diff --git a/libclamav/cpio.c b/libclamav/cpio.c
index 45e0c209d..3593d283d 100644
--- a/libclamav/cpio.c
+++ b/libclamav/cpio.c
@@ -157,7 +157,7 @@ int cli_scancpio_old(cli_ctx *ctx)
 	    if(ret == CL_EMAXFILES) {
 		return ret;
 	    } else if(ret == CL_SUCCESS) {
-		ret = cli_dumpscan(*ctx->fmap, pos, filesize, ctx);
+		ret = cli_map_scandesc(*ctx->fmap, pos, filesize, ctx);
 		if(ret == CL_VIRUS)
 		    return ret;
 	    }
@@ -234,7 +234,7 @@ int cli_scancpio_odc(cli_ctx *ctx)
 	if(ret == CL_EMAXFILES) {
 	    return ret;
 	} else if(ret == CL_SUCCESS) {
-	    ret = cli_dumpscan(*ctx->fmap, pos, filesize, ctx);
+	    ret = cli_map_scandesc(*ctx->fmap, pos, filesize, ctx);
 	    if(ret == CL_VIRUS)
 		return ret;
 	}
@@ -313,7 +313,7 @@ int cli_scancpio_newc(cli_ctx *ctx, int crc)
 	if(ret == CL_EMAXFILES) {
 	    return ret;
 	} else if(ret == CL_SUCCESS) {
-	    ret = cli_dumpscan(*ctx->fmap, pos, filesize, ctx);
+	    ret = cli_map_scandesc(*ctx->fmap, pos, filesize, ctx);
 	    if(ret == CL_VIRUS)
 		return ret;
 	}
diff --git a/libclamav/fmap.c b/libclamav/fmap.c
index 767f2540e..33e5be384 100644
--- a/libclamav/fmap.c
+++ b/libclamav/fmap.c
@@ -257,7 +257,8 @@ extern cl_fmap_t *cl_fmap_open_handle(void *handle, size_t offset, size_t len,
     m->pread_cb = pread_cb;
     m->aging = use_aging;
     m->offset = offset;
-    m->len = len;
+    m->len = len;/* m->nested_offset + m->len = m->real_len */
+    m->real_len = len;
     m->pages = pages;
     m->hdrsz = hdrsz;
     m->pgsz = pgsz;
@@ -451,8 +452,8 @@ static int fmap_readpage(fmap_t *m, unsigned int first_page, unsigned int count,
 	    pptr = (char *)m + page * m->pgsz + m->hdrsz;
 	    first_page = page;
 	}
-	if((page == m->pages - 1) && (m->len % m->pgsz))
-	    readsz += m->len % m->pgsz;
+	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 */
@@ -472,7 +473,9 @@ static const void *handle_need(fmap_t *m, size_t at, size_t len, int lock) {
     if(!len)
 	return NULL;
 
-    if(!CLI_ISCONTAINED(0, m->len, at, len))
+    at += m->nested_offset;
+
+    if(!CLI_ISCONTAINED(0, m->real_len, at, len))
 	return NULL;
 
     fmap_aging(m);
@@ -519,7 +522,7 @@ static void handle_unneed_off(fmap_t *m, size_t at, size_t len) {
 	return;
     }
 
-    if(!CLI_ISCONTAINED(0, m->len, at, len)) {
+    if(!CLI_ISCONTAINED(0, m->real_len, at, len)) {
 	cli_warnmsg("fmap: attempted oof unneed\n");
 	return;
     }
@@ -550,10 +553,10 @@ 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->len - at)
-	len_hint = m->len - at;
+    if(!len_hint || len_hint > m->real_len - at)
+	len_hint = m->real_len - at;
 
-    if(!CLI_ISCONTAINED(0, m->len, at, len_hint))
+    if(!CLI_ISCONTAINED(0, m->real_len, at, len_hint))
 	return NULL;
 
     fmap_aging(m);
@@ -588,9 +591,9 @@ 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) {
     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->len - *at), fullen = len;
+    size_t len = MIN(max_len-1, m->real_len - *at), fullen = len;
 
