dhcpcd: update README.DRAGONFLY

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

/*
 * Copyright (C) 1984-2023  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, 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

#if HAVE_PROCFS
#include <sys/statfs.h>
#if HAVE_LINUX_MAGIC_H
#include <linux/magic.h>
#endif
#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".
 */
struct bufnode {
        struct bufnode *next, *prev;
        struct bufnode *hnext, *hprev;
};

#define LBUFSIZE        8192
struct buf {
        struct bufnode node;
        BLOCKNUM block;
        unsigned int datasize;
        unsigned char data[LBUFSIZE];
};
#define bufnode_buf(bn)  ((struct buf *) bn)

/*
 * The file state is maintained in a filestate structure.
 * A pointer to the filestate is kept in the ifile structure.
 */
#define BUFHASH_SIZE    1024
struct filestate {
        struct bufnode buflist;
        struct bufnode hashtbl[BUFHASH_SIZE];
        int file;
        int flags;
        POSITION fpos;
        int nbufs;
        BLOCKNUM block;
        unsigned int offset;
        POSITION fsize;
};

#define ch_bufhead      thisfile->buflist.next
#define ch_buftail      thisfile->buflist.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    (&thisfile->buflist)
#define END_OF_HCHAIN(h) (&thisfile->hashtbl[h])
#define BUFHASH(blk)    ((blk) & (BUFHASH_SIZE-1))

/*
 * Macros to manipulate the list of buffers in thisfile->buflist.
 */
#define FOR_BUFS(bn) \
        for (bn = ch_bufhead;  bn != END_OF_CHAIN;  bn = bn->next)

#define BUF_RM(bn) \
        (bn)->next->prev = (bn)->prev; \
        (bn)->prev->next = (bn)->next;

#define BUF_INS_HEAD(bn) \
        (bn)->next = ch_bufhead; \
        (bn)->prev = END_OF_CHAIN; \
        ch_bufhead->prev = (bn); \
        ch_bufhead = (bn);

#define BUF_INS_TAIL(bn) \
        (bn)->next = END_OF_CHAIN; \
        (bn)->prev = ch_buftail; \
        ch_buftail->next = (bn); \
        ch_buftail = (bn);

/*
 * Macros to manipulate the list of buffers in thisfile->hashtbl[n].
 */
#define FOR_BUFS_IN_CHAIN(h,bn) \
        for (bn = thisfile->hashtbl[h].hnext;  \
             bn != END_OF_HCHAIN(h);  bn = bn->hnext)

#define BUF_HASH_RM(bn) \
        (bn)->hnext->hprev = (bn)->hprev; \
        (bn)->hprev->hnext = (bn)->hnext;

#define BUF_HASH_INS(bn,h) \
        (bn)->hnext = thisfile->hashtbl[h].hnext; \
        (bn)->hprev = END_OF_HCHAIN(h); \
        thisfile->hashtbl[h].hnext->hprev = (bn); \
        thisfile->hashtbl[h].hnext = (bn);

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

extern int autobuf;
extern int sigs;
extern int secure;
extern int screen_trashed;
extern int follow_mode;
extern int waiting_for_data;
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.
 */
static int ch_get(void)
{
        struct buf *bp;
        struct bufnode *bn;
        int n;
        int read_again;
        int h;
        POSITION pos;
        POSITION len;

        if (thisfile == NULL)
                return (EOI);

        /*
         * Quick check for the common case where 
         * the desired char is in the head buffer.
         */
        if (ch_bufhead != END_OF_CHAIN)
        {
                bp = bufnode_buf(ch_bufhead);
                if (ch_block == bp->block && ch_offset < bp->datasize)
                        return bp->data[ch_offset];
        }

