/*

  *  Copyright (C) 2013-2019 Cisco Systems, Inc. and/or its affiliates. All rights reserved.

  *  Copyright (C) 2009-2013 Sourcefire, Inc.

  *
  *  Authors: aCaB <acab@clamav.net>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License version 2 as
  *  published by the Free Software Foundation.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU General Public License for more details.
  *
  *  You should have received a copy of the GNU General Public License
  *  along with this program; if not, write to the Free Software
  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  *  MA 02110-1301, USA.
  */
 
 /* an mmap "replacement" which doesn't suck */
 
 #if HAVE_CONFIG_H
 #include "clamav-config.h"
 #endif
 

 #include <stdint.h>

 #include <sys/types.h>
 #include <sys/stat.h>

 #include <string.h>

 #include <libgen.h>

 #ifdef HAVE_UNISTD_H

 #include <unistd.h>

 #endif

 #ifdef ANONYMOUS_MAP

 #ifdef HAVE_SYS_MMAN_H

 #include <sys/mman.h>

 #endif
 #endif

 #include <errno.h>

 #ifdef C_LINUX

 #include <pthread.h>

 #endif

 #include "clamav.h"

 #include "others.h"

 #include "str.h"

 static inline unsigned int fmap_align_items(unsigned int sz, unsigned int al);
 static inline unsigned int fmap_align_to(unsigned int sz, unsigned int al);
 static inline unsigned int fmap_which_page(fmap_t *m, size_t at);

 #ifndef _WIN32

 /* pread proto here in order to avoid the use of XOPEN and BSD_SOURCE
    which may in turn prevent some mmap constants to be defined */
 ssize_t pread(int fd, void *buf, size_t count, off_t offset);
 

 /* vvvvv POSIX STUFF BELOW vvvvv */

 static off_t pread_cb(void *handle, void *buf, size_t count, off_t offset)
 {
     return pread((int)(ssize_t)handle, buf, count, offset);
 }
 

 
 fmap_t *fmap_check_empty(int fd, off_t offset, size_t len, int *empty) {

     STATBUF st;

     fmap_t *m;
 
     *empty = 0;

     if(FSTAT(fd, &st)) {

 	cli_warnmsg("fmap: fstat failed\n");
 	return NULL;
     }
 
     if(!len) len = st.st_size - offset; /* bound checked later */
     if(!len) {
 	cli_dbgmsg("fmap: attempted void mapping\n");
 	*empty = 1;
 	return NULL;
     }
     if(!CLI_ISCONTAINED(0, st.st_size, offset, len)) {
 	cli_warnmsg("fmap: attempted oof mapping\n");
 	return NULL;
     }
     m = cl_fmap_open_handle((void*)(ssize_t)fd, offset, len, pread_cb, 1);
     if (!m)
 	return NULL;
     m->mtime = st.st_mtime;
     m->handle_is_fd = 1;
     return m;
 }
 #else
 /* vvvvv WIN32 STUFF BELOW vvvvv */
 static void unmap_win32(fmap_t *m) { /* WIN32 */
     UnmapViewOfFile(m->data);
     CloseHandle(m->mh);
     free((void *)m);
 }
 
 fmap_t *fmap_check_empty(int fd, off_t offset, size_t len, int *empty) { /* WIN32 */
     unsigned int pages, mapsz, hdrsz;
     int pgsz = cli_getpagesize();

     STATBUF st;

     fmap_t *m;
     const void *data;
     HANDLE fh;
     HANDLE mh;
 