-    if(!len || !CLI_ISCONTAINED(0, m->len, *at, len))
+    if(!len || !CLI_ISCONTAINED(0, m->real_len, *at, len))
 	return NULL;
 
     fmap_aging(m);
@@ -650,6 +653,7 @@ extern cl_fmap_t *cl_fmap_open_memory(const void *start, size_t len)
     }
     m->data = start;
     m->len = len;
+    m->real_len = len;
     m->pgsz = pgsz;
     m->pages = fmap_align_items(len, pgsz);
     m->unmap = unmap_none;
@@ -665,7 +669,8 @@ static const void *mem_need(fmap_t *m, size_t at, size_t len, int lock) { /* WIN
     if(!len) {
 	return NULL;
     }
-    if(!CLI_ISCONTAINED(0, m->len, at, len)) {
+    at += m->nested_offset;
+    if(!CLI_ISCONTAINED(0, m->real_len, at, len)) {
 	return NULL;
     }
 
@@ -677,10 +682,10 @@ 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) {
     char *ptr = (char *)m->data + at;
 
-    if(!len_hint || len_hint > m->len - at)
-	len_hint = m->len - at;
+    if(!len_hint || len_hint > m->real_len - at)
+	len_hint = m->real_len - at;
 
-    if(!CLI_ISCONTAINED(0, m->len, at, len_hint))
+    if(!CLI_ISCONTAINED(0, m->real_len, at, len_hint))
 	return NULL;
 
     if(memchr(ptr, 0, len_hint))
@@ -690,9 +695,9 @@ 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) {
     char *src = (char *)m->data + *at, *endptr = NULL;
-    size_t len = MIN(max_len-1, m->len - *at);
+    size_t len = MIN(max_len-1, m->real_len - *at);
 
-    if(!len || !CLI_ISCONTAINED(0, m->len, *at, len))
+    if(!len || !CLI_ISCONTAINED(0, m->real_len, *at, len))
 	return NULL;
 
     if((endptr = memchr(src, '\n', len))) {
diff --git a/libclamav/fmap.h b/libclamav/fmap.h
index a47992704..ef72655be 100644
--- a/libclamav/fmap.h
+++ b/libclamav/fmap.h
@@ -52,8 +52,18 @@ struct cl_fmap {
     const void *data;
 
     /* common interface */
-    size_t offset;
-    size_t len;
+    size_t offset;/* file offset */
+    size_t nested_offset;/* buffer offset for nested scan*/
+    size_t real_len;/* amount of data mapped from file, starting at offset */
+    size_t len;/* length of data accessible via current fmap */
+
+    /* real_len = nested_offset + len
+     * file_offset = offset + nested_offset + need_offset
+     * maximum offset, length accessible via fmap API: len
+     * offset in cached buffer: nested_offset + need_offset
+     *
+     * This allows to scan a portion of an already mapped file without dumping
+     * to disk and remapping (for uncompressed archives for example) */
 
     /* vtable for implementation */
     void        (*unmap)(fmap_t*);
diff --git a/libclamav/macho.c b/libclamav/macho.c
index c83d5a6b5..1c592b3a8 100644
--- a/libclamav/macho.c
+++ b/libclamav/macho.c
@@ -552,7 +552,7 @@ int cli_scanmacho_unibin(cli_ctx *ctx)
 	cli_dbgmsg("UNIBIN: Binary %u of %u\n", i + 1, fat_header.nfats);
 	cli_dbgmsg("UNIBIN: File offset: %u\n", fat_arch.offset);
 	cli_dbgmsg("UNIBIN: File size: %u\n", fat_arch.size);
-	ret = cli_dumpscan(map, fat_arch.offset, fat_arch.size, ctx);
+	ret = cli_map_scandesc(map, fat_arch.offset, fat_arch.size, ctx);
 	if(ret == CL_VIRUS)
 	    break;
     }
diff --git a/libclamav/others.c b/libclamav/others.c
index 4e5fe21f0..b96a474c5 100644
--- a/libclamav/others.c
+++ b/libclamav/others.c
@@ -915,60 +915,6 @@ int cli_rmdirs(const char *dirname)
 }
 #endif
 