        /*
         * Look for a buffer holding the desired block.
         */
        waiting_for_data = FALSE;
        h = BUFHASH(ch_block);
        FOR_BUFS_IN_CHAIN(h, bn)
        {
                bp = bufnode_buf(bn);
                if (bp->block == ch_block)
                {
                        if (ch_offset >= bp->datasize)
                                /*
                                 * Need more data in this buffer.
                                 */
                                break;
                        goto found;
                }
        }
        if (bn == END_OF_HCHAIN(h))
        {
                /*
                 * 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 || 
                        bufnode_buf(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;
                }
                bn = ch_buftail;
                bp = bufnode_buf(bn);
                BUF_HASH_RM(bn); /* Remove from old hash chain. */
                bp->block = ch_block;
                bp->datasize = 0;
                BUF_HASH_INS(bn, h); /* Insert into new hash chain. */
        }

        for (;;)
        {
                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, SEEK_SET) == 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));
                }

                read_again = FALSE;
                if (n == READ_INTR)
                {
                        ch_fsize = pos;
                        return (EOI);
                }
                if (n == READ_AGAIN)
                {
                        read_again = TRUE;
                        n = 0;
                }
                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 (n == 0)
                {
                        /* Either end of file or no data available.
                         * read_again indicates the latter. */
                        if (!read_again)
                                ch_fsize = pos;
                        if (ignore_eoi || read_again)
                        {
                                /* Wait a while, then try again. */
                                if (!waiting_for_data)
                                {
                                        PARG parg;
                                        parg.p_string = wait_message();
                                        ixerror("%s", &parg);
                                        waiting_for_data = TRUE;
                                }
                                sleep_ms(50); /* Reduce system load */
                        }
                        if (ignore_eoi && follow_mode == FOLLOW_NAME && curr_ifile_changed())
                        {
                                /* screen_trashed=2 causes make_display to reopen the file. */
                                screen_trashed = 2;
                                return (EOI);
                        }
                        if (sigs)
                                return (EOI);
                }

                found:
                if (ch_bufhead != bn)
                {
                        /*
                         * Move the buffer to the head of the buffer chain.
                         * This orders the buffer chain, most- to least-recently used.
                         */
                        BUF_RM(bn);
                        BUF_INS_HEAD(bn);

                        /*
                         * Move to head of hash chain too.
                         */
                        BUF_HASH_RM(bn);
                        BUF_HASH_INS(bn, h);
                }

                if (ch_offset < bp->datasize)
                        break;
                /*
                 * After all that, we still don't have enough data.
                 * Go back and try again.
                 */
        }
        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(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(void)
{
        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;
        free(namelogfile);
        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(void)
{
        struct buf *bp;
        struct bufnode *bn;
        int warned = FALSE;
        BLOCKNUM block;
        BLOCKNUM nblocks;

        if (logfile < 0)
                return;
        nblocks = (ch_fpos + LBUFSIZE - 1) / LBUFSIZE;
        for (block = 0;  block < nblocks;  block++)
        {
                int wrote = FALSE;
                FOR_BUFS(bn)
                {
                        bp = bufnode_buf(bn);
                        if (bp->block == block)
                        {
                                write(logfile, (char *) bp->data, bp->datasize);
                                wrote = TRUE;
                                break;
                        }
                }
                if (!wrote && !warned)
                {
                        error("Warning: log file is incomplete",
                                NULL_PARG);
                        warned = TRUE;
                }
        }
}

#endif

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

        h = BUFHASH(block);
        FOR_BUFS_IN_CHAIN(h, bn)
        {
                bp = bufnode_buf(bn);
                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(POSITION pos)
{
        BLOCKNUM new_block;
        POSITION len;

        if (thisfile == NULL)
                return (0);

        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(void)
{
        POSITION len;

        if (thisfile == NULL)
                return (0);

        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 last position in the file that is currently buffered.
 */
public int ch_end_buffer_seek(void)
{
        struct buf *bp;
        struct bufnode *bn;
        POSITION buf_pos;
        POSITION end_pos;

        if (thisfile == NULL || (ch_flags & CH_CANSEEK))
                return (ch_end_seek());

        end_pos = 0;
        FOR_BUFS(bn)
        {
                bp = bufnode_buf(bn);
                buf_pos = (bp->block * LBUFSIZE) + bp->datasize;
                if (buf_pos > end_pos)
                        end_pos = buf_pos;
        }

        return (ch_seek(end_pos));
}

/*
 * 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(void)
{
        struct bufnode *bn;
        struct bufnode *firstbn;