     *empty = 0;

     if(FSTAT(fd, &st)) {

 	cli_warnmsg("fmap: fstat failed\n");
 	return NULL;
     }
     if(offset < 0 || offset != fmap_align_to(offset, pgsz)) {
 	cli_warnmsg("fmap: attempted mapping with unaligned offset\n");
 	return NULL;
     }
     if(!len) len = st.st_size - offset; /* bound checked later */
     if(!len) {
 	cli_dbgmsg("fmap: attempted void mapping\n");
 	*empty = 1;
 	return NULL;
     }
     if(!CLI_ISCONTAINED(0, st.st_size, offset, len)) {
 	cli_warnmsg("fmap: attempted oof mapping\n");
 	return NULL;
     }
 
     pages = fmap_align_items(len, pgsz);
     hdrsz = fmap_align_to(sizeof(fmap_t), pgsz);
 
     if((fh = (HANDLE)_get_osfhandle(fd)) == INVALID_HANDLE_VALUE) {
 	cli_errmsg("fmap: cannot get a valid handle for descriptor %d\n", fd);
 	return NULL;
     }

     if(!(mh = CreateFileMapping(fh, NULL, PAGE_READONLY, (DWORD)((len>>31)>>1), (DWORD)len, NULL))) {

 	cli_errmsg("fmap: cannot create a map of descriptor %d\n", fd);
 	CloseHandle(fh);
 	return NULL;
     }

     if(!(data = MapViewOfFile(mh, FILE_MAP_READ, (DWORD)((offset>>31)>>1), (DWORD)(offset), len))) {

 	cli_errmsg("fmap: cannot map file descriptor %d\n", fd);
 	CloseHandle(mh);
 	CloseHandle(fh);
 	return NULL;
     }
     if(!(m = cl_fmap_open_memory(data, len))) {

 	cli_errmsg("fmap: cannot allocate fmap_t\n", fd);

 	CloseHandle(mh);
 	CloseHandle(fh);
 	return NULL;
     }

     m->handle = (void*)(size_t)fd;

     m->handle_is_fd = 1;
     m->fh = fh;
     m->mh = mh;
     m->unmap = unmap_win32;
     return m;
 }
 #endif /* _WIN32 */
 
 /* vvvvv SHARED STUFF BELOW vvvvv */

 #define FM_MASK_COUNT 0x3fffffff
 #define FM_MASK_PAGED 0x40000000
 #define FM_MASK_SEEN 0x80000000
 #define FM_MASK_LOCKED FM_MASK_SEEN
 /* 2 high bits:
 00 - not seen - not paged - N/A
 01 -    N/A   -   paged   - not locked
 10 -   seen   - not paged - N/A
 11 -    N/A   -   paged   - locked
 */
 

 /* FIXME: tune this stuff */

 #define UNPAGE_THRSHLD_LO 4*1024*1024
 #define UNPAGE_THRSHLD_HI 8*1024*1024

 #define READAHEAD_PAGES 8
 

 #if defined(ANONYMOUS_MAP) && defined(C_LINUX) && defined(CL_THREAD_SAFE)

 /*
    WORKAROUND
    Relieve some stress on mmap_sem.
    When mmap_sem is heavily hammered, the scheduler
    tends to fail to wake us up properly.
 */

 pthread_mutex_t fmap_mutex = PTHREAD_MUTEX_INITIALIZER;

 #define fmap_lock pthread_mutex_lock(&fmap_mutex)
 #define fmap_unlock pthread_mutex_unlock(&fmap_mutex);
 #else
 #define fmap_lock
 #define fmap_unlock
 #endif
 

 #ifndef MADV_DONTFORK
 #define MADV_DONTFORK 0
 #endif
 

 #define fmap_bitmap (&m->placeholder_for_bitmap)

 static const void *handle_need(fmap_t *m, size_t at, size_t len, int lock);
 static void handle_unneed_off(fmap_t *m, size_t at, size_t len);
 static const void *handle_need_offstr(fmap_t *m, size_t at, size_t len_hint);
 static const void *handle_gets(fmap_t *m, char *dst, size_t *at, size_t max_len);
 static void unmap_mmap(fmap_t *m);
 static void unmap_malloc(fmap_t *m);

 extern cl_fmap_t *cl_fmap_open_handle(void *handle, size_t offset, size_t len,
 				      clcb_pread pread_cb, int use_aging)