-int cli_dumpscan(fmap_t *map, off_t offset, size_t size, cli_ctx *ctx)
-{
-	int newfd, sum = 0, ret;
-	ssize_t bread;
-	char *name;
-	const char *buff;
-
-    if(!(name = cli_gentemp(ctx->engine->tmpdir)))
-	return CL_EMEM;
-
-    if((newfd = open(name, O_RDWR|O_CREAT|O_TRUNC|O_BINARY|O_EXCL, S_IRWXU)) < 0) {
-	cli_errmsg("cli_dumpscan: Can't create file %s\n", name);
-	free(name);
-	return CL_ECREAT;
-    }
-
-    while (( buff = fmap_need_off_once_len(map, offset, FILEBUFF, &bread) )) {
-	offset += bread;
-	if((uint32_t) (sum + bread) >= size) {
-	    if(cli_writen(newfd, buff, size - sum) == -1) {
-		cli_errmsg("cli_dumpscan: Can't write to %s\n", name);
-		close(newfd);
-		cli_unlink(name);
-		free(name);
-		return CL_EWRITE;
-	    }
-	    break;
-	} else {
-	    if(cli_writen(newfd, buff, bread) == -1) {
-		cli_errmsg("cli_dumpscan: Can't write to %s\n", name);
-		close(newfd);
-		cli_unlink(name);
-		free(name);
-		return CL_EWRITE;
-	    }
-	}
-	sum += bread;
-    }
-    cli_dbgmsg("DUMP&SCAN: File extracted to %s\n", name);
-    lseek(newfd, 0, SEEK_SET);
-    if((ret = cli_magic_scandesc(newfd, ctx)) == CL_VIRUS)
-	cli_dbgmsg("cli_dumpscan: Infected with %s\n", *ctx->virname);
-
-    close(newfd);
-    if(!ctx->engine->keeptmp) {
-	if(cli_unlink(name)) {
-	    free(name);
-	    return CL_EUNLINK;
-	}
-    }
-    free(name);
-    return ret;
-}
-
 /* Implement a generic bitset, trog@clamav.net */
 
 #define BITS_PER_CHAR (8)
diff --git a/libclamav/others.h b/libclamav/others.h
index 16d4e60aa..a8d3a6df5 100644
--- a/libclamav/others.h
+++ b/libclamav/others.h
@@ -522,7 +522,7 @@ char *cli_gentemp(const char *dir);
 int cli_gentempfd(const char *dir, char **name, int *fd);
 unsigned int cli_rndnum(unsigned int max);
 int cli_filecopy(const char *src, const char *dest);
-int cli_dumpscan(fmap_t *map, off_t offset, size_t size, cli_ctx *ctx);
+int cli_mapscan(fmap_t *map, off_t offset, size_t size, cli_ctx *ctx);
 bitset_t *cli_bitset_init(void);
 void cli_bitset_free(bitset_t *bs);
 int cli_bitset_set(bitset_t *bs, unsigned long bit_offset);
diff --git a/libclamav/scanners.c b/libclamav/scanners.c
index 546da9c30..fd76eb132 100644
--- a/libclamav/scanners.c
+++ b/libclamav/scanners.c
@@ -2537,20 +2537,48 @@ int cl_scandesc(int desc, const char **virname, unsigned long int *scanned, cons
     return cl_scandesc_callback(desc, virname, scanned, engine, scanoptions, NULL);
 }
 
-static int cli_map_scandesc(cl_fmap_t *map, cli_ctx *ctx)
+/* length = 0, till the end */
+int cli_map_scandesc(cl_fmap_t *map, off_t offset, size_t length, cli_ctx *ctx)
 {
+    off_t old_off = map->nested_offset;
+    size_t old_len = map->len;
     int ret;
 
-    if (map->len <= 5) {
-	cli_dbgmsg("Small data (%u bytes)\n", (unsigned int) map->len);
+    cli_dbgmsg("cli_map_scandesc: [%ld, +%ld), [%ld, +%ld)\n",
+	       old_off, old_len, offset, length);
+    if (offset < 0 || offset >= length) {
+	cli_dbgmsg("Invalid offset: %ld\n", (long)offset);
+	return CL_CLEAN;
+    }
+
+    if (!length) length = old_len - offset;
+    if (length > old_len - offset) {
+	cli_dbgmsg("Data truncated: %ld -> %ld\n",
+		   length, old_len - offset);
+	length = old_len - offset;
+    }
+
+    if (length <= 5) {
+	cli_dbgmsg("Small data (%u bytes)\n", (unsigned int) length);
 	return CL_CLEAN;
     }
     ctx->fmap++;
     *ctx->fmap = map;
-
-    ret = magic_scandesc(ctx, CL_TYPE_ANY);
+    /* can't change offset because then we'd have to discard/move cached
+     * data, instead use another offset to reuse the already cached data */
+    map->nested_offset += offset;
+    map->len = length;
+    map->real_len = map->nested_offset + length;
+    if (CLI_ISCONTAINED(old_off, old_len, map->nested_offset, map->len)) {
+	ret = magic_scandesc(ctx, CL_TYPE_ANY);
+    } else {
+	cli_warnmsg("internal map error: %ld, %ld; %ld, %ld\n", old_off, old_off + old_len,
+		    map->offset,map->nested_offset+map->len);
+    }
 
     ctx->fmap--;
+    map->nested_offset = old_off;
+    map->len = old_len;
     return ret;
 }
 
