/* * 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 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, 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 { 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); 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, 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() { 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, SEEK_SET) != 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)) { /* * 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)) 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