 {
     unsigned int pages, mapsz, hdrsz;
     cl_fmap_t *m;
     int pgsz = cli_getpagesize();
 

     if((off_t)offset < 0 || offset != fmap_align_to(offset, pgsz)) {

 	cli_warnmsg("fmap: attempted mapping with unaligned offset\n");
 	return NULL;
     }
     if(!len) {

 	cli_dbgmsg("fmap: attempted void mapping\n");

 	return NULL;
     }

     if (offset >= len) {

 	cli_warnmsg("fmap: attempted oof mapping\n");
 	return NULL;
     }

     pages = fmap_align_items(len, pgsz);

     hdrsz = fmap_align_to(sizeof(fmap_t) + (pages-1) * sizeof(uint32_t), pgsz); /* fmap_t includes 1 bitmap slot, hence (pages-1) */

     mapsz = pages * pgsz + hdrsz;

 
 #ifndef ANONYMOUS_MAP
     use_aging = 0;
 #endif

 #ifdef ANONYMOUS_MAP

     if (use_aging) {
 	fmap_lock;
 	if ((m = (fmap_t *)mmap(NULL, mapsz, PROT_READ | PROT_WRITE, MAP_PRIVATE|/*FIXME: MAP_POPULATE is ~8% faster but more memory intensive */ANONYMOUS_MAP, -1, 0)) == MAP_FAILED) {
 	    m = NULL;
 	} else {

 #if HAVE_MADVISE

 	    madvise((void *)m, mapsz, MADV_RANDOM|MADV_DONTFORK);

 #endif /* madvise */

 	    /* fault the header while we still have the lock - we DO context switch here a lot here :@ */
 	    memset(fmap_bitmap, 0, sizeof(uint32_t) * pages);
 	}
 	fmap_unlock;

     }

 #endif /* ANONYMOUS_MAP */

     if (!use_aging) {
 	m = (fmap_t *)cli_malloc(mapsz);

     if (!(m)) {
         cli_warnmsg("fmap: map allocation failed\n");
         return NULL;
     }

 	memset(m, 0, hdrsz);
     }

     if(!m) {
 	cli_warnmsg("fmap: map allocation failed\n");

 	return NULL;
     }

     m->handle = handle;
     m->pread_cb = pread_cb;

     m->aging = use_aging;

     m->offset = offset;

     m->nested_offset = 0;

     m->len = len;/* m->nested_offset + m->len = m->real_len */
     m->real_len = len;

     m->pages = pages;
     m->hdrsz = hdrsz;

     m->pgsz = pgsz;

     m->paged = 0;

     m->dont_cache_flag = 0;

     m->unmap = use_aging ? unmap_mmap : unmap_malloc;

     m->need = handle_need;
     m->need_offstr = handle_need_offstr;
     m->gets = handle_gets;
     m->unneed_off = handle_unneed_off;

     return m;
 }

 static void fmap_aging(fmap_t *m) {

 #ifdef ANONYMOUS_MAP

     if(!m->aging) return;

     if(m->paged * m->pgsz > UNPAGE_THRSHLD_HI) { /* we alloc'd too much */
 	unsigned int i, avail = 0, freeme[2048], maxavail = MIN(sizeof(freeme)/sizeof(*freeme), m->paged - UNPAGE_THRSHLD_LO / m->pgsz) - 1;
 

 	for(i=0; i<m->pages; i++) {

 	    uint32_t s = fmap_bitmap[i];

 	    if((s & (FM_MASK_PAGED | FM_MASK_LOCKED)) == FM_MASK_PAGED ) {
 		/* page is paged and not locked: dec age */

 		if(s & FM_MASK_COUNT) fmap_bitmap[i]--;

 		/* and make it available for unpaging */

 
 		if(!avail) {
 		    freeme[0] = i;
 		    avail++;
 		} else {
 		    /* Insert sort onto a stack'd array - same performance as quickselect */

 		    unsigned int insert_to = MIN(maxavail, avail) - 1, age = fmap_bitmap[i] & FM_MASK_COUNT;
 		    if(avail <= maxavail || (fmap_bitmap[freeme[maxavail]] & FM_MASK_COUNT) > age) {
 			while((fmap_bitmap[freeme[insert_to]] & FM_MASK_COUNT) > age) {

 			    freeme[insert_to + 1] = freeme[insert_to];
 			    if(!insert_to--) break;
 			}
 			freeme[insert_to + 1] = i;
 			if(avail <= maxavail) avail++;
 		    }
 		}