        /*
         * 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.
         */
        firstbn = ch_bufhead;
        if (firstbn == END_OF_CHAIN)
                return (1);
        FOR_BUFS(bn)
        {
                if (bufnode_buf(bn)->block < bufnode_buf(firstbn)->block)
                        firstbn = bn;
        }
        ch_block = bufnode_buf(firstbn)->block;
        ch_offset = 0;
        return (0);
}

/*
 * Return the length of the file, if known.
 */
public POSITION ch_length(void)
{
        if (thisfile == NULL)
                return (NULL_POSITION);
        if (ignore_eoi)
                return (NULL_POSITION);
        if (ch_flags & CH_HELPFILE)
                return (size_helpdata);
        if (ch_flags & CH_NODATA)
                return (0);
        return (ch_fsize);
}

/*
 * Return the current position in the file.
 */
public POSITION ch_tell(void)
{
        if (thisfile == NULL)
                return (NULL_POSITION);
        return (ch_block * LBUFSIZE) + ch_offset;
}

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

        if (thisfile == NULL)
                return (EOI);
        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(void)
{
        if (thisfile == NULL)
                return (EOI);
        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(int bufspace)
{
        if (bufspace < 0)
                maxbufs = -1;
        else
        {
                int lbufk = LBUFSIZE / 1024;
                maxbufs = bufspace / lbufk + (bufspace % lbufk != 0);
                if (maxbufs < 1)
                        maxbufs = 1;
        }
}

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

        if (thisfile == NULL)
                return;

        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_BUFS(bn)
        {
                bufnode_buf(bn)->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 HAVE_PROCFS
        /*
         * 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)
        {
                struct statfs st;
                if (fstatfs(ch_file, &st) == 0)
                {
                        if (st.f_type == PROC_SUPER_MAGIC)
                        {
                                ch_fsize = NULL_POSITION;
                                ch_flags &= ~CH_CANSEEK;
                        }
                }
        }
#endif

        if (lseek(ch_file, (off_t)0, SEEK_SET) == 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(void)
{
        struct buf *bp;
        struct bufnode *bn;

        /*
         * 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;
        bn = &bp->node;

        BUF_INS_TAIL(bn);
        BUF_HASH_INS(bn, 0);
        return (0);
}

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

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

/*
 * Delete all buffers for this file.
 */
static void ch_delbufs(void)
{
        struct bufnode *bn;

        while (ch_bufhead != END_OF_CHAIN)
        {
                bn = ch_bufhead;
                BUF_RM(bn);
                free(bufnode_buf(bn));
        }
        ch_nbufs = 0;
        init_hashtbl();
}

/*
 * Is it possible to seek on a file descriptor?
 */
public int seekable(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, SEEK_SET) != BAD_LSEEK);
}

/*
 * Force EOF to be at the current read position.
 * This is used after an ignore_eof read, during which the EOF may change.
 */
public void ch_set_eof(void)
{
        if (ch_fsize != NULL_POSITION && ch_fsize < ch_fpos)
                ch_fsize = ch_fpos;
}


/*
 * Initialize file state for a new file.
 */
public void ch_init(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 *) 
                                ecalloc(1, sizeof(struct filestate));
                thisfile->buflist.next = thisfile->buflist.prev = END_OF_CHAIN;
                thisfile->nbufs = 0;
                thisfile->flags = flags;
                thisfile->fpos = 0;
                thisfile->block = 0;
                thisfile->offset = 0;
                thisfile->file = -1;
                thisfile->fsize = NULL_POSITION;
                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(void)
{
        int keepstate = FALSE;

        if (thisfile == NULL)
                return;

        if ((ch_flags & (CH_CANSEEK|CH_POPENED|CH_HELPFILE)) && !(ch_flags & CH_KEEPOPEN))
        {
                /*
                 * 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(void)
{
        if (thisfile == NULL)
                return (0);
        return (ch_flags);
}

#if 0
static void ch_dump(struct filestate *fs)
{
        struct buf *bp;
        struct bufnode *bn;
        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 (bn = fs->next; bn != &fs->buflist;  bn = bn->next)
        {
                bp = bufnode_buf(bn);
                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