@@ -2594,7 +2622,7 @@ static int scan_common(int desc, cl_fmap_t *map, const char **virname, unsigned
 #endif
 
     cli_logg_setup(&ctx);
-    rc = map ? cli_map_scandesc(map, &ctx) : cli_magic_scandesc(desc, &ctx);
+    rc = map ? cli_map_scandesc(map, 0, map->len, &ctx) : cli_magic_scandesc(desc, &ctx);
 
     cli_bitset_free(ctx.hook_lsig_matches);
     free(ctx.fmap);
diff --git a/libclamav/scanners.h b/libclamav/scanners.h
index ee0f07313..1804f8e5a 100644
--- a/libclamav/scanners.h
+++ b/libclamav/scanners.h
@@ -27,6 +27,7 @@
 
 int cli_magic_scandesc(int desc, cli_ctx *ctx);
 int cli_magic_scandesc_type(cli_ctx *ctx, cli_file_t type);
+int cli_map_scandesc(cl_fmap_t *map, off_t offset, size_t length, cli_ctx *ctx);
 int cli_found_possibly_unwanted(cli_ctx* ctx);
 
 #endif
diff --git a/libclamav/swf.c b/libclamav/swf.c
index cf73329c1..0d5a3ae1a 100644
--- a/libclamav/swf.c
+++ b/libclamav/swf.c
@@ -242,22 +242,12 @@ static const char *tagname(tag_id id)
 
 static int dumpscan(fmap_t *map, unsigned int offset, unsigned int size, const char *obj, int version, cli_ctx *ctx)
 {
-	int newfd, ret = CL_CLEAN;
-	unsigned int bread, sum = 0;
-	char buff[FILEBUFF];
-	char *name;
+    int ret = CL_CLEAN;
+    char buff[16];
 
-    if(!(name = cli_gentemp(ctx->engine->tmpdir)))
-	return CL_EMEM;
-
-    if((newfd = open(name, O_RDWR|O_CREAT|O_TRUNC|O_BINARY, S_IRWXU)) < 0) {
-	cli_errmsg("dumpscan: Can't create file %s\n", name);
-	free(name);
-	return CL_ECREAT;
-    }
-
-    while((bread = fmap_readn(map, buff, offset, sizeof(buff))) > 0) {
-	if(!sum && ctx->img_validate) {
+    memset(buff, 0, sizeof(buff));
+    fmap_readn(map, buff, offset, sizeof(buff));
+    if(ctx->img_validate) {
 	    if(!memcmp(buff, "\xff\xd8", 2)) {
 		cli_dbgmsg("SWF: JPEG image data\n");
 	    } else if(!memcmp(buff, "\xff\xd9\xff\xd8", 4)) {
@@ -284,46 +274,10 @@ static int dumpscan(fmap_t *map, unsigned int offset, unsigned int size, const c
 		ret = CL_VIRUS;
 	    }
 	    if(ret == CL_VIRUS) {
-		close(newfd);
-		cli_unlink(name);
-		free(name);
 		return ret;
 	    }
-	}
-	if(sum + bread >= size) {
-	    if(cli_writen(newfd, buff, size - sum) == -1) {
-		cli_errmsg("dumpscan: Can't write to %s\n", name);
-		close(newfd);
-		cli_unlink(name);
-		free(name);
-		return CL_EWRITE;
-	    }
-	    break;
-	} else {
-	    if(cli_writen(newfd, buff, bread) == -1) {
-		cli_errmsg("cli_dumpscan: Can't write to %s\n", name);
-		close(newfd);
-		cli_unlink(name);
-		free(name);
-		return CL_EWRITE;
-	    }
-	}
-	sum += bread;
-	offset += bread;
     }
-    cli_dbgmsg("SWF: %s data extracted to %s\n", obj, name);
-    lseek(newfd, 0, SEEK_SET);
-    if((ret = cli_magic_scandesc(newfd, ctx)) == CL_VIRUS)
-	cli_dbgmsg("cli_dumpscan: Infected with %s\n", *ctx->virname);
-
-    close(newfd);
-    if(!ctx->engine->keeptmp) {
-	if(cli_unlink(name)) {
-	    free(name);
-	    return CL_EUNLINK;
-	}
-    }
-    free(name);
+    ret = cli_map_scandesc(map, offset, size, ctx);
     if(ctx->img_validate && ret == CL_EPARSE && SCAN_ALGO) {
 	*ctx->virname = "Heuristics.SWF.SuspectImage.E";
 	return CL_VIRUS;