 	    }
 	}
 	if(avail) { /* at least one page is paged and not locked */

 	    char *lastpage = NULL;
 	    char *firstpage = NULL;

 	    for(i=0; i<avail; i++) {

 		char *pptr = (char *)m + freeme[i] * m->pgsz + m->hdrsz;

 		/* we mark the page as seen */

 		fmap_bitmap[freeme[i]] = FM_MASK_SEEN;

 		/* and we mmap the page over so the kernel knows there's nothing good in there */

 		/* reduce number of mmap calls: if pages are adjacent only do 1 mmap call */
 		if (lastpage && pptr == lastpage) {
 			lastpage = pptr + m->pgsz;
 			continue;
 		}
 		if (!lastpage) {
 			firstpage = pptr;
 			lastpage = pptr + m->pgsz;
 			continue;
 		}
 		fmap_lock;
 		if(mmap(firstpage, lastpage - firstpage, PROT_READ | PROT_WRITE, MAP_FIXED|MAP_PRIVATE|ANONYMOUS_MAP, -1, 0) == MAP_FAILED)
 		    cli_dbgmsg("fmap_aging: kernel hates you\n");
 		fmap_unlock;
 		firstpage = pptr;
 		lastpage = pptr + m->pgsz;
 	    }
 	    if (lastpage) {

 		fmap_lock;

 		if(mmap(firstpage, lastpage - firstpage, PROT_READ | PROT_WRITE, MAP_FIXED|MAP_PRIVATE|ANONYMOUS_MAP, -1, 0) == MAP_FAILED)

 		    cli_dbgmsg("fmap_aging: kernel hates you\n");

 		fmap_unlock;

 	    }
 	    m->paged -= avail;

 	}
     }

 #endif

 }
 
 

 static int fmap_readpage(fmap_t *m, unsigned int first_page, unsigned int count, unsigned int lock_count) {

     size_t readsz = 0, eintr_off;

     char *pptr = NULL, errtxt[256];

     uint32_t s;

     unsigned int i, page = first_page, force_read = 0;
 

     fmap_lock;

     for(i=0; i<count; i++) { /* prefault */

 	/* Not worth checking if the page is already paged, just ping each */

 	/* Also not worth reusing the loop below */

 	volatile char faultme;
 	faultme = ((char *)m)[(first_page+i) * m->pgsz + m->hdrsz];

     }

     fmap_unlock;

     for(i=0; i<=count; i++, page++) {
 	int lock;
 	if(lock_count) {
 	    lock_count--;
 	    lock = 1;
 	} else lock = 0;
 	if(i == count) {
 	    /* we count one page too much to flush pending reads */
 	    if(!pptr) return 0; /* if we have any */
 	    force_read = 1;

 	} else if((s=fmap_bitmap[page]) & FM_MASK_PAGED) {

 	    /* page already paged */
 	    if(lock) {
 		/* we want locking */
 		if(s & FM_MASK_LOCKED) {
 		    /* page already locked */
 		    s &= FM_MASK_COUNT;
 		    if(s == FM_MASK_COUNT) { /* lock count already at max: fial! */
 			cli_errmsg("fmap_readpage: lock count exceeded\n");
 			return 1;
 		    }
 		    /* acceptable lock count: inc lock count */

 		    fmap_bitmap[page]++;

 		} else /* page not currently locked: set lock count = 1 */

 		    fmap_bitmap[page] = 1 | FM_MASK_LOCKED | FM_MASK_PAGED;

 	    } else {
 		/* we don't want locking */
 		if(!(s & FM_MASK_LOCKED)) {
 		    /* page is not locked: we reset aging to max */

 		    fmap_bitmap[page] = FM_MASK_PAGED | FM_MASK_COUNT;

