * We don't even need to keep the filestate structure.
                 */
                free(thisfile);
                thisfile = NULL;
                set_filestate(curr_ifile, (void *) NULL);
        }
}

/*
 * Return ch_flags for the current file.
 */
        public int
ch_getflags()
{
        return (ch_flags);
}

#if 0
        public void
ch_dump(struct filestate *fs)
{
        struct buf *bp;
        unsigned char *s;

        if (fs == NULL)
        {
                printf(" --no filestate\n");
                return;
        }
        printf(" file %d, flags %x, fpos %x, fsize %x, blk/off %x/%x\n",
                fs->file, fs->flags, fs->fpos, 
                fs->fsize, fs->block, fs->offset);
        printf(" %d bufs:\n", fs->nbufs);
        for (bp = fs->buf_next; bp != (struct buf *)fs;  bp = bp->next)
        {
                printf("%x: blk %x, size %x \"",
                        bp, bp->block, bp->datasize);
                for (s = bp->data;  s < bp->data + 30;  s++)
                        if (*s >= ' ' && *s < 0x7F)
                                printf("%c", *s);
                        else
                                printf(".");
                printf("\"\n");
        }
}
#endif