 		}
 	    }

 	    if(!pptr) continue;
 	    force_read = 1;

 	}
 

 	if(force_read) {
 	    /* we have some pending reads to perform */

 	    if (m->handle_is_fd) {

 		unsigned int j;

 		int _fd = (int)(ptrdiff_t)m->handle;

 		for(j=first_page; j<page; j++) {
 		    if(fmap_bitmap[j] & FM_MASK_SEEN) {
 			/* page we've seen before: check mtime */

 			STATBUF st;
 			if(FSTAT(_fd, &st)) {

 			    cli_strerror(errno, errtxt, sizeof(errtxt));

 			    cli_warnmsg("fmap_readpage: fstat failed: %s\n", errtxt);

 			    return 1;
 			}
 			if(m->mtime != st.st_mtime) {
 			    cli_warnmsg("fmap_readpage: file changed as we read it\n");
 			    return 1;
 			}
 			break;

 		    }
 		}
 	    }
 

 	    eintr_off = 0;
 	    while(readsz) {

 		ssize_t got;

 		off_t target_offset = eintr_off + m->offset + (first_page * m->pgsz);
 		got=m->pread_cb(m->handle, pptr, readsz, target_offset);

 
 		if(got < 0 && errno == EINTR)
 		    continue;
 
 		if(got > 0) {
 		    pptr += got;
 		    eintr_off += got;
 		    readsz -= got;
 		    continue;
 		}
 

 		if(got < 0) {
 		    cli_strerror(errno, errtxt, sizeof(errtxt));

 		    cli_errmsg("fmap_readpage: pread error: %s\n", errtxt);

 		}
 		else {
 		    cli_warnmsg("fmap_readpage: pread fail: asked for %lu bytes @ offset %lu, got %lu\n", (long unsigned int)readsz, (long unsigned int)target_offset, (long unsigned int)got);
 		}

 		return 1;
 	    }

 	    pptr = NULL;

 	    force_read = 0;

 	    readsz = 0;
 	    continue;

 	}

 
 	/* page is not already paged */
 	if(!pptr) {
 	    /* set a new start for pending reads if we don't have one */
 	    pptr = (char *)m + page * m->pgsz + m->hdrsz;
 	    first_page = page;

 	}

 	if((page == m->pages - 1) && (m->real_len % m->pgsz))
 	    readsz += m->real_len % m->pgsz;

 	else
 	    readsz += m->pgsz;
 	if(lock) /* lock requested: set paged, lock page and set lock count to 1 */

 	    fmap_bitmap[page] = FM_MASK_PAGED | FM_MASK_LOCKED | 1;

 	else /* no locking: set paged and set aging to max */

 	    fmap_bitmap[page] = FM_MASK_PAGED | FM_MASK_COUNT;

 	m->paged++;

     }

     return 0;
 }
 

 static const void *handle_need(fmap_t *m, size_t at, size_t len, int lock) {

     unsigned int first_page, last_page, lock_count;

     char *ret;
 

     if(!len)

 	return NULL;
 

     at += m->nested_offset;
     if(!CLI_ISCONTAINED(0, m->real_len, at, len))

 	return NULL;

 
     fmap_aging(m);
 

     first_page = fmap_which_page(m, at);

     last_page = fmap_which_page(m, at + len - 1);

     lock_count = (lock!=0) * (last_page-first_page+1);

 #ifdef READAHED_PAGES
     last_page += READAHED_PAGES;
     if(last_page >= m->pages) last_page = m->pages - 1;
 #endif

     if(fmap_readpage(m, first_page, last_page-first_page+1, lock_count))
 	return NULL;

     ret = (char *)m;
     ret += at + m->hdrsz;

     return (void *)ret;

 }
 

 static void fmap_unneed_page(fmap_t *m, unsigned int page) {

     uint32_t s = fmap_bitmap[page];

     if((s & (FM_MASK_PAGED | FM_MASK_LOCKED)) == (FM_MASK_PAGED | FM_MASK_LOCKED)) {
 	/* page is paged and locked: check lock count */
 	s &= FM_MASK_COUNT;
 	if(s > 1) /* locked more than once: dec lock count */

 	    fmap_bitmap[page]--;

 	else if (s == 1) /* only one lock left: unlock and begin aging */

 	    fmap_bitmap[page] = FM_MASK_COUNT | FM_MASK_PAGED;

 	else 
 	    cli_errmsg("fmap_unneed: inconsistent map state\n");
 	return;
     }
     cli_warnmsg("fmap_unneed: unneed on a unlocked page\n");
     return;
 }
 

 static void handle_unneed_off(fmap_t *m, size_t at, size_t len) {

     unsigned int i, first_page, last_page;

     if(!m->aging) return;

     if(!len) {
 	cli_warnmsg("fmap_unneed: attempted void unneed\n");
 	return;
     }
 

     at += m->nested_offset;

     if(!CLI_ISCONTAINED(0, m->real_len, at, len)) {

 	cli_warnmsg("fmap: attempted oof unneed\n");

 	return;
     }

     first_page = fmap_which_page(m, at);
     last_page = fmap_which_page(m, at + len - 1);
 
     for(i=first_page; i<=last_page; i++) {
 	fmap_unneed_page(m, i);
     }
 }
 

 static void unmap_mmap(fmap_t *m)
 {

 #ifdef ANONYMOUS_MAP

     size_t len = m->pages * m->pgsz + m->hdrsz;
     fmap_lock;

     if (munmap((void *)m, len) == -1) /* munmap() failed */

         cli_warnmsg("funmap: unable to unmap memory segment at address: %p with length: %zu\n", (void *)m, len);

     fmap_unlock;

 #endif

 }

 static void unmap_malloc(fmap_t *m) {
     free((void *)m);
 }
 
 static const void *handle_need_offstr(fmap_t *m, size_t at, size_t len_hint) {

     unsigned int i, first_page, last_page;

     void *ptr = (void *)((char *)m + m->hdrsz + at);

     if(!len_hint || len_hint > m->real_len - at)
 	len_hint = m->real_len - at;

     if(!CLI_ISCONTAINED(0, m->real_len, at, len_hint))

 	return NULL;
 
     fmap_aging(m);
 
     first_page = fmap_which_page(m, at);
     last_page = fmap_which_page(m, at + len_hint - 1);
 
     for(i=first_page; i<=last_page; i++) {
 	char *thispage = (char *)m + m->hdrsz + i * m->pgsz;
 	unsigned int scanat, scansz;
 
 	if(fmap_readpage(m, i, 1, 1)) {
 	    last_page = i-1;
 	    break;
 	}
 	if(i == first_page) {
 	    scanat = at % m->pgsz;

 	    scansz = MIN(len_hint, m->pgsz - scanat);

 	} else {
 	    scanat = 0;

 	    scansz = MIN(len_hint, m->pgsz);

 	}

 	len_hint -= scansz;

 	if(memchr(&thispage[scanat], 0, scansz))
 	    return ptr;
     }
     for(i=first_page; i<=last_page; i++)
 	fmap_unneed_page(m, i);
     return NULL;
 }

 static const void *handle_gets(fmap_t *m, char *dst, size_t *at, size_t max_len) {

     unsigned int i, first_page, last_page;
     char *src = (void *)((char *)m + m->hdrsz + *at), *endptr = NULL;

     size_t len = MIN(max_len-1, m->real_len - *at), fullen = len;

     if(!len || !CLI_ISCONTAINED(0, m->real_len, *at, len))

 	return NULL;
 
     fmap_aging(m);
 
     first_page = fmap_which_page(m, *at);
     last_page = fmap_which_page(m, *at + len - 1);
 
     for(i=first_page; i<=last_page; i++) {
 	char *thispage = (char *)m + m->hdrsz + i * m->pgsz;
 	unsigned int scanat, scansz;
 
 	if(fmap_readpage(m, i, 1, 0))
 	    return NULL;
 
 	if(i == first_page) {
 	    scanat = *at % m->pgsz;
 	    scansz = MIN(len, m->pgsz - scanat);
 	} else {
 	    scanat = 0;
 	    scansz = MIN(len, m->pgsz);
 	}
 	len -= scansz;
 
 	if((endptr = memchr(&thispage[scanat], '\n', scansz))) {
 	    endptr++;
 	    break;
 	}
     }
     if(endptr) {
 	memcpy(dst, src, endptr - src);
 	dst[endptr - src] = '\0';
 	*at += endptr - src;
     } else {
 	memcpy(dst, src, fullen);
 	dst[fullen] = '\0';
 	*at += fullen;
     }
     return dst;
 }

 /* vvvvv MEMORY STUFF BELOW vvvvv */

 static const void *mem_need(fmap_t *m, size_t at, size_t len, int lock);

 static void mem_unneed_off(fmap_t *m, size_t at, size_t len);
 static const void *mem_need_offstr(fmap_t *m, size_t at, size_t len_hint);
 static const void *mem_gets(fmap_t *m, char *dst, size_t *at, size_t max_len);
 

 extern cl_fmap_t *cl_fmap_open_memory(const void *start, size_t len)
 {

     int pgsz = cli_getpagesize();

     cl_fmap_t *m = cli_calloc(1, sizeof(*m));
     if (!m) {
 	cli_warnmsg("fmap: map allocation failed\n");
 	return NULL;
     }
     m->data = start;
     m->len = len;

     m->real_len = len;

     m->pgsz = pgsz;
     m->pages = fmap_align_items(len, pgsz);

     m->unmap = unmap_malloc;

     m->need = mem_need;
     m->need_offstr = mem_need_offstr;
     m->gets = mem_gets;
     m->unneed_off = mem_unneed_off;

     return m;

 }
 

 static const void *mem_need(fmap_t *m, size_t at, size_t len, int lock) { /* WIN32 */

     UNUSEDPARAM(lock);

     if(!len) {

 	return NULL;

     }

     at += m->nested_offset;
     if(!CLI_ISCONTAINED(0, m->real_len, at, len)) {

 	return NULL;

     }
 

     return (void *)((char *)m->data + at);
 }
 

 static void mem_unneed_off(fmap_t *m, size_t at, size_t len)
 {
     UNUSEDPARAM(m);
     UNUSEDPARAM(at);
     UNUSEDPARAM(len);
 }

 static const void *mem_need_offstr(fmap_t *m, size_t at, size_t len_hint) {

     char *ptr = (char *)m->data + at;
 

     if(!len_hint || len_hint > m->real_len - at)
 	len_hint = m->real_len - at;

     if(!CLI_ISCONTAINED(0, m->real_len, at, len_hint))

 	return NULL;
 
     if(memchr(ptr, 0, len_hint))
 	return (void *)ptr;
     return NULL;
 }
 

 static const void *mem_gets(fmap_t *m, char *dst, size_t *at, size_t max_len) {

     char *src = (char *)m->data + *at, *endptr = NULL;

     size_t len = MIN(max_len-1, m->real_len - *at);

     if(!len || !CLI_ISCONTAINED(0, m->real_len, *at, len))

 	return NULL;
 

     if((endptr = memchr(src, '\n', len))) {

 	endptr++;
 	memcpy(dst, src, endptr - src);
 	dst[endptr - src] = '\0';
 	*at += endptr - src;
     } else {
 	memcpy(dst, src, len);
 	dst[len] = '\0';
 	*at += len;
     }
     return dst;
 }
 

 fmap_t *fmap(int fd, off_t offset, size_t len) {
     int unused;
     return fmap_check_empty(fd, offset, len, &unused);
 }
 

 static inline unsigned int fmap_align_items(unsigned int sz, unsigned int al) {
     return sz / al + (sz % al != 0);
 }
 
 static inline unsigned int fmap_align_to(unsigned int sz, unsigned int al) {
     return al * fmap_align_items(sz, al);
 }
 
 static inline unsigned int fmap_which_page(fmap_t *m, size_t at) {
     return at / m->pgsz;
 }

 cl_error_t fmap_dump_to_file(fmap_t* map, const char* filepath, const char* tmpdir, char** outname, int* outfd, size_t start_offset, size_t end_offset)

 {

     cl_error_t ret = CL_EARG;
 
     char* filebase = NULL;
     char* prefix = NULL;
 
     char* tmpname = NULL;
     int tmpfd = -1;
 
     size_t pos = 0, len = 0, bytes_remaining = 0, write_size = 0;
 
     if ((start_offset > map->real_len) || (end_offset < start_offset)) {
         cli_dbgmsg("fmap_dump_to_file: Invalid offset arguments: start %zu, end %zu\n", start_offset, end_offset);
         return ret;
     }
 
     pos = start_offset;
     end_offset = MIN(end_offset, map->real_len);
     bytes_remaining = end_offset - start_offset;
 
     /* Create a filename prefix that includes the original filename, if available */
     if (filepath != NULL) {
         if (CL_SUCCESS != cli_basename(filepath, strlen(filepath), &filebase)) {
             cli_dbgmsg("fmap_dump_to_file: Unable to determine basename from filepath.\n");
         } else if ((start_offset != 0) && (end_offset != map->real_len)) {
             /* If we're only dumping a portion of the file, inlcude the offsets in the prefix,...
 			 * e.g. tmp filename will become something like:  filebase.500-1200.<randhex> */
             uint32_t prefix_len = strlen(filebase) + 1 + SIZE_T_CHARLEN + 1 + SIZE_T_CHARLEN + 1;
             prefix = malloc(prefix_len);
             if (NULL == prefix) {
                 cli_errmsg("fmap_dump_to_file: Failed to allocate memory for tempfile prefix.\n");
                 if (NULL != filebase)
                     free(filebase);
                 return CL_EMEM;
             }
             snprintf(prefix, prefix_len, "%s.%zu-%zu", filebase, start_offset, end_offset);

 
             free(filebase);
             filebase = NULL;

         } else {
             /* Else if we're dumping the whole thing, use the filebase as the prefix */
             prefix = filebase;

             filebase = NULL;

         }
     }

 
     cli_dbgmsg("fmap_dump_to_file: dumping fmap not backed by file...\n");

     ret = cli_gentempfd_with_prefix(tmpdir, prefix, &tmpname, &tmpfd);
     if (ret != CL_SUCCESS) {

         cli_dbgmsg("fmap_dump_to_file: failed to generate temporary file.\n");

         if (NULL != prefix) {

             free(prefix);
             prefix = NULL;
         }

         return ret;
     }
 

     if (NULL != prefix) {

         free(prefix);
         prefix = NULL;
     }
 

     do {

         const char* b;

         len = 0;

         write_size = MIN(BUFSIZ, bytes_remaining);
 
         b = fmap_need_off_once_len(map, pos, write_size, &len);

         pos += len;

         if (b && (len > 0)) {

             if ((size_t)cli_writen(tmpfd, b, len) != len) {

                 cli_warnmsg("fmap_dump_to_file: write failed to %s!\n", tmpname);
                 close(tmpfd);
                 unlink(tmpname);
                 free(tmpname);
                 return CL_EWRITE;
             }
         }

         if (len <= bytes_remaining) {
             bytes_remaining -= len;
         } else {
             bytes_remaining = 0;
         }
     } while ((len > 0) && (bytes_remaining > 0));

     if (lseek(tmpfd, 0, SEEK_SET) == -1) {

         cli_dbgmsg("fmap_dump_to_file: lseek failed\n");
     }
 
     *outname = tmpname;
     *outfd = tmpfd;
     return CL_SUCCESS;
 }
 

 int fmap_fd(fmap_t* m)

 {

     int fd;

     if (!m->handle_is_fd)

         return -1;

     fd = (int)(ptrdiff_t)m->handle;

     lseek(fd, 0, SEEK_SET);
     return fd;
 }

 
 extern void cl_fmap_close(cl_fmap_t *map)
 {
     funmap(map);
 }